NASA Technical Reports Server (NTRS)
Perger, W. F.; Das, B. P.
1987-01-01
The parity-nonconserving electric-dipole-transition amplitudes for the 6s1/2-7s1/2 transition in cesium and the 6p1/2-7p1/2 transition in thallium have been calculated by the Dirac-Hartree-Fock method. The effects of using different Dirac-Hartree-Fock atomic core potentials are examined and the transition amplitudes for both the length and velocity gauges are given. It is found that the parity-nonconserving transition amplitudes exhibit a greater dependence on the starting potential for thallium than for cesium.
NASA Technical Reports Server (NTRS)
Perger, W. F.; Das, B. P.
1987-01-01
The parity-nonconserving electric-dipole-transition amplitudes for the 6s1/2-7s1/2 transition in cesium and the 6p1/2-7p1/2 transition in thallium have been calculated by the Dirac-Hartree-Fock method. The effects of using different Dirac-Hartree-Fock atomic core potentials are examined and the transition amplitudes for both the length and velocity gauges are given. It is found that the parity-nonconserving transition amplitudes exhibit a greater dependence on the starting potential for thallium than for cesium.
Shabaev, V. M.; Tupitsyn, I. I.; Pachucki, K.; Plunien, G.; Yerokhin, V. A.
2005-12-15
The complete gauge-invariant set of the one-loop QED corrections to the parity-nonconserving (PNC) amplitude in cesium and francium is evaluated to all orders in {alpha}Z using a local form of the Dirac-Fock potential. The calculations are performed in both length and velocity gauges for the absorbed photon and the total binding QED correction is found to be -0.27(3)% for Cs and -0.28(5)% for Fr. Moreover, a high-precision calculation of the electron-correlation and Breit-interaction effects on the 7s-8s PNC amplitude in francium using a large-scale configuration-interaction Dirac-Fock method is performed. The obtained results are employed to improve the theoretical predictions for the PNC transition amplitude in Cs and Fr. Using an average value from two most accurate measurements of the vector transition polarizability, the weak charge of {sup 133}Cs is derived to amount to Q{sub W}=-72.65(29){sub exp}(36){sub theor}. This value deviates by 1.1{sigma} from the prediction of the standard model. The values of the 7s-8s PNC amplitude in {sup 223}Fr and {sup 210}Fr are obtained to be -15.49(15) and -14.16(14), respectively, in units of ix10{sup -11}(-Q{sub W})/N a.u.
Parity nonconservation in ytterbium ion
Sahoo, B. K.; Das, B. P.
2011-07-15
We consider parity nonconservation (PNC) in singly ionized ytterbium (Yb{sup +}) arising from the neutral current weak interaction. We calculate the PNC electric dipole transition amplitude (E1{sub PNC}) and the properties associated with it using relativistic coupled-cluster theory. E1{sub PNC} for the [4f{sup 14}] {sup 2}6s{yields}[4f{sup 14}] {sup 2}5d{sub 3/2} transition in Yb{sup +} has been evaluated to within an accuracy of 5%. The improvement of this result is possible. It therefore appears that this ion is a promising candidate for testing the standard model of particle physics.
NASA Astrophysics Data System (ADS)
Sahoo, B. K.; Aoki, T.; Das, B. P.; Sakemi, Y.
2016-03-01
Employing the relativistic coupled-cluster method, comparative studies of the parity nonconserving electric dipole amplitudes for the 7 s 1/2 2S →6 d 5/2 2D transitions in 210Fr and 211Fr isotopes have been carried out. It is found that these transition amplitudes, sensitive only to the nuclear spin-dependent effects, are enhanced substantially owing to the very large contributions from the electron core-polarization effects in Fr. This translates to a relatively large and, in principle, measurable induced light shift, which would be a signature of nuclear spin-dependent parity nonconservation that is dominated by the nuclear anapole moment in a heavy atom like Fr. A plausible scheme to measure this quantity using the Cyclotron and Radioisotope Center (CYRIC) facility at Tohoku University has been outlined.
Calculation of parity nonconservation in neutral ytterbium
Dzuba, V. A.; Flambaum, V. V.
2011-04-15
We use configuration interaction and many-body perturbation theory techniques to calculate spin-independent and spin-dependent parts of the parity-nonconserving amplitudes of the transitions between the 6s{sup 2} {sup 1}S{sub 0} ground state and the 6s5d {sup 3}D{sub 1} excited state of {sup 171}Yb and {sup 173}Yb. The results are presented in a form convenient for extracting spin-dependent interaction constants (such as anapole moment) from the measurements.
NASA Astrophysics Data System (ADS)
Aoki, T.; Torii, Y.; Sahoo, B. K.; Das, B. P.; Harada, K.; Hayamizu, T.; Sakamoto, K.; Kawamura, H.; Inoue, T.; Uchiyama, A.; Ito, S.; Yoshioka, R.; Tanaka, K. S.; Itoh, M.; Hatakeyama, A.; Sakemi, Y.
2017-04-01
We present an experimental technique to measure light shifts due to the nuclear spin independent (NSI) parity-nonconserving (PNC) interaction in the 7S_{1/2}-6D_{3/2} transition in ultracold {^{210}Fr} atoms. The approach we propose is similar to the one by Fortson (Phys Rev Lett 70:2383, 10) to measure the PNC-induced light shift which arises from the interference of parity nonconserving electric dipole transition and electric quadrupole transition amplitudes. Its major advantage is that it can treat more than 10^4 ultracold {^{210}Fr} atoms to enhance the shot noise limit. A relativistic coupled-cluster method has been employed to calculate the electric dipole transition amplitudes arising from the PNC interaction. Based on these calculations, we have evaluated the PNC-induced light shifts for transitions between the hyperfine levels of the 7S_{1/2} and 6D_{3/2} states and suitable transitions are identified for carrying out PNC measurements. It is possible in principle to probe new physics beyond the standard model with our proposed experimental scheme.
Parity nonconservation in deuteron photoreactions
NASA Astrophysics Data System (ADS)
Partanen, T. M.; Niskanen, J. A.
2011-04-01
We calculate the asymmetries in parity-nonconserving deuteron photodisintegration due to circularly polarized photons ěc γ d to np with the photon laboratory energy ranging from the threshold up to 10MeV and the radiative capture of thermal polarized neutrons by protons ěc np to γ d . We use the leading-order electromagnetic Hamiltonian neglecting the smaller nuclear exchange currents. Comparative calculations are done by using the Reid93 and Argonne v18 potentials for the strong interaction and the DDH and FCDH "best" values for the weak couplings in a weak one-meson exchange potential. A weak NΔ transition potential is used to incorporate also the Δ(1232) -isobar excitation in the coupled-channels formalism.
Parity nonconserving proton-proton elastic scattering
NASA Astrophysics Data System (ADS)
Partanen, T. M.; Niskanen, J. A.; Iqbal, M. J.
2012-09-01
The parity nonconserving longitudinal analyzing power bar A_L is calculated in elastic ěc pp scattering at the energies below the approximate inelastic region T lab = 350 MeV. The short-ranged heavy meson ρ and ω exchanges as well as the longer-ranged 2 π exchanges (with and without intermediate NΔ configurations) are considered as the mediators of the parity nonconserving interactions. The DDH "best" coupling values are used as the parity nonconserving meson- NN couplings. Also three different parity nonconserving two-pion exchange potentials by various authors are compared.
Breit interaction and parity nonconservation in many-electron atoms
Dzuba, V. A.; Flambaum, V. V.; Safronova, M. S.
2006-02-15
We present accurate ab initio nonperturbative calculations of the Breit correction to the parity nonconserving (PNC) amplitudes of the 6s-7s and 6s-5d{sub 3/2} transitions in Cs, 7s-8s and 7s-6d{sub 3/2} transitions in Fr, 6s-5d{sub 3/2} transition in Ba{sup +}, 7s-6d{sub 3/2} transition in Ra{sup +}, and 6p{sub 1/2}-6p{sub 3}/{sub 2} transition in Tl. The results for the 6s-7s transition in Cs and 7s-8s transition in Fr are in good agreement with other calculations. We demonstrate that higher-orders many-body corrections to the Breit interaction are especially important for the s-d PNC amplitudes. We confirm good agreement of the PNC measurements for cesium and thallium with the standard model.
Parity nonconserving spin rotation in weak neutron-proton scattering
NASA Astrophysics Data System (ADS)
Avishai, Y.
1984-07-01
Parity nonconservation in weak n-p scattering is studied at threshold wehre neutron spin rotation might occur. We use the DDH weak NN force and a separable form with S, P and D partial waves in the strong NN interaction. The contribution of various spin-isospin components to the weak NN scattering amplitude is evaluated and the spin rotation angle is found to be -2.35 × 10 -9 rad/cm. The sources of possible errors are indicated.
Effects of parity nonconservation in a molecule of oxygen
NASA Astrophysics Data System (ADS)
Chubukov, D. V.; Skripnikov, L. V.; Andreev, O. Yu; Labzowsky, L. N.; Plunien, G.
2017-05-01
This paper is devoted to the calculation of parity nonconserving (PNC) effects in the diatomic homonuclear molecule of oxygen O2. For this purpose the magnetic dipole transition b{}1{{{Σ }}}g+≤ftarrow X{}3{{{Σ }}}g- was considered. It was believed that the weak electron-electron interaction prevails over the weak interaction of electrons with nuclei in this case. This idea appeared not to be justified for molecular oxygen. As it turns out from our calculations, the parity nonconservation degree for the weak electron-nucleus interaction is of the order {{ P }}{{eN}}=1.4\\cdot {10}-11 and for the weak electron-electron interaction is by two orders smaller {{ P }}{{ee}}=1.1\\cdot {10}-13. Nevertheless, a PNC experiment for the observation of the weak electron-nucleus interaction looks sufficiently feasible (previously, such experiments were carried out only with atoms).
Effect of nuclear quadrupole moments on parity nonconservation in atoms
NASA Astrophysics Data System (ADS)
Flambaum, V. V.; Dzuba, V. A.; Harabati, C.
2017-07-01
Nuclei with spin I ≥1 have a weak quadrupole moment which leads to tensor contribution to the parity nonconserving interaction between nuclei and electrons. We calculate this contribution for atoms of current experiment interest Yb+, Fr, and Ra+. We have also performed order of magnitude estimates and found strong enhancement of the weak quadrupole effects due to the close levels of opposite parity in many lanthanoids (e.g., Nd, Gd, Dy, Ho, Er, Pr, Sm) and Ra. Another possibility is to measure the parity-nonconservation (PNC) transitions between the hyperfine components of the ground state of Bi. Since nuclear weak charge is dominated by neutrons this opens a way of measuring quadrupole moments of neutron distribution in nuclei.
Justification of a "Crucial" Experiment: Parity Nonconservation.
ERIC Educational Resources Information Center
Franklin, Allan; Smokler, Howard
1981-01-01
Presents history, nature of evidence evaluated, and philosophical questions to justify the view that experiments on parity nonconservation were "crucial" experiments in the sense that they decided unambiguously and within a short period of time for the appropriate scientific community, between two or more competing theories or classes of theories.…
Justification of a "Crucial" Experiment: Parity Nonconservation.
ERIC Educational Resources Information Center
Franklin, Allan; Smokler, Howard
1981-01-01
Presents history, nature of evidence evaluated, and philosophical questions to justify the view that experiments on parity nonconservation were "crucial" experiments in the sense that they decided unambiguously and within a short period of time for the appropriate scientific community, between two or more competing theories or classes of theories.…
Parity-nonconserving cold neutron-parahydrogen interactions
NASA Astrophysics Data System (ADS)
Partanen, T. M.
2012-12-01
Three pion-dominated observables of the parity-nonconserving interactions between the cold neutrons and parahydrogen are calculated. The transversely polarized neutron spin rotation, unpolarized neutron longitudinal polarization, and photon asymmetry of the radiative polarized neutron capture are considered. For the numerical evaluation of the observables, the strong interactions are taken into account by the Reid93 potential and the parity-nonconserving interactions by the DDH and EFT models including two different EFT parity-nonconserving two-pion exchange potentials.
Measurement of the parity nonconserving neutral weak interaction in atomic thallium
Bucksbaum, P.H.
1980-11-01
This thesis describes an experiment to measure parity nonconservation in atomic thallium. A frequency doubled, flashlamp pumped tunable dye laser is used to excite the 6P/sub 1/2/(F = 0) ..-->.. 7P/sub 1/2/(F = 1) transition at 292.7 nm, with circularly polarized light. An electrostatic field E of 100 to 300 V/cm causes this transition to occur via Stark induced electric dipole. Two field free transitions may also occur: a highly forbidden magnetic dipole M, and a parity nonconserving electric dipole epsilon/sub P/. The latter is presumed to be due to the presence of a weak neutral current interaction between the 6p valence electron and the nucleus, as predicted by gauge theories which unite the electromagnetic and weak interactions. Both M and epsilon/sub P/ interfere with the Stark amplitude ..beta..E to produce a polarization of the 7P/sub 1/2/ state. This is measured with a circularly polarized infrared laser beam probe, tuned to the 7P/sub 1/2/ ..-->.. 8S/sub 1/2/ transition. This selectively excites m/sub F/ = +1 or -1 components of the 7P/sub 1/2/ state, and the polarization is seen as an asymmetry in 8S ..-->.. 6P/sub 3/2/ fluorescence when the probe helicity is reversed. The polarization due to M is ..delta../sub M/ = -2M/(BETAE). It is used to calibrate the analyzing efficiency. The polarization due to epsilon/sub P/ is ..delta../sub P/ = 2i epsilon/sub P//(..beta..E), and can be distinguished from ..delta../sub M/ by its properties under reversal of the 292.7 nm photon helicity and reversal of the laser direction. A preliminary measurement yielded a parity violation in agreement with the gauge theory of Weinberg and Salam.
Parity nonconservation in odd isotopes of single trapped atomic ions
Sahoo, B. K.; Mandal, P.; Mukherjee, M.
2011-03-15
We have estimated the size of the light shifts due to parity-nonconservation (PNC) interactions in different isotopes of Ba{sup +} and Ra{sup +} ions based on the work of Fortson [Phys. Rev. Lett. 70, 2383 (1993)]. We have used the nuclear-spin-independent (NSI) amplitudes calculated earlier by us [Phys. Rev. Lett. 96, 163003 (2006); Phys. Rev. A 78, 050501(R) (2008)], and we have employed the third-order many-body perturbation theory [MBPT(3)] in this work to estimate the nuclear-spin-dependent (NSD) amplitudes in these ions. Ra{sup +} is found to be more favorable than Ba{sup +} for measuring both the NSI and NSD PNC observables.
Parity nonconservation in radioactive atoms: An experimental perspective
Vieira, D.
1994-11-01
The measurement of parity nonconservation (PNC) in atoms constitutes an important test of electroweak interactions in nuclei. Great progress has been made over the last 20 years in performing these measurements with ever increasing accuracies. To date the experimental accuracies have reached a level of 1 to 2%. In all cases, except for cesium, the theoretical atomic structure uncertainties now limit the comparison of these measurements to the predictions of the standard model. New measurements involving the ratio of Stark interference transition rates for a series of Cs or Fr radioisotopes are foreseen as a way of eliminating these atomic structure uncertainties. The use of magneto-optical traps to collect and concentrate the much smaller number of radioactive atoms that are produced is considered to be one of the key steps in realizing these measurements. Plans for how these measurements will be done and progress made to date are outlined.
Parity nonconservation in Fr-like actinide and Cs-like rare-earth-metal ions
NASA Astrophysics Data System (ADS)
Roberts, B. M.; Dzuba, V. A.; Flambaum, V. V.
2013-07-01
Parity-nonconservation (PNC) amplitudes are calculated for the 7s-6d3/2 transitions of the francium isoelectronic sequence (Fr, Ra+, Ac2+, Th3+, Pa4+, U5+, and Np6+) and for the 6s-5d3/2 transitions of the cesium isoelectronic sequence (Cs, Ba+, La2+, Ce3+, and Pr4+). We show in particular that isotopes of La2+, Ac2+, and Th3+ ions have strong potential in the search for new physics beyond the standard model: The PNC amplitudes are large, the calculations are accurate, and the nuclei are practically stable. In addition, 232Th3+ ions have recently been trapped and cooled [Campbell , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.233004 102, 233004 (2009)]. We also extend previous works by calculating the s-s PNC transitions in Ra+ and Ba+ and provide calculations of several energy levels, and electric dipole and quadrupole transition amplitudes for the Fr-like actinide ions.
Nuclear-structure effects on parity nonconservation in light nuclei
Brown, B.A.; Richter, W.A.; Godwin, N.S.
1980-11-24
The nucleon-nucleon parity-nonconserving potentials given by Desplangues, Donoghue, and Holstein (DDH) are used to calculate matrix elements between states of opposite parity in /sup 10/B, /sup 16/O, /sup 18/F, /sup 19/F, /sup 20/Ne, and /sup 21/Ne. The sensitivity of the parity-nonconserving matrix elements to various approximations in the microscopic shell-model wave functions is investigated. The final results using the DDH estimates for the weak meson-nucleon coupling constants based on the Weinberg-Salam theory are several times larger than experiment.
Nuclear-Structure Effects on Parity Nonconservation in Light Nuclei
NASA Astrophysics Data System (ADS)
Brown, B. A.; Richter, W. A.; Godwin, N. S.
1980-11-01
The nucleon-nucleon parity-nonconserving potentials given by Desplangues, Donoghue, and Holstein (DDH) are used to calculate matrix elements between states of opposite parity in 10B, 16O, 18F, 19F, 20Ne, and 21Ne. The sensitivity of the parity-nonconserving matrix elements to various approximations in the microscopic shell-model wave functions is investigated. The final results using the DDH estimates for the weak mesonnucleon coupling constants based on the Weinberg-Salam theory are several times larger than experiment.
NASA Astrophysics Data System (ADS)
Wood, Chris
1998-05-01
Historically, atomic parity nonconservation (PNC) measurements have bridged the gap between high energy and low energy physics. Our recently completed 0.35% measurement of PNC in cesium(C. S. Wood et al., Science) 275, 1759 (1997) has gone a step further and created a bridge between atomic physics and nuclear physics. This measurement represents the best low energy test of electroweak unification and, in addition, we have made a 14% measurement of the parity violating nuclear anapole moment(V.V. Flambaum et al., Phys. Lett. B) 146, 367 (1984). Cesium continues to hold a special place for atomic PNC measurements due to the accuracy (1%) with which the necessary atomic structure calculations can be made(S.A. Blundell, J. Sapirstein, and W. R. Johnson, Phys. Rev. D) 45, 1602 (1992); V.A. Dzuba, V. V. Flambaum, and O. P. Sushkov, Phys. Lett. A 141, 147 (1989)., and our result has motivated new calculations. The experiment uses a Stark interference technique to measure PNC, and has achieved a factor of seven improvement over our previous result. Two frequency-stabilized diode lasers are used to optically pump an intense cesium beam, while a third is used for detection and a fourth is used to monitor the spin polarization of the atomic beam using stimulated Raman transitions. A dye laser operating at 540nm, phase locked to a finesse 100,000 power buildup cavity, is used to excite the forbidden 6S-7S transition in a region of crossed electric and magnetic fields. These fields serve to define an experimental coordinate system. We have developed 5 different ways to parity transform this coordinate system, which are crucial to our ability to suppress systematic errors. Our signal is the interference of an allowed 6S-7S transition amplitude with the PNC transition amplitude, which causes a tiny (6 ppm) fractional modulation of the 6S-7S excitation rate synchronous with all 5 parity transformations.
Parity nonconservation in {sup 207}Pb
Leuschner, M.; Cain, B.; Knott, J.E.; Komives, A.; Szymanski, J.J.; Andalkar, A.; Girit, I.C.; Petrov, M.; Bowman, J.D.
1995-07-10
Two experiments are currently underway to measure the single-particle weak mixing matrix element for the 1064 KeV transition in {sup 207}Pb. One experiment measures the circular polarization of the 1064 KeV gamma ray emitted from an unpolarized source, while the other experiment measures the forward-backward asymmetry of gamma rays emitted from a polarized source. Analysis of the first set of polarized source data yields an upper limit of 46 eV for the single-particle weak mixing matrix element. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Observation of Parity Nonconservation in Møller Scattering
NASA Astrophysics Data System (ADS)
Anthony, P. L.; Arnold, R. G.; Arroyo, C.; Baird, K.; Bega, K.; Biesiada, J.; Bosted, P. E.; Breuer, M.; Carr, R.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cooke, M.; Decker, F. J.; Decowski, P.; Deur, A.; Emam, W.; Erickson, R.; Fieguth, T.; Field, C.; Gao, J.; Gustafsson, K.; Hicks, R. S.; Holmes, R.; Hughes, E. W.; Humensky, T. B.; Jones, G. M.; Kaufman, L. J.; Kolomensky, Yu. G.; Kumar, K. S.; Lhuillier, D.; Lombard-Nelsen, R.; Mastromarino, P.; Mayer, B.; McKeown, R. D.; Michaels, R.; Olson, M.; Paschke, K. D.; Peterson, G. A.; Pitthan, R.; Pope, K.; Relyea, D.; Rock, S. E.; Saxton, O.; Shapiro, G.; Singh, J.; Souder, P. A.; Szalata, Z. M.; Tobias, W. A.; Tonguc, B. T.; Turner, J.; Tweedie, B.; Vacheret, A.; Walz, D.; Weber, T.; Weisend, J.; Whittum, D.; Woods, M.; Younus, I.
2004-05-01
We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: APV=[-175±30(stat)±20(syst)]×10-9. This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron's weak charge at low energy QeW=-0.053±0.011. This is consistent with the standard model expectation at the current level of precision: sin(2θW(MZ)MS¯=0.2293±0.0024(stat)±0.0016(syst)±0.0006(theory).
Parity nonconservation in elastic p→p scattering
NASA Astrophysics Data System (ADS)
Liu, C.-P.; Hyun, C. H.; Desplanques, B.
2006-06-01
By looking at the parity-nonconserving (PNC) asymmetries for different energies in p→p scattering, it is in principle possible to determine the PNC ρNN and ωNN couplings of a single-meson-exchange model of the PNC NN force. Analysis of the experimental data at 13.6, 45, and 221 MeV was performed by Carlson , [Phys. Rev. C 65, 035502 (2002)] who concluded the data were in agreement with the uncertainties accorded the original DDH estimates for the PNC meson-nucleon couplings. In this work it is shown first that a comparison with updated hadronic predictions of these couplings suggests the existence of some discrepancy for the PNC ωNN coupling. The effect of varying the strong coupling constants and introducing cutoffs in the one-boson-exchange weak potential is then investigated. As expected, the resulting asymmetry is quite sensitive to these parameters regardless of the energy. However, the above mentioned discrepancy persists. The dependence of this conclusion on various ingredients entering an improved description of the PNC NN force is also examined. Additional mechanisms include the two-pion resonance nature of the rho meson and some momentum dependence of the isoscalar PNC ρNN vertex. None of these corrections removes or even alleviates the above discrepancy. Their impact on the theoretical determination of the vector meson-nucleon couplings, the description of the PNC force in terms of single-meson exchange, and the interpretation of measurements are examined.
Parity nonconservation in elastic p-vectorp scattering
Liu, C.-P.; Hyun, C.H.; Desplanques, B.
2006-06-15
By looking at the parity-nonconserving (PNC) asymmetries for different energies in p-vectorp scattering, it is in principle possible to determine the PNC {rho}NN and {omega}NN couplings of a single-meson-exchange model of the PNC NN force. Analysis of the experimental data at 13.6, 45, and 221 MeV was performed by Carlson et al., [Phys. Rev. C 65, 035502 (2002)] who concluded the data were in agreement with the uncertainties accorded the original DDH estimates for the PNC meson-nucleon couplings. In this work it is shown first that a comparison with updated hadronic predictions of these couplings suggests the existence of some discrepancy for the PNC {omega}NN coupling. The effect of varying the strong coupling constants and introducing cutoffs in the one-boson-exchange weak potential is then investigated. As expected, the resulting asymmetry is quite sensitive to these parameters regardless of the energy. However, the above mentioned discrepancy persists. The dependence of this conclusion on various ingredients entering an improved description of the PNC NN force is also examined. Additional mechanisms include the two-pion resonance nature of the rho meson and some momentum dependence of the isoscalar PNC {rho}NN vertex. None of these corrections removes or even alleviates the above discrepancy. Their impact on the theoretical determination of the vector meson-nucleon couplings, the description of the PNC force in terms of single-meson exchange, and the interpretation of measurements are examined.
Probing parity nonconservation effects with laser cooled and trapped francium atoms
NASA Astrophysics Data System (ADS)
Kalita, Mukut; Aubin, Seth; Behr, John; Collister, Robert; Dehart, Austin; Gorelov, Alexandre; Garcia, Eduardo; Gwinner, Gerald; Kossin, Michael; Livermore, David; Orozco, Luis; Pearson, Matt; FrPNC Collaboration
2016-09-01
Measurements of parity nonconservation (PNC) effects in atomic systems test the Standard Model at low energies. We are developing an experiment to probe PNC effect in neutral francium atoms. Francium ions produced at the ISAC radioactive beam facility at TRIUMF are neutralized using a zirconium foil. The foil is momentarily heated and the released atoms are first trapped in a capture magneto optical trap (MOT). Then, the atoms are transported with about 50% efficiency to another MOT in a science chamber. In this chamber, in one experiment the 7S to 8S atomic transition will be probed using a laser beam, and in another experiment the ground state hyperfine transition will be probed using a microwave beam. In this talk I will report on recent developments towards the measurements. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This work is also supported by NSERC from Canada, the DOE and NSF from the USA and CONACYT from Mexico.
Yuan, V.W.
1997-08-01
Experiments using epithermal neutrons that interact to form compound-nuclear resonances serve a wide range of scientific applications. Changes in transmission which are correlated to polarization reversal in incident neutrons have been used to study parity nonconservation in the compound nucleus for a wide range of targets. The ensemble of measured parity asymmetries provides statistical information for the extraction of the rms parity-violating mean-square matrix element as a function of mass. Parity nonconservation in neutron resonances can also be used to determine the polarization of neutron beams. Finally the motion of target atoms results in an observed temperature-dependent Doppler broadening of resonance line widths. This broadening can be used to determine temperatures on a fast time scale of one microsecond or less.
Single-particle parity-nonconserving matrix elements in {sup 207}Pb
Komives, A.; Knott, J.E.; Leuschner, M.; Szymanski, J.J.; Bowman, J.D.; Jamrisk, D.
1993-10-01
Measurements of the helicity dependence of neutron scattering off of heavy nuclei by the TRIPLE collaboration have yielded multiple parity-nonconserving asymmetries. The asymmetries are predominantly positive, in contradiction to the zero average asymmetry predicted by the statistical model of neutron- nucleus scattering. Theoretical calculations that explain the non-zero average asymmetry require single-particle parity- nonconserving matrix elements 10-100 times larger than those predicted by meson exchange models. We are determining the single-particle parity non-conserving mixing in {sup 207}Pb by measuring the circular polarization of the 1.064 MeV {gamma} ray. The experiment uses a transmission polarimeter and a fast data acquisition system. Initial results are presented.
Johnson, W.R.; Safronova, M.S.; Safronova, U.I.
2003-06-01
The nuclear spin-dependent parity-nonconserving (PNC) interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s{sub 1/2}-7s{sub 1/2} transition in {sup 133}Cs, we obtain a result that is about 40% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to {sup 133}Cs leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s{sub 1/2}-8s{sub 1/2} transition in {sup 211}Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba{sup +}, Au, Tl, Fr, and Ra{sup +}.
Parity nonconservation in proton-water scattering at 800 MeV
Nagle, D.E.; Bowman, J.D.; Carlini, R.; Mischke, R.E.; Frauenfelder, H.; Harper, R.W.; Yuan, V.; McDonald, A.B.; Talaga, R.
1982-01-01
A search has been made for parity nonconservation in the scattering of 800 MeV polarized protons from an unpolarized water target. The result is for the longitudinal asymmetry, A/sub L/ = +(6.6 +- 3.2) x 10/sup -7/. Control runs with Pb, using a thickness which gave equivalent beam broadening from Coulomb multiple scattering, but a factor of ten less nuclear interactions than the water target, gave A/sub L/ = -(0.5 +- 6.0) x 10/sup -7/.
Parity Nonconservation in Proton-water Scattering at 800 MeV
DOE R&D Accomplishments Database
Nagle, D. E.; Bowman, J. D.; Carlini, R.; Mischke, R. E.; Frauenfelder, H.; Harper, R. W.; Yuan, V.; McDonald, A. B.; Talaga, R.
1982-01-01
A search has been made for parity nonconservation in the scattering of 800 MeV polarized protons from an unpolarized water target. The result is for the longitudinal asymmetry, A{sub L} = +(6.6 +- 3.2) x 10{sup -7}. Control runs with Pb, using a thickness which gave equivalent beam broadening from Coulomb multiple scattering, but a factor of ten less nuclear interactions than the water target, gave A{sub L} = -(0.5 +- 6.0) x 10{sup -7}.
Atomic parity nonconservation, neutron radii, and effective field theories of nuclei
Sil, Tapas; Centelles, M.; Vinas, X.; Piekarewicz, J.
2005-04-01
Accurately calibrated effective field theories are used to compute atomic parity nonconserving (APNC) observables. Although accurately calibrated, these effective field theories predict a large spread in the neutron skin of heavy nuclei. Whereas the neutron skin is strongly correlated to numerous physical observables, in this contribution we focus on its impact on new physics through APNC observables. The addition of an isoscalar-isovector coupling constant to the effective Lagrangian generates a wide range of values for the neutron skin of heavy nuclei without compromising the success of the model in reproducing well-constrained nuclear observables. Earlier studies have suggested that the use of isotopic ratios of APNC observables may eliminate their sensitivity to atomic structure. This leaves nuclear structure uncertainties as the main impediment for identifying physics beyond the standard model. We establish that uncertainties in the neutron skin of heavy nuclei are at present too large to measure isotopic ratios to better than the 0.1% accuracy required to test the standard model. However, we argue that such uncertainties will be significantly reduced by the upcoming measurement of the neutron radius in {sup 208}Pb at the Jefferson Laboratory.
Parity nonconservation in the {gamma} decay of polarized 17/2{sup -} isomers in {sup 93}Tc
Singh, B.S. Nara; Hass, M.; Goldring, G.; Ackermann, D.; Sulignano, B.; Gerl, J.; Hessberger, F.P.; Hofmann, S.; Kojouharov, I.; Kuusiniemi, P.; Schaffner, H.; Brown, B.A.
2005-08-01
The determination of the 0 deg. - 180 deg. asymmetry (A{sub {gamma}}), which arises because of the parity nonconserving matrix element, in the 751-keV {gamma} decay of polarized 17/2{sup -} isomers in {sup 93}Tc with respect to the direction of polarization is reported. A combined analysis of the present results together with those from our earlier work yields an effect of two standard deviations.
Calculation of energy levels, {ital E}1 transition amplitudes, and parity violation in francium
Dzuba, V.A.; Flambaum, V.V.; Sushkov, O.P.
1995-05-01
Many-body perturbation theory in the screened Coulomb interaction was used to calculate energy levels, {ital E}1 trransition amplitudes, and the parity-nonconserving (PNC) {ital E}1 amplitude of the 7{ital s}-8{ital s} transition in francium. The method takes into account the core-polarization effect, the second-order correlations, and the three dominating sequences of higher-order correlation diagrams: screening of the electron-electron interaction, particle-hole interaction, and the iterations of the self-energy operator. The result for the PNC amplitude for {sup 223}Fr is {ital E}1(7{ital s}-8{ital s})=(1.59{plus_minus}{similar_to}1%){times}10{sup {minus}10}{ital iea}{sub {ital B}}({minus}{ital Q}{sub {ital W}}/{ital N}), where {ital Q}{sub {ital W}} is the weak charge of the nucleus, {ital N}=136 is the number of neutrons, {ital e}={vert_bar}{ital e}{vert_bar} is the elementary charge, and {ital a}{sub {ital B}} is the Bohr radius. Our prediction for the position of the 8{ital s} energy level of Fr, which has not been measured yet, is 13 110 cm{sup {minus}1} below the limit of the continuous spectrum. The accuracy of the calculations was controlled by comparison with available experimental data and analogous calculations for cesium. It is estimated to be {similar_to}0.1% for the energy levels and {similar_to}1% for the transition amplitudes.
Parity Nonconservation in Proton-Proton and Proton-Water Scattering at 1.5 GeV/c
DOE R&D Accomplishments Database
Mischke, R. E.; Bowman, J. D.; Carlini, R.; MacArthur, D.; Nagle, D. E.; Frauenfelder, H.; Harper, R. W.; Yuan, V.; McDonald, A. B.; Talaga, R. L.
1984-07-01
Experiments searching for parity nonconservation in the scattering of 1.5 GeV/c (800 MeV) polarized protons from an unpolarized water target and a liquid hydrogen target are described. The intensity of the incident proton beam was measured upstream and downstream of the target by a pair of ionization detectors. The beam helicity was reversed at a 30-Hz rate. Auxiliary detectors monitored beam properties that could give rise to false effects. The result for the longitudinal asymmetry from the water is A{sub L} = (1.7 +- 3.3 +- 1.4) x 10{sup -7}, where the first error is statistical and the second is an estimate of systematic effects. The hydrogen data yield a preliminary result of A{sub L} = (1.0 +- 1.6) x 10{sup -7}. The systematic errors for p-p are expected to be < 1 x 10{sup -7}.
NASA Astrophysics Data System (ADS)
Le, Anh; Frey, Sarah; Steimle, Timothy C.
2010-06-01
There is renewed interest in the spectroscopy of heavy metal containing polar radical diatomic molecules because they provide a sensitive venue for detection of parity nonconservation (PNC) either from the determination of the electric dipole moment (EDM) of the electron, de, or detection of the interaction of the anapole moment of the nuclei with the unpaired electron. The effects due to de are nuclear spin independent and studies of both the even and odd nuclear spin isotopologues are relevant. Recently, DeMille et al proposed using an odd isotopologue of barium monofluoride, 137BaF, to measure the nuclear spin-dependent parity non-conservation (NSD-PNC) effect resulting from the interaction of the anapole moment of 137Ba with the unpaired electron of the X2Σ+ electronic state. Here we report on the analysis of the field-free spectrum of the A2Π-X2Σ+(0,0) band of 137BaF and an analysis of the 137Ba(I=3/2) and 19F(I=1/2) hyperfine interaction in the A2Π state. The hyperfine interaction in the X2Σ+ state has been previously characterized from the analysis of the pure rotation spectrum. The optimal optical transitions for monitoring 137BaF in future PNC measurements will be discussed. M. G. Kozlov, A. V. Titov, N. S. Mosyagin, and P. V. Souchko, Phys. Rev. A: At., Mol., and Opt. Phys. 56 R3326, 1997. D. DeMille, S. B.Cahn, D.Murphree, D. A. Rahmlow, and M. G.Kozlov Phys. Rev. Letts. 100 023003, 2008. Ch. Ryzlewicz, H-.U.Schutze-Pahlmann, J. Hoeft and T. Torring, Chem.Phys. 71 389, 1982.
Bast, Radovan; Schwerdtfeger, Peter; Saue, Trond
2006-08-14
A systematic four-component relativistic study of the parity nonconservation (PNC) contribution to the (isotropic) NMR shielding constants of chiral molecules is presented for the P enantiomers of the series H(2)X(2) (X=(17)O,(33)S,(77)Se,(125)Te,(209)Po). The PNC contributions are obtained within a linear response approach at the Hartree-Fock level. A careful design of the basis sets is necessary. The four-component relativistic results based on the Dirac-Coulomb Hamiltonian are compared with the nonrelativistic Levy-Leblond results and those obtained by the spin-free modified Dirac Hamiltonian. The calculations confirm the nonrelativistic scaling law Z(2.4) of the PNC contribution with respect to nuclear charge Z. However, the calculations also show that the overall scaling is significantly modified by relativistic effects. The scalar relativistic effect scales as Z(4.7) for the selected set of molecules, whereas the spin-orbit effect, of opposite sign, scales better than Z(6) and completely dominates the PNC contribution for the heaviest elements. This opens up the intriguing possibility of the experimental observation of PNC effects on NMR parameters of molecules containing heavy atoms. The presented formalism is expected to be valuable in assisting the search for suitable candidate molecules.
Explanation of parity nonconservation
Segal, I. E.; Ørsted, B.; Paneitz, S. M.; Vogan, D. A.
1987-01-01
Space inversion and other discrete symmetries are treated within the frame of a theory of fundamental forces based only on general considerations of causality, symmetry, and stability, without ad hoc differential equations. The basic space-time ˜M is the Einstein universe R1 × S3 as a causal (or conformal) rather than a pseudo-Riemannian manifold. Its connected symmetry group is then a 15-parameter group ˜G locally equivalent to SO(2, 4), while the isometry group ˜K of the Einstein universe is a 7-parameter subgroup. Correlation with conventional relativistic theory is based on a canonical imbedding of Minkowski space M0 into ˜M, together with the unique extendability of all transformations of the scaling-extended Poincaré group ˜P from M0 to global transformations on ˜M. The fundamental fermion field F and boson field B are here restricted to be real and are fully invariant under ˜Ge, where the superscript e denotes the inclusion of space and time inversions. The role of C on F is taken over by a real matrix having the eigenvalues ±i, that commutes with ˜G but anticommutes with space inversion. The spin space for B consists of the real linear transformations on that for F. There is a corresponding natural total Lagrangian that is both ˜Ge and O(2)-gauge invariant, the latter leading to lepton and baryon number conservation, and which is nonparametric except for scale. The Weyl and Maxwell equations are deduced, and compelling identifications made for neutrinos and the photon. The e and μ neutrino pairs occur in strikingly inequivalent positions in F, appearing symmetric only in the conventional relativistic limit R → ∞, where R is the (˜G-invariant) fundamental length interpretable as the radius of the space S3. The photon occurs as the lowest member of a coherent subfamily of B that includes natural candidates for bare versions of the W and Z particles. In the relativistic limit the interaction Lagrangian becomes a sum over all elementary processes, one of which appears as quantum electrodynamics with Majorana-type electrons. PMID:16593799
Explanation of parity nonconservation.
Segal, I E; Orsted, B; Paneitz, S M; Vogan, D A
1987-01-01
Space inversion and other discrete symmetries are treated within the frame of a theory of fundamental forces based only on general considerations of causality, symmetry, and stability, without ad hoc differential equations. The basic space-time M is the Einstein universe R(1) x S(3) as a causal (or conformal) rather than a pseudo-Riemannian manifold. Its connected symmetry group is then a 15-parameter group G locally equivalent to SO(2, 4), while the isometry group K of the Einstein universe is a 7-parameter subgroup. Correlation with conventional relativistic theory is based on a canonical imbedding of Minkowski space M(0) into M, together with the unique extendability of all transformations of the scaling-extended Poincaré group P from M(0) to global transformations on M. The fundamental fermion field F and boson field B are here restricted to be real and are fully invariant under G(e), where the superscript e denotes the inclusion of space and time inversions. The role of C on F is taken over by a real matrix having the eigenvalues +/-i, that commutes with G but anticommutes with space inversion. The spin space for B consists of the real linear transformations on that for F. There is a corresponding natural total Lagrangian that is both G(e) and O(2)-gauge invariant, the latter leading to lepton and baryon number conservation, and which is nonparametric except for scale. The Weyl and Maxwell equations are deduced, and compelling identifications made for neutrinos and the photon. The e and mu neutrino pairs occur in strikingly inequivalent positions in F, appearing symmetric only in the conventional relativistic limit R --> infinity, where R is the ( G-invariant) fundamental length interpretable as the radius of the space S(3). The photon occurs as the lowest member of a coherent subfamily of B that includes natural candidates for bare versions of the W and Z particles. In the relativistic limit the interaction Lagrangian becomes a sum over all elementary processes, one of which appears as quantum electrodynamics with Majorana-type electrons.
1/2/sup +/. -->. 1/2/sup -/ beta decay of /sup 19/Ne and the parity nonconserving NN force
Adelberger, E.G.; Hindi, M.M.; Hoyle, C.D.; Swanson, H.E.; Von Lintig, R.D.
1981-07-01
We obtain a branching ratio of (1.20 +- 0.20) x 10/sup -4/ for the ..beta../sup +/ decay of /sup 19/Ne to the 110 keV 1/2/sup -/ level of /sup 19/F. This transition (presumably dominated by the ..delta..J/sup ..pi../ = 0/sup -/ axial charge operator) provides a crucial test of wave functions used in interpreting the parity mixing of the ground and 110 keV levels of /sup 19/F. These wave functions, which yield a parity mixing larger than that observed experimentally, also predict too large a ..beta../sup +/ decay rate.
Small-amplitude synchrotron tune near transition
Ng, K.Y.; /Fermilab
2010-05-01
The separatrices of the rf buckets near transition are mapped when the synchronous phase is neither 0 or {pi}. The small-amplitude synchronous tune is derived when the rf frequency is changed. Synchrotron radiation is present in all electron storage ring. As a result, the synchronous phase is always offset from {phi}{sub s} = {pi} to compensate for the power loss. Even for proton storage rings with negligible synchrotron radiation, the synchronous phase is also required to be offset from {phi}{sub s} = 0 or {pi} slightly to compensate for beam loading. Thus for all storage rings operating near transition, beam particles reside in accelerating buckets instead of stationary bucket. It is of interest to map these buckets and see how they evolve near transition. When the rf frequency is varied, the closed orbit is pushed radially inward or outward. The momentum of the particle synchronous with the rf is thus changed. By measuring the small-amplitude synchrotron tune as a function of the rf frequency, the lowest first few orders of the slip factor can be inferred. Here, we derive this relationship up to the lowest first three orders of the slip factor when the particle velocity is not ultra-relativistic.
Amplitude transitions of swimmers and flexors in viscoelastic fluids
NASA Astrophysics Data System (ADS)
Guy, Robert; Thomases, Becca
2015-11-01
In both theoretical and experimental studies of the effect of fluid elasticity on micro-organism swimming, very different behavior has been observed for small and large amplitude strokes. We present simulations of an undulatory swimmer in an Oldroyd-B fluid and show that the resulting viscoelastic stresses are a nonlinear function of the amplitude. Specifically, there appears to be an amplitude dependent transition that is key to obtaining a speed-up over the Newtonian swimming speed. To understand the physical mechanism of the transition, we examine the stresses in a time-symmetric oscillatory bending beam, or flexor. We compare the flow in a neighborhood of the flexor tips with a large-amplitude oscillatory extensional flow, and we see similar amplitude dependent transitions. We relate these transitions to observed speed-ups in viscoelastic swimmers.
Graph Diagrams in Transition Amplitudes of Dipole Cosmology
NASA Astrophysics Data System (ADS)
Kisielowski, Marcin; Lewandowski, Jerzy; Puchta, Jacek
2015-01-01
The Operator Spin-network Diagrams is a new framework that enables to express Spin-foam amplitudes in a clear graphical way. Within this framework it is easy to find and characterise all the spin-foams with a given fixed boundary graph. We used this technique to characterise transition amplitudes in Dipole Cosmology in higher order in the vertex expansion.
Baryon-to-Meson Transition Distribution Amplitudes: Formalism and Models
NASA Astrophysics Data System (ADS)
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2017-03-01
In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.
Baryon to meson transition distribution amplitudes and their spectral representation
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2011-07-15
We consider the problem of construction of a spectral representation for nucleon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of nonlocal three quark operators between a nucleon and a meson states. We introduce the notion of quadruple distributions and generalize Radyshkin's factorized Ansatz for this issue. Modelling of baryon to meson TDAs in the complete domain of their definition opens the way to quantitative estimates of cross-sections for various hard exclusive reactions.
Non-gauge phase transformations in quantum transition amplitudes
NASA Technical Reports Server (NTRS)
Reiss, H. R.
1993-01-01
The prescription for introducing a gauge transformation into a quantum transition amplitude, nominally well known, contains an ambiguous feature. It is presumed by some authors that an appropriate transformation of the phase of a wave function will generate the associated gauge transformation. It is shown that this is a necessary but not sufficient step. Examples from the literature are cited to show the consequences of the failure of this procedure. One must distinguish between true gauge transformations and unitary transformations within a fixed gauge.
Transition from Amplitude to Oscillation Death via Turing Bifurcation
NASA Astrophysics Data System (ADS)
Koseska, Aneta; Volkov, Evgenii; Kurths, Jürgen
2013-07-01
Coupled oscillators are shown to experience two structurally different oscillation quenching types: amplitude death (AD) and oscillation death (OD). We demonstrate that both AD and OD can occur in one system and find that the transition between them underlies a classical, Turing-type bifurcation, providing a clear classification of these significantly different dynamical regimes. The implications of obtaining a homogeneous (AD) or inhomogeneous (OD) steady state, as well as their significance for physical and biological applications and control studies, are also pointed out.
Transition Distribution Amplitudes for γ⋆γ collisions
NASA Astrophysics Data System (ADS)
Lansberg, J. P.; Pire, B.; Szymanowski, L.
2008-11-01
We study the exclusive production of ππ and ρπ in hard γ⋆γ scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for ρπ and ππ production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BABAR).
Wigner function and transition amplitude of three mutually coupled oscillators
NASA Astrophysics Data System (ADS)
Nassar, M. M.; Sebawe Abdalla, M.
2007-04-01
A full quantum mechanical treatment of three electromagnetic fields is considered. The proposed model consists of three different coupling parameters for which the rotating and counter-rotating terms are retained. An exact solution of the wave function in the Schrödinger picture is obtained and the connection with the coherent states wave function is given. The symmetrical ordered quasi-probability distribution function ( W-Wigner function) is calculated via the wave function in the coherent states representation. The squeezing phenomenon is also examined for both single mode and squared-amplitude, where the collapse and revival phenomena are observed. For the case in which λ3=0 and ω1=ω2=ω3 (exact resonances) we find that the late phenomenon is apparent but only after long period of the time considered. The transition amplitude between two different coherent states (a state in which all the coupling parameters are involved and a state when the coupling parameter λ3=0) is calculated. It is shown that the probability amplitude is sensitive to the variation of the mean photon numbers, and the coupling parameters as well as to the field frequencies.
From 3-geometry transition amplitudes to graviton states
NASA Astrophysics Data System (ADS)
Mattei, Federico; Rovelli, Carlo; Speziale, Simone; Testa, Massimo
2006-04-01
In various background independent approaches, quantum gravity is defined in terms of a field propagation kernel: a sum over paths interpreted as a transition amplitude between 3-geometries, expected to project quantum states of the geometry on the solutions of the Wheeler-deWitt equation. We study the relation between this formalism and conventional quantum field theory methods. We consider the propagation kernel of 4d Lorentzian general relativity in the temporal gauge, defined by a conventional formal Feynman path integral, gauge fixed à la Faddeev-Popov. If space is compact, this turns out to depend only on the initial and final 3-geometries, while in the asymptotically flat case it depends also on the asymptotic proper time. We compute the explicit form of this kernel at first order around flat space, and show that it projects on the solutions of all quantum constraints, including the Wheeler-DeWitt equation, and yields the correct vacuum and n-graviton states. We also illustrate how the Newtonian interaction is coded into the propagation kernel, a key open issue in the spinfoam approach.
Multichannel 1 → 2 transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.; Walker-Loud, Andre
2015-02-03
We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B⁰ → K*l⁺l⁻) or meson photo production (e.g., πγ* → ππ). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including two processes mentioned above as well as examples where the final state is an admixture of two open channels.
Diffusion-induced periodic transition between oscillatory modes in amplitude-modulated patterns
Tang, Xiaodong; He, Yuxiu; Wang, Shaorong; Gao, Qingyu; Epstein, Irving R.; Wang, Qun
2014-06-15
We study amplitude-modulated waves, e.g., wave packets in one dimension, overtarget spirals and superspirals in two dimensions, under mixed-mode oscillatory conditions in a three-variable reaction-diffusion model. New transition zones, not seen in the homogeneous system, are found, in which periodic transitions occur between local 1{sup N−1} and 1{sup N} oscillations. Amplitude-modulated complex patterns result from periodic transition between (N − 1)-armed and N-armed waves. Spatial recurrence rates provide a useful guide to the stability of these modulated patterns.
Nucleon-to-Pion Transition Distribution Amplitudes: A Challenge for P¯ANDA
NASA Astrophysics Data System (ADS)
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2014-06-01
Baryon-to-meson transition distribution amplitudes (TDAs) appear as building blocks in the collinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples being hard exclusive pion electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a pion and a lepton pair or a charmonium. Baryon-to-meson TDAs extend both the concepts of generalized parton distributions and baryon distribution amplitudes encoding valuable complementary information on the hadronic structure. We review the basic properties of baryon-to-meson TDAs and discuss the perspectives for the experimental access with the P¯ANDA detector.
Lee, Myung W.
