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Sample records for multi-parton scattering amplitudes

  1. Bootstrapping Multi-Parton Loop Amplitudes in QCD

    SciTech Connect

    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.

  2. One-Loop Multi-Parton Amplitudes with a Vector Boson for the LHC

    SciTech Connect

    Berger, C.F.; Bern, Z.; Dixon, L.J.; Cordero, F.Febres; Forde, D.; Ita, H.; Kosower, D.A.; Maitre, D.; /SLAC

    2008-08-11

    In this talk, we present the first, numerically stable, results for the one-loop amplitudes needed for computing W; Z + 3 jet cross sections at the LHC to next-to-leading order in the QCD coupling. We implemented these processes in BlackHat, an automated program based on on-shell methods. These methods scale very well with increasing numbers of external partons, and are applicable to a wide variety of problems of phenomenological interest at the LHC.

  3. 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.

  4. Syzygies probing scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao

    2016-09-01

    We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.

  5. 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

  6. Amplitude for N-gluon superstring scattering.

    PubMed

    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.

  7. Amplitude for N-Gluon Superstring Scattering

    SciTech Connect

    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.

  8. Einstein-Yang-Mills scattering amplitudes from scattering equations

    NASA Astrophysics Data System (ADS)

    Cachazo, Freddy; He, Song; Yuan, Ellis Ye

    2015-01-01

    We present the building blocks that can be combined to produce tree-level S-matrix elements of a variety of theories with various spins mixed in arbitrary dimensions. The new formulas for the scattering of n massless particles are given by integrals over the positions of n points on a sphere restricted to satisfy the scattering equations. As applications, we obtain all single-trace amplitudes in Einstein-Yang-Mills (EYM) theory, and generalizations to include scalars. Also in EYM but extended by a B-field and a dilaton, we present all double-trace gluon amplitudes. The building blocks are made of Pfaffians and Parke-Taylor-like factors of subsets of particle labels.

  9. 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.

  10. 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.

  11. Miracles in Scattering Amplitudes: from QCD to Gravity

    SciTech Connect

    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.

  12. 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.

  13. Scattering amplitudes in gauge theories: progress and outlook Scattering amplitudes in gauge theories: progress and outlook

    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

  14. Singularity structure of maximally supersymmetric scattering amplitudes.

    PubMed

    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).

  15. Scattering Amplitudes: The Most Perfect Microscopic Structures in the Universe

    SciTech Connect

    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'.

  16. Loop Integrands for Scattering Amplitudes from the Riemann Sphere

    NASA Astrophysics Data System (ADS)

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2015-09-01

    The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n -gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory.

  17. Wilson loops and QCD/string scattering amplitudes

    SciTech Connect

    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.

  18. Effective Field Theories from Soft Limits of Scattering Amplitudes.

    PubMed

    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.

  19. Limits of applicability of the concept of scattering amplitude in small-angle scattering problems

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2014-01-01

    The applicability of the concept of scattering amplitude to the description of small-angle scattering experiments has been considered. An expression has been obtained for a scattered radiation flux on a detector under much milder conditions than the condition of Fraunhofer diffraction. The influence of incoherence of the source on the results has been evaluated.

  20. Recent progress in one-loop multi-parton calculations

    SciTech Connect

    Bern, Z.; Dixon, L.; Dunbar, D.C.; Kosower, D.A.

    1994-09-01

    The authors describe techniques that simplify the calculation of one-loop QCD amplitudes with many external legs, which are needed for next-to-leading-order (NLO) corrections to multi-jet processes. The constraints imposed by perturbative unitarity, collinear singularities and a supersymmetry-inspired organization of helicity amplitudes are particularly useful. Certain sequences of one-loop helicity amplitudes may be obtained for an arbitrary number of external gluons using these techniques. They also report on progress in completing the set of one-loop helicity amplitudes required for NLO three-jet production at hadron colliders, namely the amplitudes with two external quarks and three gluons.

  1. Ward identities and high energy scattering amplitudes in string theory

    NASA Astrophysics Data System (ADS)

    Chan, Chuan-Tsung; Ho, Pei-Ming; Lee, Jen-Chi

    2005-02-01

    High-energy limit α→∞ of stringy Ward identities derived from the decoupling of two types of zero-norm states in the old covariant first quantized (OCFQ) spectrum of open bosonic string are used to check the consistency of saddle point calculations of high energy scattering amplitudes of Gross and Mende and Gross and Manes. Some inconsistencies of their saddle point calculations are found even for the string-tree scattering amplitudes of the excited string states. We discuss and calculate the missing terms of the calculation by those authors to recover the stringy Ward identities. In addition, based on the tree-level stringy Ward identities, we give the proof of a general formula, which was proposed previously, of all high energy four-point string-tree amplitudes of arbitrary particles in the string spectrum. In this formula all such scattering amplitudes are expressed in terms of those of tachyons as conjectured by Gross. The formula is extremely simple which manifestly demonstrates the universal high energy behavior of the interactions among all string states.

  2. Effects produced by multi-parton interactions and color reconnection in small systems

    NASA Astrophysics Data System (ADS)

    Cuautle, Eleazar; Ortiz, Antonio; Paić, Guy

    2016-12-01

    Multi-parton interactions and color reconnection can produce QGP-like effects in small systems, specifically, radial flow-like patterns. For pp collisions simulated with Pythia 8.212, in this work we investigate their effects on different observables like event multiplicity, event shapes and transverse momentum distributions.

  3. The Lauricella functions and exact string scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Lai, Sheng-Hong; Lee, Jen-Chi; Yang, Yi

    2016-11-01

    We discover that the 26 D open bosonic string scattering amplitudes (SSA) of three tachyons and one arbitrary string state can be expressed in terms of the D-type Lauricella functions with associated SL(K+3,C) symmetry. As a result, SSA and symmetries or relations among SSA of different string states at various limits calculated previously can be rederived. These include the linear relations first conjectured by Gross [1-5] and later corrected and proved in [6-12] in the hard scattering limit, the recurrence relations in the Regge scattering limit with associated SL(5,C) symmetry [24-26] and the extended recurrence relations in the nonrelativistic scattering limit with associated SL(4,C) symmetry [29] discovered recently. Finally, as an application, we calculate a new recurrence relation of SSA which is valid for all energies.

  4. Unambiguous ionization amplitudes for electron-hydrogen scattering

    SciTech Connect

    Bartlett, P. L.; Bray, I.; Jones, S.; Stelbovics, A. T.; Kadyrov, A. S.; Bartschat, K.; Ver Steeg, G. L.; Scott, M. P.; Burke, P. G.

    2003-08-01

    According to quantum collision theory, scattering amplitudes are complex numbers, which are completely defined by their magnitude and phase. Although the phase information is generally not determined entirely in collision experiments, the phases are well defined and can be used to check computational models. We use four state-of-the-art approaches to calculate the magnitude and phase of the electron-hydrogen ionization amplitude in the Temkin-Poet S-wave model. We demonstrate that the correct phase can be extracted for each method by using the appropriate final-state continuum functions.

  5. Infrared singularities of scattering amplitudes in perturbative QCD

    SciTech Connect

    Becher, Thomas; Neubert, Matthias

    2013-11-01

    An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.

  6. Harmonic R matrices for scattering amplitudes and spectral regularization.

    PubMed

    Ferro, Livia; Łukowski, Tomasz; Meneghelli, Carlo; Plefka, Jan; Staudacher, Matthias

    2013-03-22

    Planar N = 4 supersymmetric Yang-Mills theory appears to be integrable. While this allows one to find this theory's exact spectrum, integrability has hitherto been of no direct use for scattering amplitudes. To remedy this, we deform all scattering amplitudes by a spectral parameter. The deformed tree-level four-point function turns out to be essentially the one-loop R matrix of the integrable N = 4 spin chain satisfying the Yang-Baxter equation. Deformed on-shell three-point functions yield novel three-leg R matrices satisfying bootstrap equations. Finally, we supply initial evidence that the spectral parameter might find its use as a novel symmetry-respecting regulator replacing dimensional regularization. Its physical meaning is a local deformation of particle helicity, a fact which might be useful for a much larger class of nonintegrable four-dimensional field theories.

  7. 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’.

  8. 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.

  9. Constraints on scattering amplitudes in multistate Landau-Zener theory

    DOE PAGES

    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.

  10. Two-loop scattering amplitudes from the Riemann sphere

    NASA Astrophysics Data System (ADS)

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2016-12-01

    The scattering equations give striking formulas for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor-string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the genus of the world sheet is equivalent to an expansion in terms of nodes of a Riemann sphere, with the nodes carrying the loop momenta. In this paper, we show how to obtain two-loop scattering equations with the correct factorization properties. We adapt genus-two integrands from the ambitwistor string to the nodal Riemann sphere and show that these yield correct answers, by matching standard results for the four-point two-loop amplitudes of maximal supergravity and super-Yang-Mills theory. In the Yang-Mills case, this requires the loop analogue of the Parke-Taylor factor carrying the color dependence, which includes nonplanar contributions.

  11. Scattering amplitudes over finite fields and multivariate functional reconstruction

    NASA Astrophysics Data System (ADS)

    Peraro, Tiziano

    2016-12-01

    Several problems in computer algebra can be efficiently solved by reducing them to calculations over finite fields. In this paper, we describe an algorithm for the reconstruction of multivariate polynomials and rational functions from their evaluation over finite fields. Calculations over finite fields can in turn be efficiently performed using machine-size integers in statically-typed languages. We then discuss the application of the algorithm to several techniques related to the computation of scattering amplitudes, such as the four- and six-dimensional spinor-helicity formalism, tree-level recursion relations, and multi-loop integrand reduction via generalized unitarity. The method has good efficiency and scales well with the number of variables and the complexity of the problem. As an example combining these techniques, we present the calculation of full analytic expressions for the two-loop five-point on-shell integrands of the maximal cuts of the planar penta-box and the non-planar double-pentagon topologies in Yang-Mills theory, for a complete set of independent helicity configurations.

  12. Propagating light through a scattering medium with specific amplitude and phase (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tseng, Snow H.; Kung, Te-Jen; Yu, Min-Lun

    2016-03-01

    By means of numerical solutions of Maxwell's equations, we model the complex light scattering phenomenon. Light propagation through scattering medium is a deterministic process; with specific amplitude and phase, light can propagate to the target position via multiple scattering. By means of numerical solutions of Maxwell's equations, the complex light scattering phenomenon can be accurately analyzed. The reported simulation enables qualitative and quantitative analyses of the effectiveness of directing light through turbid media to a targeted position

  13. Scattering amplitudes for the rationally extended PT symmetric complex potentials

    NASA Astrophysics Data System (ADS)

    Kumari, Nisha; Yadav, Rajesh Kumar; Khare, Avinash; Bagchi, Bijan; Mandal, Bhabani Prasad

    2016-10-01

    In this paper, we consider the rational extensions of two different classes of PT symmetric complex potentials namely the asymptotically vanishing Scarf II and asymptotically non-vanishing Rosen-Morse II [ RM-II] and obtain the accompanying bound state eigenfunctions in terms of the exceptional Xm Jacobi polynomials and a certain class of orthogonal polynomials. By considering the asymptotic behavior of the exceptional polynomials, we also derive the reflection and transmission amplitudes for them and discuss the various novel properties of the corresponding amplitudes.

  14. Implementation of Recursion Relations in Gluon Scattering Amplitude Calculations in AdS4 /CFT3

    NASA Astrophysics Data System (ADS)

    Dokmetzoglou, Nikolaos; Kharel, Savan

    2017-01-01

    The Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence is a duality between a theory of gravity in curved-space (AdS) and a conformally-invariant quantum field theory in flat-space (CFT). Scattering amplitudes are observables associated with the probability of the interaction of a given assembly of particles. Gluons, being the exchange particles associated with the strong nuclear force, which holds quarks together to form protons, are abundant byproducts of fundamental particle collisions. Thus, studying gluon scattering amplitudes is an effective way of deepening our understanding of these observables in AdS/CFT. Traditionally, Feynman diagrams have been used to calculate such scattering amplitudes. In this project, we use factorization properties and recursion relations to simplify these calculations. More specifically, we calculate multiple (different helicity combinations) four-point gluon scattering amplitudes in AdS4 /CFT3 (4-D AdS and 3-D CFT) as sums of products of three-point amplitudes. And then we calculate a five-point gluon scattering amplitude in AdS4 /CFT3 by decomposing it into a sum of products of these four-point and three-point amplitudes. Finally we comment on useful identities for checking these amplitudes. This work was supported by a Weinstein Davidson College Research Initiative Summer Research grant.

  15. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition. 2; Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, Aaron

    2004-01-01

    The development of a practical method of accurately calculating the full scattering amplitude, without making a partial wave decomposition is continued. The method is developed in the context of electron-hydrogen scattering, and here exchange is dealt with by considering e-H scattering in the static exchange approximation. The Schroedinger equation in this approximation can be simplified to a set of coupled integro-differential equations. The equations are solved numerically for the full scattering wave function. The scattering amplitude can most accurately be calculated from an integral expression for the amplitude; that integral can be formally simplified, and then evaluated using the numerically determined wave function. The results are essentially identical to converged partial wave results.

  16. Symmetries of tree-level scattering amplitudes in N=6 superconformal Chern-Simons theory

    SciTech Connect

    Bargheer, Till; Loebbert, Florian; Meneghelli, Carlo

    2010-08-15

    Constraints of the osp(6|4) symmetry on tree-level scattering amplitudes in N=6 superconformal Chern-Simons theory are derived. Supplemented by Feynman diagram calculations, solutions to these constraints, namely, the four- and six-point superamplitudes, are presented and shown to be invariant under Yangian symmetry. This introduces integrability into the amplitude sector of the theory.

  17. Topics in Nonsupersymmetric Scattering Amplitudes in Gauge and Gravity Theories

    NASA Astrophysics Data System (ADS)

    Nohle, Joshua David

    In Chapters 1 and 2, we introduce and review the duality between color and kinematics in Yang-Mills theory uncovered by Bern, Carrasco and Johansson (BCJ). In Chapter 3, we provide evidence in favor of the conjectured duality between color and kinematics for the case of nonsupersymmetric pure Yang-Mills amplitudes by constructing a form of the one-loop four-point amplitude of this theory that makes the duality manifest. Our construction is valid in any dimension. We also describe a duality-satisfying representation for the two-loop four-point amplitude with identical four-dimensional external helicities. We use these results to obtain corresponding gravity integrands for a theory containing a graviton, dilaton, and antisymmetric tensor, simply by replacing color factors with specified diagram numerators. Using this, we give explicit forms of ultraviolet divergences at one loop in four, six, and eight dimensions, and at two loops in four dimensions. In Chapter 4, we extend the four-point one-loop nonsupersymmetric pure Yang-Mills discussion of Chapter 3 to include fermions and scalars circulating in the loop with all external gluons. This gives another nontrivial loop-level example showing that the duality between color and kinematics holds in nonsupersymmetric gauge theory. The construction is valid in any spacetime dimension and written in terms of formal polarization vectors. We also convert these expressions into a four-dimensional form with explicit external helicity states. Using this, we compare our results to one-loop duality-satisfying amplitudes that are already present in literature. In Chapter 5, we switch from the topic of color-kinematics duality to discuss the recently renewed interest in the soft behavior of gravitons and gluons. Specifically, we discuss the subleading low-energy behavior. Cachazo and Strominger recently proposed an extension of the soft-graviton theorem found by Weinberg. In addition, they proved the validity of their extension at

  18. Scattering amplitudes to all orders in meson exchange

    SciTech Connect

    Silbar, R.R.; Mattis, M.P.

    1990-01-01

    As the number of colors in QCD, N{sub C}, becomes large, it is possible to sum up all meson-exchange contributions, however arbitrarily complicated, to meson-baryon and baryon-baryon scattering. A semi-classical structure for the two-flavor theory emerges, in close correspondence to vector-meson-augmented Skyrme models. In this limit, baryons act as extended static sources for the classical meson fields. This leads to non-linear differential equations for the classical meson fields which can be solved numerically for static radial (hedgehog-like) solutions. The non-linear terms in the equations of motion for the quantized meson fields can then be simplified, to leading order in 1/N{sub C}, by replacing all factors of the meson field but one by the previously-found classical field. This results in linear, Schroedinger-like equations, which are easily solved. For the meson-baryon case the solution can be subsequently analyzed to obtain the phase shifts for the scattering and, from these, the baryon resonance spectrum of the model. As the warm-up, we have carried out this calculation for the simple case of {sigma} mesons only, finding sensible results. 8 refs., 3 figs.

  19. Direct Calculation of the Scattering Amplitude Without Partial Wave Decomposition. III; Inclusion of Correlation Effects

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, Aaron

    2007-01-01

    In the first two papers in this series, we developed a method for studying electron-hydrogen scattering that does not use partial wave analysis. We constructed an ansatz for the wave function in both the static and static exchange approximations and calculated the full scattering amplitude. Here we go beyond the static exchange approximation, and include correlation in the wave function via a modified polarized orbital. This correlation function provides a significant improvement over the static exchange approximation: the resultant elastic scattering amplitudes are in very good agreement with fully converged partial wave calculations for electron-hydrogen scattering. A fully variational modification of this approach is discussed in the conclusion of the article Popular summary of Direct calculation of the scattering amplitude without partial wave expansion. III ....." by J. Shertzer and A. Temkin. In this paper we continue the development of In this paper we continue the development of a new approach to the way in which researchers have traditionally used to calculate the scattering cross section of (low-energy) electrons from atoms. The basic mathematical problem is to solve the Schroedinger Equation (SE) corresponding the above physical process. Traditionally it was always the case that the SE was reduced to a sequence of one-dimensional (ordinary) differential equations - called partial waves which were solved and from the solutions "phase shifts" were extracted, from which the scattering cross section was calculated.

  20. Non-Perturbative, Unitary Quantum-Particle Scattering Amplitudes from Three-Particle Equations

    SciTech Connect

    Lindesay, James V

    2002-03-19

    We here use our non-perturbative, cluster decomposable relativistic scattering formalism to calculate photon-spinor scattering, including the related particle-antiparticle annihilation amplitude. We start from a three-body system in which the unitary pair interactions contain the kinematic possibility of single quantum exchange and the symmetry properties needed to identify and substitute antiparticles for particles. We extract from it unitary two-particle amplitude for quantum-particle scattering. We verify that we have done this correctly by showing that our calculated photon-spinor amplitude reduces in the weak coupling limit to the usual lowest order, manifestly covariant (QED) result with the correct normalization. That we are able to successfully do this directly demonstrates that renormalizability need not be a fundamental requirement for all physically viable models.

  1. Analyticity properties and asymptotic behavior of scattering amplitude in higher dimensional theories

    NASA Astrophysics Data System (ADS)

    Maharana, Jnanadeva

    2017-01-01

    The properties of the high energy behavior of the scattering amplitude of massive, neutral, and spinless particles in higher dimensional field theories are investigated. The axiomatic formulation of Lehmann, Symanzik, and Zimmermann (LSZ) is adopted. The analyticity properties of the causal, the retarded, and the advanced functions associated with the four point elastic amplitudes are studied. The analog of the Lehmann-Jost-Dyson representation is obtained in higher dimensional field theories. The generalized J-L-D representation is utilized to derive the t-plane analyticity property of the amplitude. The existence of an ellipse analogous to the Lehmann ellipse is demonstrated. Thus a fixed-t dispersion relation can be written down with a finite number of subtractions due to the temperedness of the amplitudes. The domain of analyticity of scattering amplitude in s and t variables is extended by imposing unitarity constraints. A generalized version of Martin's theorem is derived to prove the existence of such a domain in D-dimensional field theories. It is shown that the amplitude can be expanded in a power series in t which converges for |" separators=" t | < R , R being s-independent. The positivity properties of absorptive amplitudes are derived to prove the t-plane analyticity of amplitude. In the extended analyticity domain dispersion relations are written with two subtractions. The bound on the total cross section is derived from LSZ axioms without any extra ad hoc assumptions.

  2. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II

    NASA Technical Reports Server (NTRS)

    Shertzer, J.; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE) can be reduced to a 2d partial differential equation (pde), and was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation. The resultant equation can be reduced to a pair of coupled pde's, to which the finite element method can still be applied. The resultant scattering amplitudes, both singlet and triplet, as a function of angle can be calculated for various energies. The results are in excellent agreement with converged partial wave results.

  3. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II: Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE), which can be reduced to a 2d partial differential equation (pde), was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation, which is reducible to a pair of coupled pde's. The resultant scattering amplitudes, both singlet and triplet, calculated as a function of energy are in excellent agreement with converged partial wave results.

  4. Non-relativistic scattering amplitude for a new multi-parameter exponential-type potential

    NASA Astrophysics Data System (ADS)

    Yazarloo, B. H.; Mehraban, H.; Hassanabadi, H.

    2016-08-01

    In this paper, we study the scattering properties of s-wave Schrödinger equation for the multi-parameter potential, which can be reduced into four special cases for different values of potential parameters, i.e., Hulthén, Manning-Rosen, and Eckart potentials. We also obtain and investigate the scattering amplitudes of these special cases. Some numerical results are also obtained and reported.

  5. Construction of Non-Perturbative, Unitary Particle-Antiparticle Amplitudes for Finite Particle Number Scattering Formalisms

    SciTech Connect

    Lindesay, James V

    2002-03-12

    Starting from a unitary, Lorentz invariant two-particle scattering amplitude, we show how to use an identification and replacement process to construct a unique, unitary particle-antiparticle amplitude. This process differs from conventional on-shell Mandelstam s,t,u crossing in that the input and constructed amplitudes can be off-diagonal and off-energy shell. Further, amplitudes are constructed using the invariant parameters which are appropriate to use as driving terms in the multi-particle, multichannel nonperturbative, cluster decomposable, relativistic scattering equations of the Faddeev-type integral equations recently presented by Alfred, Kwizera, Lindesay and Noyes. It is therefore anticipated that when so employed, the resulting multi-channel solutions will also be unitary. The process preserves the usual particle-antiparticle symmetries. To illustrate this process, we construct a J=0 scattering length model chosen for simplicity. We also exhibit a class of physical models which contain a finite quantum mass parameter and are Lorentz invariant. These are constructed to reduce in the appropriate limits, and with the proper choice of value and sign of the interaction parameter, to the asymptotic solution of the nonrelativistic Coulomb problem, including the forward scattering singularity , the essential singularity in the phase, and the Bohr bound-state spectrum.

  6. Stimulated scattering of a large amplitude electromagnetic wave by the eigenmodes of a plasma slab

    NASA Astrophysics Data System (ADS)

    Gradov, O. M.; Stenflo, L.

    1983-08-01

    New results are presented from a theoretical investigation of the scattering of an electromagnetic pump wave that is normally incident on a plasma slab. In the case considered here, the leaking surface wave eigenmode represents the scattered radiation. The generation of harmonics in the scattered wave will thus be responsible for the saturation of the wave intensities. It is shown that a large-amplitude electromagnetic pump wave can be scattered in a nonlinear process where both the low-frequency and high-frequency oscillations are eigenmodes of the plasma slab. The second harmonic generation that occurs in this case leads to efficient saturation of the scattering instability. It is pointed out that other mechanisms, for example, the screening of the pump wave by the surface mode current, may also contribute significantly to the establishment of the stationary wave.

  7. The string BCJ relations revisited and extended recurrence relations of nonrelativistic string scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Lai, Sheng-Hong; Lee, Jen-Chi; Yang, Yi

    2016-05-01

    We review and extend high energy four point string BCJ relations in both the fixed angle and Regge regimes. We then give an explicit proof of four point string BCJ relations for all energy. This calculation provides an alternative proof of the one based on monodromy of integration in string amplitude calculation. In addition, we calculate both s- t and t- u channel nonrelativistic low energy string scattering amplitudes of three tachyons and one higher spin string state at arbitrary mass levels. We discover that the mass and spin dependent nonrelativistic string BCJ relations can be expressed in terms of Gauss hypergeometry functions. As an application, for each fixed mass level N, we derive extended recurrence relations among nonrelativistic low energy string scattering amplitudes of string states with different spins and different channels.