2007-01-01
The amplitude of a bottom simulating reflection (BSR), which occurs near the phase boundary between gas hydrate-bearing sediments and underlying gas-filled sediments, strongly depends on the frequency content of a seismic signal, as well as the impedance contrast across the phase boundary. A strong-amplitude BSR, detectable in a conventional seismic profile, is a good indicator of the presence of free gas beneath the phase boundary. However, the BSR as observed in low-frequency multichannel seismic data is generally difficult to identify in high-frequency, single-channel seismic data. To investigate the frequency dependence of BSR amplitudes, single-channel seismic data acquired with an air gun source at Blake Ridge, which is located off the shore of South Carolina, were analyzed in the frequency range of 10-240 Hz. The frequency-dependent impedance contrast caused by the velocity dispersion in partially gas saturated sediments is important to accurately analyze BSR amplitude. Analysis indicates that seismic attenuation of gas hydrate-bearing sediments, velocity dispersion, and a transitional base all contribute to the frequency-dependent BSR amplitude variation in the frequency range of 10-500 Hz. When velocity dispersion is incorporated into the BSR amplitude analysis, the frequency-dependent BSR amplitude at Blake Ridge can be explained with gas hydrate-bearing sediments having a quality factor of about 250 and a transitional base with a thickness of about 1 meter.
Information Entropy Exchange in the Path Integral Formulation of Transition Amplitudes
NASA Astrophysics Data System (ADS)
Deeter, Daniel; Petridis, Athanasios
2016-09-01
The quantum mechanical transition amplitude for a free particle is calculated using the path integral formalism. This amplitude is the kernel of the Schrödinger equation. A Wick rotation of the time increment transforms the kernel into a partition function that depends on the space and time intervals of the transition, with the temperature being proportional to the inverse of the time increment. The information entropy exchange between the system and the observer during the transition is calculated from the partition function. The requirement that this be real-valued leads to uncertainty-type relations. Furthermore, the transition exhibits positive information entropy exchange for small time intervals and negative entropy for large ones. The related statistical weight is inversely proportional to the square root of the time interval. Calculations for interacting systems are in progress.
Complex semiclassical analysis of the Loschmidt amplitude and dynamical quantum phase transitions
NASA Astrophysics Data System (ADS)
Obuchi, Tomoyuki; Suzuki, Sei; Takahashi, Kazutaka
2017-05-01
We propose a computational method of the Loschmidt amplitude in a generic spin system on the basis of the complex semiclassical analysis on the spin-coherent state path integral. We demonstrate how the dynamical transitions emerge in the time evolution of the Loschmidt amplitude for the infinite-range transverse Ising model with a longitudinal field, exposed by a quantum quench of the transverse field Γ from ∞ or zero. For both initial conditions, we obtain the dynamical phase diagrams that show the presence or absence of the dynamical transition in the plane of transverse field after a quantum quench and the longitudinal field. The results of semiclassical analysis are verified by numerical experiments. Experimental observation of our findings on the dynamical transition is also discussed.
The effects of dual-channel coupling on the transition from amplitude death to oscillation death
NASA Astrophysics Data System (ADS)
Chen, Jiangnan; Liu, Weiqing; Zhu, Yun; Xiao, Jinghua
2016-07-01
Oscillation quenching including amplitude death (AD) and oscillation death (OD) in addition to the transition processes between them have been hot topics in aspect of chaos control, physical and biological applications. The effects of dual-channel coupling on the AD and OD dynamics regimes, and their transition processes in coupled nonidentical oscillators are explored numerically and theoretically. Our results indicate that an additional repulsive coupling tends to shrink the AD domain while it enlarges the OD domain, however, an additional attractive coupling acts inversely. As a result, the transitions from AD to OD are replaced by transitions from oscillation state (OS) to AD or from OS to OD in the dual-channel coupled oscillators with different frequency mismatches. Our results are helpful to better understand the control of AD and OD and their transition processes.
Atomic Beam Spectroscopy of the 1283 nm M1 Transition in Thallium
NASA Astrophysics Data System (ADS)
Majumder, P. K.; Holmes, C. D.; Green, Michael
2003-05-01
Using a new thallium atomic beam apparatus, we are undertaking a series of laser spectroscopy measurements with the goal of providing precise, independent cross-checks on the accuracy of new calculations of parity nonconservation in thallium(M. Kozlov et al.), Phys Rev. A64, 053107 (2001). In our apparatus, a laser beam interacts transversely with a 2-cm-wide thallium beam of density 4x10^11 cm-3 and reveals roughly tenfold Doppler narrowing of the absorption profile. Having completed a new 0.4% measurement of the scalar Stark shift within the 378 nm 6P_1/2-7S_1/2 E1transition(S.C. Doret et al.), Phys. Rev. A66, 052504 (2002), we have now begun to study the very weak 1283 nm 6P_1/2-6P_3/2 transition in the atomic beam environment. We will determine both the scalar and tensor Stark shift components, as well as the various components of the Stark-induced amplitude within this mixed M1/E2 transition. To enhance the visibility of the weak absorption signal, we are employing an FM spectroscopy technique. The demodulated laser transmission spectrum provides a zero-background signal with high signal/noise and includes copies of the atomic absorption spectrum separated by well-known RF sideband frequencies, offering built-in frequency scale calibration. In the longer term, we are developing an atomic beam experiment using this same 1283 nm laser to search for a long-range T-odd, but P-even interaction in thallium.
Hoang, Thai M; Bharath, Hebbe M; Boguslawski, Matthew J; Anquez, Martin; Robbins, Bryce A; Chapman, Michael S
2016-08-23
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.
NASA Astrophysics Data System (ADS)
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-08-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-01-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu–Goldstone modes and massive Anderson–Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble–Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886
Experimental observation of a transition from amplitude to oscillation death in coupled oscillators
NASA Astrophysics Data System (ADS)
Banerjee, Tanmoy; Ghosh, Debarati
2014-06-01
We report the experimental evidence of an important transition scenario, namely the transition from amplitude death (AD) to oscillation death (OD) state in coupled limit cycle oscillators. We consider two Van der Pol oscillators coupled through mean-field diffusion and show that this system exhibits a transition from AD to OD, which was earlier shown for Stuart-Landau oscillators under the same coupling scheme [T. Banerjee and D. Ghosh, Phys. Rev. E 89, 052912 (2014), 10.1103/PhysRevE.89.052912]. We show that the AD-OD transition is governed by the density of mean-field and beyond a critical value this transition is destroyed; further, we show the existence of a nontrivial AD state that coexists with OD. Next, we implement the system in an electronic circuit and experimentally confirm the transition from AD to OD state. We further characterize the experimental parameter zone where this transition occurs. The present study may stimulate the search for the practical systems where this important transition scenario can be observed experimentally.
A first look at transition amplitudes in (2 + 1)-dimensional causal dynamical triangulations
NASA Astrophysics Data System (ADS)
Cooperman, Joshua H.; Miller, Jonah M.
2014-02-01
We study a lattice regularization of the gravitational path integral—causal dynamical triangulations—for (2 + 1)-dimensional Einstein gravity with positive cosmological constant in the presence of past and future spacelike boundaries of fixed intrinsic geometries. For spatial topology of a 2-sphere, we determine the form of the Einstein-Hilbert action supplemented by the Gibbons-Hawking-York boundary terms within the Regge calculus of causal triangulations. Employing this action we numerically simulate a variety of transition amplitudes from the past boundary to the future boundary. To the extent that we have so far investigated them, these transition amplitudes appear consistent with the gravitational effective action previously found to characterize the ground state of quantum spacetime geometry within the Euclidean de Sitter-like phase. Certain of these transition amplitudes convincingly demonstrate that the so-called stalks present in this phase are numerical artifacts of the lattice regularization, seemingly indicate that the quantization technique of causal dynamical triangulations differs in detail from that of the no-boundary proposal of Hartle and Hawking, and possibly represent the first numerical simulations of portions of temporally unbounded quantum spacetime geometry within the causal dynamical triangulations approach. We also uncover tantalizing evidence suggesting that Lorentzian not Euclidean de Sitter spacetime dominates the ground state on sufficiently large scales.
Parity nonconservation and the origin of cosmic magnetic fields
NASA Technical Reports Server (NTRS)
Vilenkin, A.; Leahy, D. A.
1982-01-01
Three mechanisms of cosmic magnetic field generation are discussed: (1) asymmetric decay of particles emitted by rotating black holes; (2) asymmetric proton emission by black holes due to weak radiative corrections, and (3) equilibrium parity-violating currents. It is shown that all three mechanisms can produce a seed field sufficiently strong to account for the present galactic fields.
Parity nonconservation and the origin of cosmic magnetic fields
NASA Technical Reports Server (NTRS)
Vilenkin, A.; Leahy, D. A.
1982-01-01
Three mechanisms of cosmic magnetic field generation are discussed: (1) asymmetric decay of particles emitted by rotating black holes; (2) asymmetric proton emission by black holes due to weak radiative corrections, and (3) equilibrium parity-violating currents. It is shown that all three mechanisms can produce a seed field sufficiently strong to account for the present galactic fields.
Pion-photon transition distribution amplitudes in the Nambu-Jona-Lasinio model
Courtoy, A.; Noguera, S.
2007-11-01
We define the pion-photon transition distribution amplitudes (TDA) in a field theoretic formalism from a covariant Bethe-Salpeter approach for the determination of the bound state. We apply our formalism to the Nambu-Jona-Lasinio model, as a realistic theory of the pion. The obtained vector and axial TDAs satisfy all features required by general considerations. In particular, sum rules and the polynomiality condition are explicitly verified. We have numerically proved that the odd coefficients in the polynomiality expansion of the vector TDA vanish in the chiral limit. The role of PCAC and the presence of a pion pole are explicitly shown.
Large-amplitude oscillatory shear of methylcellulose solutions through the sol-gel transition
NASA Astrophysics Data System (ADS)
McAllister, John W.; Lott, Joseph R.; Bates, Frank S.; Lodge, Tim P.
2013-03-01
Methylcellulose (MC) is a chemically modified polysaccharide that is partially substituted by methoxy groups. Aqueous MC solutions undergo gelation and phase separation (LCST) upon heating, which is attributed to the assembly of molecules into fibrillar structures noted by cryo TEM images and small angle neutron scattering. The transition from a strain-softening solution to a strain hardening gel upon heating has been probed using large-amplitude oscillatory shear (LAOS). In addition to strain hardening, MC solutions exhibit positive normal stresses (pressing the plates of the rheometer apart) while MC gels exhibit negative normal stresses (contracting the plates together) at stresses larger than 10 Pa. Nonlinear rheological responses are a useful probe to monitor structure-property relationships as MC transitions from a solution to a gel.
Pion-to-Photon Transition Distribution Amplitudes in the Non-Local Chiral Quark Model
NASA Astrophysics Data System (ADS)
Kotko, P.; Praszałowicz, M.
2009-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross-section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDAs. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Experimental investigation of a low-amplitude transition in pipe flow
NASA Astrophysics Data System (ADS)
Mehta, V.; Cohen, J.
2016-12-01
The vast majority of experiments on transition in pipe flow have been concerned with high-amplitude disturbance (of ≈ 10 % of the centerline velocity) at Reynolds numbers around 2000 and above. In this experimental study, we concentrate on the transition process in water pipe flow where the level of the disturbance is at least an order of magnitude smaller. We follow the sequence of transitional events while varying gradually the disturbance level from a laminar state to an almost fully turbulent one, using flow visualization, pressure-drop and hot-wire measurements. This is accomplished by injection of a very small diameter jet perpendicular to the main stream at a controllable flow rate, in a downstream distance where the flow is approximately fully developed. The injection flow rate normalized by the main stream rate is of O(0.001). With increasing injection flow rates the friction coefficient (λ) increases along with changes in the nature of the flow structures. The transition begins with the generation of a streamwise counter-rotating vortex pair, followed by the formation of a packet of hairpins and their breakdown. As the injection level is increased, the separation distance between two consecutive bursts (wavelength) decreases and the breakdown to turbulence begins further upstream and consequently the value of the friction coefficient λ increases. Above and below a certain threshold of the disturbance level, turbulence is either triggered or the flow is relaminarized, respectively. Finally, it is established that the evolution of the packet of hairpins is a key element during this transition scenario, and is well explained by the three-element model recently proposed by Cohen et al (2014).
Hedrick, M S; Carney, A E
1997-12-01
Previous studies have shown that manipulation of a particular frequency region of the consonantal portion of a syllable relative to the amplitude of the same frequency region in an adjacent vowel influences the perception of place of articulation. This manipulation has been called the relative amplitude cue. Earlier studies have examined the effect of relative amplitude and formant transition manipulations upon labeling place of articulation for fricatives and stop consonants in listeners with normal hearing. The current study sought to determine if (a) the relative amplitude cue is used by adult listeners wearing a cochlear implant to label place of articulation, and (b) adult listeners wearing a cochlear implant integrated the relative amplitude and formant transition information differently than listeners with normal hearing. Sixteen listeners participated in the study, 12 with normal hearing and 4 postlingually deafened adults wearing the Nucleus 22 electrode Mini Speech Processor implant with the multipeak processing strategy. The stimuli used were synthetic consonant-vowel (CV) syllables in which relative amplitude and formant transitions were manipulated. The two speech contrasts examined were the voiceless fricative contrast /s/-"sh" and the voiceless stop consonant contrast /p/-/t/. For each contrast, listeners were asked to label the consonant sound in the syllable from the two response alternatives. Results showed that (a) listeners wearing this implant could use relative amplitude to consistently label place of articulation, and (b) listeners with normal hearing integrated the relative amplitude and formant transition information more than listeners wearing a cochlear implant, who weighted the relative amplitude information as much as 13 times that of the transition information.
Multipole amplitudes in parity-changing one-photon transitions of charmonium
Sebastian, K.J. ); Grotch, H. ); Ridener, F.L. Jr. )
1992-05-01
We calculate the normalized helicity and multipole amplitudes in the one-photon transitions {psi}{prime}{prime}{r arrow}{chi}{sub {ital J}}+{gamma}, {psi}{prime}{r arrow}{chi}{sub {ital J}}+{gamma}, and {chi}{sub {ital J}}{r arrow}{psi}+{gamma} in any potential model. In the {chi}{sub 2}{r arrow}{psi}+{gamma} and {chi}{sub 1}{r arrow}{psi}+{gamma} decays the normalized {ital M}2 amplitude is independent of the potential to order {ital k}/{ital m} (where {ital k} is the photon energy and {ital m} the {ital c}-quark mass) so long as {psi} has no {ital D}-state mixing and {chi}{sub {ital J}} has no {ital F}-state mixing. They are a multiple of {ital k}/{ital m} and can be quite appreciable. Also the {ital E}3 amplitude in {chi}{sub 2}{r arrow}{psi}+{gamma} is zero with the same approximations. The same statement can be made about the {psi}{prime}{prime}{r arrow}{chi}{sub {ital J}}+{gamma} and {psi}{prime}{r arrow}{chi}{sub {ital J}}+{gamma} decays, so long as {psi}{prime} has no {ital D}-state mixing or {psi}{prime}{prime} has no {ital S}-state mixing. But if {psi}{prime} has a significant {ital D}-state mixing or {psi}{prime}{prime} has an {ital S}-state mixing, which is quite probable, the result will be a function of certain overlap integrals which may depend on the potential. The {ital M}2 amplitude depends sensitively on any possible anomalous magnetic moment of the {ital c} quark. We also calculate the numerical values of the multipole amplitudes in {psi}{prime}{r arrow}{chi}{sub {ital J}}+{gamma}, {psi}{prime}{prime}{r arrow}{chi}{sub {ital J}}+{gamma}, and {chi}{sub {ital J}}{r arrow}{psi}+{gamma} ({ital J}=1,2) in two different potential models.
Feasibility study for the measurement of πN transition distribution amplitudes with PANDA
NASA Astrophysics Data System (ADS)
Atomssa, Ermias
2016-05-01
Transition Distribution Amplitudes (TDA) are parametrizations of the hadronic matrix elements that occur in the perturbative Quantum Chromo Dynamics (QCD) calculations of a certain family of reactions within the framework of collinear factorization. We propose a complete feasibility study of the measurement of one of the reactions covered by the TDA models p ¯p →π0J /ψ (J /ψ →e+e-) at PANDA (AntiProton ANnihilation at DArmstadt) experiment currently under construction at the future FAIR (Facility for Antiproton and Ion Research). We show that PANDA will be ideally suited to access the relevant observables, in particular the pion-to-nucleon TDAs (πN TDAs) which are important for the understanding of the pion cloud contribution in the nucleon wave function.
Calculation of energy levels and transition amplitudes for barium and radium.
Dzuba, V. A.; Flambaum, V. V.; Physics; Univ. of New South Wales
2007-01-01
The radium atom is a promising system for studying parity and time invariance violating weak interactions. However, available experimental spectroscopic data for radium are insufficient for designing an optimal experimental setup. We calculate the energy levels and transition amplitudes for radium states of significant interest. Forty states corresponding to all possible configurations consisting of the 7s, 7p and 6d single-electron states as well as the states of the 7s8s, 7s8p and 7s7d configurations have been calculated. The energies of ten of these states corresponding to the 6d{sup 2}, 7s8s, 7p{sup 2} and 6d7p configurations are not known from experiment. Calculations for barium are used to control the accuracy.
Relativistic, model-independent, multichannel 2→2 transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.
2016-07-13
We derive formalism for determining 2 + J → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of themore » $$\\rho$$-meson form factor, in which the unstable nature of the $$\\rho$$ is rigorously accommodated. In conclusion, we also discuss how this work will impact future extractions of nuclear parity and hadronic long-range matrix elements from lattice QCD.« less
πNNN-NNN problem: Connectedness, transition amplitudes, and quasiparticle approximation
NASA Astrophysics Data System (ADS)
Cattapan, G.; Canton, L.
1997-08-01
In this paper we review the present status of the πNNN-NNN problem. In particular, we reconsider the chain-labeled approach recently proposed by us, and identify a class of graphs, previously overlooked, which prevents the kernel of the corresponding πNNN-NNN equations from being connected. We propose some approximate schemes, yielding connected-kernel equations. A generalization of the residue method allows us to relate the transition amplitudes for the coupled πNNN-NNN system to the chain-labeled formalism. The quasiparticle approach is extended to the present situation, where emission/absorption of particles is allowed. The open problems for the πNNN-NNN system in light of the present and of previous approaches are finally discussed.
Consistent model for πN transition distribution amplitudes and backward pion electroproduction
NASA Astrophysics Data System (ADS)
Lansberg, J. P.; Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2012-03-01
The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), nondiagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modeling nucleon to pion (πN) TDAs. Our main tool is the spectral representation for πN TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for πN TDAs. The spectral representation is complemented with a D-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the nonperturbative part of the amplitude involves πN TDAs. Within our two component model for πN TDAs, we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a function of skewness. We find it to be sizable in the valence region and sensitive to the phenomenological input of our πN TDA model.
The generalized log-derivative method for evaluation of second-order transition amplitudes
NASA Astrophysics Data System (ADS)
Mrugała, Felicja
1989-07-01
The log-derivative method of Johnson is generalized to calculate matrix elements of multichannel Green's functions—second-order transition amplitudes—which arise from description of a variety of physical processes involving weak interactions of initial and final (bound) states with a set of strongly coupled continuum and/or bound intermediate states. A purely approximate-solution algorithm and two hybrid approximate-solution approximate-potential versions, based on the use of piecewise constant reference potentials, are presented and tested on problems concerning investigations of nonadiabatic effects in the spectroscopy of H2. A comparison with the renormalized Numerov method, extended to calculation of considered transition amplitudes, is made and superior efficiency of the hybrid log-derivative algorithms is demonstrated. It is shown both practically and theoretically that discretization errors of the hybrid algorithms grow linearly with increasing energy in calculations, whereas cubic growth of errors with energy is characteristic for the purely approximate-solution log-derivative and Numerov algorithms.
Experimental access to Transition Distribution Amplitudes with the P¯ANDA experiment at FAIR
NASA Astrophysics Data System (ADS)
Singh, B. P.; Erni, W.; Keshelashvili, I.; Krusche, B.; Steinacher, M.; Liu, B.; Liu, H.; Liu, Z.; Shen, X.; Wang, C.; Zhao, J.; Albrecht, M.; Fink, M.; Heinsius, F. H.; Held, T.; Holtmann, T.; Koch, H.; Kopf, B.; Kümmel, M.; Kuhl, G.; Kuhlmann, M.; Leyhe, M.; Mikirtychyants, M.; Musiol, P.; Mustafa, A.; Pelizäus, M.; Pychy, J.; Richter, M.; Schnier, C.; Schröder, T.; Sowa, C.; Steinke, M.; Triffterer, T.; Wiedner, U.; Beck, R.; Hammann, C.; Kaiser, D.; Ketzer, B.; Kube, M.; Mahlberg, P.; Rossbach, M.; Schmidt, C.; Schmitz, R.; Thoma, U.; Walther, D.; Wendel, C.; Wilson, A.; Bianconi, A.; Bragadireanu, M.; Caprini, M.; Pantea, D.; Pietreanu, D.; Vasile, M. E.; Patel, B.; Kaplan, D.; Brandys, P.; Czyzewski, T.; Czyzycki, W.; Domagala, M.; Hawryluk, M.; Filo, G.; Krawczyk, M.; Kwiatkowski, D.; Lisowski, E.; Lisowski, F.; Fiutowski, T.; Idzik, M.; Mindur, B.; Przyborowski, D.; Swientek, K.; Czech, B.; Kliczewski, S.; Korcyl, K.; Kozela, A.; Kulessa, P.; Lebiedowicz, P.; Malgorzata, K.; Pysz, K.; Schäfer, W.; Siudak, R.; Szczurek, A.; Biernat, J.; Jowzaee, S.; Kamys, B.; Kistryn, S.; Korcyl, G.; Krzemien, W.; Magiera, A.; Moskal, P.; Palka, M.; Psyzniak, A.; Rudy, Z.; Salabura, P.; Smyrski, J.; Strzempek, P.; Wrońska, A.; Augustin, I.; Lehmann, I.; Nicmorus, D.; Schepers, G.; Schmitt, L.; Al-Turany, M.; Cahit, U.; Capozza, L.; Dbeyssi, A.; Deppe, H.; Dzhygadlo, R.; Ehret, A.; Flemming, H.; Gerhardt, A.; Götzen, K.; Karabowicz, R.; Kliemt, R.; Kunkel, J.; Kurilla, U.; Lehmann, D.; Lühning, J.; Maas, F.; Morales Morales, C.; Mora Espí, M. C.; Nerling, F.; Orth, H.; Peters, K.; Rodríguez Piñeiro, D.; Saito, N.; Saito, T.; Sánchez Lorente, A.; Schmidt, C. J.; Schwarz, C.; Schwiening, J.; Traxler, M.; Valente, R.; Voss, B.; Wieczorek, P.; Wilms, A.; Zühlsdorf, M.; Abazov, V. M.; Alexeev, G.; Arefiev, A.; Astakhov, V. I.; Barabanov, M. Yu.; Batyunya, B. V.; Davydov, Yu. I.; Dodokhov, V. Kh.; Efremov, A. A.; Fedunov, A. G.; Festchenko, A. A.; Galoyan, A. S.; Grigoryan, S.; Karmokov, A.; Koshurnikov, E. K.; Lobanov, V. I.; Lobanov, Yu. Yu.; Makarov, A. F.; Malinina, L. V.; Malyshev, V. L.; Mustafaev, G. A.; Olshevskiy, A.; Pasyuk, M. A.; Perevalova, E. A.; Piskun, A. A.; Pocheptsov, T. A.; Pontecorvo, G.; Rodionov, V. K.; Rogov, Yu. N.; Salmin, R. A.; Samartsev, A. G.; Sapozhnikov, M. G.; Shabratova, G. S.; Skachkov, N. B.; Skachkova, A. N.; Strokovsky, E. A.; Suleimanov, M. K.; Teshev, R. Sh.; Tokmenin, V. V.; Uzhinsky, V. V.; Vodopyanov, A. S.; Zaporozhets, S. A.; Zhuravlev, N. I.; Zorin, A. G.; Branford, D.; Glazier, D.; Watts, D.; Woods, P.; Britting, A.; Eyrich, W.; Lehmann, A.; Uhlig, F.; Dobbs, S.; Seth, K.; Tomaradze, A.; Xiao, T.; Bettoni, D.; Carassiti, V.; Cotta Ramusino, A.; Dalpiaz, P.; Drago, A.; Fioravanti, E.; Garzia, I.; Savriè, M.; Stancari, G.; Akishina, V.; Kisel, I.; Kulakov, I.; Zyzak, M.; Arora, R.; Bel, T.; Gromliuk, A.; Kalicy, G.; Krebs, M.; Patsyuk, M.; Zuehlsdorf, M.; Bianchi, N.; Gianotti, P.; Guaraldo, C.; Lucherini, V.; Pace, E.; Bersani, A.; Bracco, G.; Macri, M.; Parodi, R. F.; Bianco, S.; Bremer, D.; Brinkmann, K. T.; Diehl, S.; Dormenev, V.; Drexler, P.; Düren, M.; Eissner, T.; Etzelmüller, E.; Föhl, K.; Galuska, M.; Gessler, T.; Gutz, E.; Hayrapetyan, A.; Hu, J.; Kröck, B.; Kühn, W.; Kuske, T.; Lange, S.; Liang, Y.; Merle, O.; Metag, V.; Mülhheim, D.; Münchow, D.; Nanova, M.; Novotny, R.; Pitka, A.; Quagli, T.; Rieke, J.; Rosenbaum, C.; Schnell, R.; Spruck, B.; Stenzel, H.; Thöring, U.; Ullrich, M.; Wasem, T.; Werner, M.; Zaunick, H. G.; Ireland, D.; Rosner, G.; Seitz, B.; Deepak, P. N.; Kulkarni, A. V.; Apostolou, A.; Babai, M.; Kavatsyuk, M.; Lemmens, P.; Lindemulder, M.; Löhner, H.; Messchendorp, J.; Schakel, P.; Smit, H.; van der Weele, J. C.; Tiemens, M.; Veenstra, R.; Vejdani, S.; Kalita, K.; Mohanta, D. P.; Kumar, A.; Roy, A.; Sahoo, R.; Sohlbach, H.; Büscher, M.; Cao, L.; Cebulla, A.; Deermann, D.; Dosdall, R.; Esch, S.; Georgadze, I.; Gillitzer, A.; Goerres, A.; Goldenbaum, F.; Grunwald, D.; Herten, A.; Hu, Q.; Kemmerling, G.; Kleines, H.; Kozlov, V.; Lehrach, A.; Leiber, S.; Maier, R.; Nellen, R.; Ohm, H.; Orfanitski, S.; Prasuhn, D.; Prencipe, E.; Ritman, J.; Schadmand, S.; Schumann, J.; Sefzick, T.; Serdyuk, V.; Sterzenbach, G.; Stockmanns, T.; Wintz, P.; Wüstner, P.; Xu, H.; Li, S.; Li, Z.; Sun, Z.; Xu, H.; Rigato, V.; Fissum, S.; Hansen, K.; Isaksson, L.; Lundin, M.; Schröder, B.; Achenbach, P.; Bleser, S.; Cardinali, M.; Corell, O.; Deiseroth, M.; Denig, A.; Distler, M.; Feldbauer, F.; Fritsch, M.; Jasinski, P.; Hoek, M.; Kangh, D.; Karavdina, A.; Lauth, W.; Leithoff, H.; Merkel, H.; Michel, M.; Motzko, C.; Müller, U.; Noll, O.; Plueger, S.; Pochodzalla, J.; Sanchez, S.; Schlimme, S.; Sfienti, C.; Steinen, M.; Thiel, M.; Weber, T.; Zambrana, M.
2015-08-01
Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion ( πN) TDAs from reaction with the future P¯ANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q 2, the amplitude of the signal channel admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring with the P¯ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q 2 < 4.3 GeV2 and 5 < q 2 GeV2, respectively, with a neutral pion scattered in the forward or backward cone in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the P¯ANDA detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107) at low (high) q 2 for s = 5 GeV2, and of 1 · 108 (6 · 106) at low (high) q 2 for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb-1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with P¯ANDA will provide a new test of the perturbative QCD description of a novel class of hard
The 'Higgs' amplitude mode at the two-dimensional superfluid/Mott insulator transition.
Endres, Manuel; Fukuhara, Takeshi; Pekker, David; Cheneau, Marc; Schauss, Peter; Gross, Christian; Demler, Eugene; Kuhr, Stefan; Bloch, Immanuel
2012-07-25
Spontaneous symmetry breaking plays a key role in our understanding of nature. In relativistic quantum field theory, a broken continuous symmetry leads to the emergence of two types of fundamental excitation: massless Nambu-Goldstone modes and a massive 'Higgs' amplitude mode. An excitation of Higgs type is of crucial importance in the standard model of elementary particle physics, and also appears as a fundamental collective mode in quantum many-body systems. Whether such a mode exists in low-dimensional systems as a resonance-like feature, or whether it becomes overdamped through coupling to Nambu-Goldstone modes, has been a subject of debate. Here we experimentally find and study a Higgs mode in a two-dimensional neutral superfluid close to a quantum phase transition to a Mott insulating phase. We unambiguously identify the mode by observing the expected reduction in frequency of the onset of spectral response when approaching the transition point. In this regime, our system is described by an effective relativistic field theory with a two-component quantum field, which constitutes a minimal model for spontaneous breaking of a continuous symmetry. Additionally, all microscopic parameters of our system are known from first principles and the resolution of our measurement allows us to detect excited states of the many-body system at the level of individual quasiparticles. This allows for an in-depth study of Higgs excitations that also addresses the consequences of the reduced dimensionality and confinement of the system. Our work constitutes a step towards exploring emergent relativistic models with ultracold atomic gases.
Liu, Kai; Cheng, Chun; Cheng, Zhenting; Wang, Kevin; Ramesh, Ramamoorthy; Wu, Junqiao
2012-12-12
Various mechanisms are currently exploited to transduce a wide range of stimulating sources into mechanical motion. At the microscale, simultaneously high amplitude, high work output, and high speed in actuation are hindered by limitations of these actuation mechanisms. Here we demonstrate a set of microactuators fabricated by a simple microfabrication process, showing simultaneously high performance by these metrics, operated on the structural phase transition in vanadium dioxide responding to diverse stimuli of heat, electric current, and light. In both ambient and aqueous conditions, the actuators bend with exceedingly high displacement-to-length ratios up to 1 in the sub-100 μm length scale, work densities over 0.63 J/cm(3), and at frequencies up to 6 kHz. The functionalities of actuation can be further enriched with integrated designs of planar as well as three-dimensional geometries. Combining the superior performance, high durability, diversity in responsive stimuli, versatile working environments, and microscale manufacturability, these actuators offer potential applications in microelectromechanical systems, microfluidics, robotics, drug delivery, and artificial muscles.
NASA Astrophysics Data System (ADS)
Li, Shenmin; Li, Guohui; Guo, Hua
2001-12-01
The recently proposed single Lanczos propagation method [J. Chem. Phys. 111, 9944 (1999); ibid. 114, 1467 (2001)] is extended to complex-symmetric Hamiltonians. It is shown that the complex-symmetric Lanczos algorithm possesses several useful numerical properties similar to those observed in real-symmetric cases, which enable one to compute multiple transition amplitudes with a single Lanczos propagation. The usefulness of the method is illustrated in calculating the S-matrix elements for the collinear H+H2 reaction.
Nonlinear Interaction of Detuned Instability Waves in Boundary-Layer Transition: Amplitude Equations
NASA Technical Reports Server (NTRS)
Lee, Sang Soo
1998-01-01
The non-equilibrium critical-layer analysis of a system of frequency-detuned resonant-triads is presented. In this part of the analysis, the system of partial differential critical-layer equations derived in Part I is solved analytically to yield the amplitude equations which are analyzed using a combination of asymptotic and numerical methods. Numerical solutions of the inviscid non-equilibrium oblique-mode amplitude equations show that the frequency-detuned self-interaction enhances the growth of the lower-frequency oblique modes more than the higher-frequency ones. All amplitudes become singular at the same finite downstream position. The frequency detuning delays the occurrence of the singularity. The spanwise-periodic mean-flow distortion and low-frequency nonlinear modes are generated by the critical-layer interaction between frequency-detuned oblique modes. The nonlinear mean flow and higher harmonics as well as the primary instabilities become as large as the base mean flow in the inviscid wall layer in the downstream region where the distance from the singularity is of the order of the wavelength scale.
Single-cycle Terahertz Pulses with >0.2 V/A Field Amplitudes via Coherent Transition Radiation
Daranciang, Dan; Goodfellow, John; Fuchs, Matthias; Wen, Haidan; Ghimire, Shambhu; Reis, David A.; Loos, Henrik; Fisher, Alan S.; Lindenberg, Aaron M.; /Stanford U. Materials Sci. Dept. /SIMES, Stanford /SLAC, PULSE
2012-02-15
We demonstrate terahertz pulses with field amplitudes exceeding 0.2 V/{angstrom} generated by coherent transition radiation. Femtosecond, relativistic electron bunches generated at the Linac Coherent Light Source are passed through a beryllium foil, and the emitted radiation is characterized as a function of the bunch duration and charge. Broadband pulses centered at a frequency of 10 THz with energies of 140 {mu}J are measured. These far-below-bandgap pulses drive a nonlinear optical response in a silicon photodiode, with which we perform nonlinear autocorrelations that yield information regarding the terahertz temporal profile. Simulations of the spatiotemporal profile agree well with experimental results.
Transition from amplitude to oscillation death in a network of oscillators
Nandan, Mauparna; Hens, C. R.; Dana, Syamal K.; Pal, Pinaki
2014-12-01
We report a transition from a homogeneous steady state (HSS) to inhomogeneous steady states (IHSSs) in a network of globally coupled identical oscillators. We perturb a synchronized population of oscillators in the network with a few local negative or repulsive mean field links. The whole population splits into two clusters for a certain number of repulsive mean field links and a range of coupling strength. For further increase of the strength of interaction, these clusters collapse into a HSS followed by a transition to IHSSs where all the oscillators populate either of the two stable steady states. We analytically determine the origin of HSS and its transition to IHSS in relation to the number of repulsive mean-field links and the strength of interaction using a reductionism approach to the model network. We verify the results with numerical examples of the paradigmatic Landau-Stuart limit cycle system and the chaotic Rössler oscillator as dynamical nodes. During the transition from HSS to IHSSs, the network follows the Turing type symmetry breaking pitchfork or transcritical bifurcation depending upon the system dynamics.
NASA Astrophysics Data System (ADS)
Gribin, V. G.; Gavrilov, I. Yu.; Tishchenko, A. A.; Tishchenko, V. A.; Alekseev, R. A.
2017-05-01
This paper is devoted to the wave structure of a flow at its near- and supersonic velocities in a flat turbine cascade of profiles in the zone of phase transitions. The main task was investigation of the mechanics of interaction of the condensation jump with the adiabatic jumps of packing in a change of the initial condition of the flow. The obtained results are necessary for verification of the calculation models of the moisture-steam flow in the elements of lotic parts of the steam turbines. The experimental tests were made on a stand of the wet steam contour (WSC-2) in the Moscow Power Engineering Institute (MPEI, National Research University) at various initial states of steam in a wide range of Mach numbers. In the investigation of the wave structure, use was made of an instrument based on the Schlieren-method principle. The amplitude-frequency characteristics of the flow was found by measurement of static pressure pulsations by means of the piezo resistive sensors established on a bandage plate along the bevel cut of the cascade. It is shown that appearance of phase transitions in the bevel cut of the nozzle turbine cascade leads to a change in the wave structure of the flow. In case of condensation jump, the system of adiabatic jumps in the bevel cut of the cascade becomes nonstationary, and the amplitude-frequency characteristics of static pressure pulsations are restructured. In this, a change in the frequency pulsations of pressure and amplitude takes place. It is noted that, at near-sonic speeds of the flow and the state of saturation at the input, the low-frequency pulsations of static pressure appear that lead to periodic disappearance of the condensation jump and of the adiabatic jump. As a result, in this mode, the flow discharge variations take place.
Kämpf, Kerstin; Kremmling, Beke; Vogel, Michael
2014-03-01
Using a combination of H2 nuclear magnetic resonance (NMR) methods, we study internal rotational dynamics of the perdeuterated protein C-phycocyanin (CPC) in dry and hydrated states over broad temperature and dynamic ranges with high angular resolution. Separating H2 NMR signals from methyl deuterons, we show that basically all backbone deuterons exhibit highly restricted motion occurring on time scales faster than microseconds. The amplitude of this motion increases when a hydration shell exists, while it decreases upon cooling and vanishes near 175 K. We conclude that the vanishing of the highly restricted motion marks a dynamical transition, which is independent of the time window and of a fundamental importance. This conclusion is supported by results from experimental and computational studies of the proteins myoglobin and elastin. In particular, we argue based on findings in molecular dynamics simulations that the behavior of the highly restricted motion of proteins at the dynamical transition resembles that of a characteristic secondary relaxation of liquids at the glass transition, namely the nearly constant loss. Furthermore, H2 NMR studies on perdeuterated CPC reveal that, in addition to highly restricted motion, small fractions of backbone segments exhibit weakly restricted dynamics when temperature and hydration are sufficiently high.
NASA Astrophysics Data System (ADS)
Kämpf, Kerstin; Kremmling, Beke; Vogel, Michael
2014-03-01
Using a combination of H2 nuclear magnetic resonance (NMR) methods, we study internal rotational dynamics of the perdeuterated protein C-phycocyanin (CPC) in dry and hydrated states over broad temperature and dynamic ranges with high angular resolution. Separating H2 NMR signals from methyl deuterons, we show that basically all backbone deuterons exhibit highly restricted motion occurring on time scales faster than microseconds. The amplitude of this motion increases when a hydration shell exists, while it decreases upon cooling and vanishes near 175 K. We conclude that the vanishing of the highly restricted motion marks a dynamical transition, which is independent of the time window and of a fundamental importance. This conclusion is supported by results from experimental and computational studies of the proteins myoglobin and elastin. In particular, we argue based on findings in molecular dynamics simulations that the behavior of the highly restricted motion of proteins at the dynamical transition resembles that of a characteristic secondary relaxation of liquids at the glass transition, namely the nearly constant loss. Furthermore, H2 NMR studies on perdeuterated CPC reveal that, in addition to highly restricted motion, small fractions of backbone segments exhibit weakly restricted dynamics when temperature and hydration are sufficiently high.
Nath, S K
2014-03-01
The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted.
NASA Astrophysics Data System (ADS)
Valentini, F.; Vásconez, C. L.; Pezzi, O.; Servidio, S.; Malara, F.; Pucci, F.
2017-02-01
Space plasmas are dominated by the presence of large-amplitude waves, large-scale inhomogeneities, kinetic effects and turbulence. Beside the homogeneous turbulence, the generation of small scale fluctuations can take place also in other realistic configurations, namely, when perturbations superpose to an inhomogeneous background magnetic field. When an Alfvén wave propagates in a medium where the Alfvén speed varies in a direction transverse to the mean field, it undergoes phase-mixing, which progressively bends wavefronts, generating small scales in the transverse direction. As soon as transverse scales become of the order of the proton inertial length dp, kinetic Alfvén waves (KAWs) are naturally generated. KAWs belong to the branch of Alfvén waves and propagate almost perpendicularly to the ambient magnetic field, at scales close to dp. Many numerical, observational and theoretical works have suggested that these fluctuations may play a determinant role in the development of the solar-wind turbulent cascade. In the present paper, the generation of large amplitude KAW fluctuations in inhomogeneous background, as well as their effect on the protons, have been investigated by means of hybrid Vlasov-Maxwell direct numerical simulations. Imposing a pressure balanced magnetic shear, the kinetic dynamics of protons has been investigated by varying both the magnetic configuration and the amplitude of the initial perturbations. Of particular interest here is the transition from quasi-linear to turbulent regimes, focusing in particular on the development of important non-Maxwellian features in the proton distribution function driven by KAW fluctuations. Several indicators to quantify the deviations of the protons from thermodynamic equilibrium are presented. These numerical results might help to explain the complex dynamics of inhomogeneous and turbulent astrophysical plasmas, such as the heliospheric current sheet, the magnetospheric boundary layer, and the solar
Multichannel 0→2 and 1→2 transition amplitudes for arbitrary spin particles in a finite volume
Hansen, Maxwell; Briceno, Raul
2015-10-01
We present a model-independent, non-perturbative relation between finite-volume matrix elements and infinite-volumemore » $$\\textbf{0}\\rightarrow\\textbf{2}$$ and $$\\textbf{1}\\rightarrow\\textbf{2}$$ transition amplitudes. Our result accommodates theories in which the final two-particle state is coupled to any number of other two-body channels, with all angular momentum states included. The derivation uses generic, fully relativistic field theory, and is exact up to exponentially suppressed corrections in the lightest particle mass times the box size. This work distinguishes itself from previous studies by accommodating particles with any intrinsic spin. To illustrate the utility of our general result, we discuss how it can be implemented for studies of $$N+\\mathcal{J}~\\rightarrow~(N\\pi,N\\eta,N\\eta',\\Sigma K,\\Lambda K)$$ transitions, where $$\\mathcal{J}$$ is a generic external current. The reduction of rotational symmetry, due to the cubic finite volume, manifests in this example through the mixing of S- and P-waves when the system has nonzero total momentum.« less
Quantum Electrodynamics of Heavy Ions and Atoms
Shabaev, V. M.; Artemyev, A. N.; Glazov, D. A.; Tupitsyn, I. I.; Volotka, A. V.; Yerokhin, V. A.
2006-11-07
The present status of quantum electrodynamics (QED) theory of heavy few-electrons is reviewed. The theoretical results are compared with available experimental data. A special attention is focused on tests of QED at strong fields and on determination of the fundamental constants. A recent progress on calculations of the QED corrections to the parity nonconserving 6s-7s transition amplitude in neutral Cs is also discussed.
A second look at transition amplitudes in (2 + 1)-dimensional causal dynamical triangulations
NASA Astrophysics Data System (ADS)
Cooperman, Joshua H.; Lee, Kyle; Miller, Jonah M.
2017-06-01
Studying transition amplitudes in (2 + 1)-dimensional causal dynamical triangulations, Cooperman and Miller discovered speculative evidence for Lorentzian quantum geometries emerging from its Euclidean path integral (Cooperman and Miller 2014 Class. Quantum Grav. 31 035012). On the basis of this evidence, Cooperman and Miller conjectured that Lorentzian de Sitter spacetime, not Euclidean de Sitter space, dominates the ground state of the quantum geometry of causal dynamical triangulations on large scales, a scenario akin to that of the Hartle-Hawking no-boundary proposal in which Lorentzian spacetimes dominate a Euclidean path integral (Hartle and Hawking 1983 Phys. Rev. D 28 2960). We argue against this conjecture: we propose a more straightforward explanation of their findings, and we proffer evidence for the Euclidean nature of these seemingly Lorentzian quantum geometries. This explanation reveals another manner in which the Euclidean path integral of causal dynamical triangulations behaves correctly in its semiclassical limit—the implementation and interaction of multiple constraints.
Radigan, Jacqueline
2014-12-20
Observations of variability can provide valuable information about the processes of cloud formation and dissipation in brown dwarf atmospheres. Here we report the results of an independent analysis of archival data from the Brown dwarf Atmosphere Monitoring (BAM) program. Time series data for 14 L and T dwarfs reported to be significantly variable over timescales of hours were analyzed. We confirm large-amplitude variability (amplitudes >2%) for 4 out of 13 targets and place upper limits of 0.7%-1.6% on variability in the remaining sample. For two targets we find evidence of weak variability at amplitudes of 1.3% and 1.6%. Based on our revised classification of variable objects in the BAM study, we find strong variability outside the L/T transition to be rare at near infrared wavelengths. From a combined sample of 81 L0-T9 dwarfs from the revised BAM sample and the variability survey of Radigan et al., we infer an overall observed frequency for large-amplitude variability outside the L/T transition of 3.2{sub −1.8}{sup +2.8}%, in contrast to 24{sub −9}{sup +11}% for L9-T3.5 spectral types. We conclude that while strong variability is not limited to the L/T transition, it occurs more frequently in this spectral type range, indicative of larger or more highly contrasting cloud features at these spectral types.
NASA Astrophysics Data System (ADS)
Lansberg, J. P.; Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2012-12-01
Nucleon-antinucleon annihilation into a near backward- (or forward-) produced meson and a high invariant mass lepton pair admits a factorized description in terms of antinucleon (or nucleon) distribution amplitudes and nucleon-to-meson (or antinucleon-to-meson) transition distribution amplitudes. We estimate the cross section of backward (and forward) pion and η-meson production in association with a high invariant mass lepton pair for the kinematical conditions of GSI-FAIR. The cross sections are found to be large enough to be measured with the P¯ANDA detector. Interesting phenomenological applications of the approach are thus expected.
B → ρ transition form factors and the ρ-meson transverse leading-twist distribution amplitude
NASA Astrophysics Data System (ADS)
Fu, Hai-Bing; Wu, Xing-Gang; Han, Hua-Yong; Ma, Yang
2015-05-01
The QCD light-cone sum rules (LCSR) provide an effective way for dealing with heavy-to-light transition form factors (TFFs), in which the non-perturbative dynamics are parameterized into the light-meson’s light-cone distribution amplitudes (LCDAs). By taking the chiral correlator as the starting point, we derive new LCSRs for B\\to ρ TFFs up to twist-4 accuracy. In those LCSRs, the twist-2 transverse LCDA φ 2;ρ \\bot provides dominant contribution, while the twist-3 and twist-4 contributions are δ2-suppressed (δ ≃ {{m}ρ }/{{m}b}). Thus, they provide good platforms for testing φ 2;ρ \\bot behavior. For the purpose, we suggest a WH-model for φ 2;ρ \\bot , in which a single parameter B2;ρ \\bot ˜ a2\\bot dominantly controls its longitudinal distribution. When setting B2;ρ \\bot \\in [-0.20,+0.20], φ 2;ρ \\bot varies from the single-peak behavior to the double-humped behavior. We present a detailed comparison of the LCSR estimation for B\\to ρ TFFs with those predicted by pQCD and lattice QCD calculations. The TFFs become smaller with the increment of B2;ρ \\bot and a larger B2;ρ \\bot is not allowed by lattice QCD predictions. By using the extrapolated TFFs, we further predict the Cabibbo-Kobayashi-Maskawa (CKM)-matrix element \\mid {{V}ub}\\mid with the help of two B\\to ρ semi-leptonic decays. The predicted \\mid {{V}ub}\\mid increases with the increment of B2;ρ \\bot , i.e. we have \\mid {{V}ub}\\mid =(2.91+/- 0.19)× {{10}-3} for B2;ρ \\bot =-0.20 and \\mid {{V}ub}\\mid =(3.11+/- 0.19)× {{10}-3} for B2;ρ \\bot =0.00. If treating the BABAR prediction on \\mid {{V}ub}\\mid as a criteria, we observe that B2;ρ \\bot should be within the region of [-0.20, +0.10], which indicates that the ρ-meson LCDA prefers a single-peak behavior rather than a double-humped behavior.
Parity nonconservation in nuclear fission: does it depend on fragment mass/energy?
NASA Astrophysics Data System (ADS)
Kötzle, A.; Jesinger, P.; Gönnenwein, F.; Petrov, G. A.; Petrova, V. I.; Gagarski, A. M.; Danilyan, G.; Zimmer, O.; Nesvizhevsky, V.
2000-02-01
For fission of 233U induced by polarized cold neutrons the dependence of the PNC asymmetry coefficient α nf(m LF, TKE) on light fragment mass mLF and total kinetic energy TKE was studied. Concurrently the angular distribution predicted for PNC reactions was tested. Altogether more than 2×10 10 fission events with high mass/energy resolution have been collected. This corresponds to an increase in the statistics compared to previous experiments (U. Graf, F. Gönnenwein, P. Geltenbort, et al., Z. Phys. A 351 (1995) 281 and V.A. Vesna, V.A. Knyaz'kov, E.A. Kolomenskii et al., JETP. Lett. 31 (1980) 663) by a factor of about 20. The preliminary analysis of the PNC asymmetry shows no significant variation of αnf for different fragment masses/energies, whereas the prediction concerning the angular dependence was confirmed with a precision not obtained up to now.
Lenz, Alexander; Goeckeler, Meinulf; Kaltenbrunner, Thomas; Warkentin, Nikolaus
2009-05-01
We compare a recent lattice determination of the nucleon distribution amplitudes with other approaches and models. We study the nucleon distribution amplitudes up to twist 6 in next-to-leading conformal spin and we also investigate conformal d-wave contributions to the leading-twist distribution amplitude. With the help of light-cone sum rules one can relate the distribution amplitudes to the form factors of the nucleon or the N{yields}{delta} transition at intermediate values of the momentum transfer. We compare our results with experimental data in the range 1 GeV{sup 2}{<=}Q{sup 2}{<=}10 GeV{sup 2}. Keeping in mind that we are working only in leading order QCD and next-to-leading order QCD corrections might be sizeable, we already obtain a surprisingly good agreement for the nucleon form factors G{sub M}{sup n}, G{sub M}{sup p}, G{sub A}{sup p}, and G{sub T}{sup p} and for the N{yields}{delta} transition form factor ratios R{sub EM} and R{sub SM}.
NASA Technical Reports Server (NTRS)
Cao, Chang-Qi
1996-01-01
The amplitude and transverse quadrature component squeezing of coherent light in high Q cavity by injection of atoms of two-photon transition are studied. The Golubev-Sokolov master equation and generating function approach are utilized to derive the exact variances of photon number and of transverse quadrature component as function of t. The correlation functions and power spectrums of photon number noise and of output photon current noise are also investigated.
Mackeprang, Kasper; Kjaergaard, Henrik G.; Salmi, Teemu; Hänninen, Vesa; Halonen, Lauri
2014-05-14
We describe the vibrational transitions of the donor unit in water dimer with an approach that is based on a three-dimensional local mode model. We perform a perturbative treatment of the intermolecular vibrational modes to improve the transition wavenumber of the hydrogen bonded OH-stretching transition. The model accurately predicts the transition wavenumbers of the vibrations in water dimer compared to experimental values and provides a physical picture that explains the redshift of the hydrogen bonded OH-oscillator. We find that it is unnecessary to include all six intermolecular modes in the vibrational model and that their effect can, to a good approximation, be computed using a potential energy surface calculated at a lower level electronic structure method than that used for the unperturbed model.
NASA Astrophysics Data System (ADS)
Fa, Darren Andrew
2008-11-01
In this paper I argue that there is a growing body of evidence supporting an increasingly central position of coastal environments in human evolution and dispersals, rather than as merely peripheral habitats. Eustatic fluctuations during glacial cycles have meant that most prehistoric coastlines are now underwater, and lack of evidence to date of a close relationship between people and the coast can be most plausibly ascribed to the limited studies so far on submerged sites. Coastal environments provide high diversity in food resources, consisting of multiple ecotones in close proximity, which reduces the need to forage widely. One of the richest and most easily exploited coastal resources by human populations living on the coast are molluscs from marine rocky intertidal communities, which recent evidence has highlighted as important as far back as the Middle Palaeolithic. However, the density of these resources is limited by a number of factors, and this varies geographically. One of the main large-scale factors limiting rocky intertidal mollusc densities is tidal amplitude, beyond which smaller-scale local factors such as exposure to wave action and shore aspect, further affect species distributions. The area around the Strait of Gibraltar is used as a case study of an area, which is affected by large variations in tidal amplitudes thus allowing for quantitative comparisons between taxonomically and climatically similar regions. Shorelines along the Mediterranean coast, with reduced tidal amplitudes, exhibit compressed zonations and harbour fewer macro-mollusc individuals, with the reverse being the case along the Atlantic coast, which has significantly larger tides. Data from Middle and Upper Palaeolithic sites along the Strait are used to establish harvested species and present-day data are used to model the potential distributions and associated variables such as calorific returns of key food species. An optimal foraging model is used to explore the effects of
NASA Astrophysics Data System (ADS)
Lin, Jieli; Lin, Jung Lee; Tzeng, Wen Bih
2003-12-01
We have recorded the resonant two-photon ionization (R2PI) and mass analyzed threshold ionization (MATI) spectra of deuterium substituted N-methylaniline (NMA-d1) and N-ethylaniline (NEA-d1) to investigate the influence of the N-deuteration on the transition energy and the large amplitude alkyl vibration. The origin of the S 1←S 0 electronic transition (EE) and the adiabatic ionization energy (IE) of NMA-d1 are determined to be 33,294 ± 1 and 59,801 ± 5 cm -1, whereas those of NEA-d1 are 33,301 ± 1 and 59,185 ± 5 cm -1, respectively. Comparing these data with those of NMA and NEA suggests that N-deuteration give rise to a blue shift of 2-4 cm -1 in the EE and a red shift of 19-21 cm -1 in the IE. These isotope shifts are little affected by the length of the alkyl group attached to the nitrogen atom. The present results also show that the N-deuteration influences more on the large amplitude motions of the CH 3 torsion, the C 2H 5 bending, and the N-inversion than the localized benzene ring vibrations.
NASA Astrophysics Data System (ADS)
Tokuda, K.; Katori, Y.; Aihara, K.
2013-01-01
Here we propose a possible mathematical structure of the state transition of the hippocampal local field potential (LFP) between theta rhythm and large irregular amplitude activity (LIA) in terms of nonlinear dynamics. The basic idea is that the alternation of the state between theta rhythm and LIA can be interpreted as a bifurcation of the attractor between a limit cycle and chaotic dynamics. Tsuda et al. reported that a network composed of simple class 1 model neurons connected with gap junctions shows both synchronous periodic behavior and asynchronous chaotic behavior [1]. Here we model the network of hippocampal interneurons extending their model. The network is composed of electrically coupled simple 2-dimensional neurons with natural resonant frequency in the theta frequency. We incorporate a periodic external force representing the medial septal afferent. The system converges on a limit cycle under this external force, but shows chaotic dynamics without this external force. Furthermore, the external noise realized rapid alteration of the state obeying the change of the amplitude of the septal input.
Radigan, Jacqueline; Jayawardhana, Ray; Lafreniere, David; Artigau, Etienne; Marley, Mark; Saumon, Didier
2012-05-10
We present multiple-epoch photometric monitoring in the J, H, and K{sub s} bands of the T1.5 dwarf 2MASS J21392676+0220226 (2M2139), revealing persistent, periodic (P = 7.721 {+-} 0.005 hr) variability with a peak-to-peak amplitude as high as 26% in the J band. The light curve shape varies on a timescale of days, suggesting that evolving atmospheric cloud features are responsible. Using interpolations between model atmospheres with differing cloud thicknesses to represent a heterogeneous surface, we find that the multi-wavelength variations and the near-infrared spectrum of 2M2139 can be reproduced by either (1) cool, thick cloud features sitting above a thinner cloud layer, or (2) warm regions of low condensate opacity in an otherwise cloudy atmosphere, possibly indicating the presence of holes or breaks in the cloud layer. We find that temperature contrasts between thick and thin cloud patches must be greater than 175 K and as high as 425 K. We also consider whether the observed variability could arise from an interacting binary system, but this scenario is ruled out. 2M2139 joins the T2.5 dwarf SIMP0136 discovered by Artigau and coworkers as the second L/T transition brown dwarf to display large-amplitude variability on rotational timescales, suggesting that the fragmentation of dust clouds at the L/T transition may contribute to the abrupt decline in condensate opacity and J-band brightening observed to occur over this regime.
Hutchinson, Deborah R.; Lee, Myung W.; Behrendt, John C.; Cannon, William F.; Green, Adrian
1992-01-01
True amplitude processing of The Great Lakes International Multidisciplinary Program on Crustal Evolution seismic reflection data from the Midcontinent Rift System of North America shows large differences in the reflectivity of the Moho transition zone beneath the axial rift, beneath the rift flanks, and outside of the rift. The Moho reflection from the axial rift has a discontinuous, diffractive character marginally stronger (several decibels) than an otherwise transparent lower crust and upper mantle. Beneath the axial rift, Moho is interpreted to be a synrift igneous feature. Beneath the rift flanks, the reflectivity of the Moho transition is generally well developed with two identifiable boundaries, although in places it is weakly reflective to nonreflective, similar to Moho outside the rift. The two boundaries are interpreted as the base of essentially intact, although stretched, prerift Archean crust (upper boundary) and new synrift Moho 1-2 s (6-7 km) deeper (lower boundary). Beneath the rift flanks, the layered reflection Moho transition results from the preexisting crustal composition and fabric modified by synrift igneous processes and extensional tectonic/metamorphic processes. The geologic evidence for extensive basaltic magmatism in the rift is the basis for interpreting the Moho signature as a Keweenawan structure that has been preserved for 1.1 b.y. Extension and magmatism appear to enhance reflectivity in the lower crust and Moho transition zone only where stretching factors are moderate (rift flanks) and not where they are extreme (axial rift). This leads to the prediction that the reflectivity across analogous volcanic passive continental margins should be greatest beneath the moderately stretched continental shelves and should decrease towards the ocean-continent boundary.
Vesna, V.A.; Kolomenskii, A.; Okunev, I.S.; Pirozhkov, A.N.; Smotritskii, L.M.; Shul'gina, E.V.; Kornyushkin, A.F.; Titov, N.A.; Solov'ev, S.M.; Lobashev, V.M.
1983-04-20
An upper limit is found on the difference between the cross sections for the interactions of thermal neutrons with opposite helicities with /sup 233/U: P = (sigma/sup +//sub t/-sigma/sup -//sub t/)/(sigma/sup +//sub t/ +sigma/sup -//sub t/)<1.5 x 10/sup -6/ (at a 90% confidence level). This result contradicts the value P = 10/sup -4/--10/sup -5/ estimated under the assumption that the 0.17-eV level is a p-wave level.
NASA Astrophysics Data System (ADS)
Vakulina, E. V.; Maksimenko, N. V.
2017-09-01
Spin polarizabilities of spin-1 particles typical of spin-1/2 hadrons are established within the Duffin-Kemmer-Petiau formalism using the relativistically invariant effective tensor representation of Lagrangians of two-photon interaction with hadrons. New spin polarizabilities of spin-1 particles associated with the presence of tensor polarizabilities are also determined.
Chen, Tzu-Ling; Liu, Yi-Wei
2015-09-15
To access the wavelength within the 1.1-1.3 μm region, we have developed a quantum-dot (QD) laser with an external-cavity configuration and a linewidth of kilohertz at a 1 ms integration time. The residual electroluminescence, due to the inhomogeneous broadening of the QD gain medium, was observed and filtered out using a grating. While a fiber-coupled electro-optical modulator was employed, this laser system was locked to a high-finesse (F∼18,500) optical cavity, and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy was used to observe weak transitions. The Doppler-broadened spectra of a weak N(2)O transition at 1.283 μm are obtained with a signal-to-noise ratio of 30 for a gas pressure of 54 mTorr. The minimum noise-equivalent absorption coefficient is 5.3×10(-10) cm(-1) Hz(-1/2). This system can be a powerful and stable light source for atomic parity nonconservation measurements using thallium, ytterbium, lead, and iodine.
High amplitude propagated contractions.
Bharucha, A E
2012-11-01
While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. High amplitude propagated contractions occur spontaneously, in response to pharmacological agents or colonic distention. A subset of patients with slow transit constipation have fewer HAPC. In this issue of Neurogastroenterology and Motility, Rodriguez et al. report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. High amplitude propagated contractions are also used to evaluate the motor response to a meal and pharmacological stimuli (e.g., bisacodyl, neostigmine) and to identify colonic inertia during colonic motility testing in chronic constipation. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. © 2012 Blackwell Publishing Ltd.
ERIC Educational Resources Information Center
Agnew, Jeanne L.; Choike, James R.
1987-01-01
Mathematical observations are made about some continuous curves, called transitions, encountered in well-known experiences. The transition parabola, the transition spiral, and the sidestep maneuver are presented. (MNS)
ERIC Educational Resources Information Center
Nathanson, Jeanne H., Ed.
1993-01-01
This theme issue on transitions for individuals with disabilities contains nine papers discussing transition programs and issues. "Transition Issues for the 1990s," by Michael J. Ward and William D. Halloran, discusses self-determination, school responsibility for transition, continued educational engagement of at-risk students, and service…
Jódar, Jorge; Custodio, Emilio; Lambán, Luis Javier; Martos-Rosillo, Sergio; Herrera-Lameli, Christian; Sapriza-Azuri, Gonzalo
2016-12-15
The time series of stable water isotope composition relative to meteorological stations and springs located in the high mountainous zone of the Ordesa and Monte Perdido National Park are analyzed in order to study how the seasonal isotopic content of precipitation propagates through the hydrogeological system in terms of the aquifer recharge zone elevation and transit time. The amplitude of the seasonal isotopic composition of precipitation and the mean isotopic content in rainfall vary along a vertical transect, with altitudinal slopes for δ(18)O of 0.9‰/km for seasonal amplitude and -2.2‰/km for isotopic content. The main recharge zone elevation for the sampled springs is between 1950 and 2600m·a.s.l. The water transit time for the sampled springs ranges from 1.1 to 4.5yr, with an average value of 1.85yr and a standard deviation of 0.8yr. The hydrological system tends to behave as a mixing reservoir. Copyright Â© 2016 Elsevier B.V. All rights reserved.
ERIC Educational Resources Information Center
Field, David; And Others
1992-01-01
Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)
Relativistic, model-independent, multichannel $2\to 2$ transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.
2016-07-13
We derive formalism for determining 2 + J → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the $\\rho$-meson form factor, in which the unstable nature of the $\\rho$ is rigorously accommodated. In conclusion, we also discuss how this work will impact future extractions of nuclear parity and hadronic long-range matrix elements from lattice QCD.
Relativistic, model-independent, multichannel $2\to 2$ transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.
2016-07-13
We derive formalism for determining 2 + J → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the $\\rho$-meson form factor, in which the unstable nature of the $\\rho$ is rigorously accommodated. In conclusion, we also discuss how this work will impact future extractions of nuclear parity and hadronic long-range matrix elements from lattice QCD.
ERIC Educational Resources Information Center
Thompson, Sandy, Ed.; And Others
1990-01-01
This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…
Secondary threshold amplitudes for sinuous streak breakdown
NASA Astrophysics Data System (ADS)
Cossu, Carlo; Brandt, Luca; Bagheri, Shervin; Henningson, Dan S.
2011-07-01
The nonlinear stability of laminar sinuously bent streaks is studied for the plane Couette flow at Re = 500 in a nearly minimal box and for the Blasius boundary layer at Reδ*=700. The initial perturbations are nonlinearly saturated streamwise streaks of amplitude AU perturbed with sinuous perturbations of amplitude AW. The local boundary of the basin of attraction of the linearly stable laminar flow is computed by bisection and projected in the AU - AW plane providing a well defined critical curve. Different streak transition scenarios are seen to correspond to different regions of the critical curve. The modal instability of the streaks is responsible for transition for AU = 25%-27% for the considered flows, where sinuous perturbations of amplitude below AW ≈ 1%-2% are sufficient to counteract the streak viscous dissipation and induce breakdown. The critical amplitude of the sinuous perturbations increases when the streamwise streak amplitude is decreased. With secondary perturbations amplitude AW ≈ 4%, breakdown is induced on stable streamwise streaks with AU ≈ 13%, following the secondary transient growth scenario first examined by Schoppa and Hussain [J. Fluid Mech. 453, 57 (2002)]. A cross-over, where the critical amplitude of the sinuous perturbation becomes larger than the amplitude of streamwise streaks, is observed for streaks of small amplitude AU < 5%-6%. In this case, the transition is induced by an initial transient amplification of streamwise vortices, forced by the decaying sinuous mode. This is followed by the growth of the streaks and final breakdown. The shape of the critical AU - AW curve is very similar for Couette and boundary layer flows and seems to be relatively insensitive to the nature of the edge states on the basin boundary. The shape of this critical curve indicates that the stability of streamwise streaks should always be assessed in terms of both the streak amplitude and the amplitude of spanwise velocity perturbations.
Briceño, Raúl A.; Dudek, Jozef J.; Edwards, Robert G.; Shultz, Christian J.; Thomas, Christopher E.; Wilson, David J.
2016-06-01
We present a determination of the $P$-wave $\\pi\\pi\\to\\pi\\gamma^\\star$ transition amplitude from lattice quantum chromodynamics. Matrix elements of the vector current in a finite-volume are extracted from three-point correlation functions, and from these we determine the infinite-volume amplitude using a generalization of the Lellouch-L\\"uscher formalism. We determine the amplitude for a range of discrete values of the $\\pi\\pi$ energy and virtuality of the photon, and observe the expected dynamical enhancement due to the $\\rho$ resonance. Describing the energy dependence of the amplitude, we are able to analytically continue into the complex energy plane and from the residue at the $\\rho$ pole extract the $\\rho\\to\\gamma^\\star\\pi$ transition form factor. This calculation, at $m_\\pi\\approx 400$~MeV, is the first time a form factor of a hadron resonance has been calculated within a first-principles approach to QCD.
Thermal cracking and amplitude dependent attenuation
Johnston, D.H.; Toksoez, M.N.
1980-02-10
The role of crack and grain boundary contacts in determining seismic wave attenuation in rock is investigated by examining Q as a function of thermal cycling (cracking) and wave strain amplitude. Q values are obtained using a longitudinal resonant bar technique in the 10- to 20-kHz range for maximum strain amplitudes varying from roughly 10/sup -8/ to 10/sup -5/. The samples studied include the Berea and Navajo sandstones, Plexiglas, Westerly granite, Solenhofen limestone, and Frederick diabase, the latter two relatively crack free in their virgin state. Measurements were made at room temperature and pressure in air. Q values for both sandstones are constant at low strains (<10/sup -6/) but decrease rapidly with amplitude at higher strains. There is no hysteresis of Q with amplitude. Q values for Plexiglas show no indication of amplitude dependent behavior. The granite, limestone, and diabase are thermally cycled at both fast and slow heating rates in order to induce cracking. Samples slowly cycled at 400/sup 0/C show a marked increase in Q that cannot be entirely explained by outgassing of volatiles. Cycling may also widen thin cracks and grain boundaries, reducing contact areas. Samples heated beyond 400/sup 0/C, or rapidly heated, result in generally decreasing Q values. The amplitude dependence of Q is found to be coupled to the effects of thermal cycling. For rock slowly cycled 400)C or less, the transition from low-amplitude contant Q to high-amplitude variable Q behavior decreases to lower amplitudes as a function of maximum temperature. Above 400/sup 0/C, and possibly in th rapidly heated samples also, the transition moves to higher amplitudes.
Lewis, I.A.D.
1956-05-15
This patent pentains to an electrical pulse amplitude analyzer, capable of accepting input pulses having a separation between adjacent pulses in the order of one microsecond while providing a large number of channels of classification. In its broad aspect the described pulse amplitude analyzer utilizes a storage cathode ray tube und control circuitry whereby the amplitude of the analyzed pulses controls both the intensity and vertical defiection of the beam to charge particular spots in horizontal sectors of the tube face as the beam is moved horizontally across the tube face. As soon as the beam has swept the length of the tube the information stored therein is read out by scanning individually each horizontal sector corresponding to a certain range of pulse amplitudes and applying the output signal from each scan to separate indicating means.
Greenblatt, M.H.
1958-03-25
This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.
Real topological string amplitudes
NASA Astrophysics Data System (ADS)
Narain, K. S.; Piazzalunga, N.; Tanzini, A.
2017-03-01
We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.
Protostring scattering amplitudes
NASA Astrophysics Data System (ADS)
Thorn, Charles B.
2016-11-01
We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.
New calculations of the parity nonconservation matrix element for the JπT 0+1, 0-1 doublet in 14N
NASA Astrophysics Data System (ADS)
Horoi, Mihai; Clausnitzer, Günther; Brown, B. Alex; Warburton, E. K.
1994-08-01
A new calculation of the predominantly isoscalar PNC matrix element between the JπT 0+1,0-1 (Ex~=8.7 MeV) states in 14N has been carried out in a (0+1+2+3+4)ħω model space with the Warburton-Brown interaction. The magnitude of the PNC matrix element of 0.22 to 0.54 eV obtained with the DDH PNC interaction is substantially suppressed compared with previous calculations in smaller model spaces but shows agreement with the preliminary Seattle experimental data. The calculated sign is opposite to that obtained experimentally, and the implications of this are discussed.
Vesna, V.A.; Kolomenskii, E.A.; Lobashev, V.M.; Pirozhkov, A.N.; Smotritskii, L.M.; Titov, N.A.
1982-04-20
Parity (P) nonconservation effects have been measured in the total and radiative cross sections in /sup 79,81/Br: (sigma/sup +//sub tot/-sigma/sup -//sub tot/)/(sigma/sup +//sub tot/+sigma/sup -//sub tot/) = (9.8 +- 1.0) x 10/sup -6/sigma/sub tot/) = 15.5 b and (sigma/sup +//sub ..gamma../-sigma/sup -//sub ..gamma../)/(sigma/sup +//sub ..gamma../+sigma/sup -//sub ..gamma../) = (15.5 +- 1.5) x 10/sup -6/sigma/sub ..gamma../ = 9.8 b, where the +- correspond to opposite neutron helicities. It follows from the results that the P-odd effect in the total cross section is determined by radiative capture, within the experimental error.
Vesna, V.A.; Kolomenskii, E.A.; Lobashev, V.M.; Nazarenko, V.A.; Pirozhkov, A.N.; Smotritskii, L.M.; Sobolev, Y.V.; Titov, N.A.
1982-09-05
A P-odd asymmetry has been observed in the emission of ..gamma.. rays upon the capture of polarized thermal neutrons by Cl, Br, and La nuclei. A circular polarization of the ..gamma.. rays has been observed during the capture of unpolarized neutrons by Cl, Br, Sn, and La nuclei.
Feng Bo
2007-11-20
In this talk, we will present recent progresses in perturbative calculations of scattering amplitudes at tree and one-loop levels. At tree level, we will discuss MHV-diagram method and on-shell recursion relation. At one-loop level, we will establish the framework of Unitarity cut method.
Reinforcing Saccadic Amplitude Variability
ERIC Educational Resources Information Center
Paeye, Celine; Madelain, Laurent
2011-01-01
Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…
NASA Astrophysics Data System (ADS)
Taylor, Tomasz R.
2017-05-01
This a pedagogical introduction to scattering amplitudes in gauge theories. It proceeds from Dirac equation and Weyl fermions to the two pivot points of current developments: the recursion relations of Britto, Cachazo, Feng and Witten, and the unitarity cut method pioneered by Bern, Dixon, Dunbar and Kosower. In ten lectures, it covers the basic elements of on-shell methods.
Planar amplitude ammonia sensor
NASA Astrophysics Data System (ADS)
Karasinski, Pawel; Rogozinski, Roman
2004-09-01
The paper presents the results of investigation involving the influence of the change of launching conditions on the characteristics of amplitude ammonia sensors produced with the application of strip waveguides of different refractive profiles. Strip waveguides were produced using ion exchange technique, and the absorption sensitive films were produced using sol-gel technology.
Theoretical study of some experimentally relevant states of dysprosium
Dzuba, V. A.; Flambaum, V. V.
2010-05-15
Configuration interaction method is used to calculate transition amplitudes and other properties of the low states of dysprosium which are used in cooling and in the study of the time variation of the fine structure constant and violation of fundamental symmetries. The branching ratio for the cooling state to decay to states other than ground states is found to be smaller than 10{sup -4}. The matrix element of the weak interaction between degenerate states at E=19797.96 cm{sup -1} is about 4 Hz which is consistent with the experimental limit |H{sub W}|=|2.3{+-}2.9(stat.){+-}0.7(syst.)| Hz [A. T. Nguyen, D. Budker, D. DeMille, and M. Zolotorev, Phys. Rev. A 56, 3453 (1997)] and points to feasibility of its experimental measurement. Applications include the search for physics beyond the standard model using the parity nonconservation (PNC) isotopic chain approach.
Weak boson production amplitude zeros; equalities of the helicity amplitudes
NASA Astrophysics Data System (ADS)
Mamedov, Fizuli
2002-08-01
We investigate the radiation amplitude zeros exhibited by many standard model amplitudes for triple weak gauge boson production processes. We show that WZγ production amplitudes have an especially rich structure in terms of zeros; these amplitudes have zeros originating from several different sources. It is also shown that the type-I current null zone is the special case of the equality of the specific helicity amplitudes.
NASA Astrophysics Data System (ADS)
Can, T. V.; Weber, R. T.; Walish, J. J.; Swager, T. M.; Griffin, R. G.
2017-04-01
We present a pulsed dynamic nuclear polarization (DNP) study using a ramped-amplitude nuclear orientation via electron spin locking (RA-NOVEL) sequence that utilizes a fast arbitrary waveform generator (AWG) to modulate the microwave pulses together with samples doped with narrow-line radicals such as 1,3-bisdiphenylene-2-phenylallyl (BDPA), sulfonated-BDPA (SA-BDPA), and trityl-OX063. Similar to ramped-amplitude cross polarization in solid-state nuclear magnetic resonance, RA-NOVEL improves the DNP efficiency by a factor of up to 1.6 compared to constant-amplitude NOVEL (CA-NOVEL) but requires a longer mixing time. For example, at τmix = 8 μs, the DNP efficiency reaches a plateau at a ramp amplitude of ˜20 MHz for both SA-BDPA and trityl-OX063, regardless of the ramp profile (linear vs. tangent). At shorter mixing times (τmix = 0.8 μs), we found that the tangent ramp is superior to its linear counterpart and in both cases there exists an optimum ramp size and therefore ramp rate. Our results suggest that RA-NOVEL should be used instead of CA-NOVEL as long as the electronic spin lattice relaxation T1e is sufficiently long and/or the duty cycle of the microwave amplifier is not exceeded. To the best of our knowledge, this is the first example of a time domain DNP experiment that utilizes modulated microwave pulses. Our results also suggest that a precise modulation of the microwave pulses can play an important role in optimizing the efficiency of pulsed DNP experiments and an AWG is an elegant instrumental solution for this purpose.
Erbert, G
2009-09-01
The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.
Amplitudes of Spiral Perturbations
NASA Astrophysics Data System (ADS)
Grosbol, P.; Patsis, P. A.
2014-03-01
It has proven very difficult to estimate the amplitudes of spiral perturbations in disk galaxies from observations due to the variation of mass-to-light ratio and extinction across spiral arms. Deep, near-infrared images of grand-design spiral galaxies obtained with HAWK-I/VLT were used to analyze the azimuthal amplitude and shape of arms, which, even in the K-band may, be significantly biased by the presence of young stellar populations. Several techniques were applied to evaluate the relative importance of young stars across the arms, such as surface brightness of the disk with light from clusters subtracted, number density of clusters detected, and texture of the disk. The modulation of the texture measurement, which correlates with the number density of faint clusters, yields amplitudes of the spiral perturbation in the range 0.1-0.2. This estimate gives a better estimate of the mass perturbation in the spiral arms, since it is dominated by old clusters.
Gray, G.W.; Jensen, A.S.
1957-10-22
A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.
Amplitude and phase chimeras in an ensemble of chaotic oscillators
NASA Astrophysics Data System (ADS)
Bogomolov, S. A.; Strelkova, G. I.; Schöll, E.; Anishchenko, V. S.
2016-07-01
The transition from coherence to incoherence in an ensemble of nonlocally coupled logistic maps is considered. Chimera states of two types (amplitude and phase) are found. The mechanism and conditions of their appearance are determined.
HIGH AMPLITUDE PROPAGATED CONTRACTIONS
Bharucha, Adil E.
2012-01-01
While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. HAPC occur spontaneously, in response to pharmacological agents or colonic distention. In this issue of Neurogastroenterology and Motility, Rodriguez and colleagues report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. PMID:23057554
Pion distribution amplitude and quasidistributions
Radyushkin, Anatoly V.
2017-03-27
We extend our analysis of quasidistributions onto the pion distribution amplitude. Using the formalism of parton virtuality distribution amplitudes, we establish a connection between the pion transverse momentum dependent distribution amplitude Ψ(x,k2⊥) and the pion quasidistribution amplitude (QDA) Qπ(y,p3). We build models for the QDAs from the virtuality-distribution-amplitude-based models for soft transverse momentum dependent distribution amplitudes, and analyze the p3 dependence of the resulting QDAs. As there are many models claimed to describe the primordial shape of the pion distribution amplitude, we present the p3-evolution patterns for models producing some popular proposals: Chernyak-Zhitnitsky, flat, and asymptotic distribution amplitude. Finally, ourmore » results may be used as a guide for future studies of the pion distribution amplitude on the lattice using the quasidistribution approach.« less
Compositions of bosonic string amplitudes with cylinder topology
Trisnadi, J.I.
1989-01-01
Many issues in string theory are conveniently addressed and handled in a quantum fleld theoretical framework, from which Feynman rules can then be derived. Although at present a generally acceptable quantum field theory of closed strings does not yet exist, the Feynman rules are known. This is due to another development in string theory, namely, the Polyakov path integral approach. In this approach, scattering amplitudes are calculated directly without appealing to the quantum fleld theoretical description. It is therefore important to examine if the scattering amplitude can be reconstructed by composing propagators and vertices. In general, the author is interested in knowing if Polyakov amplitudes can be consistently composed. Composition of amplitudes in general has been studied formally. Explicit composition, however, is limited to amplitudes that have been calculated explicitly. Among them is the amplitude with cylinder topology. In this dissertation, the author will rederive this cylinder amplitude. The author uses the action principle in the evaluation of the path integral. This way, the contributions of the ghost zero modes, which are usually introduced by hand, come out automatically. Then, the author studies three compositions of the cylinder amplitude: two cylinder amplitudes into one, a single cylinder amplitude into a torus amplitude, and a cylinder amplitude into a Klein-bottle amplitude. The author shows that the resulting amplitudes agree with known results. Using the cylinder amplitude, the author also demonstrates the derivation of the (imaginary time) Schrodinger equation for the free closed bosonic string. Finally, the author applies the techniques to derive the composable transition amplitude of gravity in a Friedmann-RobertsonWalker cosmology.
Large Amplitude Oscillatory Shear near Jamming
NASA Astrophysics Data System (ADS)
Tighe, Brian; Dagois-Bohy, Simon; Somfai, Ellak; van Hecke, Martin
2014-11-01
Jammed solids such as foams and emulsions can be driven with oscillatory shear at finite strain amplitude and frequency. On a macro scale, this induces nonlinearities such as strain softening and shear thinning. On the micro scale one observes the onset of irreversibility, caging, and long-time diffusion. Using simulations of soft viscous spheres, we systematically vary the distance to the jamming transition. We correlate crossovers in the microscopic and macroscopic response, and construct scaling arguments to explain their relationships.
Tsunami Focusing and Leading Amplitude
NASA Astrophysics Data System (ADS)
Kanoglu, U.
2016-12-01
Tsunamis transform substantially through spatial and temporal spreading from their source region. This substantial spreading might result unique maximum tsunami wave heights which might be attributed to the source configuration, directivity, the waveguide structures of mid-ocean ridges and continental shelves, focusing and defocusing through submarine seamounts, random focusing due to small changes in bathymetry, dispersion, and, most likely, combination of some of these effects. In terms of the maximum tsunami wave height, after Okal and Synolakis (2016 Geophys. J. Int. 204, 719-735), it is clear that dispersion would be one of the reasons to drive the leading wave amplitude in a tsunami wave train. Okal and Synolakis (2016), referring to this phenomenon as sequencing -later waves in the train becoming higher than the leading one, considered Hammack's (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp) formalism, in addition to LeMéhauté and Wang's (1995 Water waves generated by underwater explosion, World Scientific, 367 pp), to evaluate linear dispersive tsunami propagation from a circular plug uplifted on an ocean of constant depth. They identified transition distance, as the second wave being larger, performing parametric study for the radius of the plug and the depth of the ocean. Here, we extend Okal and Synolakis' (2016) analysis to an initial wave field with a finite crest length and, in addition, to a most common tsunami initial wave form of N-wave (Tadepalli and Synolakis, 1994 Proc. R. Soc. A: Math. Phys. Eng. Sci. 445, 99-112). First, we investigate the focusing feature in the leading-depression side, which enhance tsunami wave height as presented by Kanoglu et al. (2013 Proc. R. Soc. A: Math. Phys. Eng. Sci. 469, 20130015). We then discuss the results in terms of leading wave amplitude presenting a parametric study and identify a simple relation for the transition distance. The solution presented here could be used to better analyze dispersive
PULSE AMPLITUDE DISTRIBUTION RECORDER
Cowper, G.
1958-08-12
A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.
Invariant amplitudes for pion electroproduction
NASA Astrophysics Data System (ADS)
Pasquini, B.; Drechsel, D.; Tiator, L.
2007-12-01
The invariant amplitudes for pion electroproduction on the nucleon are evaluated by dispersion relations at constant t with MAID as input for the imaginary parts of these amplitudes. In the threshold region these amplitudes are confronted with the predictions of several low-energy theorems derived in the soft-pion limit. In general agreement with chiral perturbation theory, the dispersive approach yields large corrections to these theorems because of the finite pion mass.
Amplitude variations in coarticulated vowels
Jacewicz, Ewa; Fox, Robert Allen
2008-01-01
This paper seeks to characterize the nature, size, and range of acoustic amplitude variation in naturally produced coarticulated vowels in order to determine its potential contribution and relevance to vowel perception. The study is a partial replication and extension of the pioneering work by House and Fairbanks [J. Acoust. Soc. Am. 22, 105–113 (1953)], who reported large variation in vowel amplitude as a function of consonantal context. Eight American English vowels spoken by men and women were recorded in ten symmetrical CVC consonantal contexts. Acoustic amplitude measures included overall rms amplitude, amplitude of the rms peak along with its relative location in the CVC-word, and the amplitudes of individual formants F1–F4 along with their frequencies. House and Fairbanks’ amplitude results were not replicated: Neither the overall rms nor the rms peak varied appreciably as a function of consonantal context. However, consonantal context was shown to affect significantly and systematically the amplitudes of individual formants at the vowel nucleus. These effects persisted in the auditory representation of the vowel signal. Auditory spectra showed that the pattern of spectral amplitude variation as a function of contextual effects may still be encoded and represented at early stages of processing by the peripheral auditory system. PMID:18529192
On the Period-Amplitude and Amplitude-Period Relationships
NASA Technical Reports Server (NTRS)
Wilson, Robert M.; Hathaway, David H.
2008-01-01
Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.
Amplitudes of MHD Waves in Sunspots
NASA Astrophysics Data System (ADS)
Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint, Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.; Rajaguru, Paul
2016-05-01
The conversion of p-modes into MHD waves by strong magnetic fields occurs mainly in the sub-photospheric layers. The photospheric signatures of MHD waves are weak due to low amplitudes at the beta=1 equipartion level where mode-conversion occurs. We report on small amplitude oscillations observed in the photosphere with Hinode SOT/SP in which we analyze time series for sunspots ARs 12186 (11.10.2014) and 12434 (17.10.2015). No significant magnetic field oscillations are recovered in the umbra or penumbra in the ME inversion. However, periodicities in the inclination angle are found at the umbral/penumbral boundary with 5 minute periods. Upward propagating waves are indicated in the intensity signals correlated between HMI and AIA at different heights. We compare SP results with the oscillations observed in HMI data. Simultaneous IRIS data shows transition region brightening above the umbral core.
Amplitude chimeras and chimera death in dynamical networks
NASA Astrophysics Data System (ADS)
Zakharova, Anna; Kapeller, Marie; Schöll, Eckehard
2016-06-01
We find chimera states with respect to amplitude dynamics in a network of Stuart- Landau oscillators. These partially coherent and partially incoherent spatio-temporal patterns appear due to the interplay of nonlocal network topology and symmetry-breaking coupling. As the coupling range is increased, the oscillations are quenched, amplitude chimeras disappear and the network enters a symmetry-breaking stationary state. This particular regime is a novel pattern which we call chimera death. It is characterized by the coexistence of spatially coherent and incoherent inhomogeneous steady states and therefore combines the features of chimera state and oscillation death. Additionally, we show two different transition scenarios from amplitude chimera to chimera death. Moreover, for amplitude chimeras we uncover the mechanism of transition towards in-phase synchronized regime and discuss the role of initial conditions.
Stochastic aspects of nuclear large amplitude motion
Kolomietz, V.M.
1995-08-01
A consistent description of the macroscopic large amplitude dynamics and processes of internal excitation of a nucleus is suggested. The cranking model approach is used for the calculation of the response function of the nucleus in a moving frame. Using spectral statistics smearing, the collective mass, friction, and diffusion coefficients are derived. The relation of the response function in a moving frame to the correlation function in a classical chaotic system is established. The rate of dissipation due to the Landau-Zener transitions and through the Kubo mechanism is considered.
Substorm statistics: Occurrences and amplitudes
Borovsky, J.E.; Nemzek, R.J.
1994-05-01
The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.
Amplitude equation for a diffusion-reaction system: The reversible Sel'kov model
NASA Astrophysics Data System (ADS)
Dutt, A. K.
2012-12-01
For a model glycolytic diffusion-reaction system, an amplitude equation has been derived in the framework of a weakly nonlinear theory. The linear stability analysis of this amplitude equation interprets the structural transitions and stability of various forms of Turing structures. This amplitude equation also conforms to the expectation that time-invariant amplitudes in Turing structures are independent of complexing reaction with the activator species, whereas complexing reaction strongly influences Hopf-wave bifurcation.
Small amplitude quasibreathers and oscillons
Fodor, Gyula; Lukacs, Arpad; Forgacs, Peter; Horvath, Zalan
2008-07-15
Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)]. QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, D{sub crit}=4, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.
Large Amplitude Oscillations in Prominences
NASA Astrophysics Data System (ADS)
Tripathi, D.; Isobe, H.; Jain, R.
2009-12-01
Since the first reports of oscillations in prominences in the 1930s, there have been major theoretical and observational developments to understand the nature of these oscillatory phenomena, leading to the whole new field of the so-called “prominence seismology”. There are two types of oscillatory phenomena observed in prominences; “small-amplitude oscillations” (2-3 km s-1), which are quite common, and “large-amplitude oscillations” (>20 km s-1) for which observations are scarce. Large-amplitude oscillations have been found as “winking filament” in H α as well as motion in the plane-of-sky in H α, EUV, micro-wave and He 10830 observations. Historically, it has been suggested that the large-amplitude oscillations in prominences were triggered by disturbances such as fast-mode MHD waves (Moreton wave) produced by remote flares. Recent observations show, in addition, that near-by flares or jets can also create such large-amplitude oscillations in prominences. Large-amplitude oscillations, which are observed both in transverse as well as longitudinal direction, have a range of periods varying from tens of minutes to a few hours. Using the observed period of oscillation and simple theoretical models, the obtained magnetic field in prominences has shown quite a good agreement with directly measured one and, therefore, justifies prominence seismology as a powerful diagnostic tool. On rare occasions, when the large-amplitude oscillations have been observed before or during the eruption, the oscillations may be applied to diagnose the stability and the eruption mechanism. Here we review the recent developments and understanding in the observational properties of large-amplitude oscillations and their trigger mechanisms and stability in the context of prominence seismology.
Tempo and amplitude in growth.
Hermanussen, Michael
2011-01-01
Growth is defined as an increase of size over time with time usually defined as physical time. Yet, the rigid metric of physical time is not directly relevant to the internal dynamics of growth. Growth is linked to maturation. Children and adolescents differ in the tempo at which they mature. One calendar year differs in its meaning in a fast maturing, and in a slow maturing child. The slow child needs more calendar years for completing the same stage of maturity. Many characteristics in the human growth curve are tempo characteristics. Tempo - being fast or slow maturing - has to be carefully separated from amplitude - being tall or short. Several characteristic phenomena such as catch-up growth after periods of illness and starvation are largely tempo phenomena, and do usually not affect the amplitude component of growth. Applying Functional Data Analysis and Principal Component Analysis, the two main sources of height variance: tempo and amplitude can statistically be separate and quantified. Tempo appears to be more sensitive than amplitude to nutrition, health and environmental stress. An appropriate analysis of growth requires disentangling its two major components: amplitude and tempo. The assessment of the developmental tempo thus is an integral part of assessing child and adolescent growth. Though an Internet portal is currently available to process small amounts of height data (www.willi-will-wachsen.com) for separately determining amplitude and tempo in growth, there is urgent need of better and practical solutions for analyzing individual growth.
Constraints on scattering amplitudes in multistate Landau-Zener theory
Sinitsyn, Nikolai A.; Lin, Jeffmin; Chernyak, Vladimir Y.
2017-01-30
Here, we derive a set of constraints, which we will call hierarchy constraints, on scattering amplitudes of an arbitrary multistate Landau-Zener model (MLZM). The presence of additional symmetries can transform such constraints into nontrivial relations between elements of the transition probability matrix. This observation can be used to derive complete solutions of some MLZMs or, for models that cannot be solved completely, to reduce the number of independent elements of the transition probability matrix.
Constraints on scattering amplitudes in multistate Landau-Zener theory
NASA Astrophysics Data System (ADS)
Sinitsyn, Nikolai A.; Lin, Jeffmin; Chernyak, Vladimir Y.
2017-01-01
We derive a set of constraints, which we will call hierarchy constraints, on scattering amplitudes of an arbitrary multistate Landau-Zener model (MLZM). The presence of additional symmetries can transform such constraints into nontrivial relations between elements of the transition probability matrix. This observation can be used to derive complete solutions of some MLZMs or, for models that cannot be solved completely, to reduce the number of independent elements of the transition probability matrix.
Grassmannian origin of scattering amplitudes
NASA Astrophysics Data System (ADS)
Trnka, Jaroslav
Quantum field theory (QFT) is our central theoretical framework to describe the microscopic world, arising from the union of quantum mechanics and special relativity. Since QFTs play such a central role in our understanding of Nature, a deeper study of their physical properties is one of the most exciting directions of research in theoretical physics. This has led to the discovery of many important theoretical concepts, such as supersymmetry and string theory. One of the most prominent physical observable in any QFT is the scattering amplitude, which describes scattering processes of elementary particles. Theoretical progress in understanding and computing scattering amplitudes has accelerated in last few years with the discovery of amazing new mathematical structures in a close cousin of QCD, known as N=4 Super-Yang-Mills theory (SYM). In the first chapter we study integrands of loop amplitudes in planar N=4 SYM and show their astonishing simplicity when written in terms of special set of chiral integrals. In chapter two we show how to reconstruct the multi-loop integrand recursively starting from tree-level amplitudes. This approach makes the long-hidden Yangian symmetry of the theory completely manifest and provides a Lagrangian-independent approach for determining the integrand at any loop order. In chapter three we demonstrate that the problem of calculating of scattering amplitudes in planar N=4 SYM can be completely reformulated in a new framework in terms of on-shell diagrams and integrals over the positive Grassmannian G(k,n). Remarkably, the building blocks for amplitudes play a fundamental role in an active area of research in mathematics spanning algebraic geometry to combinatorics. In chapter four we sketch the argument that the amplitude itself is represented by a single geometrical object defined purely using a new striking property -- positivity -- and all physical concepts like unitarity and locality emerge as derived concepts, each having a sharp
Computing Maximally Supersymmetric Scattering Amplitudes
NASA Astrophysics Data System (ADS)
Stankowicz, James Michael, Jr.
This dissertation reviews work in computing N = 4 super-Yang--Mills (sYM) and N = 8 maximally supersymmetric gravity (mSUGRA) scattering amplitudes in D = 4 spacetime dimensions in novel ways. After a brief introduction and overview in Ch. 1, the various techniques used to construct amplitudes in the remainder of the dissertation are discussed in Ch. 2. This includes several new concepts such as d log and pure integrand bases, as well as how to construct the amplitude using exactly one kinematic point where it vanishes. Also included in this chapter is an outline of the Mathematica package on shell diagrams and numerics.m (osdn) that was developed for the computations herein. The rest of the dissertation is devoted to explicit examples. In Ch. 3, the starting point is tree-level sYM amplitudes that have integral representations with residues that obey amplitude relations. These residues are shown to have corresponding residue numerators that allow a double copy prescription that results in mSUGRA residues. In Ch. 4, the two-loop four-point sYM amplitude is constructed in several ways, showcasing many of the techniques of Ch. 2; this includes an example of how to use osdn. The two-loop five-point amplitude is also presented in a pure integrand representation with comments on how it was constructed from one homogeneous cut of the amplitude. On-going work on the two-loop n-point amplitude is presented at the end of Ch. 4. In Ch. 5, the three-loop four-point amplitude is presented in the d log representation and in the pure integrand representation. In Ch. 6, there are several examples of four- through seven-loop planar diagrams that illustrate how considerations of the singularity structure of the amplitude underpin dual-conformal invariance. Taken with the previous examples, this is additional evidence that the structure known to exist in the planar sector extends to the full theory. At the end of this chapter is a proof that all mSUGRA amplitudes have a pole at
Lorentzian proper vertex amplitude: Asymptotics
NASA Astrophysics Data System (ADS)
Engle, Jonathan; Vilensky, Ilya; Zipfel, Antonia
2016-09-01
In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semiclassical limit. The starting point of the analysis is an expression for the amplitude as an action integral with action differing from that in the Engle-Pereira-Rovelli-Livine (EPRL) case by an extra "projector" term. This extra term scales linearly with spins only in the asymptotic limit, and is discontinuous on a (lower dimensional) submanifold of the integration domain in the sense that its value at each such point depends on the direction of approach. New tools are introduced to generalize stationary phase methods to this case. For the case of boundary data which can be glued to a nondegenerate Lorentzian 4-simplex, the asymptotic limit of the amplitude is shown to equal the single Feynman term, showing that the extra term in the asymptotics of the EPRL amplitude has been eliminated.
Resolving High Amplitude Surface Motion with Diffusing Light
NASA Technical Reports Server (NTRS)
Wright, W.; Budakian, R.; Putterman, Seth J.
1996-01-01
A new technique has been developed for the purpose of imaging high amplitude surface motion. With this method one can quantitatively measure the transition to ripple wave turbulence. In addition, one can measure the phase of the turbulent state. These experiments reveal strong coherent structures in turbulent range of motion.
Factorization of chiral string amplitudes
NASA Astrophysics Data System (ADS)
Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye
2016-09-01
We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.
Modelling of grain boundary dynamics using amplitude equations
NASA Astrophysics Data System (ADS)
Hüter, Claas; Neugebauer, Jörg; Boussinot, Guillaume; Svendsen, Bob; Prahl, Ulrich; Spatschek, Robert
2017-07-01
We discuss the modelling of grain boundary dynamics within an amplitude equations description, which is derived from classical density functional theory or the phase field crystal model. The relation between the conditions for periodicity of the system and coincidence site lattices at grain boundaries is investigated. Within the amplitude equations framework, we recover predictions of the geometrical model by Cahn and Taylor for coupled grain boundary motion, and find both {<100\\rangle} and {<110\\rangle} coupling. No spontaneous transition between these modes occurs due to restrictions related to the rotational invariance of the amplitude equations. Grain rotation due to coupled motion is also in agreement with theoretical predictions. Whereas linear elasticity is correctly captured by the amplitude equations model, open questions remain for the case of nonlinear deformations.
Hansen, Maxwell; Briceno, Raul
2015-10-01
We present a model-independent, non-perturbative relation between finite-volume matrix elements and infinite-volume $\\textbf{0}\\rightarrow\\textbf{2}$ and $\\textbf{1}\\rightarrow\\textbf{2}$ transition amplitudes. Our result accommodates theories in which the final two-particle state is coupled to any number of other two-body channels, with all angular momentum states included. The derivation uses generic, fully relativistic field theory, and is exact up to exponentially suppressed corrections in the lightest particle mass times the box size. This work distinguishes itself from previous studies by accommodating particles with any intrinsic spin. To illustrate the utility of our general result, we discuss how it can be implemented for studies of $N+\\mathcal{J}~\\rightarrow~(N\\pi,N\\eta,N\\eta',\\Sigma K,\\Lambda K)$ transitions, where $\\mathcal{J}$ is a generic external current. The reduction of rotational symmetry, due to the cubic finite volume, manifests in this example through the mixing of S- and P-waves when the system has nonzero total momentum.
Large amplitude drop shape oscillations
NASA Technical Reports Server (NTRS)
Trinh, E. H.; Wang, T. G.
1982-01-01
An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.
Toward complete pion nucleon amplitudes
Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; ...
2015-10-05
We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.
Toward complete pion nucleon amplitudes
Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; Pennington, Michael R.; Schott, Diane M.; Szczepaniak, Adam P.; Fox, G.
2015-10-05
We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.
Nonlinear amplitude approximation for bilinear systems
NASA Astrophysics Data System (ADS)
Jung, Chulwoo; D'Souza, Kiran; Epureanu, Bogdan I.
2014-06-01
An efficient method to predict vibration amplitudes at the resonant frequencies of dynamical systems with piecewise-linear nonlinearity is developed. This technique is referred to as bilinear amplitude approximation (BAA). BAA constructs a single vibration cycle at each resonant frequency to approximate the periodic steady-state response of the system. It is postulated that the steady-state response is piece-wise linear and can be approximated by analyzing the response over two time intervals during which the system behaves linearly. Overall the dynamics is nonlinear, but the system is in a distinct linear state during each of the two time intervals. Thus, the approximated vibration cycle is constructed using linear analyses. The equation of motion for analyzing the vibration of each state is projected along the overlapping space spanned by the linear mode shapes active in each of the states. This overlapping space is where the vibratory energy is transferred from one state to the other when the system switches from one state to the other. The overlapping space can be obtained using singular value decomposition. The space where the energy is transferred is used together with transition conditions of displacement and velocity compatibility to construct a single vibration cycle and to compute the amplitude of the dynamics. Since the BAA method does not require numerical integration of nonlinear models, computational costs are very low. In this paper, the BAA method is first applied to a single-degree-of-freedom system. Then, a three-degree-of-freedom system is introduced to demonstrate a more general application of BAA. Finally, the BAA method is applied to a full bladed disk with a crack. Results comparing numerical solutions from full-order nonlinear analysis and results obtained using BAA are presented for all systems.