  8. Statistical density model for composite system scattering: Modified ensemble densities and bounded amplitudes

    NASA Astrophysics Data System (ADS)

    Hahn, Y. K.

    2016-09-01

    A statistical density model for composite system scattering is formulated, by incorporating the ensemble density functional approach in describing the correlation dynamics during the collision. The principal difficulty of non-integrable propagating waves is first resolved by treating the open and closed channels separately; only the closed channel part does allow a density description. The unique open/closed channel separation adopted here allows not only the closed channel Hamiltonian MQ to support integrable densities, but also to establish the important bounds on the scattering amplitude. A modified ensemble energy functional for the MQ is constructed, and the statistical densities ρmtQ for the closed channels are generated. The scattering amplitude is then formulated in terms of the ρmtQ and the coefficients of variation that connect the closed channels to the asymptotic source. Evaluation of the amplitude integrals requires the determinantal functions deduced from the ρmtQ, which also leads to a coupled channel approach. The bound property of the amplitude allows variational optimization of the coefficients. Approximate procedures for securing the orthogonality of the MQ and for evaluation of the source term itself are discussed, including a judicious choice of configurations with zero and one inner-shell holes. Validity of the several critical modifications introduced is assessed.

  9. J. J. Sakurai Prize: Scattering Amplitudes - the Story of Loops and Legs

    NASA Astrophysics Data System (ADS)

    Dixon, Lance

    2014-03-01

    Scattering amplitudes are at the interface between quantum field theory and particle experiment. Precise predictions for reactions at energy frontier machines such as the Large Hadron Collider (LHC) rely on quantum corrections to scattering amplitudes involving multiple quarks and gluons, as well as other particles. For decades, theorists used Feynman diagrams for this job. However, Feynman diagrams are just too slow, even on fast computers, to allow adequate precision for complicated events with many jets of hadrons in the final state. Such events are produced copiously at the LHC, and constitute formidable backgrounds to many searches for new physics. Over the past two decades, alternative methods to Feynman diagrams have come to fruition. The new ``on-shell'' methods are based on the old principle of unitarity. They can be much more efficient because they exploit the underlying simplicity of scattering amplitudes, and recycle lower-loop information. The same methods have also enabled new insight into the structure of gauge theory and gravity at the quantum level, especially in highly supersymmetric theories where they maintain all of the symmetries. I'll give a brief motivation for and introduction to the new methods, which will be followed by descriptions of their phenomenological and formal applications by David Kosower and Zvi Bern.

  10. Scattering of glue by glue on the light-cone worldsheet: Helicity nonconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C.B.

    2005-09-15

    We give the light-cone gauge calculation of the one-loop on-shell scattering amplitudes for gluon-gluon scattering which violate helicity conservation. We regulate infrared divergences by discretizing the p{sup +} integrations, omitting the terms with p{sup +}=0. Collinear divergences are absent diagram by diagram for the helicity nonconserving amplitudes. We also employ a novel ultraviolet regulator that is natural for the light-cone worldsheet description of planar Feynman diagrams. We show that these regulators give the known answers for the helicity nonconserving one-loop amplitudes, which do not suffer from the usual infrared vagaries of massless particle scattering. For the maximal helicity violating process we elucidate the physics of the remarkable fact that the loop momentum integrand for the on-shell Green function associated with this process, with a suitable momentum routing of the different contributing topologies, is identically zero. We enumerate the counterterms that must be included to give Lorentz covariant results to this order, and we show that they can be described locally in the light-cone worldsheet formulation of the sum of planar diagrams.

  11. J. J. Sakurai Prize: Harmony of Scattering Amplitudes: From Gauge Theory to Supergravity

    NASA Astrophysics Data System (ADS)

    Bern, Zvi

    2014-03-01

    As explained in the two previous talks by Lance Dixon and David Kosower, on-shell methods have had an important impact on our understanding of scattering amplitudes and their application to collider physics. In this talk I will describe examples where these ideas have also had impacts in more theoretical areas. The first example shows how these methods have led to the construction of all quantum corrections to specific scattering amplitudes in maximally supersymmetric gauge theory with a large number of color charges. An active area of current research is to do the same for more intricate generic amplitudes of the theory. A second example shows how on-shell methods have uncovered new algebraic structures in gauge-theory amplitudes that have applications to quantum gravity. The advances make it possible to carry out computations in quantum gravity that would have been hopeless with more traditional Feynman diagram methods and to elucidate a remarkable connection between gauge and gravity theories. The results from these investigations have renewed hope that highly supersymmetric gravity theories may be ultraviolet finite, contrary to the prevailing wisdom.

  12. Role of Möbius constants and scattering functions in Cachazo-He-Yuan scalar amplitudes

    NASA Astrophysics Data System (ADS)

    Lam, C. S.; Yao, York-Peng

    2016-05-01

    The integration over the Möbius variables leading to the Cachazo-He-Yuan double-color n -point massless scalar amplitude are carried out one integral at a time. Möbius invariance dictates the final amplitude to be independent of the three Möbius constants σr,σs,σt, but their choice affects integrations and the intermediate results. The effect of the Möbius constants, which will be held finite but otherwise arbitrary, the two sets of colors, and the scattering functions on each integration is investigated. A general systematic way to carry out the n -3 integrations is explained, each exposing one of the n -3 propagators of a single Feynman diagram. Two detailed examples are shown to illustrate the procedure, one a five-point amplitude, and the other a nine-point amplitude. Our procedure does not generate intermediate spurious poles, in contrast to what is common by choosing Möbius constants at 0, 1, and ∞ .

  13. Broadband flat-amplitude multiwavelength Brillouin-Raman fiber laser with spectral reshaping by Rayleigh scattering.

    PubMed

    Wang, Zinan; Wu, Han; Fan, Mengqiu; Li, Yi; Gong, Yuan; Rao, Yunjiang

    2013-12-02

    In this letter, we propose a novel configuration for generating multiwavelength Brillouin-Raman fiber laser (MBRFL). The spectral reshaping effect introduced by Rayleigh scattering in a 50 km single mode fiber unifies the generated Brillouin comb in terms of both power level and linewidth. As a consequence, we are able to obtain a 40 nm flat-amplitude MBRFL with wide bandwidth from 1557 nm to 1597 nm covering >500 Stokes lines. This is, to the best of our knowledge, the widest flat-amplitude bandwidth of MBRFL with uniform Stokes combs using just a single Raman pump laser. The channel-spacing is 0.08 nm and the measured OSNR is higher than 12.5 dB. We also demonstrate that the output spectrum of the MBRFL is nearly unaffected over 14 dB range of Brillouin pumping power.

  14. Scattering of glue by glue on the light-cone worldsheet. II. Helicityconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C. B.

    2006-08-15

    This is the second of a pair of articles on scattering of glue by glue,in which we give the light-cone gauge calculation of the one-loop on-shellhelicity conserving scattering amplitudes for gluon-gluon scattering (neglectingquark loops). The 1/p{sup +} factors in the gluon propagatorare regulated by replacing p{sup +} integrals with discretized sums omitting the p{sup +}=0 terms in each sum. We alsoemploy a novel ultraviolet regulator that is convenient for the light-coneworldsheet description of planar Feynman diagrams. The helicity conservingscattering amplitudes are divergent in the infrared. The infrared divergencesin the elastic one-loop amplitude are shown to cancel, in their contributionto cross sections, against ones in the cross section for unseen bremsstrahlunggluons. We include here the explicit calculation of the latter, because itassumes an unfamiliar form due to the peculiar way discretization of p{sup +} regulates infrared divergences. In resolving the infrareddivergences we employ a covariant definition of jets, which allows a transparentdemonstration of the Lorentz invariance of our final results. Because we usean explicit cutoff of the ultraviolet divergences in exactly four spacetimedimensions, we must introduce explicit counterterms to achieve this finalcovariant result. These counterterms are polynomials in the external momentaof the precise order dictated by power counting. We discuss the modificationsthey entail for the light-cone worldsheet action that reproduces the bareplanar diagrams of the gluonic sector of QCD. The simplest way to do thisis to interpret the QCD string as moving in six spacetime dimensions.

  15. Scattering Amplitudes, the AdS/CFT Correspondence, Minimal Surfaces, and Integrability

    DOE PAGES

    Alday, Luis F.

    2010-01-01

    We focus on the computation of scattering amplitudes of planar maximally supersymmetric Yang-Mill in four dimensions at strong coupling by means of the AdS/CFT correspondence and explain how the problem boils down to the computation of minimal surfaces in AdS in the first part of this paper. In the second part of this review we explain how integrability allows to give a solution to the problem in terms of a set of integral equations. The intention of the review is to give a pedagogical, rather than very detailed, exposition.

  16. Nonplanar on-shell diagrams and leading singularities of scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Baoyi; Chen, Gang; Cheung, Yeuk-Kwan E.; Li, Yunxuan; Xie, Ruofei; Xin, Yuan

    2017-02-01

    Bipartite on-shell diagrams are the latest tool in constructing scattering amplitudes. In this paper we prove that a Britto-Cachazo-Feng-Witten (BCFW) decomposable on-shell diagram process a rational top form if and only if the algebraic ideal comprised the geometrical constraints are shifted linearly during successive BCFW integrations. With a proper geometric interpretation of the constraints in the Grassmannian manifold, the rational top form integration contours can thus be obtained, and understood, in a straightforward way. All rational top form integrands of arbitrary higher loops leading singularities can therefore be derived recursively, as long as the corresponding on-shell diagram is BCFW decomposable.

  17. Retarded thermal Green's functions and forward scattering amplitudes at two loops

    NASA Astrophysics Data System (ADS)

    Brandt, F. T.; Das, Ashok; Frenkel, J.

    1999-11-01

    In this paper, we extend our earlier one loop analysis to two loops and give a simple diagrammatic description for the retarded Green's functions at finite temperature in terms of forward scattering amplitudes of on-shell thermal particles. We present a simple discussion, which can be easily generalized to any field theory, of the temperature dependent parts of the retarded two and three point functions in scalar field theory and QED. As an application of our result at two loops, we show how the infrared singularities in the thermal part of the retarded photon self-energy cancel in QED2 in the limit of vanishing electron mass.

  18. Scattering amplitude and bosonization duality in general Chern-Simons vector models

    NASA Astrophysics Data System (ADS)

    Yokoyama, Shuichi

    2016-09-01

    We present the exact large N calculus of four point functions in general Chern-Simons bosonic and fermionic vector models. Applying the LSZ formula to the four point function we determine the two body scattering amplitudes in these theories taking a special care for a non-analytic term to achieve unitarity in the singlet channel. We show that the S-matrix enjoys the bosonization duality, an unusual crossing relation and a non-relativistic reduction to Aharonov-Bohm scattering. We also argue that the S-matrix develops a pole in a certain range of coupling constants, which disappears in the range where the theory reduces to the Chern-Simons theory interacting with free fermions.

  19. Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

    NASA Astrophysics Data System (ADS)

    Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

    2001-02-01

    Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions.

  20. Calculation of Scattering Amplitude Without Partial Analysis. II; Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Temkin, Aaron; Shertzer, J.; Fisher, Richard R. (Technical Monitor)

    2002-01-01

    There was a method for calculating the whole scattering amplitude, f(Omega(sub k)), directly. The idea was to calculate the complete wave function Psi numerically, and use it in an integral expression for f, which can be reduced to a 2 dimensional quadrature. The original application was for e-H scattering without exchange. There the Schrodinger reduces a 2-d partial differential equation (pde), which was solved using the finite element method (FEM). Here we extend the method to the exchange approximation. The S.E. can be reduced to a pair of coupled pde's, which are again solved by the FEM. The formal expression for f(Omega(sub k)) consists two integrals, f+/- = f(sub d) +/- f(sub e); f(sub d) is formally the same integral as the no-exchange f. We have also succeeded in reducing f(sub e) to a 2-d integral. Results will be presented at the meeting.