Conformal basis for flat space amplitudes
NASA Astrophysics Data System (ADS)
Pasterski, Sabrina; Shao, Shu-Heng
2017-09-01
We study solutions of the Klein-Gordon, Maxwell, and linearized Einstein equations in R1 ,d +1 that transform as d -dimensional conformal primaries under the Lorentz group S O (1 ,d +1 ). Such solutions, called conformal primary wavefunctions, are labeled by a conformal dimension Δ and a point in Rd, rather than an on-shell (d +2 )-dimensional momentum. We show that the continuum of scalar conformal primary wavefunctions on the principal continuous series Δ ∈d/2 +i R of S O (1 ,d +1 ) spans a complete set of normalizable solutions to the wave equation. In the massless case, with or without spin, the transition from momentum space to conformal primary wavefunctions is implemented by a Mellin transform. As a consequence of this construction, scattering amplitudes in this basis transform covariantly under S O (1 ,d +1 ) as d -dimensional conformal correlators.
True amplitude prestack depth migration
NASA Astrophysics Data System (ADS)
Deng, Feng
Reliable analysis of amplitude variation with offset (or with angle) requires accurate amplitudes from prestack migration. In routine seismic data processing, amplitude balancing and automatic gain control are often used to reduce amplitude lateral variations. However, these methods are empirical and lack a solid physical basis; thus, there are uncertainties that might produce erroneous conclusions, and hence cause economic loss. During wavefield propagation, geometrical spreading, intrinsic attenuation, transmission losses and the energy conversion significantly distort the wavefield amplitude. Most current true-amplitude migrations usually compensate only for geometrical spreading. A new prestack depth migration based on the framework of reverse-time migration in the time-space domain was developed in this dissertation with the aim of compensating all of the propagation effects in one integrated algorithm. Geometrical spreading is automatically included because of the use of full two-way wave extrapolation. Viscoelastic wave equations are solved to handle the intrinsic attenuation with a priori quality factor. Transmission losses for both up- and down-going waves are compensated using a two-pass, recursive procedure based on extracting the angle-dependent reflection/transmission coefficients from prestack migration. The losses caused by the conversion of energy from one elastic model to another are accounted for through elastic wave extrapolation; the influence of the S wave velocity contrast on the P wave reflection coefficient is implicitly included by using the Zoeppritz equations to describe the reflection and transmission at an elastic interface. Only smooth background models are assumed to be known. The contrasts/ratios of the model parameters can be estimated by fitting the compensated angle-dependent reflection coefficients obtained from data for multiple sources. This is one useful by-product of the algorithm. Numerical tests on both 2D and 3D scalar
Pulse amplitude modulated chlorophyll fluorometer
Greenbaum, Elias; Wu, Jie
2015-12-29
Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.
Genus dependence of superstring amplitudes
Davis, Simon
2006-11-15
The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |K{sub n}|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived.
Phase variation of hadronic amplitudes
Dedonder, J.-P.; Gibbs, W. R.; Nuseirat, Mutazz
2008-04-15
The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities that control it and how well it can be determined in free space. We find that unitarity forces a moderately accurate determination of the phase in standard amplitude analyses but that the nucleon-nucleon analyses done to date do not give the phase variation needed to achieve a good representation of the data in multiple scattering calculations. Models are examined that suggest its behavior near forward angles is related to the radii of the real and absorptive parts of the interaction. The dependence of this phase on model parameters is such that if these radii are modified in the nuclear medium (in combination with the change due to the shift in energy of the effective amplitude in the medium) then the larger magnitudes of the phase needed to fit the data might be attainable but only for negative values of the phase variation parameter.
Crisis in Amplitude Control Hides in Multistability
NASA Astrophysics Data System (ADS)
Li, Chunbiao; Sprott, Julien Clinton; Xing, Hongyan
2016-12-01
A crisis of amplitude control can occur when a system is multistable. This paper proposes a new chaotic system with a line of equilibria to demonstrate the threat to amplitude control from multistability. The new symmetric system has two coefficients for amplitude control, one of which is a partial amplitude controller, while the other is a total amplitude controller that simultaneously controls the frequency. The amplitude parameter rescales the basins of attraction and triggers a state switch among different states resulting in a failure of amplitude control to the desired state.
Calculation of multi-loop superstring amplitudes
NASA Astrophysics Data System (ADS)
Danilov, G. S.
2016-12-01
The multi-loop interaction amplitudes in the closed, oriented superstring theory are obtained by the integration of local amplitudes. The local amplitude is represented by a sum over the spinning string local amplitudes. The spinning string local amplitudes are given explicitly through super-Schottky group parameters and through interaction vertex coordinates on the (1| 1) complex, non-split supermanifold. The obtained amplitudes are free from divergences. They are consistent with the world-sheet spinning string symmetries. The vacuum amplitude vanishes along with 1-, 2- and 3-point amplitudes of massless states. The vanishing of the above-mentioned amplitude occurs after the integration of the corresponding local amplitude has been performed over the super-Schottky group limiting points and over interaction vertex coordinate, except for those (3| 2) variables which are fixed due to SL(2)-symmetry.
Precise Atomic Beam Spectroscopy Measurements in Thallium
NASA Astrophysics Data System (ADS)
Richardson, David; Speck, Andrew; Majumder, Protik
2000-06-01
We have begun a series of new high-precision measurements of thallium atomic structure using a newly completed high-flux atomic beam apparatus. These experiments will extend our vapor cell spectroscopy work in which we have measured thallium transition amplitudes and excited-state hyperfine splittings. These experimental results provide important, independent cross-checks on the accuracy of ongoing calculations of parity nonconservation in thallium. We study two ground state transitions: the 6P_1/2-6P_3/2 M1 transition at 1283 nm, and the 6P_1/2 - 7S_1/2 E1 transition at 378 nm. Laser light at the UV wavelength is obtained via external resonant frequency doubling of a 5 mW, 755 nm laser diode system. Our atomic beam apparatus consists of a multiple slit oven source and 20 cm oven-to-interaction region distance, which provides a favorable balance of beam density and modest Doppler narrowing. Our interaction region includes a precisely constructed and calibrated electric field plate/high-voltage system. Using this apparatus in conjunction with an acousto-optic modulator to frequency shift the diode laser, we have begun a high-precision Stark shift measurement within the 378 nm transition. Future experiments that will focus on the 1283 nm M1 transition using the atomic beam apparatus include a sensitive test of long-range T-violating forces in thallium. Current experimental results will be presented.
Control of amplitude chimeras by time delay in oscillator networks
NASA Astrophysics Data System (ADS)
Gjurchinovski, Aleksandar; Schöll, Eckehard; Zakharova, Anna
2017-04-01
We investigate the influence of time-delayed coupling in a ring network of nonlocally coupled Stuart-Landau oscillators upon chimera states, i.e., space-time patterns with coexisting partially coherent and partially incoherent domains. We focus on amplitude chimeras, which exhibit incoherent behavior with respect to the amplitude rather than the phase and are transient patterns, and we show that their lifetime can be significantly enhanced by coupling delay. To characterize their transition to phase-lag synchronization (coherent traveling waves) and other coherent structures, we generalize the Kuramoto order parameter. Contrasting the results for instantaneous coupling with those for constant coupling delay, for time-varying delay, and for distributed-delay coupling, we demonstrate that the lifetime of amplitude chimera states and related partially incoherent states can be controlled, i.e., deliberately reduced or increased, depending upon the type of coupling delay.
Quasidistribution amplitude of heavy quarkonia
NASA Astrophysics Data System (ADS)
Jia, Yu; Xiong, Xiaonu
2016-11-01
The recently proposed quasidistributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions and distribution amplitudes (DAs), directly in the x space. Owing to its excessive simplicity, heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DAs. In the framework of nonrelativistic QCD factorization, we compute the order-αs correction to both light-cone distribution amplitudes (LCDAs) and quasi-DAs associated with the lowest-lying quarkonia, with the transverse-momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the future lattice study of quasidistributions.
Amplitude death of coupled hair bundles with stochastic channel noise
NASA Astrophysics Data System (ADS)
Kim, Kyung-Joong; Ahn, Kang-Hun
2014-04-01
Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.
Coupling of Large Amplitude Inversion with Other States
NASA Astrophysics Data System (ADS)
Pearson, John; Yu, Shanshan
2016-06-01
The coupling of a large amplitude motion with a small amplitude vibration remains one of the least well characterized problems in molecular physics. Molecular inversion poses a few unique and not intuitively obvious challenges to the large amplitude motion problem. In spite of several decades of theoretical work numerous challenges in calculation of transition frequencies and more importantly intensities persist. The most challenging aspect of this problem is that the inversion coordinate is a unique function of the overall vibrational state including both the large and small amplitude modes. As a result, the r-axis system and the meaning of the K-quantum number in the rotational basis set are unique to each vibrational state of large or small amplitude motion. This unfortunate reality has profound consequences to calculation of intensities and the coupling of nearly degenerate vibrational states. The case of NH3 inversion and inversion through a plane of symmetry in alcohols will be examined to find a general path forward.
Large amplitude relativistic plasma waves
Coffey, Timothy
2010-05-15
Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov-Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.
Oscillator death induced by amplitude-dependent coupling in repulsively coupled oscillators
NASA Astrophysics Data System (ADS)
Liu, Weiqing; Xiao, Guibao; Zhu, Yun; Zhan, Meng; Xiao, Jinghua; Kurths, Jürgen
2015-05-01
The effects of amplitude-dependent coupling on oscillator death (OD) are investigated for two repulsively coupled Lorenz oscillators. Based on numerical simulations, it is shown that as constraint strengths on the amplitude-dependent coupling change, an oscillatory state may undergo a transition to an OD state. The parameter regimes of the OD domain are theoretically determined, which coincide well with the numerical results. An electronic circuit is set up to exhibit the transition process to the OD state with an amplitude-dependent coupling. These findings may have practical importance on chaos control and oscillation depression.
Oscillator death induced by amplitude-dependent coupling in repulsively coupled oscillators.
Liu, Weiqing; Xiao, Guibao; Zhu, Yun; Zhan, Meng; Xiao, Jinghua; Kurths, Jürgen
2015-05-01
The effects of amplitude-dependent coupling on oscillator death (OD) are investigated for two repulsively coupled Lorenz oscillators. Based on numerical simulations, it is shown that as constraint strengths on the amplitude-dependent coupling change, an oscillatory state may undergo a transition to an OD state. The parameter regimes of the OD domain are theoretically determined, which coincide well with the numerical results. An electronic circuit is set up to exhibit the transition process to the OD state with an amplitude-dependent coupling. These findings may have practical importance on chaos control and oscillation depression.
Expansion of Einstein-Yang-Mills amplitude
NASA Astrophysics Data System (ADS)
Fu, Chih-Hao; Du, Yi-Jian; Huang, Rijun; Feng, Bo
2017-09-01
In this paper, we study from various perspectives the expansion of tree level single trace Einstein-Yang-Mills amplitudes into linear combination of color-ordered Yang-Mills amplitudes. By applying the gauge invariance principle, a programable recursive construction is devised to expand EYM amplitude with arbitrary number of gravitons into EYM amplitudes with fewer gravitons. Based on this recursive technique we write down the complete expansion of any single trace EYM amplitude in the basis of color-order Yang-Mills amplitude. As a byproduct, an algorithm for constructing a polynomial form of the BCJ numerator for Yang-Mills amplitudes is also outlined in this paper. In addition, by applying BCFW recursion relation we show how to arrive at the same EYM amplitude expansion from the on-shell perspective. And we examine the EYM expansion using KLT relations and show how to evaluate the expansion coefficients efficiently.
Constructing amplitudes from their soft limits
NASA Astrophysics Data System (ADS)
Boucher-Veronneau, Camille; Larkoski, Andrew J.
2011-09-01
The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an ( n - 1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which "soft" particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.
Constructing Amplitudes from Their Soft Limits
Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC
2011-12-09
The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.
Transition and laminar instability
NASA Technical Reports Server (NTRS)
Mack, L. M.
1977-01-01
The linear stability theory was applied to the problem of boundary layer transition in incompressible flow. The theory was put into a form suitable for three-dimensional boundary layers; both the temporal and spatial theories were examined; and a generalized Gaster relation for three-dimensional boundary layers was derived. Numerical examples include the stability characteristics of Falkner-Skan boundary layers, the accuracy of the two-dimensional Gaster relation for these boundary layers, and the magnitude and direction of the group velocity for oblique waves in the Blasius boundary layer. Available experiments which bear on the validity of stability theory and its relation to transition are reviewed and the stability theory is applied to transition prediction. The amplitude method is described in which the wide band disturbance amplitude in the boundary layer is estimated from stability theory and an interaction relation for the initial amplitude density of the most unstable frequency.
High-precision atomic structure measurements in thallium
NASA Astrophysics Data System (ADS)
Burkhardt, M. H.; Holmes, C. D.; Uhl, R.; Majumder, P. K.
2004-05-01
Using a thallium atomic beam apparatus, we are undertaking a series of laser spectroscopy measurements with the goal of providing precise, independent cross-checks on the accuracy of new calculations of parity nonconservation in thallium(M. Kozlov et al.), Phys Rev. A64, 053107 (2001). In our apparatus, a laser beam interacts transversely with a dense, 2-cm-wide thallium beam and reveals roughly tenfold Doppler narrowing of the absorption profile. Having completed a new 0.4% measurement of the Stark shift within the 378 nm 6P_1/2-7S_1/2 E1 transition, we have now begun to study the weak 1283 nm 6P_1/2-6P_3/2 transition in the atomic beam. We seek to determine both Stark shift components, as well as the various components of the Stark-induced amplitude within this mixed M1/E2 transition. Using these existing laser systems, we have also begun a vapor cell spectroscopy study of the 1301 nm 7S_1/2-7P_1/2 E1 transition by means of a two-step excitation from the ground state. To enhance the visibility of these weak absorption signals, we are employing an FM spectroscopy technique. The demodulated laser transmission spectrum provides a low-noise, zero-background signal, and includes replicas of the absorption spectrum separated by the well-known RF sideband frequency, offering built-in frequency scale calibration.
Calculation of Radiative Corrections to E1 matrix elements in the Neutral Alkalis
Sapirstein, J; Cheng, K T
2004-09-28
Radiative corrections to E1 matrix elements for ns-np transitions in the alkali metal atoms lithium through francium are evaluated. They are found to be small for the lighter alkalis but significantly larger for the heavier alkalis, and in the case of cesium much larger than the experimental accuracy. The relation of the matrix element calculation to a recent decay rate calculation for hydrogenic ions is discussed, and application of the method to parity nonconservation in cesium is described.
The relationship between sensory latency and amplitude.
Bodofsky, Elliot B; Cohen, Stephen J; Kumar, Rohini J; Schindelheim, Adam; Gaughan, John
2016-12-01
To prove that the relationship between sensory latencies and amplitudes is useful in determining the severity of neuropathies. This is achieved by deriving a mathematical relationship between sensory distal latency and amplitude. Determine whether sensory amplitudes below predicted correlate with a worse pathology. Patients seen for Nerve Conduction Studies by the Department of Physical Medicine and Rehabilitation at Cooper University Hospital between 12/1/12 and 12/31/14 were invited to participate in a prospective database. The median, ulnar and sural sensory latencies and amplitudes were analyzed with both linear and power regression. Patients with amplitudes above and below the regression curve were compared for latency, amplitude and velocity of other nerves. Carpal Tunnel Patients were analyzed to determine whether Median sensory amplitude below predicted correlated with more severe disease. For the Median nerve, Power Regression Analysis showed a stronger correlation (R(2)=0.54) than linear regression (R(2)=0.34). Patients with Median sensory amplitude below the power correlation curve showed significantly longer ulnar sensory latency, and lower sensory amplitude than those above. Carpal Tunnel Syndrome patients with Median sensory amplitude well below predicted by the power relationship showed more advanced disease. For the ulnar and sural sensory nerve, the difference between power and linear regression was not significant. A power regression curve correlates sensory latency and amplitude better than linear regression. The latency amplitude relationship correlates with other parameters of nerve function and severity of Carpal Tunnel Syndrome. This implies that below predicted sensory amplitude may indicate worse disease, and could be a useful diagnostic tool. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Leading Wave Amplitude of a Tsunami
NASA Astrophysics Data System (ADS)
Kanoglu, U.
2015-12-01
Okal and Synolakis (EGU General Assembly 2015, Geophysical Research Abstracts-Vol. 17-7622) recently discussed that why the maximum amplitude of a tsunami might not occur for the first wave. Okal and Synolakis list observations from 2011 Japan tsunami, which reached to Papeete, Tahiti with a fourth wave being largest and 72 min later after the first wave; 1960 Chilean tsunami reached Hilo, Hawaii with a maximum wave arriving 1 hour later with a height of 5m, first wave being only 1.2m. Largest later waves is a problem not only for local authorities both in terms of warning to the public and rescue efforts but also mislead the public thinking that it is safe to return shoreline or evacuated site after arrival of the first wave. Okal and Synolakis considered Hammack's (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp., Pasadena) linear dispersive analytical solution with a tsunami generation through an uplifting of a circular plug on the ocean floor. They performed parametric study for the radius of the plug and the depth of the ocean since these are the independent scaling lengths in the problem. They identified transition distance, as the second wave being larger, regarding the parameters of the problem. Here, we extend their analysis to an initial wave field with a finite crest length and, in addition, to a most common tsunami initial wave form of N-wave as presented by Tadepalli and Synolakis (1994, Proc. R. Soc. A: Math. Phys. Eng. Sci., 445, 99-112). We compare our results with non-dispersive linear shallow water wave results as presented by Kanoglu et al. (2013, Proc. R. Soc. A: Math. Phys. Eng. Sci., 469, 20130015), investigating focusing feature. We discuss the results both in terms of leading wave amplitude and tsunami focusing. Acknowledgment: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 603839 (Project ASTARTE - Assessment, Strategy and Risk
The Dynamics of Large-Amplitude Motion in Energized Molecules
Perry, David S.
2016-05-27
Chemical reactions involve large-amplitude nuclear motion along the reaction coordinate that serves to distinguish reactants from products. Some reactions, such as roaming reactions and reactions proceeding through a loose transition state, involve more than one large-amplitude degree of freedom. Because of the limitation of exact quantum nuclear dynamics to small systems, one must, in general, define the active degrees of freedom and separate them in some way from the other degrees of freedom. In this project, we use large-amplitude motion in bound model systems to investigate the coupling of large-amplitude degrees of freedom to other nuclear degrees of freedom. This approach allows us to use the precision and power of high-resolution molecular spectroscopy to probe the specific coupling mechanisms involved, and to apply the associated theoretical tools. In addition to slit-jet spectra at the University of Akron, the current project period has involved collaboration with Michel Herman and Nathalie Vaeck of the Université Libre de Bruxelles, and with Brant Billinghurst at the Canadian Light Source (CLS).
Amplitude-dependent station magnitude
NASA Astrophysics Data System (ADS)
Radzyner, Yael; Ben Horin, Yochai; Steinberg, David M.
2016-04-01
Magnitude, a concept first presented by Gutenberg and Richter, adjusts measurements of ground motion for epicentral distance and source depth. Following this principle, the IDC defines the j'th station body wave magnitude for event i as mb(stai,j) = log 10(Aj,i/Tj,i) + V C(Δj,i,hi) , where VC is the Veith-Clawson (VC) correction to compensate for the epicentral distance of the station and the depth of the source. The network magnitude is calculated as the average of station magnitudes. The IDC magnitude estimation is used for event characterization and discrimination and it should be as accurate as possible. Ideally, the network magnitude should be close in value to the station magnitudes. In reality, it is observed that the residuals range between -1 and 1 mu or ±25% of a given mb(neti) value. We show that the residual, mb(neti) -mb(staj,i), depends linearly on log 10(Aj,i/Tj,i), and we correct for this dependence using the following procedure: Calculate a "jackknifed" network magnitude, mbj,n(neti), i.e. an average over all participating stations except station n. Using all measurements at station n, calculate the parameters an, bn of the linear fit of the residual mbj,n(neti) - mb(stan,i to log 10(An,i/Tn,i). For each event i at station n calculate the new station magnitude mbnew(stan,i) = (an + 1)log(An,i/Tn,i) + V C(Δn,i,hi) + bn Calculate the new network magnitude: mbnew(neti) = 1N- ∑ n=1nmbnew(stan,i) The procedure was used on more than two million station-event pairs. Correcting for the station-specific dependence on log amplitude reduces the residuals by roughly a third. We have calculated the spread of the distributions, and compared the original values and those for the corrected magnitudes. The spread is the ratio between the variance of the network magnitudes, and the variance of the residual. Calculations show an increase in the ratio of the variance, meaning that the correction process presented in this document did not lead to loss of variance
Gravity and Yang-Mills amplitude relations
Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas; FengBo
2010-11-15
Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.
Minimal Basis for Gauge Theory Amplitudes
Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Vanhove, Pierre
2009-10-16
Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)exclamation amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.
Discontinuities of multi-Regge amplitudes
NASA Astrophysics Data System (ADS)
Fadin, V. S.
2015-04-01
In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.
DVCS amplitude with kinematical twist-3 terms
Radyushkin, A.V.; Weiss, C.
2000-08-01
The authors compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude they include the operators of twist-3 which appear as total derivatives of twist-2 operators. The results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. They find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.
Vertex amplitudes in spin foam loop quantum cosmology
NASA Astrophysics Data System (ADS)
Craig, David
2016-03-01
We discuss properties of the vertex expansion for homogeneous, isotropic loop quantum cosmological models sourced by a massless, minimally coupled scalar field, which in this model plays the role of an internal matter ``clock''. We show that the vertex expansion, first written down by Ashtekar, Campiglia and Henderson, must be thought of as a short-time expansion in the sense that the amplitude for volume transitions is constrained both by the order of the expansion and by the elapsed scalar field. To calculate the amplitude for significant volume changes or between large differences in the value of the scalar field requires the expansion be evaluated to very high order. This contribution describes work in collaboration with P. Singh.
Photoinduced Enhancement of the Charge Density Wave Amplitude
NASA Astrophysics Data System (ADS)
Singer, A.; Patel, S. K. K.; Kukreja, R.; Uhlíř, V.; Wingert, J.; Festersen, S.; Zhu, D.; Glownia, J. M.; Lemke, H. T.; Nelson, S.; Kozina, M.; Rossnagel, K.; Bauer, M.; Murphy, B. M.; Magnussen, O. M.; Fullerton, E. E.; Shpyrko, O. G.
2016-07-01
Symmetry breaking and the emergence of order is one of the most fascinating phenomena in condensed matter physics. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density-wave systems. Exploiting states of matter far from equilibrium can provide even more striking routes to symmetry-lowered, ordered states. Here, we demonstrate for the case of elemental chromium that moderate ultrafast photoexcitation can transiently enhance the charge-density-wave (CDW) amplitude by up to 30% above its equilibrium value, while strong excitations lead to an oscillating, large-amplitude CDW state that persists above the equilibrium transition temperature. Both effects result from dynamic electron-phonon interactions, providing an efficient mechanism to selectively transform a broad excitation of the electronic order into a well-defined, long-lived coherent lattice vibration. This mechanism may be exploited to transiently enhance order parameters in other systems with coupled degrees of freedom.
Gravitationally induced quantum transitions
NASA Astrophysics Data System (ADS)
Landry, A.; Paranjape, M. B.
2016-06-01
In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω . The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as t2. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of 1.06 ×10-5, and hence with a million ultracold neutrons, one should be able to observe transitions.
Global oscillation amplitudes excited by the Jupiter-comet collision
NASA Technical Reports Server (NTRS)
Lee, U.; Van Horn, H. M.
1994-01-01
The energy released during the collision of fragments of comet Shoemaker-Levy 9 with Jupiter in 1994 July may excite a spectrum of global oscillation modes. We estimate the maximum amplitudes to which the p-modes, discontinuity modes, inertial modes, and r-modes can be excited by assuming that the full kinetic energy of the fragment, which we take to be 10(exp 30) ergs, is converted into the energy of each individual mode. We have used two realistics Jovian models as the basis for our estimates: one with and one without the predicted 'plasma phase transition' (PPT) of hydrogen. A density discontinuity in the planet's hydrogen-helium envelope is associated with the PPT. We find that high-frequency p-modes, with periods approximately less than 15 minutes, may be excited to sufficiently large amplitudes to be observable as Doppler shifts (velocity amplitudes approximately greater than serveral m/s) or temperature variations (delta(T) approximately greater than 0.01 K) at the planetary surface. Inertial modes may also be observable. If the PPT exists in Jupiter, inertial modes with periods approximately 8 hr or approximately 2.2 days trapped in the surface region of the planet, above the PPT, may be detectable as temperature fluctuations of order delta(T) approximately 0.01 K. Inertial modes with periods of order 8-8.5 hr appear to be particularly strongly excited if the PPT exists. If the PPT does not exist in Jupiter, intertial modes with periods approximately 8-8.5 hr have much lower amplitudes. In this case, inertial modes with periods longer than approximately 18 hr may produce temperature fluctuations of order delta(T) approximately 0.01 K. Discontinuity modes associated with the PPT and r-modes unfortunately may not reach observable amplitudes.
Off-shell amplitudes and Grassmannians
NASA Astrophysics Data System (ADS)
Bork, L. V.; Onishchenko, A. I.
2017-09-01
The Grassmannian representation for gauge-invariant amplitudes for arbitrary number of legs with one of them being off-shell is derived for the case of N = 4 SYM. The obtained formula are successfully checked against known BCFW results for MHV n , NMHV4 and NMHV5 amplitudes.
BCFW construction of the Veneziano amplitude
NASA Astrophysics Data System (ADS)
Fotopoulos, Angelos
2011-06-01
In this paper we demonstrate how one can compute the Veneziano amplitude for bosonic string theory using the Britto-Cachazo-Feng-Witten method. We use an educated ansatz for the cubic amplitude of two tachyons and an arbitrary level string state.
Formant Amplitude of Children with Down's Syndrome.
ERIC Educational Resources Information Center
Pentz, Arthur L., Jr.
1987-01-01
The sustained vowel sounds of 14 noninstitutionalized 7- to 10-year-old children with Down's syndrome were analyzed acoustically for vowel formant amplitude levels. The subjects with Down's syndrome had formant amplitude intensity levels significantly lower than those of a similar group of speakers without Down's syndrome. (Author/DB)
Amplitude image processing by diffractive optics.
Cagigal, Manuel P; Valle, Pedro J; Canales, V F
2016-02-22
In contrast to the standard digital image processing, which operates over the detected image intensity, we propose to perform amplitude image processing. Amplitude processing, like low pass or high pass filtering, is carried out using diffractive optics elements (DOE) since it allows to operate over the field complex amplitude before it has been detected. We show the procedure for designing the DOE that corresponds to each operation. Furthermore, we accomplish an analysis of amplitude image processing performances. In particular, a DOE Laplacian filter is applied to simulated astronomical images for detecting two stars one Airy ring apart. We also check by numerical simulations that the use of a Laplacian amplitude filter produces less noisy images than the standard digital image processing.
Magnetospheric chorus - Amplitude and growth rate
NASA Technical Reports Server (NTRS)
Burtis, W. J.; Helliwell, R. A.
1975-01-01
A new study of the amplitude of magnetospheric chorus with 1966-1967 data from the Stanford University/Stanford Research Institute VLF receivers on Ogo 1 and Ogo 3 has confirmed the band-limited character of magnetospheric chorus in general and the double-banding of near-equatorial chorus. Chorus amplitude tended to be inversely correlated with frequency, implying lower intensities at lower L values. Individual chorus emissions often showed a characteristic amplitude variation, with rise times of 10 to 300 ms, a short duration at peak amplitude, and decay times of 100 to 3000 msec. Growth was often approximately exponential, with rates from 200 to nearly 2000 dB/sec. Rate of change of frequency was found in many cases to be independent of emission amplitude, in agreement with the cyclotron feedback theory of chorus (Helliwell, 1967, 1970).
Phase coherence and pairing amplitude in photo-excited superconductors
NASA Astrophysics Data System (ADS)
Perfetti, Luca; Piovera, Christian; Zhang, Zailan
2016-05-01
New data on Bi2Sr2CaCu2O8+δ (Bi2212) reveal interesting aspects of photoexcited superconductors. The electrons dynamics show that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop of electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behavior of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic mean-free path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude.
Color-kinematics duality for QCD amplitudes
NASA Astrophysics Data System (ADS)
Johansson, Henrik; Ochirov, Alexander
2016-01-01
We show that color-kinematics duality is present in tree-level amplitudes of quantum chromodynamics with massive flavored quarks. Starting with the color structure of QCD, we work out a new color decomposition for n-point tree amplitudes in a reduced basis of primitive amplitudes. These primitives, with k quark-antiquark pairs and ( n - 2 k) gluons, are taken in the ( n - 2)! /k! Melia basis, and are independent under the color-algebra Kleiss-Kuijf relations. This generalizes the color decomposition of Del Duca, Dixon, and Maltoni to an arbitrary number of quarks. The color coefficients in the new decomposition are given by compact expressions valid for arbitrary gauge group and representation. Considering the kinematic structure, we show through explicit calculations that color-kinematics duality holds for amplitudes with general configurations of gluons and massive quarks. The new (massive) amplitude relations that follow from the duality can be mapped to a well-defined subset of the familiar BCJ relations for gluons. They restrict the amplitude basis further down to ( n - 3)!(2 k - 2) /k! primitives, for two or more quark lines. We give a decomposition of the full amplitude in that basis. The presented results provide strong evidence that QCD obeys the color-kinematics duality, at least at tree level. The results are also applicable to supersymmetric and D-dimensional extensions of QCD.
Amplitude- and rise-time-compensated filters
Nowlin, Charles H.
1984-01-01
An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.
Hidden simplicity of gauge theory amplitudes
NASA Astrophysics Data System (ADS)
Drummond, J. M.
2010-11-01
These notes were given as lectures at the CERN Winter School on Supergravity, Strings and Gauge Theory 2010. We describe the structure of scattering amplitudes in gauge theories, focussing on the maximally supersymmetric theory to highlight the hidden symmetries which appear. Using the Britto, Cachzo, Feng and Witten (BCFW) recursion relations we solve the tree-level S-matrix in \\ {N}=4 super Yang-Mills theory and describe how it produces a sum of invariants of a large symmetry algebra. We review amplitudes in the planar theory beyond tree level, describing the connection between amplitudes and Wilson loops, and discuss the implications of the hidden symmetries.
A recursion relation for gravity amplitudes
NASA Astrophysics Data System (ADS)
Bedford, James; Brandhuber, Andreas; Spence, Bill; Travaglini, Gabriele
2005-08-01
Britto, Cachazo and Feng have recently derived a recursion relation for tree-level scattering amplitudes in Yang-Mills. This relation has a bilinear structure inherited from factorisation on multi-particle poles of the scattering amplitudes—a rather generic feature of field theory. Motivated by this, we propose a new recursion relation for scattering amplitudes of gravitons at tree level. Using this, we derive a new general formula for the MHV tree-level scattering amplitude for n gravitons. Finally, we comment on the existence of recursion relations in general field theories.
Phase and amplitude errors in FM radars
NASA Astrophysics Data System (ADS)
Griffiths, Hugh D.
The constraints on phase and amplitude errors are determined for various types of FM radar by calculating the range sidelobe levels on the point target response due to the phase and amplitude modulation of the target echo. It is shown that under certain circumstances the constraints on phase linearity appropriate for conventional pulse compression radars are unnecessarily stringent, and quite large phase errors can be tolerated provided the relative delay of the local oscillator with respect to the target echo is small compared with the periodicity of the phase error characteristic. The constraints on amplitude flatness, however, are severe under almost all circumstances.
A link representation for gravity amplitudes
NASA Astrophysics Data System (ADS)
He, Song
2013-10-01
We derive a link representation for all tree amplitudes in supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL( k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.
Amplitude dynamics favors synchronization in complex networks
Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia
2016-01-01
In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics. PMID:27108847
Stable ac phase and amplitude comparator
NASA Technical Reports Server (NTRS)
Bruce, H. P.
1967-01-01
Stable ac phase and amplitude comparator detects excessive vehicle maneuvering or vibration. It has phase demodulation, low-pass filter, and multiple threshold-setting capability designed specifically for low drifts over a wide range of temperatures.
Pion distribution amplitude from lattice QCD
NASA Astrophysics Data System (ADS)
Zhang, Jian-Hui; Chen, Jiunn-Wei; Ji, Xiangdong; Jin, Luchang; Lin, Huey-Wen
2017-05-01
We present the first lattice-QCD calculation of the pion distribution amplitude using the large-momentum effective field theory (LaMET) approach, which allows us to extract light cone parton observables from a Euclidean lattice. The mass corrections needed to extract the pion distribution amplitude from this approach are calculated to all orders in mπ2/Pz2 . We also implement the Wilson-line renormalization which is crucial to remove the power divergences in this approach, and find that it reduces the oscillation at the end points of the distribution amplitude. Our exploratory result at 310-MeV pion mass favors a single-hump form broader than the asymptotic form of the pion distribution amplitude.
The periods and amplitudes of TU Cas
NASA Technical Reports Server (NTRS)
Hodson, S. W.; Cox, A. N.
1980-01-01
Light curve observations of the double-mode Cepheid TU Cas obtained by 10 different sets of observers on several photometric systems over a time span of 67 years were carefully studied to determine the fundamental and first overtone periods and their amplitudes on the V magnitude scale. The presence of a second overtone radial pulsation is discussed, and it is concluded that a previous detection of this mode was spurious due to the lack of a proper zero point correction for two groups of observations. The amplitudes of the two modes are shown to possibly vary during the entire observing period with the fundamental mode amplitude of 0.69 + or - 0.03 and the overtone amplitude decreasing about 0.2 or 0.3 magnitude. If this Cepheid displays the two pulsation modes because it is mode switching, this switching time scale might be less than a hundred years.
Amplitude dynamics favors synchronization in complex networks
NASA Astrophysics Data System (ADS)
Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia
2016-04-01
In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics.
Large Amplitude Oscillations of a Double Pendulum
NASA Astrophysics Data System (ADS)
Gerres, Jeffrey M.; Jacobs, Robert M.; Kasun, Sara F.; Bacon, Margaret E.; Nagolu, Chakravarthi M.; Owens, Erin L.; Siehl, Kevin F.; Thomsen, Marshall; Troyer, Jon S.
2008-03-01
The nature of the normal modes of oscillation in the small angle regime of a double pendulum is well established. However, for large amplitude oscillations, a closed form solution of the differential equations of motion does not exist. Using Lagrange formalism, we explore both the in-phase and out-of-phase normal modes of oscillation of a double pendulum as a function of the mass ratio of the two bobs and their initial angular positions. We conduct the analysis using MatLab, where we initially verify our code in the known small amplitude limit. Among our results we find that certain symmetries between the in-phase and out-of-phase normal modes that exist in the small amplitude limit are no longer present at large amplitudes.
Virtuality and transverse momentum dependence of the pion distribution amplitude
Radyushkin, Anatoly V.
2016-03-08
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ → π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O (0,z)) describing a hadron with momentum p. Treated as functions of (pz) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ(x,σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) ψ(x, k), and writemore » it in terms of VDA Φ(x,σ). The results of covariant calculations, written in terms of Φ(x, σ) are converted into expressions involving ψ(x, k). Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor. Furthermore, we discuss how one can generate high-k tails from primordial soft distributions.« less
Virtuality and transverse momentum dependence of the pion distribution amplitude
Radyushkin, Anatoly V.
2016-03-08
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ → π^{0} at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O (0,z)) describing a hadron with momentum p. Treated as functions of (pz) and z^{2}, they are parametrized through virtuality distribution amplitudes (VDA) Φ(x,σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z^{2}. For intervals with z^{+} = 0, we introduce the transverse momentum distribution amplitude (TMDA) ψ(x, k), and write it in terms of VDA Φ(x,σ). The results of covariant calculations, written in terms of Φ(x, σ) are converted into expressions involving ψ(x, k). Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor. Furthermore, we discuss how one can generate high-k tails from primordial soft distributions.
Virtuality and transverse momentum dependence of the pion distribution amplitude
NASA Astrophysics Data System (ADS)
Radyushkin, A. V.
2016-03-01
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ →π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators [in the simplest case, bilocal O (0 ,z ) ] describing a hadron with momentum p . Treated as functions of (p z ) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ (x ,σ ) , with x being Fourier conjugate to (p z ) and σ Laplace conjugate to z2. For intervals with z+=0 , we introduce the transverse momentum distribution amplitude (TMDA) Ψ (x ,k⊥), and write it in terms of VDA Φ (x ,σ ). The results of covariant calculations, written in terms of Φ (x ,σ ), are converted into expressions involving Ψ (x ,k⊥). Starting with scalar toy models, we extend the analysis onto the case of spin-1 /2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BABAR and BELLE) data on the pion transition form factor. We also discuss how one can generate high-k⊥ tails from primordial soft distributions.
Quartic Amplitudes for Minkowski Higher Spin
NASA Astrophysics Data System (ADS)
Bengtsson, Anders K. H.
The old problem of finding general quartic interaction terms between fields of higher helicities on the light-front is discussed from the point of view of calculating the corresponding amplitudes directly from the cubic vertices using BCFW recursion. Amplitude based no-go results that has appeared in the literature are reviewed and discussed and it is pointed out how they may perhaps be circumvented.
Amplitude metrics for cellular circadian bioluminescence reporters.
St John, Peter C; Taylor, Stephanie R; Abel, John H; Doyle, Francis J
2014-12-02
Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary
Seismic directional beamforming using cosine amplitude distribution
NASA Astrophysics Data System (ADS)
Jiang, T.; Xu, X.; Song, J.; Jia, H.; Ge, L.
2013-12-01
o improve the signal-to-noise ratio in seismic exploration, we studied the method of time domain seismic beam-forming based on receiver array (TSBBRA). TSBBRA is useful to extract reflected waves from some target layers and decrease noise from other direction. When noise is strong enough, the control parameter of the method of TSBBRA need to be increased. It means that we have to use more raw records to form a directional seismic record. Therefore, the signal energy in beam is much denser, and the beam becomes narrower accordingly. When the beam can not cover the receiver array, the signal-to-noise ratios in different traces are quite unbalanced and average quality of data probably is still quite low. Therefore, this paper proposes seismic directional beamforming using the cosine amplitude distribution (SDBCAD). SDBCAD can adjust seismic beam shape by introducing cosine amplitude distribution, an amplitude weighting method, in the procedure of beamforming. We studied cosine amplitude weighting function, analyzed the characteristics of uniform and cosine amplitude distribution in beamforming, and compared directivity of beams from the two kind of amplitude pattern. It shows that the main beam of cosine-weighted amplitude is different from uniform distribution. The coverage of main beam from SDBCAD is wider than uniform amplitude, and the width of beam is varied with different number of cosine order. So we simulated the seismic raw record, and used TSBBRA and SDBCAD to process simulated data at the receiving array. The results show that SDBCAD can broaden directional beam, and the main beam from SDBCAD can cover the entire traces instead of partial coverage in TSBBRA. The average signal-to-noise ratio increased 0.2~4.5dB. It concludes that SDBCAD is competent to stretch beam reasonable, and it is useful to boost signal-to-noise ratio when beam from TSBBRA is too narrow to illuminate receiver array properly. Updated results will be presented at the meeting.
Nucleon Distribution Amplitudes from Lattice QCD
Goeckeler, Meinulf; Kaltenbrunner, Thomas; Warkentin, Nikolaus; Horsley, Roger; Zanotti, James M.; Nakamura, Yoshifumi; Pleiter, Dirk; Schierholz, Gerrit; Rakow, Paul E. L.; Schaefer, Andreas; Stueben, Hinnerk
2008-09-12
We calculate low moments of the leading-twist and next-to-leading-twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature.
Amplitude Metrics for Cellular Circadian Bioluminescence Reporters
St. John, Peter C.; Taylor, Stephanie R.; Abel, John H.; Doyle, Francis J.
2014-01-01
Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary
Bootstrapping One-Loop QCD Amplitudes
Berger, Carola F.; /SLAC
2006-09-08
We review the recently developed bootstrap method for the computation of high-multiplicity QCD amplitudes at one loop. We illustrate the general algorithm step by step with a six-point example. The method combines (generalized) unitarity with on-shell recursion relations to determine the not cut-constructible, rational terms of these amplitudes. Our bootstrap approach works for arbitrary configurations of gluon helicities and arbitrary numbers of external legs.
Feynman amplitudes and limits of heights
NASA Astrophysics Data System (ADS)
Amini, O.; Bloch, S. J.; Burgos Gil, J. I.; Fresán, J.
2016-10-01
We investigate from a mathematical perspective how Feynman amplitudes appear in the low-energy limit of string amplitudes. In this paper, we prove the convergence of the integrands. We derive this from results describing the asymptotic behaviour of the height pairing between degree-zero divisors, as a family of curves degenerates. These are obtained by means of the nilpotent orbit theorem in Hodge theory.
Vowel identification by amplitude and phase contrast.
Molis, Michelle R; Diedesch, Anna; Gallun, Frederick; Leek, Marjorie R
2013-02-01
Vowel identification is largely dependent on listeners' access to the frequency of two or three peaks in the amplitude spectrum. Earlier work has demonstrated that, whereas normal-hearing listeners can identify harmonic complexes with vowel-like spectral shapes even with very little amplitude contrast between "formant" components and remaining harmonic components, listeners with hearing loss require greater amplitude differences. This is likely the result of the poor frequency resolution that often accompanies hearing loss. Here, we describe an additional acoustic dimension for emphasizing formant versus non-formant harmonics that may supplement amplitude contrast information. The purpose of this study was to determine whether listeners were able to identify "vowel-like" sounds using temporal (component phase) contrast, which may be less affected by cochlear loss than spectral cues, and whether overall identification improves when congruent temporal and spectral information are provided together. Five normal-hearing and five hearing-impaired listeners identified three vowels over many presentations. Harmonics representing formant peaks were varied in amplitude, phase, or a combination of both. In addition to requiring less amplitude contrast, normal-hearing listeners could accurately identify the sounds with less phase contrast than required by people with hearing loss. However, both normal-hearing and hearing-impaired groups demonstrated the ability to identify vowel-like sounds based solely on component phase shifts, with no amplitude contrast information, and they also showed improved performance when congruent phase and amplitude cues were combined. For nearly all listeners, the combination of spectral and temporal information improved identification in comparison to either dimension alone.
Twistor-strings and gravity tree amplitudes
NASA Astrophysics Data System (ADS)
Adamo, Tim; Mason, Lionel
2013-04-01
Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.
On statistics of electric field amplitudes in Langmuir turbulence
NASA Astrophysics Data System (ADS)
Voshchepynets, Andrii; Volokitin, Alexander; Krasnoselskikh, Vladimir; Krafft, Catherine
2017-04-01
corresponding scaling parameter decreases until a universal probability distribution is reached, what is realized when the wave decay processes are sufficiently strong. This distribution is analogous to that obtained for a quasi-homogeneous plasma. Such exponential type of distribution is a specific signature of transition states in the Langmuir turbulence. Third, the square of the statistical field amplitude maximum is found to be proportional to the average energy of the Langmuir waves.
Amplitude Modulations of Acoustic Communication Signals
NASA Astrophysics Data System (ADS)
Turesson, Hjalmar K.
2011-12-01
In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a
NASA Astrophysics Data System (ADS)
Kumar, R.; Narayanan, R.; Prasad, Awadhesh
2014-12-01
Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.
Kumar, R.; Narayanan, R.; Prasad, Awadhesh
2014-12-15
Hysteresis in amplitudes of the self-excited oscillations of the floating potential and discharge current is observed in an unmagnetized co-axial electrode-geometry DC glow discharge plasma system. The nonlinearities of these oscillations are studied using standard dynamical analysis tools. The characterization revealed the transition of low-amplitude high-frequency period-n oscillations to a large amplitude low frequency period-1 oscillations through a chaotic intermediate route. The transition of the low amplitude, high frequency period-n oscillations to chaotic type is observed to be linked to the dynamical change in the plasma system, i.e., after a negative differential resistance (NDR) region, whereas the transition from chaotic to period-1 is observed to be linked to a discharge current threshold.
The finite-amplitude behavior of the Joule mode under astrophysical conditions
NASA Technical Reports Server (NTRS)
Bodo, G.; Massaglia, S.; Rosner, R.; Ferrari, A.
1991-01-01
Magnetized astrophysical plasmas reveal a great deal of structure when spatially resolved. One possible explanation for this structuring is based on the existence of filamenting instabilities driven by radiation. In this paper, previous linear calculations are extended by considering the weakly nonlinear (finite-amplitude) development of such filamenting instabilities in magnetized unstratified plasmas. It is shown that under most conditions these instabilities (in particular, the Jouse model) are unstable at finite amplitude; in particular, in the temperature and plasma-beta domains characteristic of, for example, much of the solar transition region, these modes - which can be linearly stable under these conditions - become unstable to finite-amplitude perturbations. The relevance of this to the problem of heating the solar low transition region by current dissipation is discussed.
Periodic amplitude variations in Jovian continuum radiation
NASA Technical Reports Server (NTRS)
Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.
1986-01-01
An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.
Analytic representations of Yang-Mills amplitudes
NASA Astrophysics Data System (ADS)
Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.; Feng, Bo
2016-12-01
Scattering amplitudes in Yang-Mills theory can be represented in the formalism of Cachazo, He and Yuan (CHY) as integrals over an auxiliary projective space-fully localized on the support of the scattering equations. Because solving the scattering equations is difficult and summing over the solutions algebraically complex, a method of directly integrating the terms that appear in this representation has long been sought. We solve this important open problem by first rewriting the terms in a manifestly Möbius-invariant form and then using monodromy relations (inspired by analogy to string theory) to decompose terms into those for which combinatorial rules of integration are known. The result is the foundations of a systematic procedure to obtain analytic, covariant forms of Yang-Mills tree-amplitudes for any number of external legs and in any number of dimensions. As examples, we provide compact analytic expressions for amplitudes involving up to six gluons of arbitrary helicities.
Cut-constructible part of QCD amplitudes
Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo
2006-05-15
Unitarity cuts are widely used in analytic computation of loop amplitudes in gauge theories such as QCD. We expand upon the technique introduced in hep-ph/0503132 to carry out any finite unitarity cut integral. This technique naturally separates the contributions of bubble, triangle and box integrals in one-loop amplitudes and is not constrained to any particular helicity configurations. Loop momentum integration is reduced to a sequence of algebraic operations. We discuss the extraction of the residues at higher-order poles. Additionally, we offer concise algebraic formulas for expressing coefficients of three-mass triangle integrals. As an application, we compute all remaining coefficients of bubble and triangle integrals for nonsupersymmetric six-gluon amplitudes.
Amplitude-coded color doppler: clinical applications.
Turetschek, K; Kollmann, C; Dorffner, R; Wunderbaldinger, P; Mostbeck, G
1999-01-01
Amplitude-coded color Doppler sonography (ACD) has become an useful adjunct to gray-scale US and conventional color Doppler sonography (CD) for the assessment of vascular diseases and pathologic conditions that might affect or alter tissue vascularization or perfusion. Basically, all US units that generate conventional color Doppler information through autocorrelation technique are capable of displaying ACD. This technique is also referred to as power Doppler, amplitude-mode color Doppler US, color Doppler energy (CDE), or US angiography. Amplitude-coded color Doppler sonography has already emerged as a valuable adjunct to conventional CD, particularly for evaluating flow in parts of the body where CD signal is weak because of slow flow, small blood vessels, or both.
A description of seismic amplitude techniques
NASA Astrophysics Data System (ADS)
Shadlow, James
2014-02-01
The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.
Modified π π amplitude with σ pole
NASA Astrophysics Data System (ADS)
Bydžovský, P.; Kamiński, R.; Nazari, V.
2014-12-01
A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (π π , K K ¯, and η η ) and P (π π , ρ 2 π , and ρ σ ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the π π threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or σ ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the σ pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, π π amplitudes with a heavy and broad σ meson without changing of their original mathematical structure.
Nonlinear (super)symmetries and amplitudes
NASA Astrophysics Data System (ADS)
Kallosh, Renata
2017-03-01
There is an increasing interest in nonlinear supersymmetries in cosmological model building. Independently, elegant expressions for the all-tree amplitudes in models with nonlinear symmetries, like D3 brane Dirac-Born-Infeld-Volkov-Akulov theory, were recently discovered. Using the generalized background field method we show how, in general, nonlinear symmetries of the action, bosonic and fermionic, constrain amplitudes beyond soft limits. The same identities control, for example, bosonic E 7(7) scalar sector symmetries as well as the fermionic goldstino symmetries.