  1. Proton-Nucleus Elastic Cross Sections Using Two-Body In-Medium Scattering Amplitudes

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Wilson, John W.; Cucinotta, Francis A.

    2001-01-01

    Recently, a method was developed of extracting nucleon-nucleon (NN) cross sections in the medium directly from experiment. The in-medium NN cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. The ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium NN cross sections to calculate elastic proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

  2. Improved Persistent Scatterer analysis using Amplitude Dispersion Index optimization of dual polarimetry data

    NASA Astrophysics Data System (ADS)

    Esmaeili, Mostafa; Motagh, Mahdi

    2016-07-01

    Time-series analysis of Synthetic Aperture Radar (SAR) data using the two techniques of Small BAseline Subset (SBAS) and Persistent Scatterer Interferometric SAR (PSInSAR) extends the capability of conventional interferometry technique for deformation monitoring and mitigating many of its limitations. Using dual/quad polarized data provides us with an additional source of information to improve further the capability of InSAR time-series analysis. In this paper we use dual-polarized data and combine the Amplitude Dispersion Index (ADI) optimization of pixels with phase stability criterion for PSInSAR analysis. ADI optimization is performed by using Simulated Annealing algorithm to increase the number of Persistent Scatterer Candidate (PSC). The phase stability of PSCs is then measured using their temporal coherence to select the final sets of pixels for deformation analysis. We evaluate the method for a dataset comprising of 17 dual polarization SAR data (HH/VV) acquired by TerraSAR-X data from July 2013 to January 2014 over a subsidence area in Iran and compare the effectiveness of the method for both agricultural and urban regions. The results reveal that using optimum scattering mechanism decreases the ADI values in urban and non-urban regions. As compared to single-pol data the use of optimized polarization increases initially the number of PSCs by about three times and improves the final PS density by about 50%, in particular in regions with high rate of deformation which suffer from losing phase stability over the time. The classification of PS pixels based on their optimum scattering mechanism revealed that the dominant scattering mechanism of the PS pixels in the urban area is double-bounce while for the non-urban regions (ground surfaces and farmlands) it is mostly single-bounce mechanism.

  3. Decomposition of the scattering amplitude into shadow and surface components with inclusion of spin-orbit coupling

    SciTech Connect

    Melo, German; David, Jorge; Restrepo, Albeiro

    2008-09-15

    We propose a decomposition of the scattering amplitude into shadow and surface components for proton scattering against calcium isotopes as targets at 21 MeV. We account for spin-orbit coupling effects for the optical potential in the nonrelativistic limit. Our calculations show very good agreement with experimental trends.

  4. 4D scattering amplitudes and asymptotic symmetries from 2D CFT

    NASA Astrophysics Data System (ADS)

    Cheung, Clifford; de la Fuente, Anton; Sundrum, Raman

    2017-01-01

    We reformulate the scattering amplitudes of 4D flat space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D flat space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlators via the (A)dS/CFT dictionary. The Ward identities for the 2D conserved currents are dual to 4D soft theorems, while the bulk-boundary propagators of massless (A)dS modes are superpositions of the leading and subleading Weinberg soft factors of gauge theory and gravity. In general, the massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft, single helicity sectors of 4D gauge theory and gravity. Consistent with the topological nature of Chern-Simons theory, Aharonov-Bohm effects record the "tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. Soft particle exchanges between hard processes define the Kac-Moody level and Virasoro central charge, which are thereby related to the 4D gauge coupling and gravitational strength in units of an infrared cutoff. Finally, we discuss a toy model for black hole horizons via a restriction to the Rindler region.

  5. Subharmonic scattering of phospholipid-shell microbubbles at low acoustic pressure amplitudes.

    PubMed

    Frinking, Peter J A; Brochot, Jean; Arditi, Marcel

    2010-08-01

    Subharmonic scattering of phospholipid-shell microbubbles excited at relatively low acoustic pressure amplitudes (<30 kPa) has been associated with echo responses from compression-only bubbles having initial surface tension values close to zero. In this work, the relation between sbharmonics and compression-only behavior of phospholipid-shell microbubbles was investigated, experimentally and by simulation, as a function of the initial surface tension by applying ambient overpressures of 0 and 180 mmHg. The microbubbles were excited using a 64-cycle transmit burst with a center frequency of 4 MHz and peak-negative pressure amplitudes ranging from 20 of 150 kPa. In these conditions, an increase in subharmonic response of 28.9 dB (P < 0.05) was measured at 50 kPa after applying an overpressure of 180 mmHg. Simulations using the Marmottant model, taking into account the effect of ambient overpressure on bubble size and initial surface tension, confirmed the relation between subharmonics observed in the pressure-time curves and compression-only behavior observed in the radius-time curves. The trend of an increase in subharmonic response as a function of ambient overpressure, i.e., as a function of the initial surface tension, was predicted by the model. Subharmonics present in the echo responses of phospholipid-shell microbubbles excited at low acoustic pressure amplitudes are indeed related to the echo responses from compression-only bubbles. The increase in subharmonics as a function of ambient overpressure may be exploited for improving methods for noninvasive pressure measurement in heart cavities or big vessels in the human body.

  6. Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

    2001-01-01

    Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions. c2001 Elsevier Science B.V. All rights reserved.

  7. Calculation of scattering amplitude without partial wave analysis: Inclusion of exchange

    NASA Astrophysics Data System (ADS)

    Temkin, Aaron; Shertzer, Janine

    2002-05-01

    In Ref. [1], a method is given for calculating the scattering amplitude f(Ω) directly. The idea is to calculate the complete wave function Ψ_k( r) numerically and use it in an integral expression for f(Ω). The original application was for electron scattering from static hydrogen without exchange. The Schrödinger equation (SE) reduces to a 2D partial differential equation (PDE), which is solved using the finite element method (FEM) [2]. The integral over dφr is done analytically, reducing the integral expression for f(Ω_k) to a 2D integral. Here we extend the method to include the effects of exchange. The SE can be reduced to a pair of 2D coupled PDE's which are again solved by the FEM. The formal expression for f(Ω) consists of two integrals, f^=fd f_e; fd is formally the same integral as the no-exchange f. We have also succeeded in reducing fe to a 2D integral. Results will be presented at the meeting. [1] J. Shertzer and A. Temkin, Phys. Rev. A 63, 062714 (2001). [2] J. Shertzer and J. Botero, Phys. Rev. A 49, 3673 (1994).

  8. Amplitude of Biot's slow wave scattered by a spherical inclusion in a fluid-saturated poroelastic medium

    NASA Astrophysics Data System (ADS)

    Ciz, Radim; Gurevich, Boris

    2005-03-01

    Spatial heterogeneity of hydrocarbon reservoirs causes significant attenuation and dispersion of seismic waves due to wave-induced flow of the pore fluid between more compliant and less compliant areas. This paper investigates the interaction between a plane elastic wave in a poroelastic medium with a spherical inhomogeneity of another porous material. The behaviour of both the inclusion and the background medium is described by the low-frequency variant of Biot's equations of poroelasticity with the standard boundary conditions at the inclusion surface, and for the inclusion size much smaller than the wavelength of the fast compressional wave. The scattering problem is formulated as a series expansion of displacements expressed in the spherical harmonics. The resulting scattered wavefield consists of the scattered normal compressional and shear waves and Biot's slow wave, which attenuates rapidly with distance from the inclusion and represents the main difference from the elastic case. This study concentrates on the attenuation effects caused by the mode conversion into Biot's slow wave. The solution obtained for Biot's slow wave is well described by the two terms of order n= 0 and n= 2 of the scattering series. The scattering amplitude for the term of order n= 0 is given by a simple expression. The full expression for the term of order n= 2 is very complicated, but can be simplified assuming that the amplitude of the scattered fast (normal) compressional and shear waves are well approximated by the solution of the equivalent elastic problem. This assumption yields a simple approximation for the amplitude of the scattered slow wave, which is accurate for a wide range of material properties and is sufficient for the analysis of the scattering amplitude as a function of frequency. In the low-frequency limit the scattering amplitude of the slow wave scales with ω3/2, and reduces to the asymptotic long-wavelength solution of Berryman (1985), which is valid for

  9. Elastic Scattering of Low Energy Pions by Nuclei and the In-Medium Isovector πN Amplitude

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G.

    2006-07-01

    Measurements of elastic scattering of 21.5 MeV π± by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer and absolute calibration was made by parallel measurements of Coulomb scattering of muons. Optical model fits to the data reveal the `anomalous' s-wave repulsion known from pionic atoms. Introducing a chiral-motivated density dependence of the isovector scattering amplitude, and considering the energy dependence of the free πN interaction greatly improve fits to the data and remove the `anomaly'.

  10. Large-Amplitude, Scattered Tsunami Wave Mapping Enabled by Ocean Bottom Seismometer Array Recordings

    NASA Astrophysics Data System (ADS)

    Shi, J.; Kohler, M. D.; Ampuero, J. P.; Sutton, J.

    2015-12-01

    A deployment of ocean bottom seismometers off the coast of southern California recorded the March 2011 Tohoku tsunami on 22 differential pressure gauges (DPGs). The DPG tsunami records across the entire array show multiple large-amplitude, coherent phases arriving one hour to more than 36 hours after the initial tsunami phase. Analysis of the DPG recordings reveals possible locations of the geographical sources that contributed to secondary tsunami arrivals in southern California. A beamforming technique is applied to the DPG data to determine the azimuths and arrival times of scattered wave energy. In addition, a backward ray tracing procedure is applied to a wide range of back azimuth starting values from the DPG array to map possible source locations. The results show several possible candidates of secondary tsunami source structures. These include the Alaskan Peninsula island chain producing a tsunami arrival ~60 minutes after the first arrival, and the Hawaiian Islands producing an arrival ~170 minutes after the first arrival. The results are mapped into modified tsunami warning messages to show how a time-varying hazard could be communicated with more effective message format and content. The results are demonstrating the effects of including clearly described locations, time of impact, and hazard impact consequences on message perception among the public.

  11. Partial-differential-equation-constrained amplitude-based shape detection in inverse acoustic scattering

    NASA Astrophysics Data System (ADS)

    Na, Seong-Won; Kallivokas, Loukas F.

    2008-03-01

    In this article we discuss a formal framework for casting the inverse problem of detecting the location and shape of an insonified scatterer embedded within a two-dimensional homogeneous acoustic host, in terms of a partial-differential-equation-constrained optimization approach. We seek to satisfy the ensuing Karush-Kuhn-Tucker first-order optimality conditions using boundary integral equations. The treatment of evolving boundary shapes, which arise naturally during the search for the true shape, resides on the use of total derivatives, borrowing from recent work by Bonnet and Guzina [1-4] in elastodynamics. We consider incomplete information collected at stations sparsely spaced at the assumed obstacle’s backscattered region. To improve on the ability of the optimizer to arrive at the global optimum we: (a) favor an amplitude-based misfit functional; and (b) iterate over both the frequency- and wave-direction spaces through a sequence of problems. We report numerical results for sound-hard objects with shapes ranging from circles, to penny- and kite-shaped, including obstacles with arbitrarily shaped non-convex boundaries.

  12. Elastic scattering of low energy pions by nuclei and the in-medium isovector πN amplitude

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G.

    2005-09-01

    Measurements of elastic scattering of 21.5 MeV π± by Si, Ca, Ni, and Zr were made by using a single-arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The anomalous s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the isovector scattering amplitude, which also greatly improved the fits to the data. The empirical energy dependence of the isoscalar amplitude also improves the fits to the data but, contrary to what is found with pionic atoms, on its own is incapable of removing the anomaly.

  13. On the determination of Ω - Ω scattering amplitudes from finite volume spectra

    NASA Astrophysics Data System (ADS)

    Li, Ning; Wu, Ya-Jie

    2016-12-01

    The elastic scattering phase shifts to the two-particle energy levels in a finite cubic box is related by the Lüscher’s formula. In this paper, based on the nonrelativistic quantum mechanics model which is usually assumed to be the low energy scattering case in lattice simulations, we confirmed the generalized Lüscher’s formula for the case of two-particle scattering with arbitrary spin in Ref. 1. In particular, Lüscher’s formula is synthesized for two-spin-3/2-particle scattering, i.e. Ω - Ω scattering on lattice that may help us study the promising dibaryon states.

  14. Strong-field cyclotron scattering. I - Scattering amplitudes and natural line width. [in spectra of accretion-powered X-ray pulsars

    NASA Technical Reports Server (NTRS)

    Graziani, Carlo

    1993-01-01

    The introduction of resonance line width into the QED cyclotron scattering amplitudes is considered. It is shown that the width arises from loop corrections to the electron propagator, which also bring about shifts in the Landau energy levels. A formalism is developed that allows the dressed electron propagator to be derived. It is shown that the states of Herold et al. (1982) and of Sokolov and Ternov (1968), which diagonalize the component of the magnetic moment operator parallel to the external magnetic field, are appropriate for calculation of the scattering amplitudes, whereas the states of Johnson and Lippmann (1949) are not. In addition, it is shown that the Breit-Wigner broadening approximation E tends to E - i(Gamma)/2 is consistent with the perturbation-theoretic order of the calculation, if the former basis states are chosen, but not the latter.

  15. Characterizing the solutions to scattering equations that support tree-level N k MHV gauge/gravity amplitudes

    NASA Astrophysics Data System (ADS)

    Du, Yi-Jian; Teng, Fei; Wu, Yong-Shi

    2016-11-01

    In this paper we define, independent of theories, two discriminant matrices involving a solution to the scattering equations in four dimensions, the ranks of which are used to divide the solution set into a disjoint union of subsets. We further demonstrate, entirely within the Cachazo-He-Yuan formalism, that each subset of solutions gives nonzero contribution to tree-level N k MHV gauge/gravity amplitudes only for a specific value of k. Thus the solutions can be characterized by the rank of their discriminant matrices, which in turn determines the value of k of the N k MHV amplitudes a solution can support. As another application of the technique developed, we show analytically that in Einstein-Yang-Mills theory, if all gluons have the same helicity, the tree-level single-trace amplitudes must vanish.

  16. Detecting the Amplitude Mode of Strongly Interacting Lattice Bosons by Bragg Scattering

    SciTech Connect

    Bissbort, Ulf; Hofstetter, Walter; Li Yongqiang

    2011-05-20

    We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.

  17. Amplitude-phase coupling and chirp in quantum-dot lasers: influence of charge carrier scattering dynamics.

    PubMed

    Lingnau, Benjamin; Chow, Weng W; Lüdge, Kathy

    2014-03-10

    We investigate the dependence of the amplitude-phase coupling in quantum-dot (QD) lasers on the charge-carrier scattering timescales. The carrier scattering processes influence the relaxation oscillation parameters, as well as the frequency chirp, which are both important parameters when determining the modulation performance of the laser device and its reaction to optical perturbations. We find that the FM/AM response exhibits a strong dependence on the modulation frequency, which leads to a modified optical response of QD lasers when compared to conventional laser devices. Furthermore, the frequency response curve changes with the scattering time scales, which can allow for an optimization of the laser stability towards optical perturbations.

  18. The Analytic Structure of Scattering Amplitudes in N = 4 Super-Yang-Mills Theory

    NASA Astrophysics Data System (ADS)

    Litsey, Sean Christopher

    We begin the dissertation in Chapter 1 with a discussion of tree-level amplitudes in Yang-. Mills theories. The DDM and BCJ decompositions of the amplitudes are described and. related to one another by the introduction of a transformation matrix. This is related to the. Kleiss-Kuijf and BCJ amplitude identities, and we conjecture a connection to the existence. of a BCJ representation via a condition on the generalized inverse of that matrix. Under. two widely-believed assumptions, this relationship is proved. Switching gears somewhat, we introduce the RSVW formulation of the amplitude, and the extension of BCJ-like features to residues of the RSVW integrand is proposed. Using the previously proven connection of BCJ representations to the generalized inverse condition, this extension is validated, including a version of gravitational double copy. The remainder of the dissertation involves an analysis of the analytic properties of loop. amplitudes in N = 4 super-Yang-Mills theory. Chapter 2 contains a review of the planar case, including an exposition of dual variables and momentum twistors, dual conformal symmetry, and their implications for the amplitude. After defining the integrand and on-shell diagrams, we explain the crucial properties that the amplitude has no poles at infinite momentum and that its leading singularities are dual-conformally-invariant cross ratios, and can therefore be normalized to unity. We define the concept of a dlog form, and show that it is a feature of the planar integrand as well. This leads to the definition of a pure integrand basis. The proceeding setup is connected to the amplituhedron formulation, and we put forward the hypothesis that the amplitude is determined by zero conditions. Chapter 3 contains the primary computations of the dissertation. This chapter treats. amplitudes in fully nonplanar N = 4 super-Yang-Mills, analyzing the conjecture that they. follow the pattern of having no poles at infinity, can be written in dlog

  19. Application of scattering theory to P-wave amplitude fluctuations in the crust

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Kazuo; Takemura, Shunsuke; Kobayashi, Manabu

    2015-12-01

    The amplitudes of high-frequency seismic waves generated by local and/or regional earthquakes vary from site to site, even at similar hypocentral distances. It had been suggested that, in addition to local site effects (e.g., variable attenuation and amplification in surficial layers), complex wave propagation in inhomogeneous crustal media is responsible for this observation. To quantitatively investigate this effect, we performed observational, theoretical, and numerical studies on the characteristics of seismic amplitude fluctuations in inhomogeneous crust. Our observations of P-wave amplitude for small to moderately sized crustal earthquakes revealed that fluctuations in P-wave amplitude increase with increasing frequency and hypocentral distance, with large fluctuations showing up to ten-times difference between the largest and the smallest P-wave amplitudes. Based on our theoretical investigation, we developed an equation to evaluate the amplitude fluctuations of time-harmonic waves that radiated isotropically from a point source and propagated spherically in acoustic von Kármán-type random media. Our equation predicted relationships between amplitude fluctuations and observational parameters (e.g., wave frequency and hypocentral distance). Our numerical investigation, which was based on the finite difference method, enabled us to investigate the characteristics of wave propagation in both acoustic and elastic random inhomogeneous media using a variety of source time functions. The numerical simulations indicate that amplitude fluctuation characteristics differ a little between medium types (i.e., acoustic or elastic) or source time function durations. These results confirm the applicability of our analytical equation to practical seismic data analysis.

  20. Flat amplitude multiwavelength Brillouin-Raman comb fiber laser in Rayleigh-scattering-enhanced linear cavity.

    PubMed

    Zamzuri, A K; Mahdi, M A; Ahmad, A; Md Ali, M I; Al-Mansoori, M H

    2007-03-19

    We investigate the amplitude flatness of Rayleigh-assisted Brillouin-Raman comb laser in a linear cavity in which feedbacks are formed by high-reflectivity mirror. The optimization of Brillouin pump power and wavelength is very crucial in order to obtain a uniform power level between Stokes lines. The Brillouin pump must have a relatively large power and its wavelength must be located closer to the Raman peak gain region. The flat-amplitude bandwidth is also determined by the choice of Raman pump wavelengths. A flat-amplitude bandwidth of 30.7 nm from 1527.32 to 1558.02 nm is measured when Raman pump wavelengths are set to 1435 and 1450 nm. 357 uniform Brillouin Stokes lines with 0.086 nm spacing are generated across the wavelength range. The average signal-to-noise ratio of 17 dB is obtained for all the Brillouin Stokes lines.

  1. In-Medium Isovector πN Amplitude from Low-Energy Pion Scattering

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Meier, R.; Wagner, G. J.; Yaari, G.

    2004-09-01

    Differential cross sections for elastic scattering of 21.5MeV positive and negative pions by Si, Ca, Ni, and Zr have been measured as part of a study of the pion-nucleus potential across the threshold. The “anomalous” repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.

  2. From finite geometry exact quantities to (elliptic) scattering amplitudes for spin chains: the 1/2-XYZ

    NASA Astrophysics Data System (ADS)

    Fioravanti, Davide; Rossi, Marco

    2005-08-01

    Initially, we derive a nonlinear integral equation for the vacuum counting function of the spin 1/2-XYZ chain in the disordered regime, thus paralleling similar results by Klümper [1], achieved through a different technique in the antiferroelectric regime. In terms of the counting function we obtain the usual physical quantities, like the energy and the transfer matrix (eigenvalues). Then, we introduce a double scaling limit which appears to describe the sine-Gordon theory on cylindrical geometry, so generalising famous results in the plane by Luther [2] and Johnson et al. [3]. Furthermore, after extending the nonlinear integral equation to excitations, we derive scattering amplitudes involving solitons/antisolitons first, and bound states later. The latter case comes out as manifestly related to the Deformed Virasoro Algebra of Shiraishi et al. [4]. Although this nonlinear integral equations framework was contrived to deal with finite geometries, we prove it to be effective for discovering or rediscovering S-matrices. As a particular example, we prove that this unique model furnishes explicitly two S-matrices, proposed respectively by Zamolodchikov [5] and Lukyanov-Mussardo-Penati [6,7] as plausible scattering description of unknown integrable field theories.

  3. Application of a folding-model optical potential to analyzing inelastic pion-nucleus scattering and the in-medium effect on a pion-nucleon amplitude

    NASA Astrophysics Data System (ADS)

    Lukyanov, V. K.; Zemlyanaya, E. V.; Lukyanov, K. V.; Abdul-Magead, I. A. M.

    2016-11-01

    The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π ±-mesons on 28Si, 40Ca, 58Ni, and 208Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2+ and 3- collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion-nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole ( β 2) and octupole ( β 3) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion-nucleon amplitude is emphasized.

  4. Empirical parametrization of the nucleon-nucleon elastic scattering amplitude at high beam momenta for Glauber calculations and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Uzhinsky, V.; Galoyan, A.; Hu, Q.; Ritman, J.; Xu, H.

    2016-12-01

    A parametrization of the nucleon-nucleon elastic scattering amplitude is needed for future experiments with nucleon and nuclear beams in the beam momentum range of 2-50 GeV /c /nucleon. There are many parametrizations of the amplitude at Plab> 25-50 GeV /c , and at Plab≤5 GeV /c . Our paper is aimed at covering the range between 5-50 GeV /c . The amplitude is used in Glauber calculations of various cross sections and Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the differential nucleon-nucleon elastic scattering cross sections are described by an exponential expression. Corresponding experimental data on p p interactions at |t |> 0.005 (GeV /c )2 and |t |≤0.125 (GeV /c )2 have been fit. We propose formulas to approximate the beam momentum dependence of these parameters in the momentum range considered. The same was done for n p interactions at |t |≤0.5 (GeV /c )2. Expressions for the momentum dependence of the total and elastic cross sections, and the ratio of real to imaginary parts of the amplitude at zero momentum transfer are also given for p p and n p collisions. These results are sufficient for a first approximation of the Glauber calculations. For more exact calculations we fit the data at |t |>0.005 (GeV /c )2 without restrictions on the maximum value of |t | using an expression based on two coherent exponentials. The parameters of the fits are found for the beam momentum range 2-50 GeV /c .

  5. 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.

  6. Acoustical Scattering from an Elastic Sphere in Water: Surface Wave Glory, Resonances, and the Sommerfeld-Watson Transformation for Amplitudes

    DTIC Science & Technology

    1985-08-01

    Marston, my thesis advisor. He has a special combination of theoretical and experimental talents which he is very willing to share with his students...cylinders and spheres," Ph.D. Thesis , Rarvard University, Cambridge, Massachusetts (1951). 3. J. J. Faran, "Sound scattering by solid cylinders and spheres...t*(uc(l)-t*(uc(12)-t*(uc(13)-t*uc(14))))) end if ztaz32 = (1.0d0,0.OdO)/(zata*zetal2) do 8 i-I,ntorms ar(i) a (0.OdO,0.OdO) br(i) - (0. QdO ,O.OdO

  7. High-energy scattering amplitudes of Yang-Mills theories in generalized leading-term approximation and eikonal formulas

    SciTech Connect

    Lo, C.Y.