Coherent quantum states from classical oscillator amplitudes
NASA Astrophysics Data System (ADS)
Briggs, John S.; Eisfeld, Alexander
2012-05-01
In the first days of quantum mechanics Dirac pointed out an analogy between the time-dependent coefficients of an expansion of the Schrödinger equation and the classical position and momentum variables solving Hamilton's equations. Here it is shown that the analogy can be made an equivalence in that, in principle, systems of classical oscillators can be constructed whose position and momenta variables form time-dependent amplitudes which are identical to the complex quantum amplitudes of the coupled wave function of an N-level quantum system with real coupling matrix elements. Hence classical motion can reproduce quantum coherence.
Constructing Chaotic Systems with Total Amplitude Control
NASA Astrophysics Data System (ADS)
Li, Chunbiao; Sprott, Julien Clinton; Yuan, Zeshi; Li, Hongtao
A general method is introduced for controlling the amplitude of the variables in chaotic systems by modifying the degree of one or more of the terms in the governing equations. The method is applied to the Sprott B system as an example to show its flexibility and generality. The method may introduce infinite lines of equilibrium points, which influence the dynamics in the neighborhood of the equilibria and reorganize the basins of attraction, altering the multistability. However, the isolated equilibrium points of the original system and their stability are retained with their basic properties. Electrical circuit implementation shows the convenience of amplitude control, and the resulting oscillations agree well with results from simulation.
Topographic quantitative EEG amplitude in recovered alcoholics.
Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S
1992-05-01
Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.
Amplitude Models for Discrimination and Yield Estimation
Phillips, William Scott
2016-09-01
This seminar presentation describes amplitude models and yield estimations that look at the data in order to inform legislation. The following points were brought forth in the summary: global models that will predict three-component amplitudes (R-T-Z) were produced; Q models match regional geology; corrected source spectra can be used for discrimination and yield estimation; three-component data increase coverage and reduce scatter in source spectral estimates; three-component efforts must include distance-dependent effects; a community effort on instrument calibration is needed.
Dual amplitude pulse generator for radiation detectors
Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.
2001-01-01
A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.
Singularity structure of maximally supersymmetric scattering amplitudes.
Arkani-Hamed, Nima; Bourjaily, Jacob L; Cachazo, Freddy; Trnka, Jaroslav
2014-12-31
We present evidence that loop amplitudes in maximally supersymmetric (N=4) Yang-Mills theory (SYM) beyond the planar limit share some of the remarkable structures of the planar theory. In particular, we show that through two loops, the four-particle amplitude in full N=4 SYM has only logarithmic singularities and is free of any poles at infinity--properties closely related to uniform transcendentality and the UV finiteness of the theory. We also briefly comment on implications for maximal (N=8) supergravity theory (SUGRA).
Amplitude for N-Gluon Superstring Scattering
Stieberger, Stephan; Taylor, Tomasz R.
2006-11-24
We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope {alpha}{sup '}. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in {alpha}{sup '}, for the so-called maximally helicity violating configurations, with N=4, 5 and N=6. We also obtain the leading O({alpha}{sup '2}) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.
Amplitude for N-gluon superstring scattering.
Stieberger, Stephan; Taylor, Tomasz R
2006-11-24
We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope alpha'. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in alpha', for the so-called maximally helicity violating configurations, with N = 4, 5 and N = 6. We also obtain the leading O(alpha '2) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.
Numerical simulation of transitional flow
NASA Technical Reports Server (NTRS)
Biringen, Sedat
1986-01-01
The applicability of active control of transition by periodic suction-blowing is investigated via direct simulations of the Navier-Stokes equations. The time-evolution of finite-amplitude disturbances in plane channel flow is compared in detail with and without control. The analysis indicates that, for relatively small three-dimensional amplitudes, a two-dimensional control effectively reduces disturbance growth rates even for linearly unstable Reynolds numbers. After the flow goes through secondary instability, three-dimensional control seems necessary to stabilize the flow. An investigation of the temperature field suggests that passive temperature contamination is operative to reflect the flow dynamics during transition.
Mode Transition of Trichel pulses
NASA Astrophysics Data System (ADS)
Kexin, Zhang; Yongjun, Piao; Miao, Tang; Jingfeng, Tang; Liqiu, Wei; Chaohai, Zhang
2015-11-01
The trichel pulse is a typical kind of negative corona current observed in electronegative gases. In this work, stochastic behavior of the trichel pulse has been investigated. The experiment is performed in a negative corona reactor consisting of a stainless steel pin and a stainless steel powered by a dc high voltage source. The characteristic parameters distributions of corona current pulses, including the amplitude, rise time, half-wave time, and repetition frequency, are analyzed statistically. The results show there is a mode transition during the period of voltage increasing. This transition process happens in a certain voltage region, and change of pulse amplitude is the main difference between the two modes.
Active Control of Transition and Turbulence
NASA Technical Reports Server (NTRS)
Maestrello, Lucio
1987-01-01
Two active means of manipulating boundary-layer flow developed, one controlling laminar-to-turbulent transition, other controlling amplitude of turbulent fluctuation. Purpose to control skin-friction drag over surfaces inside inlets and ducts. Resulting turbulence downstream has lower skin-friction drag than equivalent flow developing over same surfaces in absence of intervention. Heating strips trigger turbulence while transition amplitude and bandwidth controlled by acoustic signal.
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Baldini Ferroli, R.; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Cibinetto, G.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Dou, Z. L.; Du, S. X.; Duan, P. F.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Farinelli, R.; Fava, L.; Fedorov, O.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. L.; Gao, X. Y.; Gao, Y.; Gao, Z.; Garzia, I.; Goetzen, K.; Gong, L.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Hao, X. Q.; Harris, F. A.; He, K. L.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. S.; Huang, J. S.; Huang, X. T.; Huang, X. Z.; Huang, Y.; Huang, Z. L.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. W.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kiese, P.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kupsc, A.; Kühn, W.; Lange, J. S.; Lara, M.; Larin, P.; Leithoff, H.; Leng, C.; Li, C.; Li, Cheng; Li, D. M.; Li, F.; Li, F. Y.; Li, G.; Li, H. B.; Li, H. J.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, Q. Y.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. M.; Li, X. N.; Li, X. Q.; Li, Y. B.; Li, Z. B.; Liang, H.; Liang, J. J.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B.; Liu, B. J.; Liu, C. X.; Liu, D.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. B.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, T.; Ma, X. N.; Ma, X. Y.; Ma, Y. M.; Maas, F. E.; Maggiora, M.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Mezzadri, G.; Min, J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales Morales, C.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, Y.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Poling, R.; Prasad, V.; Qi, H. R.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Rosner, Ch.; Ruan, X. D.; Sarantsev, A.; Savrié, M.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Shi, M.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. H.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, B. L.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, S. G.; Wang, W.; Wang, W. P.; Wang, X. F.; Wang, Y.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, L. J.; Wu, Z.; Xia, L.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, H.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, J. J.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zeng, Z.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, S. Q.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. N.; Zhang, Y. T.; Zhang, Yu; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zotti, L.; Zou, B. S.; Zou, J. H.; Besiii Collaboration
2017-04-01
Using 106 ×1 06 ψ (3686 ) events collected with the BESIII detector, we measure multipole amplitudes for the decay ψ (3686 )→γ χc 1 ,2→γ γ J /ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for ψ (3686 )→γ χc 1 ,2→γ γ J /ψ and the normalized electric-octupole amplitudes for ψ (3686 )→γ χc 2 , χc 2→γ J /ψ are determined. The M2 amplitudes for ψ (3686 )→γ χc 1 and χc 1 ,2→γ J /ψ are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of ψ (3686 ) and J /ψ decays to χc 1 ,2 , b21/b22=1.35 ±0.72 and a21/a22=0.617 ±0.083 , which agree well with theoretical expectations. By considering the multipole contributions of χc 1 ,2, we measure the product branching fractions for the cascade decays ψ (3686 )→γ χc 0 ,1 ,2→γ γ J /ψ and search for the process ηc(2 S )→γ J /ψ through ψ (3686 )→γ ηc(2 S ) . The product branching fraction for ψ (3686 )→γ χc 0→γ γ J /ψ is 3 σ larger than published measurements, while those of ψ (3686 )→γ χc 1 ,2→γ γ J /ψ are consistent. No significant signal for the decay ψ (3686 )→γ ηc(2 S )→γ γ J /ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.
Active control of transition by periodic suction-blowing
NASA Technical Reports Server (NTRS)
Biringen, S.
1984-01-01
A numerical study is conducted to investigate a new method of transition control by periodic suction-blowing. It is shown that significant reduction in the amplitudes of two- and three-dimensional finite-amplitude disturbances can be obtained by the application of this method to transition in plane channel flow.
Travel-Time and Amplitude Sensitivity Kernels
2011-09-01
amplitude sensitivity kernels shown in the lower panels concentrate about the corresponding eigenrays . Each 3D kernel exhibits a broad negative...in 2 and 3 dimensions have similar 11 shapes to corresponding travel-time sensitivity kernels (TSKs), centered about the respective eigenrays
Connected formulas for amplitudes in standard model
NASA Astrophysics Data System (ADS)
He, Song; Zhang, Yong
2017-03-01
Witten's twistor string theory has led to new representations of S-matrix in massless QFT as a single object, including Cachazo-He-Yuan formulas in general and connected formulas in four dimensions. As a first step towards more realistic processes of the standard model, we extend the construction to QCD tree amplitudes with massless quarks and those with a Higgs boson. For both cases, we find connected formulas in four dimensions for all multiplicities which are very similar to the one for Yang-Mills amplitudes. The formula for quark-gluon color-ordered amplitudes differs from the pure-gluon case only by a Jacobian factor that depends on flavors and orderings of the quarks. In the formula for Higgs plus multi-parton amplitudes, the massive Higgs boson is effectively described by two additional massless legs which do not appear in the Parke-Taylor factor. The latter also represents the first twistor-string/connected formula for form factors.
The CMU Baryon Amplitude Analysis Program
Matt Bellis
2007-10-01
The PWA group at Carnegie Mellon University has developed a comprehensive approach and analysis package for the purpose of extracting the amplitudes for photoproduced baryon resonances. The end goal is to identify any missing resonances that are predicted by the constituent quark model, but not definitively observed in experiments. The data comes from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab.
Consonant confusions in amplitude-expanded speech.
Freyman, R L; Nerbonne, G P
1996-12-01
The perceptual consequences of expanding the amplitude variations in speech were studied under conditions in which spectral information was obscured by signal correlated noise that had an envelope correlated with the speech envelope, but had a flat amplitude spectrum. The noise samples, created individually from 22 vowel-consonant-vowel nonsense words, were used as maskers of those words, with signal-to-noise ratios ranging from -15 to 0 dB. Amplitude expansion was by a factor of 3.0 in terms of decibels. In the first experiment, presentation level for speech peaks was 80 dB SPL. Consonant recognition performance for expanded speech by 50 listeners with normal hearing was as much as 30 percentage points poorer than for unexpanded speech and the types of errors were dramatically different, especially in the midrange of S-N ratios. In a second experiment presentation level was varied to determine whether reductions in consonant levels produced by expansion were responsible for the differences between conditions. Recognition performance for unexpanded speech at 40 dB SPL was nearly equivalent to that for expanded speech at 80 dB SPL. The error patterns obtained in these two conditions were different, suggesting that the differences between conditions in Experiment 1 were due largely to expanded amplitude envelopes rather than differences in audibility.
Scattering amplitudes for dark and bright excitons
NASA Astrophysics Data System (ADS)
Shiau, Shiue-Yuan; Combescot, Monique; Combescot, Roland; Dubin, François; Chang, Yia-Chung
2017-05-01
Using the composite boson many-body formalism that takes single-exciton states rather than free carrier states as a basis, we derive the integral equation fulfilled by the exciton-exciton effective scattering from which the role of fermion exchanges can be unraveled. For excitons made of (+/-1/2) -spin electrons and (+/-3/2) -spin holes, as in GaAs heterostructures, one major result is that most spin configurations lead to brightness-conserving scatterings with equal amplitude Δ, despite differences in the carrier exchanges involved. A brightness-changing channel also exists when two opposite-spin excitons scatter: dark excitons (2,-2) can end either in the same dark states with an amplitude Δe , or in opposite-spin bright states (1,-1) , with a different amplitude Δo , the number of carrier exchanges involved in these scatterings being even or odd, respectively. Another major result is that these amplitudes are linked by a striking relation, Δ_e+Δ_o=Δ , which has decisive consequence on exciton Bose-Einstein condensation. By using Born values, we show that the exciton condensate can be optically observed through a bright part when excitons have large dipole only, that is, when the electrons and holes are in two well-separated layers, as in current experiments.
Audio steganography by amplitude or phase modification
NASA Astrophysics Data System (ADS)
Gopalan, Kaliappan; Wenndt, Stanley J.; Adams, Scott F.; Haddad, Darren M.
2003-06-01
This paper presents the results of embedding short covert message utterances on a host, or cover, utterance by modifying the phase or amplitude of perceptually masked or significant regions of the host. In the first method, the absolute phase at selected, perceptually masked frequency indices was changed to fixed, covert data-dependent values. Embedded bits were retrieved at the receiver from the phase at the selected frequency indices. Tests on embedding a GSM-coded covert utterance on clean and noisy host utterances showed no noticeable difference in the stego compared to the hosts in speech quality or spectrogram. A bit error rate of 2 out of 2800 was observed for a clean host utterance while no error occurred for a noisy host. In the second method, the absolute phase of 10 or fewer perceptually significant points in the host was set in accordance with covert data. This resulted in a stego with successful data retrieval and a slightly noticeable degradation in speech quality. Modifying the amplitude of perceptually significant points caused perceptible differences in the stego even with small changes of amplitude made at five points per frame. Finally, the stego obtained by altering the amplitude at perceptually masked points showed barely noticeable differences and excellent data recovery.
The CMU Baryon Amplitude Analysis Program
NASA Astrophysics Data System (ADS)
Bellis, Matt
2007-05-01
The PWA group at Carnegie Mellon University has developed a comprehensive approach and analysis package for the purpose of extracting the amplitudes for photoproduced baryon resonances. The end goal is to identify any missing resonances that are predicted by the constituent quark model, but not definitively observed in experiments. The data comes from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab.
Particle Distribution Modification by Low Amplitude Modes
White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.
2009-08-28
Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.
Amplitude Frequency Response Measurement: A Simple Technique
ERIC Educational Resources Information Center
Satish, L.; Vora, S. C.
2010-01-01
A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…
Large Amplitude Patterns for Two Competing Species.
1980-06-01
scalar equation arising in population genetics . Mimura and Nishiura, [14], have obtained small amplitude spatial patterns for a system arising in...A nonlinear eigenvalue problem occuring in population genetics , preprint. [17] Peletier, L. A., Fife, P.: Nonlinear diffusion in population genetics . Arch
Holographic corrections to the Veneziano amplitude
NASA Astrophysics Data System (ADS)
Armoni, Adi; Ireson, Edwin
2017-08-01
We propose a holographic computation of the 2 → 2 meson scattering in a curved string background, dual to a QCD-like theory. We recover the Veneziano amplitude and compute a perturbative correction due to the background curvature. The result implies a small deviation from a linear trajectory, which is a requirement of the UV regime of QCD.
Amplitude Frequency Response Measurement: A Simple Technique
ERIC Educational Resources Information Center
Satish, L.; Vora, S. C.
2010-01-01
A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…
Amplitude of Supersonic Diffuser Flow Pulsations
NASA Technical Reports Server (NTRS)
Sterbentz, William H.; Davids, Joseph
1952-01-01
A theoretical method for evaluating the stability characteristics and the amplitude and the frequency of pulsation of ram-jet engines without heat addition is presented herein. Experimental verification of the theoretical results are included where data were available. Theory and experiment show that the pulsation amplitude of a high mass-flow-ratio diffuser having no cone surface flow separation increases with decreasing mass flow. The theoretical trends for changes in amplitude, frequency, and mean-pressure recovery with changes in plenum-chamber volume were experimentally confirmed. For perforated convergent-divergent-type diffusers, a stability hysteresis loop was predicted on the pressure-recovery mass-flow-ratio curve. At a given mean mass-flow ratio, the higher.value of mean pressure recovery corresponded to oscillatory flow in the diffuser while the lower branch was stable. This hysteresis has been observed experimentally. The theory indicates that for a ram-jet engine of given diameter, the amplitude of pulsation of a supersonic diffuser is increased by decreasing the relative size of the plenum chamber with respect to the diffuser volume down to a critical value at which oscillations cease. In the region of these critical values, the stable mass-flow range of the diffuser may be increased either by decreasing the combustion chamber volume or by increasing the length of the diffuser.
ABJM amplitudes and the positive orthogonal Grassmannian
NASA Astrophysics Data System (ADS)
Huang, Yu-tin; Wen, CongKao
2014-02-01
A remarkable connection between perturbative scattering amplitudes of four dimensional planar SYM, and the stratification of the positive Grassmannian, was revealed in the seminal work of Arkani-Hamed et al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities thereof, to the stratification of the positive orthogonal Grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG2 orthogonal Grassmannian to form a larger OG k , where 2 k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OG k that manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.
Quantitative laryngeal electromyography: turns and amplitude analysis.
Statham, Melissa McCarty; Rosen, Clark A; Nandedkar, Sanjeev D; Munin, Michael C
2010-10-01
Laryngeal electromyography (LEMG) is primarily a qualitative examination, with no standardized approach to interpretation. The objectives of our study were to establish quantitative norms for motor unit recruitment in controls and to compare with interference pattern analysis in patients with unilateral vocal fold paralysis (VFP). Retrospective case-control study We performed LEMG of the thyroarytenoid-lateral cricoarytenoid muscle complex (TA-LCA) in 21 controls and 16 patients with unilateral VFP. Our standardized protocol used a concentric needle electrode with subjects performing variable force TA-LCA contraction. To quantify the interference pattern density, we measured turns and mean amplitude per turn for ≥10 epochs (each 500 milliseconds). Logarithmic regression analysis between amplitude and turns was used to calculate slope and intercept. Standard deviation was calculated to further define the confidence interval, enabling generation of a linear-scale graphical "cloud" of activity containing ≥90% of data points for controls and patients. Median age of controls and patients was similar (50.7 vs. 48.5 years). In controls, TA-LCA amplitude with variable contraction ranged from 145-1112 μV, and regression analysis comparing mean amplitude per turn to root-mean-square amplitude demonstrated high correlation (R = 0.82). In controls performing variable contraction, median turns per second was significantly higher compared to patients (450 vs. 290, P = .002). We first present interference pattern analysis in the TA-LCA in healthy adults and patients with unilateral VFP. Our findings indicate that motor unit recruitment can be quantitatively measured within the TA-LCA. Additionally, patients with unilateral VFP had significantly reduced turns when compared with controls.
Optical factors influencing the amplitude of accommodation.
López-Alcón, Diego; Marín-Franch, Iván; Fernández-Sánchez, Vicente; López-Gil, Norberto
2016-09-23
The purpose of this work was to find plausible predictors among optical parameters that may explain the inter-individual differences in subjective amplitude of accommodation not explained by age. An exploratory multivariable regression analysis was carried out retrospectively on a dataset with 180 eyes from 97 subjects (ages ranged from 20 to 58years). Subjective amplitudes of accommodation were recorded with the use of a custom-made Badal system. A commercial aberrometer was used to obtain each eye's wavefront during the full range of accommodation. The plausible predictors under study were pupil diameter in the unaccommodated eye, its reduction with accommodation; fourth- and six-order Zernike spherical aberration, their reduction with accommodation, and subjective refraction. At a significance level of 0.05, only fourth- and sixth-order Zernike spherical aberration were found to be predictors of subjective amplitude of accommodation not explained by age, each explaining on their own less than 5% of the variance, and about 9% together. All other optical parameters explained less than 2%. Spherical aberration did not explain the greater variability for younger eyes than for older eyes. The remainder variability in amplitude of accommodation not explained by age or spherical aberration was about ±2.6D for 20year-old subjects, ±1.5D for 40year-old subjects, and about ±0.6D for 55year-old subjects. Optical factors do not seem to account for much of the inter-individual differences in subjective amplitude of accommodation. Most of the variability not explained by age must be due to anatomical differences and physiological, psychological, or other factors. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.
Large amplitude fluxional behaviour of elemental calcium under high pressure
Tse, J. S.; Desgreniers, S.; Ohishi, Y.; Matsuoka, T.
2012-01-01
Experimental evidences are presented showing unusually large and highly anisotropic vibrations in the “simple cubic” (SC) unit cell adopted by calcium over a broad pressure ranging from 30–90 GPa and at temperature as low as 40 K. X-ray diffraction patterns show a preferential broadening of the (110) Bragg reflection indicating that the atomic displacements are not isotropic but restricted to the [110] plane. The unusual observation can be rationalized invoking a simple chemical perspective. As the result of pressure-induced s → d transition, Ca atoms situated in the octahedral environment of the simple cubic structure are subjected to Jahn-Teller distortions. First-principles molecular dynamics calculations confirm this suggestion and show that the distortion is of dynamical nature as the cubic unit cell undergoes large amplitude tetragonal fluctuations. The present results show that, even under extreme compression, the atomic configuration is highly fluxional as it constantly changes. PMID:22523635
Single Polymer Dynamics under Large Amplitude Oscillatory Extensional (LAOE) Flow
NASA Astrophysics Data System (ADS)
Zhou, Yuecheng; Schroeder, Charles M.
Over the past two decades, advances in fluorescence imaging and particle manipulation have enabled the direct observation of single polymer dynamics in model flows such as shear flow and planar extensional flow. The vast majority of single polymer studies, however, has focused on chain dynamics using simple transient step forcing functions. In order to study single polymer dynamics in non-idealized model flows, there is a clear need to implement more complicated transient flow forcing functions. In bulk rheology, large amplitude oscillatory shear (LAOS) was widely used to study the linear and nonlinear viscoelasticity of materials, but not yet been applied to molecular rheology. In this work, we directly probe single polymer dynamics using oscillatory extensional flow in precisely controlled microfluidic devices. We are able to generate large and small amplitude sinusoidal oscillatory extensional flow in a cross-slot microfluidic device while imaging the conformational dynamics of a single polymer trapped at the stagnation point. In this flow, polymer chains are stretched, squeezed, and rotated between extensional/compressional axes in a highly dynamic and transient manner. Using this technique, we studied the dynamics and coil-stretch transition of a single λ-DNA as a function of the Weissenberg number (Wi) and Deborah number (De). Moreover, we use Brownian dynamics simulation to map a wide range of Pipkin space for polymers from linear steady-state conditions to non-linear unsteady-states. Our results reveal a critical Wi at the coil-stretch transition that is function of the De in LAOE flow. Department of Materials Science and Engineering.
NASA Astrophysics Data System (ADS)
Paulo, Álvaro San; García, Ricardo
2001-11-01
Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.
Stability of amplitude chimeras in oscillator networks
NASA Astrophysics Data System (ADS)
Tumash, L.; Zakharova, A.; Lehnert, J.; Just, W.; Schöll, E.
2017-01-01
We show that amplitude chimeras in ring networks of Stuart-Landau oscillators with symmetry-breaking nonlocal coupling represent saddle-states in the underlying phase space of the network. Chimera states are composed of coexisting spatial domains of coherent and of incoherent oscillations. We calculate the Floquet exponents and the corresponding eigenvectors in dependence upon the coupling strength and range, and discuss the implications for the phase-space structure. The existence of at least one positive real part of the Floquet exponents indicates an unstable manifold in phase space, which explains the nature of these states as long-living transients. Additionally, we find a Stuart-Landau network of minimum size N = 12 exhibiting amplitude chimeras.
Multilayered models for electromagnetic reflection amplitudes
NASA Technical Reports Server (NTRS)
Linlor, W. I.
1976-01-01
The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.
Constructing QCD one-loop amplitudes
Forde, Darren; /SLAC /UCLA
2008-02-22
In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 {var_epsilon}. The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally
Is DAMAs modulation amplitude changing with time?
NASA Astrophysics Data System (ADS)
Kelso, Chris
2016-06-01
If dark matter is composed of weakly interacting particles, Earth's orbital motion induces a small annual variation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a 9.3σ confidence level (CL) such an annual modulation in their event rate over two detector iterations, DAMA/NaI and DAMA/LIBRA, each with about 7 years of observations. We examine the nature of this modulation signal and find the modulation amplitude for the two detectors is inconsistent at the 3σ CL over 2-6 keVee. Such a time-dependence in the modulation amplitude is unexpected behavior for a dark matter signal, at least for dark matter halo morphologies consistent with the DAMA signal. We also find unusual behavior over the 5-6 keVee energy range that might indicate problems with the data.
Photon Counting Chirped Amplitude Modulation Ladar
2008-03-01
135 S. Taylor Ave., Room 103, Louisville, CO 80027-3025 14. ABSTRACT This work developed a method using Geiger - mode avalanche photodiode (GM-APD...effort to develop a method using Geiger - mode avalanche photodiode (GM-APD) photon counting detectors in the U.S. Army Research Laboratory’s chirped...architecture are discussed. 15. SUBJECT TERMS laser radar, ladar, avalanche photo-detectors, Geiger mode detectors, chirped amplitude modulation
Chiral extrapolation of SU(3) amplitudes
Ecker, Gerhard
2011-05-23
Approximations of chiral SU(3) amplitudes at NNLO are proposed to facilitate the extrapolation of lattice data to the physical meson masses. Inclusion of NNLO terms is essential for investigating convergence properties of chiral SU(3) and for determining low-energy constants in a controllable fashion. The approximations are tested with recent lattice data for the ratio of decay constants F{sub K}/F{sub {pi}}.
Automatic generation of tree level helicity amplitudes
NASA Astrophysics Data System (ADS)
Stelzer, T.; Long, W. F.
1994-11-01
The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.
Automatic generation of tree level helicity amplitudes
NASA Astrophysics Data System (ADS)
Stelzer, T.; Long, W. F.
1994-07-01
The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.
Amplitude calibration experiment for SIR-B
NASA Technical Reports Server (NTRS)
Held, D. N.; Ulaby, F. T.
1984-01-01
The objectives, approach, and expected results of the amplitude calibration experiment for the Shuttle Imaging Radar-B (SIR-B) are outlined. Specific objectives include: (1) the determination of the repeatability (stability) of the SIR-B; (2) the absolute and relative calibration of the system; and (3) the ground truth verification of the calibration accuracy using measurements made by a ground spectrometer and an airborne synthetic aperture radar.
Understanding the amplitudes of noise correlation measurements
Tsai, Victor C.
2011-01-01
Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.
Attenuation of ground-motion spectral amplitudes in southeastern Australia
Allen, T.I.; Cummins, P.R.; Dhu, T.; Schneider, J.F.
2007-01-01
A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 ??? M ??? 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low-frequency spectral amplitudes can be approximated by the coefficient of R-1.3 (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypocentral distance range, geometrical spreading is approximately R+0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source-receiver distance, having a geometrical spreading coefficient of R-1.6. The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)2 + 0.058 (log f)3 for frequencies 0.78 ??? f ??? 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) Models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations develooed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations
[Amplitude modulation in sound signals by mammals].
Nikol'skiĭ, A A
2012-01-01
Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.
Prominence Seismology Using Small Amplitude Oscillations
NASA Astrophysics Data System (ADS)
Oliver, Ramón
2009-12-01
Quiescent prominences can be modeled as thin slabs of cold, dense plasma embedded in the much hotter and rarer solar corona. Although their global shape is rather irregular, they are often characterised by an internal structure consisting of a large number of thin, parallel threads piled together. Prominences often display periodic disturbances mostly observed in the Doppler displacement of spectral lines and with an amplitude typically of the order of or smaller than 2-3 km s-1, a value which seems to be much smaller than the characteristic speeds of the prominence plasma (namely the Alfvén and sound velocities). Two particular features of these small amplitude prominence oscillations are that they seem to damp in a few periods and that they seem not to affect the whole prominence structure. In addition, in high spatial resolution observations, in which threads can be discerned, small amplitude oscillations appear to be clearly associated to these fine structure constituents. Prominence seismology tries to bring together the results from these observations (e.g. periods, wavelengths, damping times) and their theoretical modeling (by means of the magnetohydrodynamic theory) to gain insight into physical properties of prominences that cannot be derived from direct observation. In this paper we discuss works that have not been described in previous reviews, namely the first seismological application to solar prominences and theoretical advances on the attenuation of prominence oscillations.
Continuous phase and amplitude holographic elements
NASA Technical Reports Server (NTRS)
Maker, Paul D. (Inventor); Muller, Richard E. (Inventor)
1995-01-01
A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.
Zeroing in on Supersymmetric Radiation Amplitude Zeros
Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC
2012-02-15
Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.
Mellin amplitudes for dual conformal integrals
NASA Astrophysics Data System (ADS)
Paulos, Miguel F.; Spradlin, Marcus; Volovich, Anastasia
2012-08-01
Motivated by recent work on the utility of Mellin space for representing conformal correlators in AdS/CFT, we study its suitability for representing dual conformal integrals of the type which appear in perturbative scattering amplitudes in super-Yang-Mills theory. We discuss Feynman-like rules for writing Mellin amplitudes for a large class of integrals in any dimension, and find explicit representations for several familiar toy integrals. However we show that the power of Mellin space is that it provides simple representations even for fully massive integrals, which except for the single case of the 4-mass box have not yet been computed by any available technology. Mellin space is also useful for exhibiting differential relations between various multi-loop integrals, and we show that certain higher-loop integrals may be written as integral operators acting on the fully massive scalar n-gon in n dimensions, whose Mellin amplitude is exactly 1. Our chief example is a very simple formula expressing the 6-mass double box as a single integral of the 6-mass scalar hexagon in 6 dimensions.
NASA Astrophysics Data System (ADS)
Bogomolov, Sergey A.; Slepnev, Andrei V.; Strelkova, Galina I.; Schöll, Eckehard; Anishchenko, Vadim S.
2017-02-01
We explore the bifurcation transition from coherence to incoherence in ensembles of nonlocally coupled chaotic systems. It is firstly shown that two types of chimera states, namely, amplitude and phase, can be found in a network of coupled logistic maps, while only amplitude chimera states can be observed in a ring of continuous-time chaotic systems. We reveal a bifurcation mechanism by analyzing the evolution of space-time profiles and the coupling function with varying coupling coefficient and formulate the necessary and sufficient conditions for realizing the chimera states in the ensembles.
Amplitude equations for collective spatio-temporal dynamics in arrays of coupled systems.
Yanchuk, S; Perlikowski, P; Wolfrum, M; Stefański, A; Kapitaniak, T
2015-03-01
We study the coupling induced destabilization in an array of identical oscillators coupled in a ring structure where the number of oscillators in the ring is large. The coupling structure includes different types of interactions with several next neighbors. We derive an amplitude equation of Ginzburg-Landau type, which describes the destabilization of a uniform stationary state and close-by solutions in the limit of a large number of nodes. Studying numerically an example of unidirectionally coupled Duffing oscillators, we observe a coupling induced transition to collective spatio-temporal chaos, which can be understood using the derived amplitude equations.
Amplitude equations for collective spatio-temporal dynamics in arrays of coupled systems
Yanchuk, S.; Wolfrum, M.; Perlikowski, P.; Stefański, A.; Kapitaniak, T.
2015-03-15
We study the coupling induced destabilization in an array of identical oscillators coupled in a ring structure where the number of oscillators in the ring is large. The coupling structure includes different types of interactions with several next neighbors. We derive an amplitude equation of Ginzburg-Landau type, which describes the destabilization of a uniform stationary state and close-by solutions in the limit of a large number of nodes. Studying numerically an example of unidirectionally coupled Duffing oscillators, we observe a coupling induced transition to collective spatio-temporal chaos, which can be understood using the derived amplitude equations.
ERIC Educational Resources Information Center
Statfeld, Jenna L.
2011-01-01
Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…
Loop-quantum-gravity vertex amplitude.
Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo
2007-10-19
Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.
Fatigue damage analysis under variable amplitude cycling
NASA Technical Reports Server (NTRS)
Leis, B. N.; Forte, T. P.
1983-01-01
This paper explores the suitability of a recently proposed mean stress parameter and introduces a nonlinear damage accumulation procedure. Data covering a range of positive and negative stress ratios from +0.6 to -2.66, for several aluminum alloys and steels, are assembled and shown to be well correlated by a simple damage parameter. A nonlinear damage accumulation postulate is advanced to replace the usual linear procedure. Results of critical experiments performed to assess the suitability of the postulate are introduced and shown to support a non-linear criterion. The implications of this work related to variable amplitude life prediction are discussed.
Fatigue crack growth under variable amplitude loading
NASA Astrophysics Data System (ADS)
Sidawi, Jihad A.
1994-09-01
Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.
Fatigue crack growth under variable amplitude loading
NASA Technical Reports Server (NTRS)
Sidawi, Jihad A.
1994-01-01
Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.
Phase amplitude conformal symmetry in Fourier transforms
NASA Astrophysics Data System (ADS)
Kuwata, S.
2015-04-01
For the Fourier transform ℑ : L2(R) → L2(R) of a complex-valued even or odd function ψ, it is found that the amplitude invariance |ℑψ| = |ψ| leads to a phase invariance or inversion as arg(ℑψ) = ±argψ + θ (θ = constant). The converse holds unless arg ψ = constant. The condition |ψ| = |ℑψ| is required in dealing with, for example, the minimum uncertainty relation between position and momentum. Without the evenness or oddness of ψ, |ℑψ| = |ψ| does not necessarily imply arg(ℑψ) = ±argψ + θ, nor is the converse.
In-Medium Pion Valence Distribution Amplitude
NASA Astrophysics Data System (ADS)
Tsushima, K.; de Melo, J. P. B. C.
2017-03-01
After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
The small amplitude magnetohydrodynamic Riemann problem
NASA Technical Reports Server (NTRS)
Wu, C. C.; Kennel, C. F.
1993-01-01
The small-amplitude MHD Riemann problem is studied using the Cohen-Kulsrud-Burgers equations. Unlike the coplanar Riemann problem, the evolution of noncoplanar Riemann problems is not self-similar and its flow structures could change in time. But its large-time behavior is very simple and a time-dependent 2 - 3 intermediate shock is always involved for the noncoplanar field rotations. The time-dependent 2 - 3 intermediate shock has a well-defined structure and exists for any degree of field rotation.
The large-amplitude combustion oscillation in a single-side expansion scramjet combustor
NASA Astrophysics Data System (ADS)
Ouyang, Hao; Liu, Weidong; Sun, Mingbo
2015-12-01
The combustion oscillation in scramjet combustor is believed not existing and ignored for a long time. Compared with the flame pulsation, the large-amplitude combustion oscillation in scramjet combustor is indeed unfamiliar and difficult to be observed. In this study, the specifically designed experiments are carried out to investigate this unusual phenomenon in a single-side expansion scramjet combustor. The entrance parameter of combustor corresponds to scramjet flight Mach number 4.0 with a total temperature of 947 K. The obtained results show that the large-amplitude combustion oscillation can exist in scramjet combustor, which is not occasional and can be reproduced. Under the given conditions of this study, moreover, the large-amplitude combustion oscillation is regular and periodic, whose principal frequency is about 126 Hz. The proceeding of the combustion oscillation is accompanied by the transformation of the flame-holding pattern and combustion mode transition between scramjet mode combustion and ramjet mode combustion.
Mechanism for Amplitude Alternans in Electrocardiograms and the Initiation of Spatiotemporal Chaos
NASA Astrophysics Data System (ADS)
Chen, Diandian Diana; Gray, Richard A.; Uzelac, Ilija; Herndon, Conner; Fenton, Flavio H.
2017-04-01
It is widely believed that one major life-threatening transition to chaotic fibrillation occurs via spiral-wave breakup that is preceded by spatiotemporal dispersion of refractoriness due to alternations in the duration of the cardiac action potential (AP). However, recent clinical and experimental evidence suggests that other characteristics of the AP may contribute to, and perhaps drive, this dangerous dynamical instability. To identify the relative roles of AP characteristics, we performed experiments in rabbit hearts under conditions to minimize AP duration dynamics which unmasked pronounced AP amplitude alternans just before the onset of fibrillation. We used a simplified ionic cell model to derive a return map and a stability condition that elucidates a novel underlying mechanism for AP alternans and spiral breakup. We found that inactivation of the sodium current is key to developing amplitude alternans and is directly connected to conduction block and initiation of arrhythmias. Simulations in 2D where AP amplitude alternation led to turbulence confirm our hypothesis.
Higher-order multipole amplitude measurement in ψ'→γχc2
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Alberto, D.; An, F. F.; An, Q.; An, Z. H.; Bai, J. Z.; Baldini, R.; Ban, Y.; Becker, J.; Berger, N.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Calcaterra, A. C.; Cao, G. F.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, Y.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denysenko, I.; Destefanis, M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Han, Y. L.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, B.; Huang, G. M.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jia, L. K.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Kuehn, W.; Lai, W.; Lange, J. S.; Leung, J. K. C.; Li, C. H.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, Lei; Li, N. B.; Li, Q. J.; Li, S. L.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, X. T.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H.; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K.; Liu, K. Y.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. H.; Liu, Y. B.; Liu, Y. W.; Liu, Yong; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X.; Ma, X. Y.; Maggiora, M.; Malik, Q. A.; Mao, H.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Muchnoi, N. Yu.; Nefedov, Y.; Nikolaev, I. B.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Park, J. W.; Pelizaeus, M.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pun, C. S. J.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. D.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tian, H. L.; Toth, D.; Varner, G. S.; Wang, B.; Wang, B. Q.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, Q. J.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Q. J.; Xu, X. P.; Xu, Y.; Xu, Z. R.; Xu, Z. Z.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, T.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, S. P.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, S. H.; Zhang, T. R.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. S.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhao, Z. L.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zheng, Z. P.; Zhong, B.; Zhong, J.; Zhong, L.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, X. W.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Zuo, J. X.
2011-11-01
Using 106×106 ψ' events collected with the BESIII detector at the BEPCII storage ring, the higher-order multipole amplitudes in the radiative transition ψ'→γχc2→γπ+π-/γK+K- are measured. A fit to the χc2 production and decay angular distributions yields M2=0.046±0.010±0.013 and E3=0.015±0.008±0.018, where the first errors are statistical and the second systematic. Here M2 denotes the normalized magnetic quadrupole amplitude and E3 the normalized electric octupole amplitude. This measurement shows evidence for the existence of the M2 signal with 4.4σ statistical significance and is consistent with the charm quark having no anomalous magnetic moment.
PERIOD AND AMPLITUDE VARIABILITY OF THE HIGH-AMPLITUDE {delta} SCUTI STAR GP ANDROMEDAE
Zhou, A.-Y.; Jiang, S.-Y.
2011-10-15
Extensive differential time-series CCD photometry has been carried out between 2003 and 2009 for the high-amplitude {delta} Scuti (HADS) star GP And. We acquired 12,583 new measurements consisting of 41 nights (153.3 hr) spanning over 2221 days. This is the largest time-series data set to date for the star. Based upon these data and others available in the literature, a comprehensive analysis has been conducted to investigate the pulsational properties of the star. Except for the known fundamental period and its harmonics we failed to detect any additional pulsation periods either radial or nonradial. We show clear amplitude variability, but we failed to verify the previously claimed periodic amplitude modulation. Classic O-C analysis indicates that the fundamental pulsation period of GP And is slowly increasing at a rate of P-dot /P = (5.49 {+-} 0.1)x10{sup -8} yr{sup -1} in accordance with the predictions of stellar evolutionary models. Findings of nonradial oscillations in previously known radial high-amplitude pulsators are being increasingly reported. We have briefly reviewed the current status of multiperiodicity and nonradial pulsation features among the high-amplitude pulsators in the classic instability strip.
Converted Ps amplitude variations on the dipping slab Moho beneath the Kii Peninsula, central Japan
NASA Astrophysics Data System (ADS)
Shiomi, K.; Park, J. J.
2011-12-01
parameter dependence into account. In order to avoid this contamination, we select limited events with ray parameters in the range 0.055-0.077. We also apply amplitude corrections. We confirmed that the Ps amplitudes decrease from 11% of the primary P wave to 7% as the oceanic Moho deepens to 40km. Deeper than 40 km, the Ps amplitudes are roughly constant, at 5-7% of the primary P wave. According to the P-T diagram of the Kii Peninsula region, we say that the Ps amplitude decrease likely reflects a phase transition from lawsonite blueschist to lawsonite-amphibole eclogite as water is released to the overlying layer, and this metamorphic fluids likely influence the occurrence of low-frequency nonvolcanic tremor, as we already reported. On the one hand, the regionality of standard amplitude distribution within the Kii Peninsula becomes unclear. To understand what happens along the subducting slab interface, it is important to construct models to explain the observed amplitude change as the next step.
Amplitude enhancement by a gold dimer
NASA Astrophysics Data System (ADS)
Hong, Xin; Wang, Jingxin; Jin, Zheng
2016-10-01
The unique optical properties such as brightness, non-bleaching, good bio-compatibility make gold particles ideal label candidates for molecular probes. Due to the strongly enhanced field, aggregation of gold nanoparticles finds themselves plenty of applications in bio-imaging. But limited by its small cross-section associated with nanometer sized particle, it is a big challenge to employ it in a single molecular detection. The field enhancement results from the effect of plasmonic coupling between two closely attached gold nanoparticle under the right excitation condition. With the aim to apply the gold dimer probe to find the molecules in our recently established optical detection method, we compared of the amplitude enhancement by the dimer relative to a single particle. The amplitude distribution under a highly focused illumination objective was calculated, whose results suggest that at the optimized excitation condition, the local field can be enhanced 190 fold. In consequence, experimental detection was carried out. Gold dimers were linked together by the hybridization of two single chain DNAs. Dimer and single particle probes were mixed together in one detection. Overwhelming contrast between these two kinds of probes were clearly exhibited in the experimental detection image. This method can provide a way to a high specific detection in early diagnosis.
Wrist Proprioception: Amplitude or Position Coding?
Marini, Francesca; Squeri, Valentina; Morasso, Pietro; Masia, Lorenzo
2016-01-01
This work examines physiological mechanisms underlying the position sense of the wrist, namely, the codification of proprioceptive information related to pointing movements of the wrist toward kinesthetic targets. Twenty-four healthy subjects participated to a robot-aided assessment of their wrist proprioceptive acuity to investigate if the sensorimotor transformation involved in matching targets located by proprioceptive receptors relies on amplitude or positional cues. A joint position matching test was performed in order to explore such dichotomy. In this test, the wrist of a blindfolded participant is passively moved by a robotic device to a preset target position and, after a removal movement from this position, the participant has to actively replicate and match it as accurately as possible. The test involved two separate conditions: in the first, the matching movements started from the same initial location; in the second one, the initial location was randomly assigned. Target matching accuracy, precision, and bias in the two conditions were then compared. Overall results showed a consistent higher performance in the former condition than in the latter, thus supporting the hypothesis that the joint position sense is based on vectorial or amplitude coding rather than positional. PMID:27807417
Resonant π+γ→π+π0 amplitude from Quantum Chromodynamics
Briceño, Raúl A.; Dudek, Jozef J.; Edwards, Robert G.; ...
2015-12-08
We present the first ab initio calculation of a radiative transition of a hadronic resonance within Quantum Chromodynamics (QCD). We compute the amplitude formore » $$\\pi\\pi \\to \\pi\\gamma^\\star$$, as a function of the energy of the $$\\pi\\pi$$ pair and the virtuality of the photon, in the kinematic regime where $$\\pi\\pi$$ couples strongly to the unstable $$\\rho$$ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to $$m_\\pi \\approx 400$$ MeV. As a result, we obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the $$\\rho$$ pole and identify from its residue the $$\\rho \\to \\pi\\gamma^\\star$$ form-factor.« less
Resonant π^{+}γ→π^{+}π^{0} Amplitude from Quantum Chromodynamics.
Briceño, Raúl A; Dudek, Jozef J; Edwards, Robert G; Shultz, Christian J; Thomas, Christopher E; Wilson, David J
2015-12-11
We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for ππ→πγ^{⋆}, as a function of the energy of the ππ pair and the virtuality of the photon, in the kinematic regime where ππ couples strongly to the unstable ρ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to m_{π}≈400 MeV. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the ρ pole and identify from its residue the ρ→πγ^{⋆} form factor.
Color-kinematic duality in ABJM theory without amplitude relations
NASA Astrophysics Data System (ADS)
Sivaramakrishnan, Allic
2017-01-01
We explicitly show that the Bern-Carrasco-Johansson color-kinematic duality holds at tree level through at least eight points in Aharony-Bergman-Jafferis-Maldacena theory with gauge group SU(N) × SU(N). At six points we give the explicit form of numerators in terms of amplitudes, displaying the generalized gauge freedom that leads to amplitude relations. However, at eight points no amplitude relations follow from the duality, so the diagram numerators are fixed unique functions of partial amplitudes. We provide the explicit amplitude-numerator decomposition and the numerator relations for eight-point amplitudes.
Spurious cross-frequency amplitude-amplitude coupling in nonstationary, nonlinear signals
NASA Astrophysics Data System (ADS)
Yeh, Chien-Hung; Lo, Men-Tzung; Hu, Kun
2016-07-01
Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, including the correlation between the amplitude envelopes of two brain waves at different frequencies - cross-frequency amplitude-amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.
Amplitude and phase effects in Josephson qubits driven by a biharmonic electromagnetic field
NASA Astrophysics Data System (ADS)
Satanin, A. M.; Denisenko, M. V.; Gelman, A. I.; Nori, Franco
2014-09-01
We investigate the amplitude and phase effects of qubit dynamics and excited-state population under the influence of a biharmonic control field. It is demonstrated that the biharmonic driving field can have a significant effect on the behavior of quasienergy level crossing as well as on multiphoton transitions. Also, the interference pattern for the populations of qubit excited states is sensitive to the signal parameters. We discuss the possibility of using these effects for manipulating qubit states and calibrating nanosecond pulses.
2.75-4.75 GHz QPSK modulator with low amplitude and phase errors
NASA Astrophysics Data System (ADS)
Kumar, S.; Wells, G.
1990-07-01
A QPSK modulator with a 2.75-4.75 GHz operating frequency range is presented. The modulator is realized using a broadband power divider, microstrip-slotline-microstrip transitions and Lange couplers. Computer optimized matching circuits are used to maintain a phase error less than 5 deg and an amplitude phase imbalance error across the band of less than 0.5 dB. The modulator is suitable for MMIC implementation.
NASA Technical Reports Server (NTRS)
Fu, Y.; Hall, P.
1992-01-01
The weakly nonlinear development of large-amplitude Goertler vortices in a small neighborhood of the neutral stability position given by the linear theory is considered. It is shown that if the basic state and the wall curvature satisfy a certain condition, the Goertler vortices will grow until they become so large as to drive a mean flow correction as large as the basic state. Attention is then given to the further downstream evolution of these large-amplitude vortices, and it is shown that the vortices have a triple layer structure which consists of a region of vortex activity bounded by two transition layers over which the amplitude of the harmonic part of the vortex decays to zero exponentially. The positions of the two transition layers are found to be governed by a free boundary problem, which is solved for a number of curvature distribution cases. The secondary instability of the two transition layers is investigated with respect to traveling waves which are pi/2 out of phase in the spanwise direction with the steady Goertler vortices.
Nonlinear rocket motor stability prediction: Limit amplitude, triggering, and mean pressure shifta)
NASA Astrophysics Data System (ADS)
Flandro, Gary A.; Fischbach, Sean R.; Majdalani, Joseph
2007-09-01
High-amplitude pressure oscillations in solid propellant rocket motor combustion chambers display nonlinear effects including: (1) limit cycle behavior in which the fluctuations may dwell for a considerable period of time near their peak amplitude, (2) elevated mean chamber pressure (DC shift), and (3) a triggering amplitude above which pulsing will cause an apparently stable system to transition to violent oscillations. Along with the obvious undesirable vibrations, these features constitute the most damaging impact of combustion instability on system reliability and structural integrity. The physical mechanisms behind these phenomena and their relationship to motor geometry and physical parameters must, therefore, be fully understood if instability is to be avoided in the design process, or if effective corrective measures must be devised during system development. Predictive algorithms now in use have limited ability to characterize the actual time evolution of the oscillations, and they do not supply the motor designer with information regarding peak amplitudes or the associated critical triggering amplitudes. A pivotal missing element is the ability to predict the mean pressure shift; clearly, the designer requires information regarding the maximum chamber pressure that might be experienced during motor operation. In this paper, a comprehensive nonlinear combustion instability model is described that supplies vital information. The central role played by steep-fronted waves is emphasized. The resulting algorithm provides both detailed physical models of nonlinear instability phenomena and the critically needed predictive capability. In particular, the origin of the DC shift is revealed.
Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point
NASA Astrophysics Data System (ADS)
Hong, Tao; Matsumoto, Masashige; Qiu, Yiming; Chen, Wangchun; Gentile, Thomas R.; Watson, Shannon; Awwadi, Firas F.; Turnbull, Mark M.; Dissanayake, Sachith E.; Agrawal, Harish; Toft-Petersen, Rasmus; Klemke, Bastian; Coester, Kris; Schmidt, Kai P.; Tennant, David A.
2017-07-01
Spontaneous symmetry-breaking quantum phase transitions play an essential role in condensed-matter physics. The collective excitations in the broken-symmetry phase near the quantum critical point can be characterized by fluctuations of phase and amplitude of the order parameter. The phase oscillations correspond to the massless Nambu-Goldstone modes whereas the massive amplitude mode, analogous to the Higgs boson in particle physics, is prone to decay into a pair of low-energy Nambu-Goldstone modes in low dimensions. Especially, observation of a Higgs amplitude mode in two dimensions is an outstanding experimental challenge. Here, using inelastic neutron scattering and applying the bond-operator theory, we directly and unambiguously identify the Higgs amplitude mode in a two-dimensional S = 1/2 quantum antiferromagnet C9H18N2CuBr4 near a quantum critical point in two dimensions. Owing to an anisotropic energy gap, it kinematically prevents such decay and the Higgs amplitude mode acquires an infinite lifetime.
Evaluation of new spin foam vertex amplitudes
NASA Astrophysics Data System (ADS)
Khavkine, Igor
2009-06-01
The Christensen-Egan algorithm is extended and generalized to efficiently evaluate new spin foam vertex amplitudes proposed by Engle, Pereira and Rovelli and Freidel and Krasnov, with or without (factored) boundary states. A concrete pragmatic proposal is made for comparing the different models using uniform methodologies, applicable to the behavior of large spin asymptotics and of expectation values of specific semiclassical observables. The asymptotics of the new models exhibit non-oscillatory, power-law decay similar to that of the Barrett-Crane model, though with different exponents. Also, an analysis of the semiclassical wave packet propagation problem indicates that the Magliaro, Rovelli and Perini's conjecture of good semiclassical behavior of the new models does not hold for generic factored states, which neglect spin-spin correlations.
Amplitude Scaling of Active Separation Control
NASA Technical Reports Server (NTRS)
Stalnov, Oksana; Seifert, Avraham
2010-01-01
Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.
Low Amplitude Impact of Damaged PBX 9501
NASA Astrophysics Data System (ADS)
Idar, Deanne
1999-06-01
Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.
Speech recognition with amplitude and frequency modulations
NASA Astrophysics Data System (ADS)
Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli
2005-02-01
Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis
Presynaptic spike broadening reduces junctional potential amplitude.
Spencer, A N; Przysiezniak, J; Acosta-Urquidi, J; Basarsky, T A
1989-08-24
Presynaptic modulation of action potential duration may regulate synaptic transmission in both vertebrates and invertebrates. Such synaptic plasticity is brought about by modifications to membrane currents at presynaptic release sites, which, in turn, lead to changes in the concentration of cytosolic calcium available for mediating transmitter release. The 'primitive' neuromuscular junction of the jellyfish Polyorchis penicillatus is a useful model of presynaptic modulation. In this study, we show that the durations of action potentials in the motor neurons of this jellyfish are negatively correlated with the amplitude of excitatory junctional potentials. We present data from in vitro voltage-clamp experiments showing that short duration voltage spikes, which elicit large excitatory junctional potentials in vivo, produce larger and briefer calcium currents than do long duration action potentials, which elicit small excitatory junctional potentials.
Amplitude envelope synchronization in coupled chaotic oscillators.
Gonzalez-Miranda, J M
2002-03-01
A peculiar type of synchronization has been found when two Van der Pol-Duffing oscillators, evolving in different chaotic attractors, are coupled. As the coupling increases, the frequencies of the two oscillators remain different, while a synchronized modulation of the amplitudes of a signal of each system develops, and a null Lyapunov exponent of the uncoupled systems becomes negative and gradually larger in absolute value. This phenomenon is characterized by an appropriate correlation function between the returns of the signals, and interpreted in terms of the mutual excitation of new frequencies in the oscillators power spectra. This form of synchronization also occurs in other systems, but it shows up mixed with or screened by other forms of synchronization, as illustrated in this paper by means of the examples of the dynamic behavior observed for three other different models of chaotic oscillators.
Bootstrapping an NMHV amplitude through three loops
NASA Astrophysics Data System (ADS)
Dixon, Lance J.; von Hippel, Matt
2014-10-01
We extend the hexagon function bootstrap to the next-to-maximally-helicity-violating (NMHV) configuration for six-point scattering in planar = 4 super-Yang-Mills theory at three loops. Constraints from the differential equation, from the operator product expansion (OPE) for Wilson loops with operator insertions, and from multi-Regge factorization, lead to a unique answer for the three-loop ratio function. The three-loop result also predicts additional terms in the OPE expansion, as well as the behavior of NMHV amplitudes in the multi-Regge limit at one higher logarithmic accuracy (NNLL) than was used as input. Both predictions are in agreement with recent results from the flux-tube approach. We also study the multi-particle factorization of multi-loop amplitudes for the first time. We find that the function controlling this factorization is purely logarithmic through three loops. We show that a function U , which is closely related to the parity-even part of the ratio function V , is remarkably simple; only five of the nine possible final entries in its symbol are non-vanishing. We study the analytic and numerical behavior of both the parity-even and parity-odd parts of the ratio function on simple lines traversing the space of cross ratios ( u, v, w), as well as on a few two-dimensional planes. Finally, we present an empirical formula for V in terms of elements of the coproduct of the six-gluon MHV remainder function R 6 at one higher loop, which works through three loops for V (four loops for R 6).
Localized finite-amplitude disturbances and selection of solitary waves
Kliakhandler; Porubov; Velarde
2000-10-01
It turns out that evolution of localized finite-amplitude disturbances in perturbed KdV equation is qualitatively different compared with conventional small-amplitude initial conditions. Namely, relatively fast solitary waves, with one and the same amplitude and velocity, are formed ahead of conventional chaotic-like irregular structures. The amplitude and velocity of the waves, obtained from the asymptotic theory, are in excellent agreement with numerics.
Chiral closed strings: four massless states scattering amplitude
NASA Astrophysics Data System (ADS)
Leite, Marcelo M.; Siegel, Warren
2017-01-01
We compute the scattering amplitudes of four massless states for chiral (closed) bosonic and type II superstrings using the Kawai-Lewellen-Tye ( KLT ) factorization method. The amplitude in the chiral bosonic case is identical to a field theory amplitude corresponding to the spin-2 tachyon, massless gravitational sector and massive spin-2 tardyon states of the spectrum. Chiral type II superstrings amplitude only possess poles associated with the massless gravitational sector. We briefly discuss the extension of the calculation to heterotic superstrings.
Multidimensional Large Amplitude Dynamics in the Pyridine-Water Complex.
Mackenzie, Rebecca B; Dewberry, Christopher T; Cornelius, Ryan D; Smith, C J; Leopold, Kenneth R
2017-02-02
Aqueous pyridine plays an important role in a variety of catalytic processes aimed at harnessing solar energy. In this work, the pyridine-water interaction is studied by microwave spectroscopy and density functional theory calculations. Water forms a hydrogen bond to the nitrogen with the oxygen tilted slightly toward either of the ortho-hydrogens of the pyridine, and a tunneling motion involving in-plane rocking of the water interconverts the resulting equivalent structures. A pair of tunneling states with severely perturbed rotational spectra is identified and their energy separation, ΔE, is inferred from the perturbations and confirmed by direct measurement. Curiously, values of ΔE are 10404.45 and 13566.94 MHz for the H2O and D2O complexes, respectively, revealing an inverted isotope effect upon deuteration. Small splittings in some transitions suggest an additional internal motion making this complex an interesting challenge for theoretical treatments of large amplitude motion. The results underscore the significant effect of the ortho-hydrogens on the intermolecular interaction of pyridine.
Fouad, Nadya A; Bynner, John
2008-01-01
Individuals make choices in, and adjust to, a world of work that is often a moving target. Because work is so central to human functioning, and transitions in and out of work can have major mental health repercussions, the authors argue that applied psychologists in health services need to understand those transitions. This article focuses on the different types of transition throughout a person's working life and the resources needed at different stages to ensure the success of these transitions. The authors start by examining the roles of capability and adaptability in supporting and facilitating adjustment to work transitions and their relation to identity development. They then examine the role of social and institutional contexts in shaping work transitions and their outcomes. The authors focus on voluntary versus involuntary transitions and then broaden the lens in discussing the policy implications of research on work transitions.
Bond patterns and charge-order amplitude in quarter-filled charge-transfer solids
NASA Astrophysics Data System (ADS)
Clay, R. T.; Ward, A. B.; Gomes, N.; Mazumdar, S.
2017-03-01
Most quasi-one-dimensional (quasi-1D) quarter-filled organic charge-transfer solids (CTS) with insulating ground states have two thermodynamic transitions: a high-temperature metal-insulator transition followed by a low-temperature magnetic transition. This sequence of transitions can be understood within the 1D Peierls-extended Hubbard (PEH) model. However, in some quasi-1D CTS both transitions occur simultaneously in a direct metal to spin-gapped insulator transition. In this second class of materials the organic stack bond distortion pattern does not follow the pattern of a second dimerization of a dimer lattice. These materials also display charge ordering of a large amplitude below the transition. Using quantum Monte Carlo methods we show that the same PEH model can be used to understand both classes of materials, however, within different parameter regions. We discuss the relevance of our work to experiments on several quarter-filled conductors, focusing in particular on the materials (EDO-TTF)2X and (DMEDO-TTF)2X .
Feed-forward digital phase and amplitude correction system
Yu, D.U.L.; Conway, P.H.
1994-11-15
Phase and amplitude modifications in repeatable RF pulses at the output of a high power pulsed microwave amplifier are made utilizing a digital feed-forward correction system. A controlled amount of the output power is coupled to a correction system for processing of phase and amplitude information. The correction system comprises circuitry to compare the detected phase and amplitude with the desired phase and amplitude, respectively, and a digitally programmable phase shifter and attenuator and digital logic circuitry to control the phase shifter and attenuator. The phase and amplitude of subsequent are modified by output signals from the correction system. 11 figs.
Feed-forward digital phase and amplitude correction system
Yu, David U. L.; Conway, Patrick H.
1994-01-01
Phase and amplitude modifications in repeatable RF pulses at the output of a high power pulsed microwave amplifier are made utilizing a digital feed-forward correction system. A controlled amount of the output power is coupled to a correction system for processing of phase and amplitude information. The correction system comprises circuitry to compare the detected phase and amplitude with the desired phase and amplitude, respectively, and a digitally programmable phase shifter and attenuator and digital logic circuitry to control the phase shifter and attenuator. The Phase and amplitude of subsequent are modified by output signals from the correction system.
Atomic Structure Measurements and Fundamental Symmetry Tests in a Thallium Atomic Beam
NASA Astrophysics Data System (ADS)
Majumder, P. K.; Doret, S. C.
2002-05-01
Using a recently constructed thallium atomic beam apparatus, we have begun a series of laser spectroscopy measurements with the goal of providing precise, independent cross-checks on the accuracy of new calculations of parity nonconservation in thallium(M. Kozlov et al.), Phys Rev. A64, 053107 (2001). We are currently completing a measurement of the Stark shift within the 378 nm 6P_1/2-7S_1/2 transition. For this experiment, we use a frequency-stabilized external cavity diode laser system at 755 nm, an acousto-optic modulator, and external resonant frequency-doubling cavity to obtain a small amount of tunable UV light. The laser beam intersects the collimated atomic beam at right angles, and we can apply a precisely-calibrated electric field of up to 30 kV/cm in the interaction region. We observe a factor of ten Doppler narrowing and roughly 30% absorption on resonance of the strongest hyperfine line within this transition. We will present precise Stark shift results based on several very different experimental methods. We plan next to introduce 1283 nm light into the atomic beam to study the 6P_1/2-6P_3/2 `forbidden' M1 transition. Using a double FM modulation/detection scheme to improve our signal-to-noise ratio, we will measure both the Stark shift and the Stark-induced amplitudes here. In the longer term, we are developing an atomic beam experiment using the 1283 nm laser to search for a long-range T-odd, but P-even interaction in thallium.
Amplitude interpretation and visualization of three-dimensional reflection data
Enachescu, M.E. )
1994-07-01
Digital recording and processing of modern three-dimensional surveys allow for relative good preservation and correct spatial positioning of seismic reflection amplitude. A four-dimensional seismic reflection field matrix R (x,y,t,A), which can be computer visualized (i.e., real-time interactively rendered, edited, and animated), is now available to the interpreter. The amplitude contains encoded geological information indirectly related to lithologies and reservoir properties. The magnitude of the amplitude depends not only on the acoustic impedance contrast across a boundary, but is also strongly affected by the shape of the reflective boundary. This allows the interpreter to image subtle tectonic and structural elements not obvious on time-structure maps. The use of modern workstations allows for appropriate color coding of the total available amplitude range, routine on-screen time/amplitude extraction, and late display of horizon amplitude maps (horizon slices) or complex amplitude-structure spatial visualization. Stratigraphic, structural, tectonic, fluid distribution, and paleogeographic information are commonly obtained by displaying the amplitude variation A = A(x,y,t) associated with a particular reflective surface or seismic interval. As illustrated with several case histories, traditional structural and stratigraphic interpretation combined with a detailed amplitude study generally greatly enhance extraction of subsurface geological information from a reflection data volume. In the context of three-dimensional seismic surveys, the horizon amplitude map (horizon slice), amplitude attachment to structure and [open quotes]bright clouds[close quotes] displays are very powerful tools available to the interpreter.
Writing CFT correlation functions as AdS scattering amplitudes
NASA Astrophysics Data System (ADS)
Penedones, Joao
2011-03-01
We explore the Mellin representation of conformal correlation functions recently proposed by Mack. Examples in the AdS/CFT context reinforce the analogy between Mellin amplitudes and scattering amplitudes. We conjecture a simple formula relating the bulk scattering amplitudes to the asymptotic behavior of Mellin amplitudes and show that previous results on the flat space limit of AdS follow from our new formula. We find that the Mellin amplitudes are particularly useful in the case of conformal gauge theories in the planar limit. In this case, the four point Mellin amplitudes are meromorphic functions whose poles and their residues are entirely determined by two and three point functions of single-trace operators. This makes the Mellin amplitudes the ideal objects to attempt the conformal bootstrap program in higher dimensions.
Efficient reverse time migration with amplitude encoding
NASA Astrophysics Data System (ADS)
Hu, Jiangtao; Wang, Huazhong; Zhao, Lei; Shao, Yu; Wang, Meixia; Osen, Are
2015-08-01
Reverse time migration (RTM) is an accurate seismic imaging method for imaging the complex subsurface structure. Traditional common shot RTM suffers from low efficiency due to the large number of single shot gathers, especially for marine seismic data. Phase encoding is commonly used to reduce the computational cost of RTM. Phase encoding in the frequency domain is usually related to time shift in the time domain. Therefore, phase-encoding-based RTM needs time padding to avoid information loss which degrades the efficiency of the time-domain wavefield extrapolator. In this paper, an efficient time-domain RTM scheme based on the amplitude encoding is proposed. This scheme uses the orthogonal cosine basis as the encoding function, which has similar physical meaning to plane wave encoding (i.e. plane-wave components with different surface shooting angles). The proposed scheme can generate a qualified imaging result as well as common shot RTM but with less computational cost. Since this scheme does not need time padding, it is more efficient than the phase encoding schemes and can be conveniently implemented in the time domain. Numerical examples on the Sigsbee2a synthetic dataset demonstrate the feasibility of the proposed method.
[Amplitude modulation following responses in audiological diagnostics].
Pethe, J; Mühler, R; von Specht, H
2002-12-01
The registration of brainstem potentials currently represents one of the most common methods in objective audiological diagnostics. However, regardless of their use, they are still known to possess important disadvantages, such as low specificity and validity in the lower frequency range due to broadband stimuli, or uncertainties due to the need for subjective evaluation. One potential solution to these problems could involve the registration of amplitude modulation following responses (AMFR). These potentials are being discussed much more regularly within the anglo-american literature due to their known frequency specificity within the high frequency range (resulting from a very narrow frequency band of stimulation), and also their ability to permit assessment of the hearing threshold at lower frequencies. Another additional advantage of AMFR results from the simple statistical verification of its presence.Extensive studies on the influence of both stimulating and recording parameters have also shown that the registration of AMFR could prove to be a very promising audiological tool, with past interest being focussed primarily on the optimal modulation frequency, the influence of vigilance of the generation of potentials, and the precise assessment of an objective threshold.
A generalized fidelity amplitude for open systems.
Gorin, T; Moreno, H J; Seligman, T H
2016-06-13
We consider a central system which is coupled via dephasing to an open system, i.e. an intermediate system which in turn is coupled to another environment. Considering the intermediate and far environment as one composite system, the coherences in the central system are given in the form of fidelity amplitudes for a certain perturbed echo dynamics in the composite environment. On the basis of the Born-Markov approximation, we derive a master equation for the reduction of that dynamics to the intermediate system alone. In distinction to an earlier paper (Moreno et al 2015 Phys. Rev. A 92, 030104. (doi:10.1103/PhysRevA.92.030104)), where we discussed the stabilizing effect of the far environment on the decoherence in the central system, we focus here on the possibility of using the measurable coherences in the central system for probing the open quantum dynamics in the intermediate system. We illustrate our results for the case of chaotic dynamics in the near environment, where we compare random matrix simulations with our analytical result. © 2016 The Author(s).
Nonlinear amplitude dynamics in flagellar beating
NASA Astrophysics Data System (ADS)
Oriola, David; Gadêlha, Hermes; Casademunt, Jaume
2017-03-01
The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive cross-linkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models. The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatio-temporal dynamics of dynein populations and flagellum shape for different regimes of motor activity, medium viscosity and flagellum elasticity. Unstable modes saturate via the coupling of dynein kinetics and flagellum shape without the need of invoking a nonlinear axonemal response. Hence, our work reveals a novel mechanism for the saturation of unstable modes in axonemal beating.
Sensitivity to changes in amplitude envelope
NASA Astrophysics Data System (ADS)
Gallun, Erick; Hafter, Ervin R.; Bonnel, Anne-Marie
2002-05-01
Detection of a brief increment in a tonal pedestal is less well predicted by energy-detection (e.g., Macmillan, 1973; Bonnel and Hafter, 1997) than by sensitivity to changes in the stimulus envelope. As this implies a mechanism similar to an envelope extractor (Viemeister, 1979), sinusoidal amplitude modulation was used to mask a single ramped increment (10, 45, or 70 ms) added to a 1000-ms pedestal with carrier frequency (cf)=477 Hz. As in informational masking (Neff, 1994) and ``modulation-detection interference'' (Yost and Sheft, 1989), interference occurred with masker cfs of 477 and 2013 Hz. While slight masking was found with modulation frequencies (mfs) from 16 to 96 Hz, masking grew inversely with still lower mfs, being greatest for mf=4 Hz. This division is reminiscent of that said to separate sensations of ``roughness'' and ``beats,'' respectively (Terhardt, 1974), with the latter also being related to durations associated with auditory groupings in music and speech. Importantly, this result held for all of the signal durations and onset-offset ramps tested, suggesting that an increment on a pedestal is treated as a single auditory object whose detection is most difficult in the presence of other objects (in this case, ``beats'').
Baseline blood oxygenation modulates response amplitude
Lu, Hanzhang; Zhao, Chenguang; Ge, Yulin; Lewis-Amezcua, Kelly
2008-01-01
Although BOLD fMRI provides a useful tool for probing neuronal activities, large inter-subject variations in signal amplitude are commonly observed. Understanding the physiologic basis for these variations will have a significant impact on many fMRI studies. First, the physiologic modulator can be used as a regressor to reduce variations across subjects, thereby improving statistical power for detecting group differences. Second, if a pathologic condition or a drug treatment is shown to change fMRI responses, monitoring this modulatory parameter is useful in correctly interpreting the fMRI changes to neuronal deficits/recruitments. Here we present evidence that the task-evoked fMRI signals are modulated by baseline blood oxygenation. To measure global blood oxygenation, we used a recently developed technique, T2-Relaxation-Under-Spin-Tagging MRI, yielding baseline oxygenation of 63.7±7.2% in sagittal sinus with an estimation error of 1.3%. It was found that individuals with higher baseline oxygenation tend to have a smaller fMRI signal and vice versa. For every 10% difference in baseline oxygenation across subjects, the BOLD and cerebral blood flow signal differ by -0.4% and -30.0%, respectively, when using visual stimulation. TRUST MRI is a useful measurement for fMRI studies to control for the modulatory effects of baseline oxygenation that are unique to each subject. PMID:18666103
Nonlinear amplitude dynamics in flagellar beating
Casademunt, Jaume
2017-01-01
The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive cross-linkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models. The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatio-temporal dynamics of dynein populations and flagellum shape for different regimes of motor activity, medium viscosity and flagellum elasticity. Unstable modes saturate via the coupling of dynein kinetics and flagellum shape without the need of invoking a nonlinear axonemal response. Hence, our work reveals a novel mechanism for the saturation of unstable modes in axonemal beating. PMID:28405357
The pulsed amplitude unit for the SLC
Rolfe, J.; Browne, M.J.; Jobe, R.K.
1987-02-01
There is a recurring requirement in the SLC for the control of devices such as magnets, phase shifters, and attenuators on a beam-by-beam basis. The Pulsed Amplitude Unit (PAU) is a single width CAMAC module developed for this purpose. It provides digitally programmed analog output voltages on a beam-by-beam basis. Up to 32 preprogrammed values of output voltage are available from the single analog output of the module, and any of these values can be associated with any of the 256 possible SLC beam definitions. A 12-bit Analog-to-Digital Converter (ADC) digitizes an analog input signal at the appropriate beam time and stores it in a buffer memory. This feature is normally used to monitor the response of the device being controlled by the PAU at each beam time. Initial application of the PAU is a part of the system that controls the output of Klystrons in the SLC. The PAU combines several different functions in a single module. In order to accommodate these functions in a single width CAMAC module, field programmed logic is used extensively. Field Programmable Logic Arrays, Programmed Array Logic, and a Field Programmable Logic Sequencer are employed.
An amplitude modulated radio frequency plasma generator
NASA Astrophysics Data System (ADS)
Lei, Fan; Li, Xiaoping; Liu, Yanming; Liu, Donglin; Yang, Min; Xie, Kai; Yao, Bo
2017-04-01
A glow discharge plasma generator and diagnostic system has been developed to study the effects of rapidly variable plasmas on electromagnetic wave propagation, mimicking the plasma sheath conditions encountered in space vehicle reentry. The plasma chamber is 400 mm in diameter and 240 mm in length, with a 300-mm-diameter unobstructed clear aperture. Electron densities produced are in the mid 1010 electrons/cm3. An 800 W radio frequency (RF) generator is capacitively coupled through an RF matcher to an internally cooled stainless steel electrode to form the plasma. The RF power is amplitude modulated by a waveform generator that operates at different frequencies. The resulting plasma contains electron density modulations caused by the varying power levels. A 10 GHz microwave horn antenna pair situated on opposite sides of the chamber serves as the source and detector of probe radiation. The microwave power feed to the source horn is split and one portion is sent directly to a high-speed recording oscilloscope. On mixing this with the signal from the pickup horn antenna, the plasma-induced phase shift between the two signals gives the path-integrated electron density with its complete time dependent variation. Care is taken to avoid microwave reflections and extensive shielding is in place to minimize electronic pickup. Data clearly show the low frequency modulation of the electron density as well as higher harmonics and plasma fluctuations.
Surface Wave Amplitude Anomalies in the Western United States
NASA Astrophysics Data System (ADS)
Eddy, C.; Ekstrom, G.
2011-12-01
We determine maps of local surface wave amplitude factors across the Western United States for Rayleigh and Love waves at discrete periods between 25 and 125s. Measurements of raw amplitude anomalies are made from data recorded at 1161 USArray stations for minor arc arrivals of earthquakes with Mw>5.5 occurring between 2006 and 2010. We take the difference between high-quality amplitude anomaly measurements for events recorded on station pairs less than 2 degrees apart. The mean of these differences for each station pair is taken as the datum. Surface wave amplitudes are controlled by four separate mechanisms: focusing due to elastic structure, attenuation due to anelastic structure, source effects, and receiver effects. By taking the mean of the differences of amplitude anomalies for neighboring stations, we reduce the effects of focusing, attenuation, and the seismic source, thus isolating amplitude anomalies due to near-receiver amplitude effects. We determine local amplitude factors for each USArray station by standard linear inversion of the differential data set. The individual station amplitude factors explain the majority of the variance of the data. For example, derived station amplitude factors for 50s Rayleigh waves explain 92% of the variance of the data. We explore correlations between derived station amplitude factors and local amplitude factors predicted by crust and upper mantle models. Maps of local amplitude factors show spatial correlation with topography and geologic structures in the Western United States, particularly for maps derived from Rayleigh wave amplitude anomalies. A NW-SE trending high in amplitude factors in Eastern California is evident in the 50s map, corresponding to the location of the Sierra Nevada Mountains. High amplitude factors are observed in Colorado and New Mexico in the 50s-125s maps in the location of the highest peaks of the Rocky Mountains. High amplitude factors are also seen in Southern Idaho and Eastern Wyoming in
2012-06-05
It appeared that New Yorkers were not going to be able to see the transit of the planet Venus across the Sun, but just before the transit was over the sun broke through the clouds and Yvette Lee Kang was able to catch a glimpse of the transit on Tuesday, June 5, 2012 in New York. A transit of Venus occurs when the planet passes directly between the sun and earth. This alignment is rare, coming in pairs that are eight years apart but separated by over a century. The next Venus transit will be in December 2117. Photo Credit: (NASA/Bill Ingalls)
2012-06-05
It appeared that New Yorkers were not going to be able to see the transit of the planet Venus across the Sun, but just before the transit was over the sun broke through the clouds and Liz Heller and Andriel Mesznik were able to catch a glimpse of the transit on Tuesday, June 5, 2012 in New York. A transit of Venus occurs when the planet passes directly between the sun and earth. This alignment is rare, coming in pairs that are eight years apart but separated by over a century. The next Venus transit will be in December 2117. Photo Credit: (NASA/Bill Ingalls)
Calculation of radiative corrections to E1 matrix elements in the neutral alkali metals
Sapirstein, J.; Cheng, K.T.
2005-02-01
Radiative corrections to E1 matrix elements for ns-np transitions in the alkali-metal atoms lithium through francium are evaluated. They are found to be small for the lighter alkali metals but significantly larger for the heavier alkali metals, and in the case of cesium much larger than the experimental accuracy. The relation of the matrix element calculation to a recent decay rate calculation for hydrogenic ions is discussed, and application of the method to parity nonconservation in cesium is described.
[Dependence of "amplitude modulation following response" on attention].
Pethe, J; Mühler, R; von Specht, H
2001-03-01
Amplitude modulation following responses (AMFR) allows good estimation of the hearing threshold due to the very narrow band excitation of the cochlea. Audiological use of AMFR requires knowledge of the relationship of these responses to the state of vigilance. The few studies published compared only qualitatively the amplitude of AMFR recorded in awake subjects to that recorded in sleeping subjects. A quantitative determination of the level of vigilance on the basis of recorded physiological parameters has not yet been carried out. In the present study, the relationship between the amplitude of AMFR and the level of vigilance was investigated quantitatively. In eight adults with normal hearing, the relationship between the AMFR amplitude and EEG amplitude in the delta- and theta-band was determined. The amplitude in both frequency bands was used to indicate the state of vigilance. The subjects were studied during natural and drug-induced sleep. A 1-kHz carrier tone with a sinusoidally modulated amplitude of 40 Hz or 80 Hz was used as stimulus. At 40-Hz modulation frequency, the AMFR amplitude correlates with the EEG amplitude both in natural and drug-induced sleep. An increase in EEG activity is paralleled by a significant reduction of AMFR amplitude. At 80-Hz modulation frequency, no relationship between AMFR amplitude and EEG activity could be detected. Under all conditions, the amplitudes of AMFR evoked by a modulation frequency of 80 Hz were significantly lower than those evoked by 40 Hz. These results suggest that for an audiological use of the 40-Hz AMFR the state of vigilance should be stabilised at a constantly high level. In spite of the lower influence of vigilance on the 80-Hz AMFR, this response appears less ideal for threshold estimation in adults due to the significantly smaller amplitudes.
Transition control by periodic suction-blowing
NASA Technical Reports Server (NTRS)
Biringen, S.; Nutt, W. E.; Caruso, M. J.
1985-01-01
The applicability of active control of transition by period suction-blowing is investigated via direct numerical simulations of the Navier-Stokes equations. The time-evolution of finite-amplitude disturbances in plane channel flow is compared in detail with and without control. The analysis indicates that for relatively small three-dimensional amplitudes, a two-dimensional control effectively reduces disturbance growth rates even for linearly unstable Reynolds numbers. After the flow goes through secondary instability, three-dimensional control seems necessary to stabilize the flow. An investigation of the temperature field suggests that passive temperature contamination is operative to reflect the vorticity dynamics during transition.
Nucleon Resonance Transition Form factors
Burkert, Volker D.; Mokeev, Viktor I.; Aznauryan, Inna G.
2016-08-01
We discuss recent results from CLAS on electromagnetic resonance transition amplitudes and their dependence on the distance scale (Q2). From the comparison of these results with most advanced theoretical calculations within QCD-based approaches there is clear evidence that meson-baryon contributions are present and important at large distances, i.e. small Q2, and that quark core contributions dominate the short distance behavior.
Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light
NASA Astrophysics Data System (ADS)
Grujić, Z. D.; Weis, A.
2013-07-01
In recent years diode laser sources have become widespread and reliable tools in magneto-optical spectroscopy. In particular, laser-driven atomic magnetometers have found a wide range of practical applications. More recently, so-called magnetically silent variants of atomic magnetometers have been developed. While in conventional magnetometers the magnetic resonance transitions between atomic sublevels are phase-coherently driven by a weak oscillating magnetic field, silent magnetometers use schemes in which either the frequency or the amplitude of the light beam is modulated. Here we present a theoretical model that yields algebraic expressions for the parameters of the multiple resonances that occur when either amplitude-, frequency-, or polarization-modulated light of circular polarization is used to drive the magnetic resonance transition in a transverse magnetic field. The relative magnitudes of the resonances that are observed in the transmitted light intensity at harmonic m of the Larmor frequency ωL (either by DC or phase sensitive detection at harmonics q of the modulation frequency ωmod) of the transmitted light are expressed in terms of the Fourier coefficients of the modulation function. Our approach is based on an atomic multipole moment representation that is valid for spin-oriented atomic states with arbitrary angular momentum F in the low light power limit. We find excellent quantitative agreement with an experimental case study using (square-wave) amplitude-modulated light.
Maximal Values of the Auger Amplitudes and Propensity Rules for their Quantum Numbers
NASA Astrophysics Data System (ADS)
Kyiene, A.; Karazija, R.
2004-01-01
The maximal values of the Auger amplitudes corresponding to transitions of the type n1l14l1 + 1 n2l2N → n1l14l1 + 2n2l2N - 2ɛlj are investigated. It is shown that the maximal values of amplitudes vary within a relatively narrow interval and rather smoothly with N. Though the amplitude has a complicated expression for the considered transitions the quantum numbers of its maximal values obey rather general and strict propensity rules. They are also established for the quantum numbers of the initial and final states. It is shown that these rules are mainly determined by the two-electron fractional parentage coefficients. The existence of such rules indicates the additional properties of the interconfiguration matrix elements of the Coulomb interaction operator. The experimental data for the Auger spectra of atoms with closed shells confirm the validity of these rules for the determination of the most intensive line in the spectrum.
Scattering Amplitudes Interpolating Between Instant Form and Front Form of Relativistic Dynamics
NASA Astrophysics Data System (ADS)
Ji, Chueng-Ryong; Bakker, Bernard L. G.; Li, Ziyue; Suzuki, Alfredo T.
2014-06-01
Among the three forms of relativistic Hamiltonian dynamics proposed by Dirac in 1949, the front form has the largest number of kinematic generators. This distinction provides useful consequences in the analysis of physical observables in hadron physics. Using the method of interpolation between the instant form and the front form, we introduce the interpolating scattering amplitude that links the corresponding time-ordered amplitudes between the two forms of dynamics and provide the physical meaning of the kinematic transformations as they allow the invariance of each individual time-ordered amplitude for an arbitrary interpolation angle. We discuss the rationale for using front form dynamics, nowadays known as light-front dynamics (LFD), and present a few explicit examples of hadron phenomenology that LFD uniquely can offer from first-principles quantum chromodynamics. In particular, model-independent constraints are provided for the analyses of deuteron form factors and the N Δ transition form factors at large momentum transfer squared Q 2. The swap of helicity amplitudes between the collinear and non-collinear kinematics is also discussed in deeply virtual Compton scattering.
Amplitude and phase effects on the synchronization of delay-coupled oscillators
D'Huys, O.; Vicente, R.; Danckaert, J.; Fischer, I.
2010-12-15
We consider the behavior of Stuart-Landau oscillators as generic limit-cycle oscillators when they are interacting with delay. We investigate the role of amplitude and phase instabilities in producing symmetry-breaking/restoring transitions. Using analytical and numerical methods we compare the dynamics of one oscillator with delayed feedback, two oscillators mutually coupled with delay, and two delay-coupled elements with self-feedback. Taking only the phase dynamics into account, no chaotic dynamics is observed, and the stability of the identical synchronization solution is the same in each of the three studied networks of delay-coupled elements. When allowing for a variable oscillation amplitude, the delay can induce amplitude instabilities. We provide analytical proof that, in case of two mutually coupled elements, the onset of an amplitude instability always results in antiphase oscillations, leading to a leader-laggard behavior in the chaotic regime. Adding self-feedback with the same strength and delay as the coupling stabilizes the system in the transverse direction and, thus, promotes the onset of identically synchronized behavior.
The Effects of Rhythmicity and Amplitude on Transfer of Motor Learning
Ben-Tov, Mor; Levy-Tzedek, Shelly; Karniel, Amir
2012-01-01
We perform rhythmic and discrete arm movements on a daily basis, yet the motor control literature is not conclusive regarding the mechanisms controlling these movements; does a single mechanism generate both movement types, or are they controlled by separate mechanisms? A recent study reported partial asymmetric transfer of learning from discrete movements to rhythmic movements. Other studies have shown transfer of learning between large-amplitude to small-amplitude movements. The goal of this study is to explore which aspect is important for learning to be transferred from one type of movement to another: rhythmicity, amplitude or both. We propose two hypotheses: (1) Rhythmic and discrete movements are generated by different mechanisms; therefore we expect to see a partial or no transfer of learning between the two types of movements; (2) Within each movement type (rhythmic/discrete), there will be asymmetric transition of learning from larger movements to smaller ones. We used a learning-transfer paradigm, in which 70 participants performed flexion/extension movements with their forearm, and switched between types of movement, which differed in amplitude and/or rhythmicity. We found partial transfer of learning between discrete and rhythmic movements, and an asymmetric transfer of learning from larger movements to smaller movements (within the same type of movement). Our findings suggest that there are two different mechanisms underlying the generation of rhythmic and discrete arm movements, and that practicing on larger movements helps perform smaller movements; the latter finding might have implications for rehabilitation. PMID:23056549
The attenuation of Fourier amplitudes for rock sites in eastern North America
Atkinson, Gail M.; Boore, David M.
2014-01-01
We develop an empirical model of the decay of Fourier amplitudes for earthquakes of M 3–6 recorded on rock sites in eastern North America and discuss its implications for source parameters. Attenuation at distances from 10 to 500 km may be adequately described using a bilinear model with a geometric spreading of 1/R1.3 to a transition distance of 50 km, with a geometric spreading of 1/R0.5 at greater distances. For low frequencies and distances less than 50 km, the effective geometric spreading given by the model is perturbed using a frequency‐ and hypocentral depth‐dependent factor defined in such a way as to increase amplitudes at lower frequencies near the epicenter but leave the 1 km source amplitudes unchanged. The associated anelastic attenuation is determined for each event, with an average value being given by a regional quality factor of Q=525f 0.45. This model provides a match, on average, between the known seismic moment of events and the inferred low‐frequency spectral amplitudes at R=1 km (obtained by correcting for the attenuation model). The inferred Brune stress parameters from the high‐frequency source terms are about 600 bars (60 MPa), on average, for events of M>4.5.
Amplitude death induced by fractional derivatives in nonlinear coupled oscillators
NASA Astrophysics Data System (ADS)
Liu, Q. X.; Liu, J. K.; Chen, Y. M.
2017-07-01
This paper presents a study on amplitude death in nonlinear coupled oscillators containing fractional derivatives. Analytical criterion for amplitude death region is obtained by eigenvalue analysis and verified by numerical results. It is found that amplitude death regions can be enlarged to a large extent by fractional derivatives. For this reason, amplitude death can be detected in fractional Stuart-Landau systems with weak coupling strength and low frequency, whereas it never appears in integer-order systems. Interestingly, the widening of amplitude death region induced by fractional derivative is shared by a variety of oscillators with different types of coupling mechanisms. An interpretation for the underlying mechanism of this phenomenon is briefly addressed, based on which we further suggest a coupling organization leading to amplitude death only in fractional oscillators.
Image measurement technique on vibration amplitude of ultrasonic horn
NASA Astrophysics Data System (ADS)
Zhang, Yong-bin; Wu, Zhi-qun; Zhu, Jian-ping; He, Jian-guo; Liu, Guang-min
2013-10-01
The paper proposes a method to measure vibration amplitude of ultrasonic horn which is a very important component in the spindle for micro-electrical-chemical discharging machining. The method of image measuring amplitude on high frequency vibration is introduced. Non-contact measurement system based on vision technology is constructed. High precision location algorithm on image centroid, quadratic location algorithm, is presented to find the center of little light spot. Measurement experiments have been done to show the effect of image measurement technique on vibration amplitude of ultrasonic horn. In the experiments, precise calibration of the vision system is implemented using a normal graticule to obtain the scale factor between image pixel and real distance. The vibration amplitude of ultrasonic horn is changed by modifying the voltage amplitude of pulse power supply. The image of feature on ultrasonic horn is captured and image processing is carried out. The vibration amplitudes are got at different voltages.
Detection of combined frequency and amplitude modulation.
Moore, B C; Sek, A
1992-12-01
This article is concerned with the detection of mixed modulation (MM), i.e., simultaneously occurring amplitude modulation (AM) and frequency modulation (FM). In experiment 1, an adaptive two-alternative forced-choice task was used to determine thresholds for detecting AM alone. Then, thresholds for detecting FM were determined for stimuli which had a fixed amount of AM in the signal interval only. The amount of AM was always less than the threshold for detecting AM alone. The FM thresholds depended significantly on the magnitude of the coexisting AM. For low modulation rates (4, 16, and 64 Hz), the FM thresholds did not depend significantly on the relative phase of modulation for the FM and AM. For a high modulation rate (256 Hz) strong effects of modulator phase were observed. These phase effects are as predicted by the model proposed by Hartmann and Hnath [Acustica 50, 297-312 (1982)], which assumes that detection of modulation at modulation frequencies higher than the critical modulation frequency is based on detection of the lower sideband in the modulated signal's spectrum. In the second experiment, psychometric functions were measured for the detection of AM alone and FM alone, using modulation rates of 4 and 16 Hz. Results showed that, for each type of modulation, d' is approximately a linear function of the square of the modulation index. Application of this finding to the results of experiment 1 suggested that, at low modulation rates, FM and AM are not detected by completely independent mechanisms. In the third experiment, psychometric functions were again measured for the detection of AM alone and FM alone, using a 10-Hz modulation rate. Detectability was then measured for combined AM and FM, with modulation depths selected so that each type of modulation would be equally detectable if presented alone. Significant effects of relative modulator phase were found when detectability was relatively high. These effects were not correctly predicted by either a
Log-periodic Critical Amplitudes: A Perturbative Approach
NASA Astrophysics Data System (ADS)
Derrida, Bernard; Giacomin, Giambattista
2013-06-01
Log-periodic amplitudes appear in the critical behavior of a large class of systems, in particular when a discrete scale invariance is present. Here we show how to compute these critical amplitudes perturbatively when they originate from a renormalization map which is close to a monomial. In this case, the log-periodic amplitudes of the subdominant corrections to the leading critical behavior can also be calculated.
N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop
Bern, Z.; Boucher-Veronneau, C.; Johansson, H.; /Saclay
2011-08-19
We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N {ge} 4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.
Calculation and modular properties of multiloop superstring amplitudes
Danilov, G. S.
2013-06-15
Multiloop superstring amplitudes are calculated within an extensively used gauge where the two-dimensional gravitino field carries Grassmann moduli. In general, the amplitudes possess, instead of modular symmetry, symmetry with respect to modular transformation supplemented with appropriate transformations of two-dimensional local supersymmetry. If the number of loops is larger than three, the integrationmeasures are notmodular forms, while the expression for the amplitude contains integrals along the boundary of the fundamental region of the modular group.
Mass of nonrelativistic meson from leading twist distribution amplitudes
NASA Astrophysics Data System (ADS)
Braguta, V. V.
2011-01-01
In this paper distribution amplitudes of pseudoscalar and vector nonrelativistic mesons are considered. Using equations of motion for the distribution amplitudes, relations are derived which allow one to calculate the masses of nonrelativistic pseudoscalar and vector meson if the leading twist distribution amplitudes are known. These relations can be also rewritten as relations between the masses of nonrelativistic mesons and infinite series of QCD operators, what can be considered as an exact version of Gremm-Kapustin relation in NRQCD.
Tree-level split helicity amplitudes in ambitwistor space
NASA Astrophysics Data System (ADS)
Chen, Bin; Wu, Jun-Bao
2009-12-01
We study all tree-level split helicity gluon amplitudes by using the recently proposed Britto-Cachazo-Feng-Witten recursion relation and Hodges diagrams in ambitwistor space. We pick out the contributing diagrams and find that all of them can be divided into triangles in a suitable way. We give the explicit expressions for all of these amplitudes. As an example, we reproduce the six-gluon split next-to-maximally-helicity-violating amplitudes in momentum space.
Scattering amplitudes and BCFW recursion in twistor space
NASA Astrophysics Data System (ADS)
Mason, Lionel; Skinner, David
2010-01-01
Twistor ideas have led to a number of recent advances in our understanding of scattering amplitudes. Much of this work has been indirect, determining the twistor space support of scattering amplitudes by examining the amplitudes in momentum space. In this paper, we construct the actual twistor scattering amplitudes themselves. We show that the recursion relations of Britto, Cachazo, Feng and Witten have a natural twistor formulation that, together with the three-point seed amplitudes, allows us to recursively construct general tree amplitudes in twistor space. We obtain explicit formulae for n-particle MHV and NMHV super-amplitudes, their CPT conjugates (whose representations are distinct in our chiral framework), and the eight particle N2MHV super-amplitude. We also give simple closed form formulae for the mathcal{N} = 8 supergravity recursion and the MHV and overline {text{MHV}} amplitudes. This gives a formulation of scattering amplitudes in maximally supersymmetric theories in which superconformal symmetry and its breaking is manifest. For N k MHV, the amplitudes are given by 2 n - 4 integrals in the form of Hilbert transforms of a product of n - k - 2 purely geometric, superconformally invariant twistor delta functions, dressed by certain sign operators. These sign operators subtly violate conformal invariance, even for tree-level amplitudes in mathcal{N} = 4 super Yang-Mills, and we trace their origin to a topological property of split signature space-time. We develop the twistor transform to relate our work to the ambidextrous twistor diagram approach of Hodges and of Arkani-Hamed, Cachazo, Cheung and Kaplan.
Amplitude-modulated circular-harmonic filter for pattern recognition.
Chen, X W; Chen, Z P
1995-02-10
An amplitude-modulated circular-harmonic filter is proposed for rotation-invariant pattern recognition. We investigate the filter characteristics by varying two design parameters, A(ρ) and B(ρ), and select optimum values to design an amplitude-modulated circular-harmonic filter. When compared with the phase-only circular-harmonic filter, the amplitude-modulated circular-harmonic filter is found to yield a sharper correlation peak, a better noise tolerance, and an improved correlation discrimination.
Amplitudes and Ultraviolet Behavior of N = 8 Supergravity
Bern, Zvi; Carrasco, John Joseph; Dixon, Lance J.; Johansson, Henrik; Roiban, Radu; /Penn State U.
2011-05-20
In this contribution we describe computational tools that permit the evaluation of multi-loop scattering amplitudes in N = 8 supergravity, in terms of amplitudes in N = 4 super-Yang-Mills theory. We also discuss the remarkable ultraviolet behavior of N = 8 supergravity, which follows from these amplitudes, and is as good as that of N = 4 super-Yang-Mills theory through at least four loops.
Cluster functions and scattering amplitudes for six and seven points
NASA Astrophysics Data System (ADS)
Harrington, Thomas; Spradlin, Marcus
2017-07-01
Scattering amplitudes in planar super-Yang-Mills theory satisfy several basic physical and mathematical constraints, including physical constraints on their branch cut structure and various empirically discovered connections to the mathematics of cluster algebras. The power of the bootstrap program for amplitudes is inversely proportional to the size of the intersection between these physical and mathematical constraints: ideally we would like a list of constraints which determine scattering amplitudes uniquely. We explore this intersection quantitatively for two-loop six- and seven-point amplitudes by providing a complete taxonomy of the Gr(4, 6) and Gr(4, 7) cluster polylogarithm functions of [15] at weight 4.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William [Overland Park, KS
2008-10-21
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-03
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-10-02
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-17
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William [Overland Park, KS
2009-09-01
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-03
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Phase and amplitude control system for Stanford Linear Accelerator
Yoo, S.J.
1983-09-26
The computer controlled phase and amplitude detection system measures the instantaneous phase and amplitude of a 1 micro-second 2856 MHz rf pulse at a 180 Hz rate. This will be used for phase feedback control, and also for phase and amplitude jitter measurement. The program, which was originally written by John Fox and Keith Jobe, has been modified to improve the function of the system. The software algorithms used in the measurement are described, as is the performance of the prototype phase and amplitude detector system.
Cluster functions and scattering amplitudes for six and seven points
Harrington, Thomas; Spradlin, Marcus
2017-07-05
Scattering amplitudes in planar super-Yang-Mills theory satisfy several basic physical and mathematical constraints, including physical constraints on their branch cut structure and various empirically discovered connections to the mathematics of cluster algebras. The power of the bootstrap program for amplitudes is inversely proportional to the size of the intersection between these physical and mathematical constraints: ideally we would like a list of constraints which determine scattering amplitudes uniquely. Here, we explore this intersection quantitatively for two-loop six- and seven-point amplitudes by providing a complete taxonomy of the Gr(4, 6) and Gr(4, 7) cluster polylogarithm functions of [15] at weight 4.
HD 47147 - A small-amplitude extreme metal-poor RRab pulsating variable
NASA Astrophysics Data System (ADS)
Grenon, M.; Waelkens, C.
1986-01-01
The photometric variations and physical and kinematical properties of HD 47147, a ninth magnitude metal-deficient star, are discussed. The long period (0.79732 days), the small amplitude (0.17 mag in the visual band), and the mean effective temperature of 6160 K of this RR Lyrae pulsating variable can be understood by its location near the red edge of the instability strip. The extreme Population II characteristics of HD 47147 are confirmed by its kinematical properties. The temperature and the relatively high luminosity derived are consistent with both possibilities that HD 47147 is a red horizontal branch star or that it is a suprahorizontal branch star actually evolving redward toward the asymptotic branch. Its low amplitude suggests the possibility that the red edge of the instability strip corresponds to a smooth transition from variable to non-variable stars.
Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids.
Jaafar, Miriam; Martínez-Martín, David; Cuenca, Mariano; Melcher, John; Raman, Arvind; Gómez-Herrero, Julio
2012-01-01
We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode.
Collective amplitude mode fluctuations in a flat band superconductor formed at a semimetal surface
NASA Astrophysics Data System (ADS)
Kauppila, V. J.; Hyart, T.; Heikkilä, T. T.
2016-01-01
We study the fluctuations of the amplitude (i.e., the Higgs-Anderson) mode in a superconducting system of coupled Dirac particles proposed as a model for possible surface or interface superconductivity in rhombohedral graphite. This system also serves as a generic model of a topological semimetal with an interaction-driven transition on its surface. We show that the absence of Fermi energy and vanishing of the excitation gap of the collective amplitude mode in the model leads to a large fluctuation contribution to thermodynamic quantities, such as the heat capacity. As a consequence, the mean-field theory becomes inaccurate, indicating that the interactions lead to a strongly correlated state. We also present a microscopic derivation of the Ginzburg-Landau theory corresponding to this model.