    1981-01-15

    In this paper, we study the apparent discrepancy between Feynman diagrams and the eikonal formulas, and the apparent paradox between the eikonal formulas and the s-u crossing symmetry. We analyze the generalized leading-term approximation (GLA), which generates the terms of the eikonal formulas from Feynman diagrams. This analysis is done through using the techniques of decomposing diagrammatically the isospin factors (or group-theoretical weights in general) of Feynman diagrams. As a result, we modify the GLA into a generalized complex leading-term approximation. We calculate, with this new formalism, the high-energy limit (s..-->..infinity with t fixed) of the vector-meson--vector-meson elastic amplitude of a Yang-Mills theory with SU(2) symmetry through tenth perturbative order. With this new method, we resolve the apparent discrepancy and paradox mentioned above. This method is generalizable to other non-Abelian gauge theories.

  8. Resonance of the exchange amplitude of a photon by an electron scattering in a pulsed laser field

    NASA Astrophysics Data System (ADS)

    Nedoreshta, V. N.; Roshchupkin, S. P.; Voroshilo, A. I.

    2015-06-01

    Resonant scattering of a photon by an electron in the presence of the field of the low intensity circularly polarized pulsed laser wave is studied theoretically. The approximation used the case in which a laser-pulse duration is significantly greater than the characteristic oscillation time. The resonance conditions of the exchange diagrams by electron and positron intermediate states were determined. The probability of such a process is calculated. It is demonstrated that the resonant probability may be six to ten orders of magnitude higher than the probability of the Compton effect in the absence of the external field. Obtained results can be verified experimentally in the framework of modern research projects (SLAC, FAIR, XFEL, and ELI).

  9. Singularity structure of the πN scattering amplitude in a meson-exchange model up to energies W⩽2.0 GeV

    NASA Astrophysics Data System (ADS)

    Tiator, L.; Kamalov, S. S.; Ceci, S.; Chen, Guan Yeu; Drechsel, D.; Svarc, A.; Yang, Shin Nan

    2010-11-01

    Within the previously developed Dubna-Mainz-Taipei meson-exchange model, the singularity structure of the πN scattering amplitudes has been investigated. For all partial waves up to F waves and c.m. energies up to W~2 GeV, the T-matrix poles have been calculated by three different techniques: analytic continuation into the complex energy plane and speed-plot and regularization method. For all four-star resonances except the S11(1535), we find very good agreement between the analytic continuation and the regularization method. We also find resonance poles for resonances that are not so well established, but in these cases the pole positions and residues obtained by analytic continuation can substantially differ from the results predicted by the speed-plot and regularization methods.

  10. Lorentzian amplitude and phase pulse shaping for nonresonant background suppression and enhanced spectral resolution in coherent anti-Stokes Raman scattering spectroscopy and microscopy.

    PubMed

    Konorov, Stanislav O; Blades, Michael W; Turner, Robin F B

    2010-07-01

    Femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy offers several advantages over spontaneous Raman spectroscopy due to the inherently high sensitivity and low average power deposition in the sample. Femtosecond CARS can be implemented in a collinear pump/probe beam configuration for microspectroscopy applications and has emerged as a powerful technique for chemical imaging of biological specimens. However, one serious limitation of this approach is the presence of a high nonresonant background component that often obscures the resonant signals of interest. We report here an innovative pulse-shaping method based on Lorentzian amplitude and phase spectral modulation of a broadband femtosecond probe pulse that yields spectra with both high spectral resolution and no nonresonant background. No further mathematical analysis is needed to extract Raman spectra. The utility of the proposed method for CARS microscopy is demonstrated using a mixture of polystyrene and latex beads, as well as dry-fixed embryonic stem cells.

  11. Mathematical Aspects of Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Duhr, Claude

    In these lectures we discuss some of the mathematical structures that appear when computing multi-loop Feynman integrals. We focus on a specific class of special functions, the so-called multiple polylogarithms, and introduce their Hopf algebra structure. We show how these mathematical concepts are useful in physics by illustrating on several examples how these algebraic structures are useful to perform analytic computations of loop integrals, in particular to derive functional equations among polylogarithms.

  12. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    PubMed

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  13. Amplitudes of Field Theories

    SciTech Connect

    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.

  14. Off-shell extrapolation of Regge-model NN scattering amplitudes describing final state interactions in 2H(e,e'p)

    SciTech Connect

    Ford, William Paul; van Orden, Wally

    2013-11-25

    In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.

  15. Off-shell extrapolation of Regge-model NN scattering amplitudes describing final state interactions in 2H(e,e'p)

    DOE PAGES

    Ford, William Paul; van Orden, Wally

    2013-11-25

    In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.

  16. Off-shell CHY amplitudes

    NASA Astrophysics Data System (ADS)

    Lam, C. S.; Yao, York-Peng

    2016-06-01

    The Cachazo-He-Yuan (CHY) formula for on-shell scattering amplitudes is extended off-shell. The off-shell amplitudes (amputated Green's functions) are Möbius invariant, and have the same momentum poles as the on-shell amplitudes. The working principles which drive the modifications to the scattering equations are mainly Möbius covariance and energy momentum conservation in off-shell kinematics. The same technique is also used to obtain off-shell massive scalars. A simple off-shell extension of the CHY gauge formula which is Möbius invariant is proposed, but its true nature awaits further study.

  17. CHY formula and MHV amplitudes

    NASA Astrophysics Data System (ADS)

    Du, Yi-Jian; Teng, Fei; Wu, Yong-Shi

    2016-05-01

    In this paper, we study the relation between the Cachazo-He-Yuan (CHY) formula and the maximal-helicity-violating (MHV) amplitudes of Yang-Mills and gravity in four dimensions. We prove that only one special rational solution of the scattering equations found by Weinzierl supports the MHV amplitudes. Namely, localized at this solution, the integrated CHY formula produces the Parke-Taylor formula for MHV Yang-Mills amplitudes as well as the Hodges formula for MHV gravitational amplitudes, with an arbitrary number of external gluons/gravitons. This is achieved by developing techniques, in a manifestly Möbius covariant formalism, to explicitly compute relevant reduced Pfaffians/determinants. We observe and prove two interesting properties (or identities), which facilitate the computations. We also check that all the other ( n - 3)! - 1 solutions to the scattering equations do not support the MHV amplitudes, and prove analytically that this is indeed true for the other special rational solution proposed by Weinzierl, that actually supports the anti-MHV amplitudes. Our results reveal a mysterious feature of the CHY formalism that in Yang-Mills and gravity theory, solutions of scattering equations, involving only external momenta, somehow know about the configuration of external polarizations of the scattering amplitudes.

  18. On-Shell Methods in Perturbative QCD

    SciTech Connect

    Bern, Zvi; Dixon, Lance J.; Kosower, David A.

    2007-04-25

    We review on-shell methods for computing multi-parton scattering amplitudes in perturbative QCD, utilizing their unitarity and factorization properties. We focus on aspects which are useful for the construction of one-loop amplitudes needed for phenomenological studies at the Large Hadron Collider.

  19. Microstructure and rheology of a thermoreversible gel under large amplitude oscillatory shear (LAOS) deformation using time-resolved oscillatory rheo-small-angle neutron scattering (tOr-SANS)

    NASA Astrophysics Data System (ADS)

    Kim, Jung Min; Gurnon, A. Kate; Wagner, Norman; Eberle, Aaron

    2013-03-01

    Large amplitude oscillatory shear (LAOS) rheology is an effective way of studying the nonlinear dynamics of complex fluids. Here, we present a new method for a direct, quantitative study of the microstructure under LAOS deformation in the framework of the alignment factor, Af. We use a model thermoreversible adhesive hard-sphere system composed of octadecyl-coated silica particles suspended in n-tetradecane. With temperature the particle potential is controlled and the system is shifted from behaving as a near hard-sphere to an adhesive hard-sphere system leading to aggregation and ultimately a dynamical arrest transition to macroscopic gelation. Time-resolved oscillatory rheo-small-angle neutron scattering (tOr-SANS) measurements in the 1-3 plane are performed by stroboscopically probing the structural evolution as a function of time during LAOS. Under strong shear, the 2D scattering pattern of the system in the gelled state exhibits a strong anisotropy commonly known as a ``butterfly'' pattern, which corresponds to the stretching of the microstructure along the flow direction. The first structure-Lissajous plots of this model system are presented in terms of an order parameter and Af as a function of instantaneous strain and strain rate. This new analysis demonstrates a novel method for simultaneously measuring the rheology and microstructure during a time-dependent deformation (LAOS).

  20. Toward complete pion nucleon amplitudes

    DOE PAGES

    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.

  1. Constraining higher derivative supergravity with scattering amplitudes

    DOE PAGES

    Wang, Yifan; Yin, Xi

    2015-08-31

    We study supersymmetry constraints on higher derivative deformations of type IIB supergravity by consideration of superamplitudes. Thus, combining constraints of on-shell supervertices and basic results from string perturbation theory, we give a simple argument for the non-renormalization theorem of Green and Sethi, and some of its generalizations.

  2. Recent Developments in Perturbative QCD

    SciTech Connect

    Dixon, Lance J.; /SLAC

    2005-07-11

    I review recent progress in perturbative QCD on two fronts: extending next-to-next-to-leading order QCD corrections to a broader range of collider processes, and applying twistor-space methods (and related spinoffs) to computations of multi-parton scattering amplitudes.

  3. DVCS amplitude with kinematical twist-3 terms

    SciTech Connect

    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.

  4. Scattering of fermions by gravitons

    NASA Astrophysics Data System (ADS)

    Ulhoa, S. C.; Santos, A. F.; Khanna, Faqir C.

    2017-04-01

    The interaction between gravitons and fermions is investigated in the teleparallel gravity. The scattering of fermions and gravitons in the weak field approximation is analyzed. The transition amplitudes of M\\varnothing ller, Compton and new gravitational scattering are calculated.

  5. 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.

  6. Phase variation of hadronic amplitudes

    SciTech Connect

    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.

  7. Perturbative QCD correlations in multi-parton collisions

    NASA Astrophysics Data System (ADS)

    Blok, B.; Dokshitzer, Yu.; Frankfurt, L.; Strikman, M.

    2014-06-01

    We examine the role played in double-parton interactions (DPI) by the parton-parton correlations originating from perturbative QCD parton splittings. Also presented are the results of the numerical analysis of the integrated DPI cross sections at Tevatron and LHC energies. To obtain the numerical results the knowledge of the single-parton GPDs gained by the HERA experiments was used to construct the non-perturbative input for generalized double-parton distributions. The perturbative two-parton correlations induced by three-parton interactions contribute significantly to a resolution of the longstanding puzzle of an excess of multi-jet production events in the back-to-back kinematics observed at the Tevatron.

  8. PULSE AMPLITUDE ANALYZER

    DOEpatents

    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.

  9. 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.

  10. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Maung, Khin Maung; Wilson, John W.; Buck, Warren W.

    1989-01-01

    The derivations of the Lippmann-Schwinger equation and Watson multiple scattering are given. A simple optical potential is found to be the first term of that series. The number density distribution models of the nucleus, harmonic well, and Woods-Saxon are used without t-matrix taken from the scattering experiments. The parameterized two-body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to the imaginary part of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen as our solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  11. 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.

  12. Amplitude Models for Discrimination and Yield Estimation

    SciTech Connect

    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.

  13. Compositions of bosonic string amplitudes with cylinder topology

    SciTech Connect

    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.

  14. 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.

  15. 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…

  16. 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.

  17. 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.

  18. 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.

  19. Amplitude Modulator Chassis

    SciTech Connect

    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.

  20. PULSE AMPLITUDE ANALYZER

    DOEpatents

    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.

  1. 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.

  2. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Buck, Warren W.; Maung, Khin M.