On large amplitude motions of simplest amides in the ground and excited electronic states
NASA Astrophysics Data System (ADS)
Tukachev, N. V.; Bataev, V. A.; Godunov, I. A.
2016-12-01
For the formamide, acetamide, N-methylformamide and N-methylacetamide molecules in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states equilibrium geometry parameters, harmonic vibrational frequencies, barriers to conformational transitions and conformer energy differences were estimated by means of MP2, CCSD(T), CASSCF, CASPT2 and MRCI ab initio methods. One-, two- and three-dimensional potential energy surface (PES) sections corresponding to different large amplitude motions (LAM) were calculated by means of MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1,T1). For these molecules, in each excited electronic state six minima were found on 2D PES sections. Using PES sections, different anharmonic vibrational problems were solved and the frequencies of large amplitude vibrations were determined.
On a study of optically coupled memristive Chua circuits-rhythmogenesis and amplitude death
NASA Astrophysics Data System (ADS)
Chakraborty, Arindam; Ray, Anirban; Basak, Sankar; Roy Chowdhury, A.
2015-07-01
Properties of memristive inductorless Chua circuits are studied when they are coupled optically to characterize the oscillation quenching phenomenon of amplitude death (AD) and oscillation generation procedure of rhythmogenesis. The behaviors of these systems, when studied under coupled condition, show some new features which are not seen previously. This phenomenon is really a novel one as it is the generation of oscillation due to the interaction of two such systems each at their respective steady states. The other event is amplitude death (AD) observed by increase in the coupling strength. The numerical simulation is supported with the data obtained via analogue circuit implementation of the system. Two circuits coupled through a LED (light emitting diode) and LDR (photo resistor) pair show transition to chaotic state under parameter variation. The experimental data was collected with the help of digital to analog converter system. Our data indicates that there exist two different routes to chaos-either through period doubling or without it.
Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids
Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind
2012-01-01
Summary We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. PMID:22563531
Bulk amplitude and degree of divergence in 4D spin foams
NASA Astrophysics Data System (ADS)
Chen, Lin-Qing
2016-11-01
We study the 4D holomorphic spin foam amplitude on arbitrary connected 2-complexes and degrees of divergence. With recently developed tools and a truncation scheme, we derive a formula for a certain class of graphs, which allows us to write down the value of bulk amplitudes simply based on graph properties. We then generalize the result to arbitrarily connected 2-complexes and extract a simple expression for the degree of divergence only in terms of combinatorial properties and topological invariants. The distinct behaviors of the model in different regions of parameter space signal phase transitions. In the regime which is of physical interest for recovering diffeomorphism symmetry in the continuum limit, the most divergent configurations are melonic graphs. We end with a discussion of physical implications.
Amplitude equation and long-range interactions in underwater sand ripples in one dimension.
Schnipper, Teis; Mertens, Keith; Ellegaard, Clive; Bohr, Tomas
2008-10-01
We present an amplitude equation for sand ripples under oscillatory flow in a situation where the sand is moving in a narrow channel and the height profile is practically one dimensional. The equation has the form ht = - epsilon(h-h)+((hx)2-1)hxx-hxxxx+delta((hx)2)xx which, due to the first term, is neither completely local (it has long-range coupling through the average height h) nor has local sand conservation. We argue that this is reasonable and show that the equation compares well with experimental observations in narrow channels. We focus in particular on the so-called doubling transition, a secondary instability caused by the sudden decrease in the amplitude of the water motion, leading to the appearance of a new ripple in each trough. This transition is well reproduced for sufficiently large delta (asymmetry between trough and crest). We finally present surprising experimental results showing that long-range coupling is indeed seen in the initial details of the doubling transition, where in fact two small ripples are initially formed, followed by global symmetry breaking removing one of them.
Semiclassical Analysis of Fundamental Amplitudes in Loop Quantum Gravity
NASA Astrophysics Data System (ADS)
Hedeman, Austin J.
Spin networks arise in many areas of physics and are a key component in both the canonical formulation (loop quantum gravity) and the path-integral formulation (spin-foam gravity) of quantum gravity. In loop quantum gravity the spin networks are used to construct a countable basis for the physical Hilbert space of gravity. The basis states may be interpreted as gauge-invariant wavefunctionals of the connection. Evaluating the wavefunctional on a specific classical connection involves embedding the spin network into a spacelike hypersurface and finding the holonomy around the network. This is equivalent to evaluating a ''g-inserted'' spin network (a spin network with a group action acting on all of the edges of the network). The spin-foam approach to quantum gravity is a path-integral formulation of loop quantum gravity in which the paths are world-histories of embedded spin networks. Depending on the spin-foam model under consideration the vertex amplitude (the contribution a spin-foam vertex makes to the transition amplitude) may be represented by a specific simple closed spin network. The most important examples use the 6j-symbol, the 15j-symbol, and the Riemannian 10j-symbol. The semiclassical treatment of spin networks is the main theme of this dissertation. To show that classical solutions of general relativity emerge in the appropriate limits of loop quantum gravity or spin-foam gravity requires knowledge of the semiclassical limits of spin networks. This involves interpreting the spin networks as inner products and then treating the inner products semiclassically using the WKB method and the stationary phase approximation. For any given spin network there are many possible inner product models which correspond to how the spin network is ''split up'' into pieces. For example the 6 j-symbol has been studied in both a model involving four angular momenta (Aquilanti et al 2012) and a model involving twelve angular momenta (Roberts 1999). Each of these models
Source-Space Cross-Frequency Amplitude-Amplitude Coupling in Tinnitus
Zobay, Oliver; Adjamian, Peyman
2015-01-01
The thalamocortical dysrhythmia (TCD) model has been influential in the development of theoretical explanations for the neurological mechanisms of tinnitus. It asserts that thalamocortical oscillations lock a region in the auditory cortex into an ectopic slow-wave theta rhythm (4–8 Hz). The cortical area surrounding this region is hypothesized to generate abnormal gamma (>30 Hz) oscillations (“edge effect”) giving rise to the tinnitus percept. Consequently, the model predicts enhanced cross-frequency coherence in a broad range between theta and gamma. In this magnetoencephalography study involving tinnitus and control cohorts, we investigated this prediction. Using beamforming, cross-frequency amplitude-amplitude coupling (AAC) was computed within the auditory cortices for frequencies (f1, f2) between 2 and 80 Hz. We find the AAC signal to decompose into two distinct components at low (f1, f2 < 30 Hz) and high (f1, f2 > 30 Hz) frequencies, respectively. Studying the correlation of AAC with several key covariates (age, hearing level (HL), tinnitus handicap and duration, and HL at tinnitus frequency), we observe a statistically significant association between age and low-frequency AAC. Contrary to the TCD predictions, however, we do not find any indication of statistical differences in AAC between tinnitus and controls and thus no evidence for the predicted enhancement of cross-frequency coupling in tinnitus. PMID:26665004
NASA Astrophysics Data System (ADS)
Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia
2011-11-01
This issue aims to serve as an introduction to our current understanding of the structure of scattering amplitudes in gauge theory, an area which has seen particularly rapid advances in recent years following decades of steady progress. The articles contained herein provide a snapshot of the latest developments which we hope will serve as a valuable resource for graduate students and other scientists wishing to learn about the current state of the field, even if our continually evolving understanding of the subject might soon render this compilation incomplete. Why the fascination with scattering amplitudes, which have attracted the imagination and dedicated effort of so many physicists? Part of it stems from the belief, supported now by numerous examples, that unexpected simplifications of otherwise apparently complicated calculations do not happen by accident. Instead they provide a strong motivation to seek out an underlying explanation. The insight thereby gained can subsequently be used to make the next class of seemingly impossible calculations not only possible, but in some cases even trivial. This two-pronged strategy of exploring and exploiting the structure of gauge theory amplitudes appeals to a wide audience from formal theorists interested in mathematical structure for the sake of its own beauty to more phenomenologically-minded physicists eager to speed up the next generation of analysis software. Understandably it is the maximally supersymmetric 𝒩 = 4 Yang-Mills theory (SYM) which has the simplest structure and has correspondingly received the most attention. Rarely in theoretical physics are we fortunate enough to encounter a toy model which is simple enough to be solved completely yet rich enough to possess interesting non-trivial structure while simultaneously, and most importantly, being applicable (even if only as a good approximation) to a wide range of 'real' systems. The canonical example in quantum mechanics is of course the harmonic
ERIC Educational Resources Information Center
Naylor, Mary; Keating, Stacen A.
2008-01-01
Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…
ERIC Educational Resources Information Center
Naylor, Mary; Keating, Stacen A.
2008-01-01
Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…
Ratios of helicity amplitudes for exclusive ρ ^0 electroproduction on transversely polarized protons
NASA Astrophysics Data System (ADS)
Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Belostotski, S.; Blok, H. P.; Borissov, A.; Bryzgalov, V.; Capitani, G. P.; Ciullo, G.; Contalbrigo, M.; Deconinck, W.; De Leo, R.; De Sanctis, E.; Düren, M.; Elbakian, G.; Ellinghaus, F.; Felawka, L.; Frullani, S.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Goloskokov, S. V.; Holler, Y.; Ivanilov, A.; Jackson, H. E.; Joosten, S.; Kaiser, R.; Karyan, G.; Kisselev, A.; Korotkov, V.; Kozlov, V.; Kravchenko, P.; Kroll, P.; Lagamba, L.; Lapikás, L.; Lehmann, I.; Lenisa, P.; Lorenzon, W.; Manaenkov, S. I.; Marianski, B.; Marukyan, H.; Miyachi, Y.; Movsisyan, A.; Muccifora, V.; Nass, A.; Nowak, W.-D.; Pappalardo, L. L.; Petrosyan, A.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Ryckbosch, D.; Salomatin, Y.; Schäfer, A.; Schnell, G.; Seitz, B.; Shibata, T.-A.; Shutov, V.; Statera, M.; Terkulov, A.; Truty, R.; Trzcinski, A.; Tytgat, M.; Van Haarlem, Y.; Van Hulse, C.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Yaschenko, S.; Zihlmann, B.; Zupranski, P.
2017-06-01
Exclusive ρ ^0-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV^2amplitudes describing ρ 0-meson production by a virtual photon. The denominator of those ratios is the dominant amplitude, the nucleon-helicity-non-flip amplitude F_{01/201/2}, which describes the production of a longitudinal ρ 0-meson by a longitudinal virtual photon. The ratios of nucleon-helicity-non-flip amplitudes are found to be in good agreement with those from the previous HERMES analysis. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to F_{01/201/2}. Results obtained in a handbag approach based on generalized parton distributions taking into account the contribution from pion exchange are found to be in good agreement with these ratios. Within the model, the data favor a positive sign for the π -ρ transition form factor. By also exploiting the longitudinal beam polarization, a total of 71 ρ ^0 spin-density matrix elements is determined from the extracted 25 parameters, in contrast to only 53 elements as directly determined in earlier analyses.
Statistics of electric fields' amplitudes in Langmuir turbulence: A numerical simulation study
NASA Astrophysics Data System (ADS)
Voshchepynets, A.; Volokitin, A.; Krasnoselskikh, V.; Krafft, C.
2017-04-01
A systematic study of the properties of Langmuir turbulence generated by electron beams via bump-on-tail instabilities in strongly nonhomogeneous plasmas is presented. A statistical analysis of the Langmuir waves' amplitudes using numerical simulations based on two theoretical models is performed: a dynamical one and a probabilistic one. The former describes the self-consistent dynamics of wave-particle and wave-wave interactions. The latter is a modified version of the quasi-linear theory. To analyze the simulation data provided by the probabilistic model, a Pearson technique is used to classify the calculated probability distribution functions (PDFs) of the logarithm of the waves' amplitudes. It is demonstrated that the core parts of the PDFs belong to the Pearson types I, IV, and VI distributions, while the high-amplitude parts of the PDFs follow power law or exponential decay. Analysis of the PDFs calculated using the numerical simulations based on the dynamical model leads to the following additional results. In the small-amplitude parts of the PDFs, a universal scaling parameter is found, with a value not depending on the average levels of the density fluctuations and of the Langmuir turbulence. Second, the PDFs are obtained in the presence of wave decay processes. When those are weak, the PDFs show at large fields' amplitudes an exponential asymptotic behavior; during time evolution, the corresponding scaling parameter decreases until a universal probability distribution is reached, indicating that the wave decay processes are sufficiently strong. Such exponential type of distribution is a specific signature of transition states in the Langmuir turbulence.
Amplitudes in N = 4 Super-Yang-Mills Theory
NASA Astrophysics Data System (ADS)
Spradlin, Marcus
These lecture notes provide a lightning introduction to some aspects of scattering amplitudes in maximally supersymmetric theory, aimed at the audience of students attending the 2014 TASI summer school "Journeys Through the Precision Frontier: Amplitudes for Colliders". Emphasis is placed on explaining modern terminology so that students needing to delve further may more easily access the available literature.
Proof of a new colour decomposition for QCD amplitudes
NASA Astrophysics Data System (ADS)
Melia, Tom
2015-12-01
Recently, Johansson and Ochirov conjectured the form of a new colour decom-position for QCD tree-level amplitudes. This note provides a proof of that conjecture. The proof is based on `Mario World' Feynman diagrams, which exhibit the hierarchical Dyck structure previously found to be very useful when dealing with multi-quark amplitudes.
Proof of a new colour decomposition for QCD amplitudes
Melia, Tom
2015-12-16
Recently, Johansson and Ochirov conjectured the form of a new colour decom-position for QCD tree-level amplitudes. This note provides a proof of that conjecture. The proof is based on ‘Mario World’ Feynman diagrams, which exhibit the hierarchical Dyck structure previously found to be very useful when dealing with multi-quark amplitudes.
Simple parametrization of the π-N amplitude
NASA Astrophysics Data System (ADS)
McLeod, R. J.; Afnan, I. R.
1985-07-01
We present a simple parametrization of the S-, P-, and D-wave π-N amplitudes using separable potentials for Tπ<1 GeV. The effect of the inelasticity is included in the Green's function while maintaining consistency with unitarity. The P11 amplitude is written as a pole plus nonpole in order to describe pion absorption in A>=2.
Miracles in Scattering Amplitudes: from QCD to Gravity
Volovich, Anastasia
2016-10-09
The goal of my research project "Miracles in Scattering Amplitudes: from QCD to Gravity" involves deepening our understanding of gauge and gravity theories by exploring hidden structures in scattering amplitudes and using these rich structures as much as possible to aid practical calculations.
Abnormal Selective Attention Normalizes P3 Amplitudes in PDD
ERIC Educational Resources Information Center
Hoeksma, Marco R.; Kemner, Chantal; Kenemans, J. Leon; van Engeland, Herman
2006-01-01
This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in…
Automated force controller for amplitude modulation atomic force microscopy
Miyagi, Atsushi E-mail: simon.scheuring@inserm.fr; Scheuring, Simon E-mail: simon.scheuring@inserm.fr
2016-05-15
Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.
High frequency amplitude detector for GMI magnetic sensors.
Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul
2014-12-19
A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.
High Frequency Amplitude Detector for GMI Magnetic Sensors
Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul
2014-01-01
A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003
Reinforcing saccadic amplitude variability in a visual search task.
Paeye, Céline; Madelain, Laurent
2014-11-20
Human observers often adopt rigid scanning strategies in visual search tasks, even though this may lead to suboptimal performance. Here we ask whether specific levels of saccadic amplitude variability may be induced in a visual search task using reinforcement learning. We designed a new gaze-contingent visual foraging task in which finding a target among distractors was made contingent upon specific saccadic amplitudes. When saccades of rare amplitudes led to displaying the target, the U values (measuring uncertainty) increased by 54.89% on average. They decreased by 41.21% when reinforcing frequent amplitudes. In a noncontingent control group no consistent change in variability occurred. A second experiment revealed that this learning transferred to conventional visual search trials. These results provide experimental support for the importance of reinforcement learning for saccadic amplitude variability in visual search. © 2014 ARVO.
Discontinuities of BFKL amplitudes and the BDS ansatz
NASA Astrophysics Data System (ADS)
Fadin, V. S.; Fiore, R.
2015-12-01
We perform an examination of discontinuities of multiple production amplitudes, which are required for further development of the BFKL approach. It turns out that the discontinuities of 2 → 2 + n amplitudes obtained in the BFKL approach contradict to the BDS ansatz for amplitudes with maximal helicity violation in N = 4 supersymmetric Yang-Mills theory with large number of colors starting with n = 2. Explicit expressions for the discontinuities of the 2 → 3 and 2 → 4 amplitudes in the invariant mass of pairs of produced gluons are obtained in the planar N = 4 SYM in the next-to-leading logarithmic approximation. These expressions can be used for checking the conjectured duality between the light-like Wilson loops and the MHV amplitudes.
Effective Field Theories from Soft Limits of Scattering Amplitudes.
Cheung, Clifford; Kampf, Karol; Novotny, Jiri; Trnka, Jaroslav
2015-06-05
We derive scalar effective field theories-Lagrangians, symmetries, and all-from on-shell scattering amplitudes constructed purely from Lorentz invariance, factorization, a fixed power counting order in derivatives, and a fixed order at which amplitudes vanish in the soft limit. These constraints leave free parameters in the amplitude which are the coupling constants of well-known theories: Nambu-Goldstone bosons, Dirac-Born-Infeld scalars, and Galilean internal shift symmetries. Moreover, soft limits imply conditions on the Noether current which can then be inverted to derive Lagrangians for each theory. We propose a natural classification of all scalar effective field theories according to two numbers which encode the derivative power counting and soft behavior of the corresponding amplitudes. In those cases where there is no consistent amplitude, the corresponding theory does not exist.
New formulas for amplitudes from higher-dimensional operators
NASA Astrophysics Data System (ADS)
He, Song; Zhang, Yong
2017-02-01
In this paper we study tree-level amplitudes from higher-dimensional operators, including F 3 operator of gauge theory, and R 2, R 3 operators of gravity, in the Cachazo-He-Yuan formulation. As a generalization of the reduced Pfaffian in Yang-Mills theory, we find a new, gauge-invariant object that leads to gluon amplitudes with a single insertion of F 3, and gravity amplitudes by Kawai-Lewellen-Tye relations. When reduced to four dimensions for given helicities, the new object vanishes for any solution of scattering equations on which the reduced Pfaffian is non-vanishing. This intriguing behavior in four dimensions explains the vanishing of graviton helicity amplitudes produced by the Gauss-Bonnet R 2 term, and provides a scattering-equation origin of the decomposition into self-dual and anti-self-dual parts for F 3 and R 3 amplitudes.
Gravity Amplitudes as Generalized Double Copies of Gauge-Theory Amplitudes
NASA Astrophysics Data System (ADS)
Bern, Zvi; Carrasco, John Joseph; Chen, Wei-Ming; Johansson, Henrik; Roiban, Radu
2017-05-01
Whenever the integrand of a gauge-theory loop amplitude can be arranged into a form where the Bern-Carrasco-Johansson duality between color and kinematics is manifest, a corresponding gravity integrand can be obtained simply via the double-copy procedure. However, finding such gauge-theory representations can be challenging, especially at high loop orders. Here, we show that we can, instead, start from generic gauge-theory integrands, where the duality is not manifest, and apply a modified double-copy procedure to obtain gravity integrands that include contact terms generated by violations of dual Jacobi identities. We illustrate this with three-, four- and five-loop examples in N =8 supergravity.
Gravity Amplitudes as Generalized Double Copies of Gauge-Theory Amplitudes.
Bern, Zvi; Carrasco, John Joseph; Chen, Wei-Ming; Johansson, Henrik; Roiban, Radu
2017-05-05
Whenever the integrand of a gauge-theory loop amplitude can be arranged into a form where the Bern-Carrasco-Johansson duality between color and kinematics is manifest, a corresponding gravity integrand can be obtained simply via the double-copy procedure. However, finding such gauge-theory representations can be challenging, especially at high loop orders. Here, we show that we can, instead, start from generic gauge-theory integrands, where the duality is not manifest, and apply a modified double-copy procedure to obtain gravity integrands that include contact terms generated by violations of dual Jacobi identities. We illustrate this with three-, four- and five-loop examples in N=8 supergravity.
Comment on ``Multiphoton-ionization transition amplitudes and the Keldysh approximation''
NASA Astrophysics Data System (ADS)
Neto, H. S.; Davidovich, L.; Milonni, P. W.
1990-04-01
We show that the approach of Trombetta, Basile, and Ferrante [Phys. Rev. A 40, 2774 (1989)] does not establish the Keldysh ansatz as a well-defined approximation. In particular, it in effect replaces a vanishing contribution to the ionization rate by a nonvanishing one.
γvNN^* Transition Amplitudes and Excited Baryon Structure from CLAS
NASA Astrophysics Data System (ADS)
Mokeev, Victor
2013-04-01
Studying excited nucleon structure through exclusive-meson electroproduction reactions is key for understanding the nature of the strong interaction in the non-perturbative regime. With its nearly complete coverage of the final-state phase space, the CLAS detector at JLab has provided the lion's share of the world's meson-electroproduction data for differential cross sections and the asymmetries arising from single- and double-polarization observables. Electrocouplings for most of the excited nucleon states (N^*) in mass range of up to 1.8 GeV have been determined from several analyses of the CLAS data for photon virtualities (Q^2) up to 5.0 GeV^2 for the ^amp;+n, ^0p, and ηp channels [1,3] as well as for the ^amp;+^amp;-p reaction for Q^2 < 1.5 GeV^2 [2,3]. Physics analyses of these N^* electrocouplings [2,3] have revealed that the structure of excited nucleon is formed of an internal core of dressed quarks with an external meson-baryon cloud. Our N^*-electrocoupling results afford access to the non-perturbative strong interaction responsible for generating the different N^* states and will also provide testing ground for the inspired by QCD quark model predictions. A dedicated experiment will run after the 12 GeV upgrade to JLab on the extraction of the N^* electrocouplings in the yet unexplored region of high photon virtualities ranging from 5.0 to 12 GeV^2. The anticipated results are of particular importance in providing a understanding of the nature of confinement and dynamical chiral symmetry breaking in baryons based upon the QCD [3].[4pt] [1] I.G. Aznauryan and V.D. Burkert, Prog. Part. Nucl. Phys. 67, 1 (2012).[0pt] [2] V.I. Mokeev et al. (CLAS Collaboration), Phys. Rev. C86, 035203 (2012).[0pt] [3] I.G. Aznauryan et al., ``Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction,'' arXiv:1212.4891[nucl-th].
Multi-channel 1-to-2 transition amplitudes in a finite volume
Briceno, Raul; Hansen, Maxwell; Walker-Loud, Andre P
2015-04-01
We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the external current to inject arbitrary momentum into the system and we allow for the final state to be composed an arbitrary number of strongly coupled two-particle states with arbitrary partial waves (including partial-wave mixing induced by the volume). We also illustrate how our general result can be applied to some key examples, such as heavy meson decays and meson photo production. Finally, we point out complications that arise involving unstable resonance states, such as B to K*+l+l when staggered or mixed-action/partially-quenched calculations are performed.
One-loop transition amplitudes in the D1D5 CFT
NASA Astrophysics Data System (ADS)
Carson, Zaq; Hampton, Shaun; Mathur, Samir D.
2017-01-01
We consider the issue of thermalization in the D1D5 CFT. Thermalization is expected to correspond to the formation of a black hole in the dual gravity theory. We start from the orbifold point, where the theory is essentially free, and does not thermalize. In earlier work it was noted that there was no clear thermalization effect when the theory was deformed off the orbifold point to first order in the relevant twist perturbation. In this paper we consider the deformation to second order in the twist, where we do find effects that can cause thermalization of an initial perturbation. We consider a 1-loop process where two untwisted copies of the CFT are twisted to one copy and then again untwisted to two copies. We start with a single oscillator excitation on the initial CFT, and compute the effect of the two twists on this state. We find simple approximate expressions for the Bogoliubov coefficients and the behavior of the single oscillator excitation in the continuum limit, where the mode numbers involved are taken to be much larger than unity. We also prove a number of useful relationships valid for processes with an arbitrary number of twist insertions.
Vidanović, Ivana; Bogojević, Aleksandar; Belić, Aleksandar
2009-12-01
We analyze the method for calculation of properties of nonrelativistic quantum systems based on exact diagonalization of space-discretized short-time evolution operators. In this paper we present a detailed analysis of the errors associated with space discretization. Approaches using direct diagonalization of real-space discretized Hamiltonians lead to polynomial errors in discretization spacing Delta . Here we show that the method based on the diagonalization of the short-time evolution operators leads to substantially smaller discretization errors, vanishing exponentially with 1/Delta(2). As a result, the presented calculation scheme is particularly well suited for numerical studies of few-body quantum systems. The analytically derived discretization errors estimates are numerically shown to hold for several models. In the follow up paper [I. Vidanović, A. Bogojević, A. Balaz, and A. Belić, Phys. Rev. E 80, 066706 (2009)] we present and analyze substantial improvements that result from the merger of this approach with the recently introduced effective-action scheme for high-precision calculation of short-time propagation.
Single-Molecule Analysis of Protein Large-Amplitude Conformational Transitions
NASA Astrophysics Data System (ADS)
Yang, Haw
2011-03-01
Proteins have evolved to harness thermal fluctuations, rather than frustrated by them, to carry out chemical transformations and mechanical work. What are, then, the operation and design principles of protein machines? To frame the problem in a tractable way, several basic questions have been formulated to guide the experimental design: (a) How many conformational states can a protein sample on the functionally important timescale? (b) What are the inter-conversion rates between states? (c) How do ligand binding or interactions with other proteins modulate the motions? (d) What are the structural basis of flexibility and its underlying molecular mechanics? Guided by this framework, we have studied protein tyrosine phosphatase B, PtpB, from M. tuberculosis (a virulence factor of tuberculosis and a potential drug target) and adenylate kinase, AK, from E. coli (a ubiquitous energy-balancing enzyme in cells). These domain movements have been followed in real time on their respective catalytic timescales using high-resolution single-molecule Förster resonance energy transfer (FRET) spectroscopy. It is shown quantitatively that both PtpB and AK are capable of dynamically sampling two distinct states that correlate well with those observed by x-ray crystallography. Integrating these microscopic dynamics into macroscopic kinetics allows us to place the experimentally measured free-energy landscape in the context of enzymatic turnovers.
2014-09-11
This image, taken by NASA Mars Reconnaissance Orbiter, shows the transition between the Murray Formation, in which layers are poorly expressed and difficult to trace from orbit, and the hematite ridge, which is made up of continuous layers.
Near gap excitation of a CDW amplitude mode by time-resolved photoelectron spectroscopy
NASA Astrophysics Data System (ADS)
Leuenberger, Dominik; Yang, Shuolong; Sobota, Jonathan; Giraldo, Paula; Kirchmann, Patrick; Fisher, Ian; Shen, Zhi-Xun
2014-03-01
We present time-, angle- and energy-resolved photoelectron spectroscopy data from the light rear-earth tritelluride compound CeTe3. An in-plane Peierls distortion in the tellurium slabs leads to the formation of an incommensurate Charge Density Wave (CDW), accompanied by a CDW gap at the Fermi level. Ultrafast optical laser excitation and subsequent relaxation by means of electron-phonon coupling can coherently excite a periodic modulation of the CDW band position and the gap size in rear-earth tritellurides. In this work, the use of tuneable near infrared laser pulses allows for optical excitation slightly above and below the measured gap value of 570 meV. The smaller excitation phase space not only leads to cleaner amplitude mode signal but also helps to pin down the optical transitions, which are the driving mechanisms for the transient CDW phase transition. Financial support by the Swiss National Science Foundation is duly acknowledged.
Amplitude path corrections for regional phases in China
Phillips, W.S.; Velasco, A.A.; Taylor, S.R.; Randall, G.E.
1998-12-31
The authors investigate the effectiveness of amplitude path corrections for regional phases on seismic event discrimination and magnitude estimation. Waveform data from digital stations in China for regional, shallow (< 50 km) events were obtained from the IRIS Data Management Center (DMC) for years 1986 to 1996 using the USGS Preliminary Determination of Epicenters (PDE) and the Chinese State Seismological Bureau (SSB) catalogs. For each event, the amplitudes for each regional phase (P{sub n}, P{sub g}, S{sub n}, L{sub g}) were measured, as well as the P{sub g} and L{sub g} coda. Measured amplitudes were corrected for source scaling using estimates of m{sub b} and for distance using a power law that accounts for attenuation and spreading. The amplitude residuals were interpolated and mapped as 2-D amplitude correction surfaces. The authors employ several methods to create the amplitude correction surfaces: a waveguide method, and two interpolation methods (Baysian kriging and a circular moving window mean smoother). They explore the sensitivities of the surfaces to the method and to regional propagation, and apply these surfaces to correct amplitude data to reduce scatter in discrimination ratios and magnitude estimates.
Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves
Zeng, Liang; Lin, Jing; Huang, Liping; Zhao, Ming
2016-01-01
Besides the phase and group velocities, the amplitude of guided wave mode is also frequency dependent. This amplitude dispersion also influences the performance of guided wave methods in nondestructive evaluation (NDE) and structural health monitoring (SHM). In this paper, the effects of amplitude dispersion to the spectrum and waveform of a propagating wave-packet are investigated. It is shown that the amplitude dispersion results in distortion in the spectrum of guided wave response, and thus influences the waveform of the wave-packet. To remove these effects, an amplitude dispersion compensation method is established on the basis of Vold–Kalman filter and Taylor series expansion. The performance of that method is then investigated by experimental examples. The results show that with the application of the amplitude dispersion compensation, the time reversibility could be preserved, which ensures the applicability of the time reversal method for damage detection. Besides, through amplitude dispersion compensation, the testing resolution of guided waves could be improved, so that the structural features located in the close proximity may be separately identified. PMID:27706067
Discriminating simulated vocal tremor source using amplitude modulation spectra.
Carbonell, Kathy M; Lester, Rosemary A; Story, Brad H; Lotto, Andrew J
2015-03-01
Sources of vocal tremor are difficult to categorize perceptually and acoustically. This article describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor), and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. These results supply initial support for an amplitude-envelope-based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. Copyright © 2015 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
Bootstrapping Multi-Parton Loop Amplitudes in QCD
Bern, Zvi; Dixon, Lance J.; Kosower, David A.; /Saclay, SPhT
2005-07-06
The authors present a new method for computing complete one-loop amplitudes, including their rational parts, in non-supersymmetric gauge theory. This method merges the unitarity method with on-shell recursion relations. It systematizes a unitarity-factorization bootstrap approach previously applied by the authors to the one-loop amplitudes required for next-to-leading order QCD corrections to the processes e{sup +}e{sup -} {yields} Z, {gamma}* {yields} 4 jets and pp {yields} W + 2 jets. We illustrate the method by reproducing the one-loop color-ordered five-gluon helicity amplitudes in QCD that interfere with the tree amplitude, namely A{sub 5;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}) and A{sub 5;1}(1{sup -}, 2{sup +}, 3{sup -}, 4{sup +}, 5{sup +}). Then we describe the construction of the six- and seven-gluon amplitudes with two adjacent negative-helicity gluons, A{sub 6;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}) and A{sub 7;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}, 7{sup +}), which uses the previously-computed logarithmic parts of the amplitudes as input. They present a compact expression for the six-gluon amplitude. No loop integrals are required to obtain the rational parts.
Frequency adaptation for enhanced radiation force amplitude in dynamic elastography.
Ouared, Abderrahmane; Montagnon, Emmanuel; Kazemirad, Siavash; Gaboury, Louis; Robidoux, André; Cloutier, Guy
2015-08-01
In remote dynamic elastography, the amplitude of the generated displacement field is directly related to the amplitude of the radiation force. Therefore, displacement improvement for better tissue characterization requires the optimization of the radiation force amplitude by increasing the push duration and/or the excitation amplitude applied on the transducer. The main problem of these approaches is that the Food and Drug Administration (FDA) thresholds for medical applications and transducer limitations may be easily exceeded. In the present study, the effect of the frequency used for the generation of the radiation force on the amplitude of the displacement field was investigated. We found that amplitudes of displacements generated by adapted radiation force sequences were greater than those generated by standard nonadapted ones (i.e., single push acoustic radiation force impulse and supersonic shear imaging). Gains in magnitude were between 20 to 158% for in vitro measurements on agar-gelatin phantoms, and 170 to 336% for ex vivo measurements on a human breast sample, depending on focus depths and attenuations of tested samples. The signal-to-noise ratio was also improved more than 4-fold with adapted sequences. We conclude that frequency adaptation is a complementary technique that is efficient for the optimization of displacement amplitudes. This technique can be used safely to optimize the deposited local acoustic energy without increasing the risk of damaging tissues and transducer elements.
Large amplitude ion-acoustic solitons in dusty plasmas
Tiwari, R. S.; Jain, S. L.; Mishra, M. K.
2011-08-15
Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW{sup 2} of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW{sup 2}), are discussed in detail.
Broadband metasurface holograms: toward complete phase and amplitude engineering
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-01-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519
Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra
Carbonell, Kathy M.; Lester, Rosemary A.; Story, Brad H.; Lotto, Andrew J.
2014-01-01
Objectives/Hypothesis Sources of vocal tremor are difficult to categorize perceptually and acoustically. This paper describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Study Design Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Methods Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor) and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. Results The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. Conclusions These results supply initial support for an amplitude-envelope based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. PMID:25532813
Broadband metasurface holograms: toward complete phase and amplitude engineering
NASA Astrophysics Data System (ADS)
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-09-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.
Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves.
Zeng, Liang; Lin, Jing; Huang, Liping; Zhao, Ming
2016-09-30
Besides the phase and group velocities, the amplitude of guided wave mode is also frequency dependent. This amplitude dispersion also influences the performance of guided wave methods in nondestructive evaluation (NDE) and structural health monitoring (SHM). In this paper, the effects of amplitude dispersion to the spectrum and waveform of a propagating wave-packet are investigated. It is shown that the amplitude dispersion results in distortion in the spectrum of guided wave response, and thus influences the waveform of the wave-packet. To remove these effects, an amplitude dispersion compensation method is established on the basis of Vold-Kalman filter and Taylor series expansion. The performance of that method is then investigated by experimental examples. The results show that with the application of the amplitude dispersion compensation, the time reversibility could be preserved, which ensures the applicability of the time reversal method for damage detection. Besides, through amplitude dispersion compensation, the testing resolution of guided waves could be improved, so that the structural features located in the close proximity may be separately identified.
Coronagraphic Amplitude and Phase Correction for Detecting Planets
NASA Technical Reports Server (NTRS)
Woodgate, Bruce E.; Bowers, Charles W.
2003-01-01
Detection of earth-like planets around other stars using coronagraphy requires the optical beam into the coronagraph to be extremely uniform in both phase and amplitude. Errors in phase can be corrected using a deformable mirror, and error in amplitude can be corrected using a spatial light modulator, both in the pupil plan,a. These corrections can be combined using a Michelson interferometer. If amplitude corrections of only a few percent range are needed, the required accuracy of 10 (circumflex) -4 can be obtained with spatial light modulators with the modest dynamic range of 8 bits.
Direct Calculation of the Scattering Amplitude Without Partial Wave Analysis
NASA Technical Reports Server (NTRS)
Shertzer, J.; Temkin, A.; Fisher, Richard R. (Technical Monitor)
2001-01-01
Two new developments in scattering theory are reported. We show, in a practical way, how one can calculate the full scattering amplitude without invoking a partial wave expansion. First, the integral expression for the scattering amplitude f(theta) is simplified by an analytic integration over the azimuthal angle. Second, the full scattering wavefunction which appears in the integral expression for f(theta) is obtained by solving the Schrodinger equation with the finite element method (FEM). As an example, we calculate electron scattering from the Hartree potential. With minimal computational effort, we obtain accurate and stable results for the scattering amplitude.
Direct numerical approach to one-loop amplitudes
NASA Astrophysics Data System (ADS)
Duplančić, G.; Klajn, B.
2017-01-01
We present a completely numerical method of calculating one-loop amplitudes. Our approach is built upon two different existing methods: the contour deformation and the extrapolation methods. Taking the best features of each of them, we devise an intuitive, stable and robust procedure which circumvents the problem of large cancellations and related numerical instabilities by calculating the complete amplitude at once. As a proof of concept, we use our method to calculate the 2 γ →(N -2 )γ benchmark process, as well as the Higgs decay amplitude H →γ γ .
Analytical formula for three points sinusoidal signals amplitude estimation errors
NASA Astrophysics Data System (ADS)
Nicolae Vizireanu, Dragos; Viorica Halunga, Simona
2012-01-01
In this note, we show that the amplitude estimation of sinusoidal signals proposed in Wu and Hong [Wu, S.T., and Hong, J.L. (2010), 'Five-point Amplitude Estimation of Sinusoidal Signals: With Application to LVDT Signal Conditioning', IEEE Transactions on Instrumentation and Measurement, 59, 623-630] is a particular case of Vizireanu and Halunga [Vizireanu, D.N, and Halunga, S.V. (2011), 'Single Sine Wave Parameters Estimation Method Based on Four Equally Spaced Samples', International Journal of Electronics, 98(7), pp. 941-948]. An analytical formula for amplitude estimation errors as effects of sampling period deviation is obtained.
One-loop amplitudes of gluons in supersymmetric QCD
Britto, Ruth; Buchbinder, Evgeny; Cachazo, Freddy; Feng Bo
2005-09-15
One-loop amplitudes of gluons in supersymmetric Yang-Mills are four-dimensional cut-constructible. This means that they can be determined from their unitarity cuts. We present a new systematic procedure to explicitly carry out any finite unitarity cut integral. The procedure naturally separates the contributions from bubble, triangle and box scalar integrals. This technique allows the systematic calculation of N=1 amplitudes of gluons. As an application we compute all next-to-MHV six-gluon amplitudes in N=1 super-Yang-Mills.
Phase Synchronization of Coupled Rossler Oscillators: Amplitude Effect
NASA Astrophysics Data System (ADS)
Li, Xiao-Wen; Zheng, Zhi-Gang
2007-02-01
Phase synchronization of two linearly coupled Rossler oscillators with parameter misfits is explored. It is found that depending on parameter mismatches, the synchronization of phases exhibits different manners. The synchronization regime can be divided into three regimes. For small mismatches, the amplitude-insensitive regime gives the phase-dominant synchronization; When the parameter misfit increases, the amplitudes and phases of oscillators are correlated, and the amplitudes will dominate the synchronous dynamics for very large mismatches. The lag time among phases exhibits a power law when phase synchronization is achieved.
Scattering Amplitudes: The Most Perfect Microscopic Structures in the Universe
Dixon, Lance J.; /CERN /SLAC
2011-11-04
This article gives an overview of many of the recent developments in understanding the structure of relativistic scattering amplitudes in gauge theories ranging from QCD to N = 4 super-Yang-Mills theory, as well as (super)gravity. I also provide a pedagogical introduction to some of the basic tools used to organize and illuminate the color and kinematic structure of amplitudes. This article is an invited review introducing a special issue of Journal of Physics A devoted to 'Scattering Amplitudes in Gauge Theories'.
Renormalization Scale-Fixing for Complex Scattering Amplitudes
Brodsky, Stanley J.; Llanes-Estrada, Felipe J.; /Madrid U.
2005-12-21
We show how to fix the renormalization scale for hard-scattering exclusive processes such as deeply virtual meson electroproduction by applying the BLM prescription to the imaginary part of the scattering amplitude and employing a fixed-t dispersion relation to obtain the scale-fixed real part. In this way we resolve the ambiguity in BLM renormalization scale-setting for complex scattering amplitudes. We illustrate this by computing the H generalized parton distribution at leading twist in an analytic quark-diquark model for the parton-proton scattering amplitude which can incorporate Regge exchange contributions characteristic of the deep inelastic structure functions.
Segmentation Of Multifrequency Complex-Amplitude SAR Data
NASA Technical Reports Server (NTRS)
Rignot, Eric J.; Chellappa, Ramalingam
1994-01-01
Several mathematical models and associated algorithms implement method of segmenting multifrequency, highly speckled, high-resolution, complex-amplitude (amplitude and phase) synthetic-aperture-radar (SAR) digitized image into regions, within each of which radar backscattering characteristics are similar or homogeneous from place to place. Typically, each region represents different type of terrain or other surface; e.g., forest, agricultural land, sea ice, or water. Method of segmentation of SAR scene into regions is product of generalization, to multifrequency case, of single-frequency method described in "Algorithms for Segmentation of Complex-Amplitude SAR Data" (NPO-18524).
Two-color pyrometry for low amplitude periodic heating
NASA Astrophysics Data System (ADS)
Bennett, T. D.; Silveira, V. B.; Valdes, R.
2017-02-01
Specimens subject to periodic heating must be probed for a calibrated temperature response if standard measurements of thermal diffusivity are to be extended to determine thermal conductivity. A variation on two-color pyrometry is developed to measure both the offset and harmonic amplitudes of temperature fluctuations caused by periodic heating. The requisite pyrometric formulae are derived for low amplitude heating using an expansion of the nonlinear thermal emission. Well-defined uncertainties in the temperature values are determined from experimental uncertainties in radiometric measurements. The accuracy demonstrated in this work is better than 2% for the temperature offset and 3%-8% for the fluctuating temperature amplitude.
Simple relation between the γN→N(1535) helicity amplitudes
NASA Astrophysics Data System (ADS)
Ramalho, G.; Tsushima, K.
2011-09-01
It is shown that the helicity amplitudes A1/2 and S1/2 in the γN→N(1535) reaction, can be well related by S1/2=-(1+τ)/(2)(MS2-M2)/(2MSQ)A1/2 in the region Q2>2GeV2, where M and MS are the nucleon and N(1535) masses, q2=-Q2 the four-momentum transfer squared, and τ=(Q2)/((MS+M)2). This follows from the fact that the Pauli-type transition form factor F2* extracted from the experimental data, turns up to show F2*≃0 for Q2>1.5GeV2. The observed relation is tested by the experimentally extracted helicity amplitudes and the MAID parametrization (Mainz group). A direct consequence of the relation is that the assumption |A1/2|≫|S1/2| is not valid for high Q2. Instead, both amplitudes A1/2 and S1/2 have the same Q2 dependence in the high Q2 region; aside from that S1/2 has an extra factor, -(1)/(2)(MS-M)/(2MS). The origin of this relation is interpreted in a perspective of a quark model.
Characterizing the ``Higgs'' amplitude mode in a Spin-1 Bose Einstein Condensate
NASA Astrophysics Data System (ADS)
Hebbe Madhusudhana, Bharath; Boguslawski, Matthew; Anquez, Martin; Robbins, Bryce; Barrios, Maryrose; Hoang, Thai; Chapman, Michael
2016-05-01
Spontaneous symmetry breaking in a physical system is often characterized by massless Nambu-Goldstone modes and massive Anderson-Higgs modes. It occurs when a system crosses a quantum critical point (QCP) reaching a state does not share the symmetry of the underlying Hamiltonian. In a spin-1 Bose Einstein condensate, the transverse spin component can be considered as an order parameter. A quantum phase transition (QPT) of this system results in breaking of the symmetry group U(1) × SO(2) shared by the Hamiltonian. As a result, two massless coupled phonon-magnon modes are produced along with a single massive mode or a Higgs-like mode, in the form of amplitude excitations of the order parameter. Here we characterize the amplitude excitations experimentally by inducing coherent oscillation in the spin population. We further use the amplitude oscillations to measure the energy gap for different phases of the QPT. At the QCP, finite size effects lead to a non-zero gap, and our measurements are consistent with this prediction.
Revealing Extremely Low Energy Amplitude Modes in the Charge-Density-Wave Compound LaAgSb2
NASA Astrophysics Data System (ADS)
Chen, R. Y.; Zhang, S. J.; Zhang, M. Y.; Dong, T.; Wang, N. L.
2017-03-01
Using infrared spectroscopy and ultrafast pump probe measurement, we have studied the two charge-density-wave (CDW) instabilities in the layered compound LaAgSb2 . The development of CDW energy gaps was clearly observed by optical spectroscopy, which removed most of the free carrier spectral weight. More interestingly, our time-resolved measurements revealed two coherent oscillations that softened by approaching the two phase transition temperatures, respectively. We addressed that these two oscillations come from the amplitude modes of CDW collective excitations, the surprisingly low energies (0.12 THz and 0.34 THz for the higher and lower temperature ones, respectively) of which are associated with the extremely small nesting wave vectors. Additionally, the amplitude and relaxation time of photoinduced reflectivity of LaAgSb2 single crystals stayed unchanged across the CDW phase transitions, which is quite rare and deserves further investigation.
Revealing Extremely Low Energy Amplitude Modes in the Charge-Density-Wave Compound LaAgSb_{2}.
Chen, R Y; Zhang, S J; Zhang, M Y; Dong, T; Wang, N L
2017-03-10
Using infrared spectroscopy and ultrafast pump probe measurement, we have studied the two charge-density-wave (CDW) instabilities in the layered compound LaAgSb_{2}. The development of CDW energy gaps was clearly observed by optical spectroscopy, which removed most of the free carrier spectral weight. More interestingly, our time-resolved measurements revealed two coherent oscillations that softened by approaching the two phase transition temperatures, respectively. We addressed that these two oscillations come from the amplitude modes of CDW collective excitations, the surprisingly low energies (0.12 THz and 0.34 THz for the higher and lower temperature ones, respectively) of which are associated with the extremely small nesting wave vectors. Additionally, the amplitude and relaxation time of photoinduced reflectivity of LaAgSb_{2} single crystals stayed unchanged across the CDW phase transitions, which is quite rare and deserves further investigation.
Facilitation of epileptic activity during sleep is mediated by high amplitude slow waves.
Frauscher, Birgit; von Ellenrieder, Nicolás; Ferrari-Marinho, Taissa; Avoli, Massimo; Dubeau, François; Gotman, Jean
2015-06-01
Epileptic discharges in focal epilepsy are frequently activated during non-rapid eye movement sleep. Sleep slow waves are present during this stage and have been shown to include a deactivated ('down', hyperpolarized) and an activated state ('up', depolarized). The 'up' state enhances physiological rhythms, and we hypothesize that sleep slow waves and particularly the 'up' state are the specific components of non-rapid eye movement sleep that mediate the activation of epileptic activity. We investigated eight patients with pharmaco-resistant focal epilepsies who underwent combined scalp-intracerebral electroencephalography for diagnostic evaluation. We analysed 259 frontal electroencephalographic channels, and manually marked 442 epileptic spikes and 8487 high frequency oscillations during high amplitude widespread slow waves, and during matched control segments with low amplitude widespread slow waves, non-widespread slow waves or no slow waves selected during the same sleep stages (total duration of slow wave and control segments: 49 min each). During the slow waves, spikes and high frequency oscillations were more frequent than during control segments (79% of spikes during slow waves and 65% of high frequency oscillations, both P ∼ 0). The spike and high frequency oscillation density also increased for higher amplitude slow waves. We compared the density of spikes and high frequency oscillations between the 'up' and 'down' states. Spike and high frequency oscillation density was highest during the transition from the 'up' to the 'down' state. Interestingly, high frequency oscillations in channels with normal activity expressed a different peak at the transition from the 'down' to the 'up' state. These results show that the apparent activation of epileptic discharges by non-rapid eye movement sleep is not a state-dependent phenomenon but is predominantly associated with specific events, the high amplitude widespread slow waves that are frequent, but not
Facilitation of epileptic activity during sleep is mediated by high amplitude slow waves
von Ellenrieder, Nicolás; Ferrari-Marinho, Taissa; Avoli, Massimo; Dubeau, François; Gotman, Jean
2015-01-01
Epileptic discharges in focal epilepsy are frequently activated during non-rapid eye movement sleep. Sleep slow waves are present during this stage and have been shown to include a deactivated (‘down’, hyperpolarized) and an activated state (‘up’, depolarized). The ‘up’ state enhances physiological rhythms, and we hypothesize that sleep slow waves and particularly the ‘up’ state are the specific components of non-rapid eye movement sleep that mediate the activation of epileptic activity. We investigated eight patients with pharmaco-resistant focal epilepsies who underwent combined scalp-intracerebral electroencephalography for diagnostic evaluation. We analysed 259 frontal electroencephalographic channels, and manually marked 442 epileptic spikes and 8487 high frequency oscillations during high amplitude widespread slow waves, and during matched control segments with low amplitude widespread slow waves, non-widespread slow waves or no slow waves selected during the same sleep stages (total duration of slow wave and control segments: 49 min each). During the slow waves, spikes and high frequency oscillations were more frequent than during control segments (79% of spikes during slow waves and 65% of high frequency oscillations, both P ∼ 0). The spike and high frequency oscillation density also increased for higher amplitude slow waves. We compared the density of spikes and high frequency oscillations between the ‘up’ and ‘down’ states. Spike and high frequency oscillation density was highest during the transition from the ‘up’ to the ‘down’ state. Interestingly, high frequency oscillations in channels with normal activity expressed a different peak at the transition from the ‘down’ to the ‘up’ state. These results show that the apparent activation of epileptic discharges by non-rapid eye movement sleep is not a state-dependent phenomenon but is predominantly associated with specific events, the high amplitude widespread slow
Some tree-level string amplitudes in the NSR formalism
NASA Astrophysics Data System (ADS)
Becker, Katrin; Becker, Melanie; Melnikov, Ilarion V.; Robbins, Daniel; Royston, Andrew B.
2015-12-01
We calculate tree level scattering amplitudes for open strings using the NSR formalism. We present a streamlined symmetry-based and pedagogical approach to the computations, which we first develop by checking two-, three-, and four-point functions involving bosons and fermions. We calculate the five-point amplitude for massless gluons and find agreement with an earlier result by Brandt, Machado and Medina. We then compute the five-point amplitudes involving two and four fermions respectively, the general form of which has not been previously obtained in the NSR formalism. The results nicely confirm expectations from the supersymmetric F 4 effective action. Finally we use the prescription of Kawai, Lewellen and Tye (KLT) to compute the amplitudes for the closed string sector.
Movement amplitude and tempo change in piano performance
NASA Astrophysics Data System (ADS)
Palmer, Caroline
2004-05-01
Music performance places stringent temporal and cognitive demands on individuals that should yield large speed/accuracy tradeoffs. Skilled piano performance, however, shows consistently high accuracy across a wide variety of rates. Movement amplitude may affect the speed/accuracy tradeoff, so that high accuracy can be obtained even at very fast tempi. The contribution of movement amplitude changes in rate (tempo) is investigated with motion capture. Cameras recorded pianists with passive markers on hands and fingers, who performed on an electronic (MIDI) keyboard. Pianists performed short melodies at faster and faster tempi until they made errors (altering the speed/accuracy function). Variability of finger movements in the three motion planes indicated most change in the plane perpendicular to the keyboard across tempi. Surprisingly, peak amplitudes of motion before striking the keys increased as tempo increased. Increased movement amplitudes at faster rates may reduce or compensate for speed/accuracy tradeoffs. [Work supported by Canada Research Chairs program, HIMH R01 45764.
Effect of vibration amplitude on vapor cavitation in journal bearings
NASA Technical Reports Server (NTRS)
Brewe, D. E.; Jacobson, B. O.
1986-01-01
Computational movies were used to analyze the formation and collapse of vapor cavitation bubbles in a submerged journal bearing. The effect of vibration amplitude on vapor cavitation was studied for a journal undergoing circular whirl. The boundary conditions were implemented using Elrod's algorithm, which conserves mass flow through the cavitation bubble as well as through the oil-film region of the bearing. The vibration amplitudes for the different cases studied resulted in maximum eccentricity ratios ranging from 0.4 to 0.9. The minimum eccentricity ratio reached in each case was 0.1. For the least vibration amplitude studied in which the eccentricity ratio varied between 0.1 and 0.4, no vapor cavitation occurred. The largest vibration amplitude (i.e., eccentricity ratios of 0.1 to 0.9) resulted in vapor cavitation present 76 percent of one complete orbit.
Amplitude analysis of the charmed decay D0 to KKpipi
NASA Astrophysics Data System (ADS)
Skidmore, Nicola
2017-01-01
An amplitude analysis of the 4-body charmed decay D0 -> KKππ is presented using data collected from electron-positron collisions at the CLEO experiment. Both flavour tagged and CP tagged data are utilized in the analysis making it unique from amplitude analyses performed at other colliders and providing extra sensitivity to the phases of the amplitude components. The amplitude model is used to search for CP violation in the D0 decay by analysing D0 and D0 decays separately. The model is also crucial input for a model-dependent measurement of the CP-violating phase γ using B+/- ->D0(-> KKππ) K+/- decays, which remains one of the least constrained parameters of the Standard Model. Forum on International Physics Distinguished Student Seminar Program, and European Research Council
Amplitude death of identical oscillators in networks with direct coupling
NASA Astrophysics Data System (ADS)
Illing, Lucas
2016-08-01
It is known that amplitude death can occur in networks of coupled identical oscillators if they interact via diffusive time-delayed coupling links. Here we consider networks of oscillators that interact via direct time-delayed coupling links. It is shown analytically that amplitude death is impossible for directly coupled Stuart-Landau oscillators, in contradistinction to the case of diffusive coupling. We demonstrate that amplitude death in the strict sense does become possible in directly coupled networks if the node dynamics is governed by second-order delay differential equations. Finally, we analyze in detail directly coupled nodes whose dynamics are described by first-order delay differential equations and find that, while amplitude death in the strict sense is impossible, other interesting oscillation quenching scenarios exist.
N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops
Boucher-Veronneau, C.; Dixon, L.J.; /SLAC
2012-02-15
We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.
Off-Shell Amplitudes for Nonoriented Closed Strings
NASA Astrophysics Data System (ADS)
Cappiello, Luigi; Marotta, Raffaele; Pettorino, Roberto; Pezzella, Franco
In the context of the bosonic closed string theory, by using the operatorial formalism, we give a simple expression of the off-shell amplitude with an arbitrary number of external massless states inserted on the Klein bottle.
Properties of scattering amplitudes at very high energies
NASA Technical Reports Server (NTRS)
Mickens, R. E.
1975-01-01
The research is reported concerning the (1) total cross sections as the energy becomes infinite, (2) elastic scattering amplitude for nonforward directions, and (3) upper bound of neutrino scattering cross sections.
Moments of pseudoscalar meson distribution amplitudes from the lattice
Braun, V. M.; Goeckeler, M.; Horsley, R.; Zanotti, J. M.; Perlt, H.; Schiller, A.; Pleiter, D.; Schroers, W.; Schierholz, G.; Stueben, H.
2006-10-01
Based on lattice simulations with two flavors of dynamical, O(a)-improved Wilson fermions we present results for the first two moments of the distribution amplitudes of pseudoscalar mesons at several values of the valence quark masses. By extrapolating our results to the physical masses of up/down and strange quarks, we find the first two moments of the K{sup +} distribution amplitude and the second moment of the {pi}{sup +} distribution amplitude. We use nonperturbatively determined renormalization coefficients to obtain results in the MS scheme. At a scale of 4 GeV{sup 2} we find a{sub 2}{sup {pi}}=0.201(114) for the second Gegenbauer moment of the pion's distribution amplitude, while for the kaon, a{sub 1}{sup K}=0.0453(9)(29) and a{sub 2}{sup K}=0.175(18)(47)
Interdecadal Modulation of ENSO Amplitude During the Last Millennium
NASA Astrophysics Data System (ADS)
Li, J.; Xie, S.; Cook, E.; Huang, G.; D'Arrigo, R.; Liu, F.; Ma, J.; Zheng, X.
2010-12-01
El Niño/Southern Oscillation (ENSO) is the dominant mode of interannual variability, and affects climate around the globe. ENSO amplitude displays considerable variations on the instrumental record, and its future change is highly uncertain. Here we analyze a newly updated version of the tree-ring derived North American Drought Atlas (NADA) for the past 1100 years, and show that ENSO variance displays a quasi-regular cycle of 50-90 years. Interannual variability and its low-frequency amplitude modulation in NADA are in broad agreement with independent proxy records in the Pacific and surrounding regions. Large volcanic eruptions tend to trigger El Niño, but for the past millennium solar variations seem to drive amplitude modulation of ENSO. Simulating the quasi-periodic ENSO amplitude modulation may hold the key to improving models and their prediction of ENSO behavior in global warming.
Amplitude sorting of oscillatory burst signals by sampling
Davis, Thomas J.
1977-01-01
A method and apparatus for amplitude sorting of oscillatory burst signals is described in which the burst signal is detected to produce a burst envelope signal and an intermediate or midportion of such envelope signal is sampled to provide a sample pulse output. The height of the sample pulse is proportional to the amplitude of the envelope signal and to the maximum burst signal amplitude. The sample pulses are fed to a pulse height analyzer for sorting. The present invention is used in an acoustic emission testing system to convert the amplitude of the acoustic emission burst signals into sample pulse heights which are measured by a pulse height analyzer for sorting the pulses in groups according to their height in order to identify the material anomalies in the test material which emit the acoustic signals.
Laser beam complex amplitude measurement by phase diversity.
Védrenne, Nicolas; Mugnier, Laurent M; Michau, Vincent; Velluet, Marie-Thérèse; Bierent, Rudolph
2014-02-24
The control of the optical quality of a laser beam requires a complex amplitude measurement able to deal with strong modulus variations and potentially highly perturbed wavefronts. The method proposed here consists in an extension of phase diversity to complex amplitude measurements that is effective for highly perturbed beams. Named camelot for Complex Amplitude MEasurement by a Likelihood Optimization Tool, it relies on the acquisition and processing of few images of the beam section taken along the optical path. The complex amplitude of the beam is retrieved from the images by the minimization of a Maximum a Posteriori error metric between the images and a model of the beam propagation. The analytical formalism of the method and its experimental validation are presented. The modulus of the beam is compared to a measurement of the beam profile, the phase of the beam is compared to a conventional phase diversity estimate. The precision of the experimental measurements is investigated by numerical simulations.
High Amplitude (delta)-Scutis in the Large Magellanic Cloud
Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M
2010-01-25
The authors present 2323 High-Amplitude {delta}-Scutis (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, they find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. They also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).
The Last of the Finite Loop Amplitudes in QCD
Bern, Zvi; Dixon, Lance J.; Kosower, David A.
2005-05-31
We use on-shell recursion relations to determine the one-loop QCD scattering amplitudes with a massless external quark pair and an arbitrary number (n - 2) of positive-helicity gluons. These amplitudes are the last of the unknown infrared- and ultraviolet-finite loop amplitudes of QCD. The recursion relations are similar to ones applied at tree level, but contain new non-trivial features corresponding to poles present for complex momentum arguments but absent for real momenta. We present the relations and the compact solutions to them, valid for all n. We also present compact forms for the previously-computed one-loop n-gluon amplitudes with a single negative helicity and the rest positive helicity.
Euclidean to Minkowski Bethe-Salpeter amplitude and observables
NASA Astrophysics Data System (ADS)
Carbonell, J.; Frederico, T.; Karmanov, V. A.
2017-01-01
We propose a method to reconstruct the Bethe-Salpeter amplitude in Minkowski space given the Euclidean Bethe-Salpeter amplitude - or alternatively the light-front wave function - as input. The method is based on the numerical inversion of the Nakanishi integral representation and computing the corresponding weight function. This inversion procedure is, in general, rather unstable, and we propose several ways to considerably reduce the instabilities. In terms of the Nakanishi weight function, one can easily compute the BS amplitude, the LF wave function and the electromagnetic form factor. The latter ones are very stable in spite of residual instabilities in the weight function. This procedure allows both, to continue the Euclidean BS solution in the Minkowski space and to obtain a BS amplitude from a LF wave function.
Non-perturbative QCD amplitudes in quenched and eikonal approximations
Fried, H.M.; Grandou, T.; Sheu, Y.-M.
2014-05-15
Even though approximated, strong coupling non-perturbative QCD amplitudes remain very difficult to obtain. In this article, in eikonal and quenched approximations at least, physical insights are presented that rely on the newly-discovered property of effective locality. The present article also provides a more rigorous mathematical basis for the crude approximations used in the previous derivation of the binding potential of quarks and nucleons. Furthermore, the techniques of Random Matrix calculus along with Meijer G-functions are applied to analyze the generic structure of fermionic amplitudes in QCD. - Highlights: • We discuss the physical insight of effective locality to QCD fermionic amplitudes. • We show that an unavoidable delta function goes along with the effective locality property. • The generic structure of QCD fermion amplitudes is obtained through Random Matrix calculus.
A Pn Spreading Model Constrained with Observed Amplitudes in Asia
2011-09-01
of observed Pn amplitudes from the tectonically active regions of Asia to evaluate the performance of Y2007 and to develop new, observation-based...a set of observed Pn amplitudes from the tectonically active regions of Asia to evaluate the performance of Y2007 and to develop new observation-based...tomographic inversions to map the lateral Pn attenuation variation. RESEARCH ACCOMPLISHED Introduction It has long been recognized that the
Bootstrapping a five-loop amplitude using Steinmann relations
Caron-Huot, Simon; Dixon, Lance J.; McLeod, Andrew; ...
2016-12-05
Here, the analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.
Bootstrapping a Five-Loop Amplitude Using Steinmann Relations.
Caron-Huot, Simon; Dixon, Lance J; McLeod, Andrew; von Hippel, Matt
2016-12-09
The analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.
T-wave amplitude is related to physical fitness status.
Arbel, Yaron; Birati, Edo Y; Shapira, Itzhak; Topilsky, Yan; Wirguin, Michal; Canaani M D, Jonathan
2012-07-01
Abnormalities in repolarization may reflect underlying myocardial pathology and play a prominent role in arrhythmogenesis The T-wave amplitude has been associated with cardiovascular outcome in patients with acute myocardial infarction (MI) Additionally, T-wave amplitude is considered a predictor of arrhythmias, as well as being related to an individual's inflammatory status. The combined influence of different variables, such as inflammation, cardiovascular risk factors and physical fitness status, on the T-wave amplitude has not been evaluated to date. The aim of this study was to identify factors that affect the T-wave amplitude. Data from 255 consecutive apparently healthy individuals included in the Tel Aviv Medical Center Inflammation Survey (TAMCIS) were reviewed. All patients had undergone a physical examination and an exercise stress test, and different inflammatory and metabolic biomarkers (fibrinogen, potassium, and high-sensitivity C-reactive protein) were measured. Multivariate stepwise analysis revealed that the body mass index and the resting heart rate were significantly associated with the T-wave amplitude (β=-0.34, P < 0.001; β=-0.19, P = 0.03, respectively) in males, while the recovery rate and the usage of statins significantly affected the T-wave amplitude in females (β= 0.36, P = 0.002; β= 0.35, P = 0.002, respectively). Inflammatory variables had no significant affect on the T-wave amplitude of either gender. In conclusion, the T-wave amplitude is linked to an individual's physical fitness and not to his/her inflammatory status. ©2012, Wiley Periodicals, Inc.
A cluster bootstrap for two-loop MHV amplitudes
NASA Astrophysics Data System (ADS)
Golden, John; Spradlin, Marcus
2015-02-01
We apply a bootstrap procedure to two-loop MHV amplitudes in planar super-Yang-Mills theory. We argue that the mathematically most complicated part (the Λ2 B 2 coproduct component) of the n-particle amplitude is uniquely determined by a simple cluster algebra property together with a few physical constraints (dihedral symmetry, analytic structure, supersymmetry, and well-defined collinear limits). We present a concise, closed-form expression which manifests these properties for all n.
Three-point disc amplitudes in the RNS formalism
NASA Astrophysics Data System (ADS)
Becker, Katrin; Becker, Melanie; Robbins, Daniel; Su, Ning
2016-06-01
We calculate all tree level string theory vacuum to Dp-brane disc amplitudes involving an arbitrary RR-state and two NS-NS vertex operators. This computation was earlier performed by K. Becker, Guo, and Robbins for the simplest case of a RR-state of type C (p - 3). Here we use the aid of a computer to calculate all possible three-point amplitudes involving a RR-vertex operator of type C (p + 1 + 2 k).
PAPR Advantage of Amplitude Clipped OFDM/TDM
NASA Astrophysics Data System (ADS)
Gacanin, Haris; Adachi, Fumiyuki
OFDM combined with TDM (OFDM/TDM) can be used to reduce a high peak-to-average power ratio (PAPR) of OFDM, but the PAPR reduction is not sufficient. To further reduce the PAPR, an amplitude clipping can be applied. In this letter, we investigate the effect of clipping on OFDM/TDM with and without channel coding. It is shown that amplitude clipped OFDM/TDM has an advantage over clipped OFDM with respect to the PAPR.
Wilson loops and QCD/string scattering amplitudes
Makeenko, Yuri; Olesen, Poul
2009-07-15
We generalize modern ideas about the duality between Wilson loops and scattering amplitudes in N=4 super Yang-Mills theory to large N QCD by deriving a general relation between QCD meson scattering amplitudes and Wilson loops. We then investigate properties of the open-string disk amplitude integrated over reparametrizations. When the Wilson-loop is approximated by the area behavior, we find that the QCD scattering amplitude is a convolution of the standard Koba-Nielsen integrand and a kernel. As usual poles originate from the first factor, whereas no (momentum-dependent) poles can arise from the kernel. We show that the kernel becomes a constant when the number of external particles becomes large. The usual Veneziano amplitude then emerges in the kinematical regime, where the Wilson loop can be reliably approximated by the area behavior. In this case, we obtain a direct duality between Wilson loops and scattering amplitudes when spatial variables and momenta are interchanged, in analogy with the N=4 super Yang-Mills theory case.
Light Diffraction by Large Amplitude Ultrasonic Waves in Liquids
NASA Technical Reports Server (NTRS)
Adler, Laszlo; Cantrell, John H.; Yost, William T.
2016-01-01
Light diffraction from ultrasound, which can be used to investigate nonlinear acoustic phenomena in liquids, is reported for wave amplitudes larger than that typically reported in the literature. Large amplitude waves result in waveform distortion due to the nonlinearity of the medium that generates harmonics and produces asymmetries in the light diffraction pattern. For standing waves with amplitudes above a threshold value, subharmonics are generated in addition to the harmonics and produce additional diffraction orders of the incident light. With increasing drive amplitude above the threshold a cascade of period-doubling subharmonics are generated, terminating in a region characterized by a random, incoherent (chaotic) diffraction pattern. To explain the experimental results a toy model is introduced, which is derived from traveling wave solutions of the nonlinear wave equation corresponding to the fundamental and second harmonic standing waves. The toy model reduces the nonlinear partial differential equation to a mathematically more tractable nonlinear ordinary differential equation. The model predicts the experimentally observed cascade of period-doubling subharmonics terminating in chaos that occurs with increasing drive amplitudes above the threshold value. The calculated threshold amplitude is consistent with the value estimated from the experimental data.
A proposed physical analog for a quantum probability amplitude
NASA Astrophysics Data System (ADS)
Boyd, Jeffrey
What is the physical analog of a probability amplitude? All quantum mathematics, including quantum information, is built on amplitudes. Every other science uses probabilities; QM alone uses their square root. Why? This question has been asked for a century, but no one previously has proposed an answer. We will present cylindrical helices moving toward a particle source, which particles follow backwards. Consider Feynman's book QED. He speaks of amplitudes moving through space like the hand of a spinning clock. His hand is a complex vector. It traces a cylindrical helix in Cartesian space. The Theory of Elementary Waves changes direction so Feynman's clock faces move toward the particle source. Particles follow amplitudes (quantum waves) backwards. This contradicts wave particle duality. We will present empirical evidence that wave particle duality is wrong about the direction of particles versus waves. This involves a paradigm shift; which are always controversial. We believe that our model is the ONLY proposal ever made for the physical foundations of probability amplitudes. We will show that our ``probability amplitudes'' in physical nature form a Hilbert vector space with adjoints, an inner product and support both linear algebra and Dirac notation.
Scattering amplitudes and Wilson loops in twistor space
NASA Astrophysics Data System (ADS)
Adamo, Tim; Bullimore, Mathew; Mason, Lionel; Skinner, David
2011-11-01
This paper reviews the recent progress in twistor approaches to Wilson loops, amplitudes and their duality for {N}=4 super-Yang-Mills. Wilson loops and amplitudes are derived from first principles using the twistor action for maximally supersymmetric Yang-Mills theory. We start by deriving the MHV rules for gauge theory amplitudes from the twistor action in an axial gauge in twistor space, and show that this gives rise to the original momentum space version given by Cachazo, Svrček and Witten. We then go on to obtain from these the construction of the momentum twistor space loop integrand using (planar) MHV rules and show how it arises as the expectation value of a holomorphic Wilson loop in twistor space. We explain the connection between the holomorphic Wilson loop and certain light-cone limits of correlation functions. We give a brief review of other ideas in connection with amplitudes in twistor space: twistor-strings, recursion in twistor space, the Grassmannian residue formula for leading singularities and amplitudes as polytopes. This paper is an invited review for a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Scattering amplitudes in gauge theories’.
Amplitude relations in non-linear sigma model
NASA Astrophysics Data System (ADS)
Chen, Gang; Du, Yi-Jian
2014-01-01
In this paper, we investigate tree-level scattering amplitude relations in U( N) non-linear sigma model. We use Cayley parametrization. As was shown in the recent works [23,24], both on-shell amplitudes and off-shell currents with odd points have to vanish under Cayley parametrization. We prove the off-shell U(1) identity and fundamental BCJ relation for even-point currents. By taking the on-shell limits of the off-shell relations, we show that the color-ordered tree amplitudes with even points satisfy U(1)-decoupling identity and fundamental BCJ relation, which have the same formations within Yang-Mills theory. We further state that all the on-shell general KK, BCJ relations as well as the minimal-basis expansion are also satisfied by color-ordered tree amplitudes. As a consequence of the relations among color-ordered amplitudes, the total 2 m-point tree amplitudes satisfy DDM form of color decomposition as well as KLT relation.
Ball bearing vibrations amplitude modeling and test comparisons
NASA Technical Reports Server (NTRS)
Hightower, Richard A., III; Bailey, Dave
1995-01-01
Bearings generate disturbances that, when combined with structural gains of a momentum wheel, contribute to induced vibration in the wheel. The frequencies generated by a ball bearing are defined by the bearing's geometry and defects. The amplitudes at these frequencies are dependent upon the actual geometry variations from perfection; therefore, a geometrically perfect bearing will produce no amplitudes at the kinematic frequencies that the design generates. Because perfect geometry can only be approached, emitted vibrations do occur. The most significant vibration is at the spin frequency and can be balanced out in the build process. Other frequencies' amplitudes, however, cannot be balanced out. Momentum wheels are usually the single largest source of vibrations in a spacecraft and can contribute to pointing inaccuracies if emitted vibrations ring the structure or are in the high-gain bandwidth of a sensitive pointing control loop. It is therefore important to be able to provide an a priori knowledge of possible amplitudes that are singular in source or are a result of interacting defects that do not reveal themselves in normal frequency prediction equations. This paper will describe the computer model that provides for the incorporation of bearing geometry errors and then develops an estimation of actual amplitudes and frequencies. Test results were correlated with the model. A momentum wheel was producing an unacceptable 74 Hz amplitude. The model was used to simulate geometry errors and proved successful in identifying a cause that was verified when the parts were inspected.
Dependence of kink oscillation damping on the amplitude
NASA Astrophysics Data System (ADS)
Goddard, C. R.; Nakariakov, V. M.
2016-05-01
Context. Kink oscillations of coronal loops are one of the most intensively studied oscillatory phenomena in the solar corona. In the large-amplitude rapidly damped regime, these oscillations are observed to have a low quality factor with only a few cycles of oscillation detected before they are damped. The specific mechanism responsible for rapid damping is commonly accepted to be associated with the linear coupling between collective kink oscillations and localised torsional oscillations, the phenomenon of resonant absorption of the kink mode. The role of finite amplitude effects, however, is still not clear. Aims: We investigated the empirical dependence of the kink oscillation damping time and its quality factor, which is defined as the ratio of damping time to oscillation period, on the oscillation amplitude. Methods: We analysed decaying kink oscillation events detected previously with TRACE, SDO/AIA and and STEREO/EUVI in the extreme ultraviolet (EUV) 171 Å band. Results: We found that the ratio of the kink oscillation damping time to the oscillation period systematically decreases with the oscillation amplitude. We approximated the quality factor dependence on the oscillation displacement amplitude via the power-law dependence with the exponent of -1/2, however we stress that this is a by-eye estimate, and a more rigorous estimation of the scaling law requires more accurate measurements and increased statistics. We conclude that damping of kink oscillations of coronal loops depends on the oscillation amplitude, indicating the possible role of non-linear mechanisms for damping.
Composite representation invariants and unoriented topological string amplitudes
NASA Astrophysics Data System (ADS)
Paul, Chandrima; Borhade, Pravina; Ramadevi, P.
2010-12-01
Sinha and Vafa [1] had conjectured that the SO Chern-Simons gauge theory on S must be dual to the closed A-model topological string on the orientifold of a resolved conifold. Though the Chern-Simons free energy could be rewritten in terms of the topological string amplitudes providing evidence for the conjecture, we needed a novel idea in the context of Wilson loop observables to extract cross-cap c=0,1,2 topological amplitudes. Recent paper of Marino [2] based on the work of Morton and Ryder [3] has clearly shown that the composite representation placed on the knots and links plays a crucial role to rewrite the topological string cross-cap c=0 amplitude. This enables extracting the unoriented cross-cap c=2 topological amplitude. In this paper, we have explicitly worked out the composite invariants for some framed knots and links carrying composite representations in U(N) Chern-Simons theory. We have verified generalised Rudolph's theorem, which relates composite invariants to the invariants in SO(N) Chern-Simons theory, and also verified Marino's conjectures on the integrality properties of the topological string amplitudes. For some framed knots and links, we have tabulated the BPS integer invariants for cross-cap c=0 and c=2 giving the open-string topological amplitude on the orientifold of the resolved conifold.
Mapping Pn amplitude spreading and attenuation in Asia
Yang, Xiaoning; Phillips, William S; Stead, Richard J
2010-12-06
Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.
Kim, Juntae; Helgeson, Matthew E.; Merger, Dimitri; Wilhelm, Manfred
2014-09-01
We investigate yielding in a colloidal gel that forms a heterogeneous structure, consisting of a two-phase bicontinuous network of colloid-rich domains of fractal clusters and colloid-poor domains. Combining large amplitude oscillatory shear measurements with simultaneous small and ultra-small angle neutron scattering (rheo-SANS/USANS), we characterize both the nonlinear mechanical processes and strain amplitude-dependent microstructure underlying yielding. We observe a broad, three-stage yielding process that evolves over an order of magnitude in strain amplitude between the onset of nonlinearity and flow. Analyzing the intracycle response as a sequence of physical processes reveals a transition from elastic straining to elastoplastic thinning (which dominates in region I) and eventually yielding (which evolves through region II) and flow (which saturates in region III), and allows quantification of instantaneous nonlinear parameters associated with yielding. These measures exhibit significant strain rate amplitude dependence above a characteristic frequency, which we argue is governed by poroelastic effects. Correlating these results with time-averaged rheo-USANS measurements reveals that the material passes through a cascade of structural breakdown from large to progressively smaller length scales. In region I, compression of the fractal domains leads to the formation of large voids. In regions II and III, cluster-cluster correlations become increasingly homogeneous, suggesting breakage and eventually depercolation of intercluster bonds at the yield point. All significant structural changes occur on the micron-scale, suggesting that large-scale rearrangements of hundreds or thousands of particles, rather than the homogeneous rearrangement of particle-particle bonds, dominate the initial yielding of heterogeneous colloidal gels.
Keenan, Kevin G.; Valero-Cuevas, Francisco J.
2008-01-01
Researchers and clinicians routinely rely on interference electromyograms (EMGs) to estimate muscle forces and command signals in the neuromuscular system (e.g., amplitude, timing, and frequency content). The amplitude cancellation intrinsic to interference EMG, however, raises important questions about how to optimize these estimates. For example, what should the length of the epoch (time window) be to average an EMG signal to reliably estimate muscle forces and command signals? Shorter epochs are most practical, and significant reductions in epoch have been reported with high-pass filtering and whitening. Given that this processing attenuates power at frequencies of interest (< 250 Hz), however, it is unclear how it improves the extraction of physiologically-relevant information. We examined the influence of amplitude cancellation and high-pass filtering on the epoch necessary to accurately estimate the “true” average EMG amplitude calculated from a 28 s EMG trace (EMGref) during simulated constant isometric conditions. Monte Carlo iterations of a motor-unit model simulating 28 s of surface EMG produced 245 simulations under 2 conditions: with and without amplitude cancellation. For each simulation, we calculated the epoch necessary to generate average full-wave rectified EMG amplitudes that settled within 5% of EMGref. For the no-cancellation EMG, the necessary epochs were short (e.g., < 100 ms). For the more realistic interference EMG (i.e., cancellation condition), epochs shortened dramatically after using high-pass filter cutoffs above 250 Hz, producing epochs short enough to be practical (i.e., < 500 ms). We conclude that the need to use long epochs to accurately estimate EMG amplitude is likely the result of unavoidable amplitude cancellation, which helps to clarify why high-pass filtering (> 250 Hz) improves EMG estimates. PMID:19081815
Dynamo transition under Taylor-Green forcing
NASA Astrophysics Data System (ADS)
Yadav, R.; Chandra, M.; Verma, M. K.; Paul, S.; Wahi, P.
2010-09-01
We perform pseudo-spectral simulations of the Taylor-Green dynamo for magnetic Prandtl number of one and produce a bifurcation diagram near the dynamo transition. We observe that the primary dynamo transition is through a supercritical pitchfork bifurcation. We show that the planar magnetic structures near the dynamo transition are due to the emergence of the B(0, 0, 1) and B(0, 0, 2) magnetic Fourier modes, which are born as a result of triadic interactions. Near the transition, the kinetic energy (Eu) and the magnetic energy (Eb) grow linearly with the forcing amplitude F0 with the same slope. The ratio Eb/Eu for F0=[0, 40] ranges from 0 to 3. Beyond the transition, the numerical simulations reveal complex dynamo states with windows of constant, periodic, quasiperiodic, and chaotic magnetic field configurations.
First-Order Dynamical Phase Transitions
NASA Astrophysics Data System (ADS)
Canovi, Elena; Werner, Philipp; Eckstein, Martin
2014-12-01
Recently, dynamical phase transitions have been identified based on the nonanalytic behavior of the Loschmidt echo in the thermodynamic limit [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. By introducing conditional probability amplitudes, we show how dynamical phase transitions can be further classified, both mathematically, and potentially in experiment. This leads to the definition of first-order dynamical phase transitions. Furthermore, we develop a generalized Keldysh formalism which allows us to use nonequilibrium dynamical mean-field theory to study the Loschmidt echo and dynamical phase transitions in high-dimensional, nonintegrable models. We find dynamical phase transitions of first order in the Falicov-Kimball model and in the Hubbard model.
NASA Astrophysics Data System (ADS)
Alcock-Zeilinger, J.; Weigert, H.
2017-05-01
In this paper, we give a generic algorithm of the transition operators between Hermitian Young projection operators corresponding to equivalent irreducible representations of 𝖲𝖴 (N ) , using the compact expressions of Hermitian Young projection operators derived in the work of Alcock-Zeilinger and Weigert [eprint arXiv:1610.10088 [math-ph
2006-06-09
Podesta for the Heads of Executive Departments and Agencies, “Presidential Transition Guidance,” Nov. 13, 2000. 89 U.S. General Services Administration...2000, presidential election, White House Chief of Staff John Podesta issued a November 13, 2000, memorandum to executive branch agencies stating that
ERIC Educational Resources Information Center
Cassidy, Joan
1998-01-01
Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)
2012-06-05
Leslie Lowes from the NASA Jet Propulsion Laboratory in Pasadena, Calif., views the June 5, 2012, Venus transit through a solar telescope. Lowes participated in an education workshop at the INFINITY at NASA Stennis Space Center visitor center and joined others to view the rare celestial event when Venus traverses the face of the sun.
2012-06-05
Guests at the INFINITY at NASA Stennis Space Center visitor center use special solar sunglasses to catch a lifetime view of the Venus transit June 5, 2012. The rare celestial event in which the planet Venus traverses the face of the sun will not be visible from Earth again until 2117.
ERIC Educational Resources Information Center
Kofoed, Jette
2008-01-01
This analysis concentrates on the case of a child, Jenny. The paper suggests that the concept of liminality may hold the key to an understanding of muted subject positions like the one assumed by Jenny in a school class. Liminality is proposed as a way of conceptualizing transitions where the subject in question transgresses established rules and…
ERIC Educational Resources Information Center
Cassidy, Joan
1998-01-01
Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)
Retrieving impulse response function amplitudes from the ambient seismic field
NASA Astrophysics Data System (ADS)
Viens, Loïc; Denolle, Marine; Miyake, Hiroe; Sakai, Shin'ichi; Nakagawa, Shigeki
2017-07-01
Seismic interferometry is now widely used to retrieve the impulse response function of the Earth between two distant seismometers. The phase information has been the focus of most passive imaging studies, as conventional seismic tomography uses traveltime measurements. The amplitude information, however, is harder to interpret because it strongly depends on the distribution of ambient seismic field sources and on the multitude of processing methods. Our study focuses on the latter by comparing the amplitudes of the impulse response functions calculated between seismic stations in the Kanto sedimentary basin, Japan, using several processing techniques. This region provides a unique natural laboratory to test the reliability of the amplitudes with complex wave propagation through the basin, and dense observations from the Metropolitan Seismic Observation network. We compute the impulse response functions using the cross correlation, coherency and deconvolution techniques of the raw ambient seismic field and the cross correlation of 1-bit normalized data. To validate the amplitudes of the impulse response functions, we use a shallow Mw 5.8 earthquake that occurred on the eastern edge of Kanto Basin and close to a station that is used as the virtual source. Both S and surface waves are retrieved in the causal part of the impulse response functions computed with all the different techniques. However, the amplitudes obtained from the deconvolution method agree better with those of the earthquake. Despite the expected wave attenuation due to the soft sediments of the Kanto Basin, seismic amplification caused by the basin geometry dominates the amplitudes of S and surface waves and is captured by the ambient seismic field. To test whether or not the anticausal part of the impulse response functions from deconvolution also contains reliable amplitude information, we use another virtual source located on the western edge of the basin. We show that the surface wave amplitudes
Forecasting Wave Amplitudes after the Arrival of a Tsunami
NASA Astrophysics Data System (ADS)
Nyland, David; Huang, Paul
2014-12-01
The destructive Pacific Ocean tsunami generated off the east coast of Honshu, Japan, on 11 March 2011 prompted the West Coast and Alaska Tsunami Warning Center (WCATWC) to issue a tsunami warning and advisory for the coastal regions of Alaska, British Columbia, Washington, Oregon, and California. Estimating the length of time the warning or advisory would remain in effect proved difficult. To address this problem, the WCATWC developed a technique to estimate the amplitude decay of a tsunami recorded at tide stations within the Warning Center's Area of Responsibly (AOR). At many sites along the West Coast of North America, the tsunami wave amplitudes will decay exponentially following the arrival of the maximum wave ( Mofjeld et al., Nat Hazards 22:71-89, 2000). To estimate the time it will take before wave amplitudes drop to safe levels, the real-time tide gauge data are filtered to remove the effects of tidal variations. The analytic envelope is computed and a 2 h sequence of amplitude values following the tsunami peak is used to obtain a least squares fit to an exponential function. This yields a decay curve which is then combined with an average West Coast decay function to provide an initial tsunami amplitude-duration forecast. This information may then be provided to emergency managers to assist with response planning.
Bagolini glasses: do they affect the horizontal prism fusion amplitude?
Schultinga, L; Burggraaf, F; Polling, J R; Gutter, M
2013-06-01
Bagolini striated glasses (BSG) can be used while performing the prism fusion amplitude to verify the maintenance of binocularity. The aim of this clinical study was to evaluate whether these glasses affect the prism fusion amplitude. Fifty-six subjects were examined at the Eye Care Clinic at the University of Applied Sciences Utrecht. The positive and negative prism fusion amplitudes were measured, incorporating the BSG at random, for both near and distance, with right and left eye fixating. Fifty-two normal subjects with a mean age of 21 years (range 17-28) were recruited. The median prism fusion amplitude at near was 10 BI to 33 BO with the BSG and 13 BI to 38 BO without (p < 0.001). At distance the median amplitude was 8 BI to 33 BO both with and without these glasses (p = 0.104). Although BSG are useful to verify whether binocularity is maintained, significantly smaller fusional ranges were obtained during measurements at near. In clinical terms, fusional ranges can vary significantly when using the BSG.
Name that percussive tune: Associative memory and amplitude envelope.
Schutz, Michael; Stefanucci, Jeanine K; H Baum, Sarah; Roth, Amber
2017-07-01
A series of experiments demonstrated novel effects of amplitude envelope on associative memory, with tones exhibiting naturally decaying amplitude envelopes (e.g., those made by two wine glasses clinking) better associated with target objects than amplitude-invariant tones. In Experiment 1 participants learned associations between household objects and 4-note tone sequences constructed of spectrally matched pure tones with either "flat" or "percussive" amplitude envelopes. Those hearing percussive tones correctly recalled significantly more sequence-object associations. Experiment 2 demonstrated that participants hearing percussive tones learned the associations more quickly. Experiment 3 used "reverse percussive" tones (percussive tones played backwards) to test whether differences in overall energy might account for this effect, finding they did not lead to the same level of performance as percussive tones. Experiment 4 varied the envelope at encoding and retrieval to determine which stage of the task was most affected by the envelope manipulation. Participants hearing percussive tones at both encoding and retrieval performed significantly better than the other three groups (i.e., flat at encoding/percussive at retrieval, etc.). We conclude that amplitude envelope plays an important role in learning and memory, a finding with relevance to psychological research on audition and associative memory, as well as practical relevance for improving human-computer interface design.
Brain and human pain: topographic EEG amplitude and coherence mapping.
Chen, A C; Rappelsberger, P
1994-01-01
Nineteen young healthy volunteers (8 males and 11 females) participated in an experimental ice-cube cold pressor test to study topographic changes of EEG parameters in response to painful stimulation. EEG was recorded with 19 electrodes and quantified by amplitude and coherence analyses. Mean amplitudes and values for local (between adjacent electrodes) and interhemispheric (between electrodes on homologous sites of both hemispheres) coherences were computed for six frequency bands. For the evaluation of changes between EEG at rest (baseline) and EEG during painful stimulation (right or left hand), non-parametric paired Wilcoxon tests were performed. The obtained descriptive error probabilities were presented in probability maps. In the behavioural pain tolerance and subjective pain ratings, no difference in gender or stimulation condition was observed. Under painful stimulation the results showed: (A) most pronounced decrease of Alpha amplitude in the central areas and some increase of high Beta amplitude; (B) increase of local coherence for Alpha and Beta 2 mainly in central regions and centro-frontal leads; and (C) increase of interhemispheric coherence for Alpha and Beta 2 in the central areas. The results of this study indicate clearly that peripheral painful stimulation is reflected by EEG changes. Decrease of EEG amplitude and simultaneous increase of EEG coherence in the central regions can be cortical correlates of human pain.
All Tree-level Amplitudes in Massless QCD
Dixon, Lance J.; Henn, Johannes M.; Plefka, Jan; Schuster, Theodor; /Humboldt U., Berlin
2010-10-25
We derive compact analytical formulae for all tree-level color-ordered gauge theory amplitudes involving any number of external gluons and up to three massless quark-anti-quark pairs. A general formula is presented based on the combinatorics of paths along a rooted tree and associated determinants. Explicit expressions are displayed for the next-to-maximally helicity violating (NMHV) and next-to-next-to-maximally helicity violating (NNMHV) gauge theory amplitudes. Our results are obtained by projecting the previously-found expressions for the super-amplitudes of the maximally supersymmetric Yang-Mills theory (N = 4 SYM) onto the relevant components yielding all gluon-gluino tree amplitudes in N = 4 SYM. We show how these results carry over to the corresponding QCD amplitudes, including massless quarks of different flavors as well as a single electroweak vector boson. The public Mathematica package GGT is described, which encodes the results of this work and yields analytical formulae for all N = 4 SYM gluon-gluino trees. These in turn yield all QCD trees with up to four external arbitrary-flavored massless quark-anti-quark-pairs.
Simulation of absolute amplitudes of ultrasound signals using equivalent circuits.
Johansson, Jonny; Martinsson, Pär-Erik; Delsing, Jerker
2007-10-01
Equivalent circuits for piezoelectric devices and ultrasonic transmission media can be used to cosimulate electronics and ultrasound parts in simulators originally intended for electronics. To achieve efficient system-level optimization, it is important to simulate correct, absolute amplitude of the ultrasound signal in the system, as this determines the requirements on the electronics regarding dynamic range, circuit noise, and power consumption. This paper presents methods to achieve correct, absolute amplitude of an ultrasound signal in a simulation of a pulse-echo system using equivalent circuits. This is achieved by taking into consideration loss due to diffraction and the effect of the cable that connects the electronics and the piezoelectric transducer. The conductive loss in the transmission line that models the propagation media of the ultrasound pulse is used to model the loss due to diffraction. Results show that the simulated amplitude of the echo follows measured values well in both near and far fields, with an offset of about 10%. The use of a coaxial cable introduces inductance and capacitance that affect the amplitude of a received echo. Amplitude variations of 60% were observed when the cable length was varied between 0.07 m and 2.3 m, with simulations predicting similar variations. The high precision in the achieved results show that electronic design and system optimization can rely on system simulations alone. This will simplify the development of integrated electronics aimed at ultrasound systems.
Three beams phase-shifting interferometry by their amplitude variation
NASA Astrophysics Data System (ADS)
Meneses-Fabian, Cruz; Rivera-Ortega, Uriel
2011-10-01
A novel phase shifting interferometry method based on the variation of the electric field under the scheme of a three beams interferometer is proposed. One beam contains the object under study, that makes this beam the probe beam; the other two will be consider as the reference beams with a phase difference of p 2 . Due to this, one of the three resulting interference terms will be cancelled and the two remaining will be in quadrature. Applying some trigonometric identities, we show that the resulting interference pattern could become modeled by the interfering of two beams with an additional phase term; we obtain that the tangent function of the additional phase depends on the division of the amplitude of the third field divided by the amplitude of the first, and it is possible to group the sum of the squares of these fields in a square amplitude. To recover the phase by using the phase shifting interferometry techniques it is necessary to keep constant the visibility of the interference pattern, at first sight we can think that this is not possible because the variations of the field amplitude affect the visibility of the patterns. However this problem is solved if the values of the amplitude corresponding to the fields one and three are seen as an ordered pair contained over an arc segment at the first quadrant. We justify the viability of this method by a theoretical analysis and a numerical simulation of the interference of three beams under the conditions mentioned above.
Ultraviolet divergences and factorization for coordinate-space amplitudes
NASA Astrophysics Data System (ADS)
Erdoǧan, Ozan; Sterman, George
2015-03-01
We consider the coordinate-space matrix elements that correspond to fixed-angle scattering amplitudes involving partons and Wilson lines in coordinate space, working in Feynman gauge. In coordinate space, both collinear and short-distance limits produce ultraviolet divergences. We classify singularities in coordinate space, and identify neighborhoods associated unambiguously with individual subspaces (pinch surfaces) where the integrals are singular. The set of such regions is finite for any diagram. Within each of these regions, coordinate-space soft-collinear and hard-collinear approximations reproduce singular behavior. Based on this classification of regions and approximations, we develop a series of nested subtraction approximations by analogy to the formalism in momentum space. This enables us to rewrite each amplitude as a sum of terms to which gauge-theory Ward identities can be applied, factorizing them into hard, jet and soft factors, and to confirm the multiplicative renormalizability of products of lightlike Wilson lines. We study in some detail the simplest case, the color-singlet cusp linking two Wilson lines, and show that the logarithm of this amplitude, which is a sum of diagrams known as webs, is closely related to the corresponding subtracted amplitude order by order in perturbation theory. This enables us to confirm that the logarithm of the cusp can be written as the integral of an ultraviolet-finite function over a surface. We study to what extent this result generalizes to amplitudes involving multiple Wilson lines.
Joint amplitude and frequency analysis of tremor activity.
Foerster, F; Smeja, M
1999-01-01
Clinical tremor analysis mostly is used for the measurement of tremor frequency. The analysis is based on short segments of EMG recordings and on clinical ratings of tremor intensity. Accelerometry appears to have some practical advantages. The present study was concerned with the development of a methodology for assessing tremor activity using the three parameters, frequency (Hz), amplitude (g), and occurrence of tremor (in per cent of time). These parameters were derived from joint amplitude frequency analysis of the calibrated accelerometer raw signal and from appropriate decision rules. This methodology was used in connection with 27 patients with Parkinson's disease, to investigate the aforesaid parameters of tremor activity. Postural tremor had a higher occurrence time (right-hand only) and higher frequency (left-hand only) than resting tremor, however, the average amplitudes did not differ. The correlations between right-hand and left-hand measures were higher during postural tremor test. Frequency was not correlated to amplitude or occurrence time, however, moderate correlations did exist between amplitude and occurrence time. In addition to the assessment of tremor activity, multi-channel accelerometry may be used for the detection of posture and motion. Further applications of this methodology, for example, in 24 hr ambulatory monitoring of tremor, are discussed.
Lorentz constraints on massive three-point amplitudes
NASA Astrophysics Data System (ADS)
Conde, Eduardo; Marzolla, Andrea
2016-09-01
Using the helicity-spinor language we explore the non-perturbative constraints that Lorentz symmetry imposes on three-point amplitudes where the asymptotic states can be massive. As it is well known, in the case of only massless states the three-point amplitude is fixed up to a coupling constant by these constraints plus some physical requirements. We find that a similar statement can be made when some of the particles have mass. We derive the generic functional form of the three-point amplitude by virtue of Lorentz symmetry, which displays several functional structures accompanied by arbitrary constants. These constants can be related to the coupling constants of the theory, but in an unambiguous fashion only in the case of one massive particle. Constraints on these constants are obtained by imposing that in the UV limit the massive amplitude matches the massless one. In particular, there is a certain Lorentz frame, which corresponds to projecting all the massive momenta along the same null momentum, where the three-point massive amplitude is fully fixed, and has a universal form.
Propagation and amplitude decay mechanisms of internal solitary waves
NASA Astrophysics Data System (ADS)
Wang, Ling-ling; Wang, Chun-ling; Tang, Hong-wu; Chen, Hong
2016-12-01
In this paper, a modified dynamic coherent eddy model (DCEM) of large eddy simulation is applied to study internal solitary waves in a numerical flume. The model was verified by physical experiment and applied to investigate the potential influence factors on internal wave amplitude. In addition, we discussed the energy loss of internal solitary wave as well as hydrodynamics in the propagation. The results of our study show that (1) Step-depth is the most sensitive factor on wave amplitude for the "step-pool" internal wave generation method and the wave amplitudes obey a linear increase with step depth, and the increase rate is about 0.4. (2) Wave energy loss obeys a linear decrease with the propagation distance and its loss rate of large amplitude waves is smaller than that of small amplitude waves. (3) Loss of kinetic energy in wave valley is larger than that near the interface due to relative high fluctuating frequency. (4) Discovered boundary jet-flow can intensify the bottom shear, which might be one of the mechanisms of substance transportation, and the boundary layers of jet flows are easily influenced by the adjacent waves.
Optimization of phase contrast in bimodal amplitude modulation AFM
Damircheli, Mehrnoosh; Payam, Amir F
2015-01-01
Summary Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079
Calculating phases between B{yields}K*{pi} amplitudes
Gronau, Michael; Pirjol, Dan; Rosner, Jonathan L.
2010-05-01
A phase {Delta}{Phi} between amplitudes for B{sup 0{yields}}K*{sup 0{pi}0} and B{sup 0{yields}}K*{sup +{pi}-} plays a crucial role in a method for constraining Cabibbo-Kobayashi-Maskawa parameters. We present a general argument for destructive interference between amplitudes for B{sup 0{yields}}K*{sup +{pi}-} and B{sup 0{yields}}K*{sup 0{pi}0} forming together a smaller I(K*{pi})=3/2 amplitude. Applying flavor SU(3) and allowing for conservative theoretical uncertainties, we obtain lower limits on |{Delta}{Phi}| and its charge conjugate. Values of these two phases favored by the BABAR collaboration are in good agreement with our bounds.
Phase and amplitude stabilization of beam-loaded superconducting resonators
Delayen, J.R.
1992-01-01
A model has been developed to analyze the static and dynamic behavior of superconducting accelerating cavities operated in self-excited loops in the presence of phase and amplitude feedback, ponderomotive effects, and beam loading. This is an extension of an earlier analysis of the stabilization of superconducting cavities which has been the basis of the control system of several superconducting accelerators but did not include beam loading. Conditions have been derived to ensure static and dynamic stability in the presence of ponderomotive effects (coupling between the mechanical and electromagnetic modes of the cavity through the radiation pressure). Expressions for the effect of fluctuations of cavity frequency and beam amplitude and phase on the cavity-field amplitude and phase and beam-energy gain have been obtained.
Phase and amplitude stabilization of beam-loaded superconducting resonators
Delayen, J.R.
1992-10-01
A model has been developed to analyze the static and dynamic behavior of superconducting accelerating cavities operated in self-excited loops in the presence of phase and amplitude feedback, ponderomotive effects, and beam loading. This is an extension of an earlier analysis of the stabilization of superconducting cavities which has been the basis of the control system of several superconducting accelerators but did not include beam loading. Conditions have been derived to ensure static and dynamic stability in the presence of ponderomotive effects (coupling between the mechanical and electromagnetic modes of the cavity through the radiation pressure). Expressions for the effect of fluctuations of cavity frequency and beam amplitude and phase on the cavity-field amplitude and phase and beam-energy gain have been obtained.