    1989-01-01

    Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  3. An algebraic approach to the scattering equations

    NASA Astrophysics Data System (ADS)

    Huang, Rijun; Rao, Junjie; Feng, Bo; He, Yang-Hui

    2015-12-01

    We employ the so-called companion matrix method from computational algebraic geometry, tailored for zero-dimensional ideals, to study the scattering equations. The method renders the CHY-integrand of scattering amplitudes computable using simple linear algebra and is amenable to an algorithmic approach. Certain identities in the amplitudes as well as rationality of the final integrand become immediate in this formalism.

  4. Purely bianisotropic scatterers

    NASA Astrophysics Data System (ADS)

    Albooyeh, M.; Asadchy, V. S.; Alaee, R.; Hashemi, S. M.; Yazdi, M.; Mirmoosa, M. S.; Rockstuhl, C.; Simovski, C. R.; Tretyakov, S. A.

    2016-12-01

    The polarization response of molecules or meta-atoms to external electric and magnetic fields, which defines the electromagnetic properties of materials, can either be direct (electric field induces electric moment and magnetic field induces magnetic moment) or indirect (magnetoelectric coupling in bianisotropic scatterers). Earlier studies suggest that there is a fundamental bound on the indirect response of all passive scatterers: It is believed to be always weaker than the direct one. In this paper, we prove that there exist scatterers which overcome this bound substantially. Moreover, we show that the amplitudes of electric and magnetic polarizabilities can be negligibly small as compared to the magnetoelectric coupling coefficients. However, we prove that if at least one of the direct-excitation coefficients vanishes, magnetoelectric coupling effects in passive scatterers cannot exist. Our findings open a way to a new class of electromagnetic scatterers and composite materials.

  5. Rutherford scattering of electron vortices

    NASA Astrophysics Data System (ADS)

    Van Boxem, Ruben; Partoens, Bart; Verbeeck, Johan

    2014-03-01

    By considering a cylindrically symmetric generalization of a plane wave, the first-order Born approximation of screened Coulomb scattering unfolds two new dimensions in the scattering problem: transverse momentum and orbital angular momentum of the incoming beam. In this paper, the elastic Coulomb scattering amplitude is calculated analytically for incoming Bessel beams. This reveals novel features occurring for wide-angle scattering and quantitative insights for small-angle vortex scattering. The result successfully generalizes the well-known Rutherford formula, incorporating transverse and orbital angular momentum into the formalism.

  6. Λ scattering equations

    NASA Astrophysics Data System (ADS)

    Gomez, Humberto

    2016-06-01

    The CHY representation of scattering amplitudes is based on integrals over the moduli space of a punctured sphere. We replace the punctured sphere by a double-cover version. The resulting scattering equations depend on a parameter Λ controlling the opening of a branch cut. The new representation of scattering amplitudes possesses an enhanced redundancy which can be used to fix, modulo branches, the location of four punctures while promoting Λ to a variable. Via residue theorems we show how CHY formulas break up into sums of products of smaller (off-shell) ones times a propagator. This leads to a powerful way of evaluating CHY integrals of generic rational functions, which we call the Λ algorithm.

  7. Weak Deeply Virtual Compton Scattering

    SciTech Connect

    Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin

    2007-03-01

    We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.

  8. Bootstrapping a Five-Loop Amplitude Using Steinmann Relations.

    PubMed

    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.

  9. Particle Distribution Modification by Low Amplitude Modes

    SciTech Connect

    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.

  10. PULSE AMPLITUDE DISTRIBUTION RECORDER

    DOEpatents

    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.

  11. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  12. Monte Carlo eikonal scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Dedonder, J. P.

    2012-08-01

    Background: The eikonal approximation is commonly used to calculate heavy-ion elastic scattering. However, the full evaluation has only been done (without the use of Monte Carlo techniques or additional approximations) for α-α scattering.Purpose: Develop, improve, and test the Monte Carlo eikonal method for elastic scattering over a wide range of nuclei, energies, and angles.Method: Monte Carlo evaluation is used to calculate heavy-ion elastic scattering for heavy nuclei including the center-of-mass correction introduced in this paper and the Coulomb interaction in terms of a partial-wave expansion. A technique for the efficient expansion of the Glauber amplitude in partial waves is developed.Results: Angular distributions are presented for a number of nuclear pairs over a wide energy range using nucleon-nucleon scattering parameters taken from phase-shift analyses and densities from independent sources. We present the first calculations of the Glauber amplitude, without further approximation, and with realistic densities for nuclei heavier than helium. These densities respect the center-of-mass constraints. The Coulomb interaction is included in these calculations.Conclusion: The center-of-mass and Coulomb corrections are essential. Angular distributions can be predicted only up to certain critical angles which vary with the nuclear pairs and the energy, but we point out that all critical angles correspond to a momentum transfer near 1 fm-1.

  13. Inelastic Light Scattering Processes

    NASA Technical Reports Server (NTRS)

    Fouche, Daniel G.; Chang, Richard K.

    1973-01-01

    Five different inelastic light scattering processes will be denoted by, ordinary Raman scattering (ORS), resonance Raman scattering (RRS), off-resonance fluorescence (ORF), resonance fluorescence (RF), and broad fluorescence (BF). A distinction between fluorescence (including ORF and RF) and Raman scattering (including ORS and RRS) will be made in terms of the number of intermediate molecular states which contribute significantly to the scattered amplitude, and not in terms of excited state lifetimes or virtual versus real processes. The theory of these processes will be reviewed, including the effects of pressure, laser wavelength, and laser spectral distribution on the scattered intensity. The application of these processes to the remote sensing of atmospheric pollutants will be discussed briefly. It will be pointed out that the poor sensitivity of the ORS technique cannot be increased by going toward resonance without also compromising the advantages it has over the RF technique. Experimental results on inelastic light scattering from I(sub 2) vapor will be presented. As a single longitudinal mode 5145 A argon-ion laser line was tuned away from an I(sub 2) absorption line, the scattering was observed to change from RF to ORF. The basis, of the distinction is the different pressure dependence of the scattered intensity. Nearly three orders of magnitude enhancement of the scattered intensity was measured in going from ORF to RF. Forty-seven overtones were observed and their relative intensities measured. The ORF cross section of I(sub 2) compared to the ORS cross section of N2 was found to be 3 x 10(exp 6), with I(sub 2) at its room temperature vapor pressure.

  14. Hadron scattering and resonances in QCD

    SciTech Connect

    Dudek, Jozef J.

    2016-05-01

    I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study pi pi elastic scattering, including the rho resonance, as well as coupled-channel pi K, eta K scattering. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.

  15. Hadron scattering and resonances in QCD

    NASA Astrophysics Data System (ADS)

    Dudek, Jozef J.

    2016-05-01

    I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel π >K, ηK scattering. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.

  16. Integration rules for scattering equations

    NASA Astrophysics Data System (ADS)

    Baadsgaard, Christian; Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.

    2015-09-01

    As described by Cachazo, He and Yuan, scattering amplitudes in many quantum field theories can be represented as integrals that are fully localized on solutions to the so-called scattering equations. Because the number of solutions to the scattering equations grows quite rapidly, the contour of integration involves contributions from many isolated components. In this paper, we provide a simple, combinatorial rule that immediately provides the result of integration against the scattering equation constraints fo any Möbius-invariant integrand involving only simple poles. These rules have a simple diagrammatic interpretation that makes the evaluation of any such integrand immediate. Finally, we explain how these rules are related to the computation of amplitudes in the field theory limit of string theory.

  17. 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.

  18. N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops

    SciTech Connect

    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.

  19. The Last of the Finite Loop Amplitudes in QCD

    SciTech Connect

    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.

  20. Scattering Via Conformal Higher Spin Exchanges

    NASA Astrophysics Data System (ADS)

    Tseytlin, A. A.

    We consider a model of massless scalars interacting (via bilinear conserved currents) with conformal higher spin fields in flat space. We compute the tree-level four-scalar scattering amplitude using a natural prescription for summation over an infinite set of conformal higher spin exchanges and find that it vanishes. Independently, we show that the vanishing of the scalar scattering amplitude is, in fact, implied by the global conformal higher spin symmetry of this model.

  1. Amplitude path corrections for regional phases in China

    SciTech Connect

    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.

  2. Small amplitude quasibreathers and oscillons

    SciTech Connect

    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.

  3. Tempo and amplitude in growth.

    PubMed

    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.

  4. 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.

  5. A survey of the physical optics inverse scattering identity

    NASA Astrophysics Data System (ADS)

    Bojarski, N. N.

    1982-09-01

    An inverse scattering identity relating the characteristic function of a scatterer to the three-dimensional spatial Fourier transform of the augmented far field scattering amplitude is derived by applying the physical optics approximation to the acoustic and electromagnetic direct scattering integral representation. Because this identity requires full scattering data for all frequencies and aspect angles, an integral equation is developed for incomplete scattering data which solves for the unknown characteristic function of the scatterer in terms of the known incomplete scattering data. A regularized analytic closed form solution to this integral equation is obtained, and synthesized numerico-experimental results verifying the solution are presented.

  6. 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.

  7. Scattering calculations and confining interactions

    NASA Technical Reports Server (NTRS)

    Buck, Warren W.; Maung, Khin M.

    1993-01-01

    Most of the research work performed under this grant were concerned with strong interaction processes ranging from kaon-nucleon interaction to proton-nucleus scattering calculations. Research performed under this grant can be categorized into three groups: (1) parametrization of fundamental interactions, (2) development of formal theory, and (3) calculations based upon the first two. Parametrizations of certain fundamental interactions, such as kaon-nucleon interaction, for example, were necessary because kaon-nucleon scattering amplitude was needed to perform kaon-nucleus scattering calculations. It was possible to calculate kaon-nucleon amplitudes from the first principle, but it was unnecessary for the purpose of the project. Similar work was also done for example for anti-protons and anti-nuclei. Formal developments to some extent were also pursued so that consistent calculations can be done.

  8. 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.

  9. K- nuclear potentials based on chiral meson-baryon amplitudes

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Cieplý, A.; Gazda, D.; Friedman, E.; Gal, A.

    2012-09-01

    K- nuclear optical potentials are constructed from in-medium subthreshold K¯N scattering amplitudes within a chirally motivated coupled-channel model. We demonstrate how the strong energy and density dependence of the scattering amplitudes at and below threshold leads to a deep K- nuclear potential VK- for kaonic atoms and K- nuclear quasibound states. Selfconsistent evaluations yield K- potential depths -ReVK- (ρ0) of order 100 MeV. Allowing for K- NN absorption, better agreement with K- atoms data is achieved, leading to increased potential depths, -ReVK- (ρ0) ˜ 175 MeV, in accord with density dependent potentials obtained in purely phenomenological fits. Self consistent dynamical calculations of K- nuclear quasibound states are reported and discussed, as well.

  10. Graviton and Gluon Scattering from First Principles.

    PubMed

    Boels, Rutger H; Medina, Ricardo

    2017-02-10

    Graviton and gluon scattering are studied from minimal physical assumptions such as Poincare and gauge symmetry as well as unitarity. The assumptions lead to an interesting and surprisingly restrictive set of linear equations. This shows gluon and graviton scattering to be related in many field and string theories, explaining and extending several known results. By systematic analysis exceptional graviton scattering amplitudes are derived, which in general dimensions cannot be related to gluon amplitudes. The simplicity of the formalism guarantees wide further applicability to gauge and gravity theories.

  11. 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.

  12. Massive superstring scatterings in the Regge regime

    SciTech Connect

    He Song; Lee, Jen-Chi; Takahashi, Keijiro; Yang Yi

    2011-03-15

    We calculate four classes of high-energy massive string scattering amplitudes of fermionic string theory at arbitrary mass levels in the Regge regime (RR). We show that all four leading order amplitudes in the RR can be expressed in terms of the Kummer function of the second kind. Based on the summation algorithm of a set of extended signed Stirling number identities, we show that all four ratios calculated previously by the method of decoupling of zero-norm states among scattering amplitudes in the Gross regime can be extracted from this Kummer function in the RR. Finally, we conjecture and give evidence that the existence of these four Gross regime ratios in the RR persists to subleading orders in the Regge expansion of all high-energy fermionic string scattering amplitudes.

  13. Scattering problem in deformed space with minimal length

    SciTech Connect

    Stetsko, M. M.; Tkachuk, V. M.

    2007-07-15

    We investigated the elastic scattering problem with deformed Heisenberg algebra leading to the existence of a minimal length. The continuity equations for the moving particle in deformed space were constructed. We obtained the Green's function for a free particle, the scattering amplitude, and the cross section in deformed space. We also calculated the scattering amplitudes and differential cross sections for the Yukawa and the Coulomb potentials in the Born approximation.

  14. Diffraction phenomena in elastic scattering of heavy ions

    SciTech Connect

    Kotlyar, V.V.; Shebeko, A.V.

    1981-08-01

    Nuclear diffraction phenomena in elastic scattering of heavy ions are studied in the intermediate energy range. Examination is carried out using the strong absorption models for the S-matrix in the angular momentum representation. New asymptotic expressions for the diffraction scattering amplitudes are obtained. The main attention is paid to the study of the relation between the Fresnel and the Fraunhofer parts of the amplitudes obtained in different regions of scattering angles.

  15. Zero energy scattering calculation in Euclidean space

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Karmanov, V. A.

    2016-03-01

    We show that the Bethe-Salpeter equation for the scattering amplitude in the limit of zero incident energy can be transformed into a purely Euclidean form, as it is the case for the bound states. The decoupling between Euclidean and Minkowski amplitudes is only possible for zero energy scattering observables and allows determining the scattering length from the Euclidean Bethe-Salpeter amplitude. Such a possibility strongly simplifies the numerical solution of the Bethe-Salpeter equation and suggests an alternative way to compute the scattering length in Lattice Euclidean calculations without using the Luscher formalism. The derivations contained in this work were performed for scalar particles and one-boson exchange kernel. They can be generalized to the fermion case and more involved interactions.

  16. Einstein-Yang-Mills from pure Yang-Mills amplitudes

    NASA Astrophysics Data System (ADS)

    Nandan, Dhritiman; Plefka, Jan; Schlotterer, Oliver; Wen, Congkao

    2016-10-01

    We present new relations for scattering amplitudes of color ordered gluons and gravitons in Einstein-Yang-Mills theory. Tree-level amplitudes of arbitrary multiplicities and polarizations involving up to three gravitons and up to two color traces are reduced to partial amplitudes of pure Yang-Mills theory. In fact, the double-trace identities apply to Einstein-Yang-Mills extended by a dilaton and a B-field. Our results generalize recent work of Stieberger and Taylor for the single graviton case with a single color trace. As the derivation is made in the dimension-agnostic Cachazo-He-Yuan formalism, our results are valid for external bosons in any number of spacetime dimensions. Moreover, they generalize to the superamplitudes in theories with 16 supercharges.

  17. Superstring disk amplitudes in a rolling tachyon background

    SciTech Connect

    Jokela, Niko; Majumder, Jaydeep; Keski-Vakkuri, Esko

    2006-02-15

    We study the tree level scattering or emission of n closed superstrings from a decaying non-BPS brane in Type II superstring theory. We attempt to calculate generic n-point superstring disk amplitudes in the rolling tachyon background. We show that these can be written as infinite power series of Toeplitz determinants, related to expectation values of a periodic function in Circular Unitary Ensembles. Further analytical progress is possible in the special case of bulk-boundary disk amplitudes. These are interpreted as probability amplitudes for emission of a closed string with initial conditions perturbed by the addition of an open string vertex operator. This calculation has been performed previously in bosonic string theory, here we extend the analysis for superstrings. We obtain a result for the average energy of closed superstrings produced in the perturbed background.

  18. Thermodynamic constraints on the amplitude of quantum oscillations

    NASA Astrophysics Data System (ADS)

    Shekhter, Arkady; Modic, K. A.; McDonald, R. D.; Ramshaw, B. J.

    2017-03-01

    Magneto-quantum oscillation experiments in high-temperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B. J. Ramshaw et al., Science 348, 317 (2014), 10.1126/science.aaa4990; H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010), 10.1103/PhysRevLett.104.057008; P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013), 10.1103/PhysRevLett.110.257002]—in support of a quantum-critical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may directly indicate the increasing role of quantum fluctuations that suppress the quantum oscillation amplitude through inelastic scattering. We show that the traditional theoretical approaches beyond Lifshitz-Kosevich to calculate the oscillation amplitude in correlated metals result in a contradiction with the third law of thermodynamics and suggest a way to rectify this problem.

  19. 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.

  20. Quasi-steady, marginally unstable electron cyclotron harmonic wave amplitudes

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojia; Angelopoulos, Vassilis; Ni, Binbin; Thorne, Richard M.; Horne, Richard B.

    2013-06-01

    Electron cyclotron harmonic (ECH) waves have long been considered a potential driver of diffuse aurora in Earth's magnetotail. However, the scarcity of intense ECH emissions in the outer magnetotail suggests that our understanding of the amplification and the relative importance of these waves for electron scattering is lacking. We conduct a comprehensive study of wave growth and quasi-linear diffusion to estimate the amplitude of loss-cone-driven ECH waves once diffusion and growth balance but before convection or losses alter the background hot plasma sheet population. We expect this to be the most common state of the plasma sheet between episodes of fast convection. For any given wave amplitude, we model electron diffusion caused by interaction with ECH waves using a 2-D bounce-averaged Fokker-Planck equation. After fitting the resultant electron distributions as a superposition of multicomponent subtracted bi-Maxwellians, we estimate the maximum path-integrated gain using the HOTRAY ray-tracing code. We argue that the wave amplitude during quasi-steady state is the inflection point on a gain-amplitude curve. During quasi-steady state, ECH wave amplitudes can be significant (~1 mV/m) at L ~ 8 but drop to very low values (<~0.1 mV/m) in the outer magnetotail (L ~ 16) and likely fall below the sensitivity of typical instrumentation relatively close to Earth mainly because of the smallness of the loss cone. Our result reinforces the potentially important role of ECH waves in driving diffuse aurora and suggests that careful comparison of theoretical wave amplitude estimates and observations is required for resolving the equatorial scattering mechanism of diffuse auroral precipitation.

  1. Helicity selection rules and noninterference for BSM amplitudes

    NASA Astrophysics Data System (ADS)

    Azatov, Aleksandr; Contino, Roberto; Machado, Camila S.; Riva, Francesco

    2017-03-01

    Precision studies of scattering processes at colliders provide powerful indirect constraints on new physics. We study the helicity structure of scattering amplitudes in the standard model (SM) and in the context of an effective Lagrangian description of beyond-the-SM (BSM) dynamics. Our analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 →2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. In such situations, the naive expectation that dimension-6 operators represent the leading BSM contribution is compromised, as corrections from dimension-8 operators can become equally (if not more) important well within the validity of the effective field theory approach.

  2. 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).

  3. Structured light, transmission, and scattering

    NASA Astrophysics Data System (ADS)

    Andrews, David L.

    2011-03-01

    Numerous theoretical and experimental studies have established the principle that beams conveying orbital angular momentum offer a rich scope for information transfer. However, it is not clear how far it is practicable to operate such a concept at the single-photon level - especially when such a beam propagates through a system in which scattering can occur. In cases where scattering leads to photon deflection, it produces losses; however in terms of the retention of information content, there should be more concern over forward scattering. Based on a quantum electrodynamical formulation of theory, this paper aims to frame and resolve the key issues. A quantum amplitude is constructed for the representation of single and multiple scattering events in the propagation an individual photon, from a suitably structured beam. The analysis identifies potential limitations of principle, undermining complete fidelity of quantum information transmission.

  4. Pulse amplitude modulated chlorophyll fluorometer

    DOEpatents

    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.

  5. Genus dependence of superstring amplitudes

    SciTech Connect

    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.

  6. Multiple scattering and charged-particle - hydrogen-atom collisions

    NASA Technical Reports Server (NTRS)

    Franco, V.; Thomas, B. K.

    1979-01-01

    Glauber-approximation scattering amplitudes for charged-particle - hydrogen-atom elastic and inelastic collisions are derived directly in terms of the known particle-electron and particle-proton Coulomb scattering amplitudes and the known hydrogen-atom form factors. It is shown that the particle-hydrogen amplitude contains no single-scattering term. The double-scattering term is obtained as a two-dimensional integral in momentum space. It is demonstrated how the result can be used as the starting point for an alternative and relatively simple derivation, in closed form, of the Glauber particle-hydrogen scattering amplitude for transitions from the ground state to an arbitrary (nlm) state.

  7. 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.

  8. Type 0 open string amplitudes and the tensionless limit

    NASA Astrophysics Data System (ADS)

    Rojas, Francisco

    2014-12-01

    The sum over planar multiloop diagrams in the NS + sector of type 0 open strings in flat spacetime has been proposed by Thorn as a candidate to resolve nonperturbative issues of gauge theories in the large N limit. With S U (N ) Chan-Paton factors, the sum over planar open string multiloop diagrams describes the 't Hooft limit N →∞ with N gs2 held fixed. By including only planar diagrams in the sum the usual mechanism for the cancellation of loop divergences (which occurs, for example, among the planar and Möbius strip diagrams by choosing a specific gauge group) is not available and a renormalization procedure is needed. In this article the renormalization is achieved by suspending total momentum conservation by an amount p ≡∑ i n ki≠0 at the level of the integrands in the integrals over the moduli and analytically continuing them to p =0 at the very end. This procedure has been successfully tested for the 2 and 3 gluon planar loop amplitudes by Thorn. Gauge invariance is respected and the correct running of the coupling in the limiting gauge field theory was also correctly obtained. In this article we extend those results in two directions. First, we generalize the renormalization method to an arbitrary n -gluon planar loop amplitude giving full details for the 4-point case. One of our main results is to provide a fully renormalized amplitude which is free of both UV and the usual spurious divergences leaving only the physical singularities in it. Second, using the complete renormalized amplitude, we extract the high-energy scattering regime at fixed angle (tensionless limit). Apart from obtaining the usual exponential falloff at high energies, we compute the full dependence on the scattering angle which shows the existence of a smooth connection between the Regge and hard scattering regimes.

  9. 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.

  10. Coupled-channel scattering on a torus

    DOE PAGES

    Guo, Peng; Dudek, Jozef Jon; Edwards, Robert G.; ...

    2013-07-01

    Based on the Hamiltonian formalism approach, a generalized Luscher's formula for two particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice QCD computations.

  11. Scattering of sound waves by a compressible vortex

    NASA Technical Reports Server (NTRS)

    Colonius, Tim; Lele, Sanjiva K.; Moin, Parviz

    1991-01-01

    Scattering of plane sound waves by a compressible vortex is investigated by direct computation of the two-dimensional Navier-Stokes equations. Nonreflecting boundary conditions are utilized, and their accuracy is established by comparing results on different sized domains. Scattered waves are directly measured from the computations. The resulting amplitude and directivity pattern of the scattered waves is discussed, and compared to various theoretical predictions. For compact vortices (zero circulation), the scattered waves directly computed are in good agreement with predictions based on an acoustic analogy. Strong scattering at about + or - 30 degrees from the direction of incident wave propagation is observed. Back scattering is an order of magnitude smaller than forward scattering. For vortices with finite circulation refraction of the sound by the mean flow field outside the vortex core is found to be important in determining the amplitude and directivity of the scattered wave field.

  12. Effect of Multiple Scattering in a Quantum Well

    NASA Astrophysics Data System (ADS)

    Sheng, Hanyu; Chua, Soo-Jin; Sinkkonen, Juha

    This paper gives a potentially useful application to quantum well of the theory of scattering in the Born approximation. The simple formulae for multiple scattering in a quantum well of double barrier structure are derived. The multiple scattering parameter is the complex mean free path. We show that the amplitude of the coherent wave will be exponentially attenuated and the phase of the wave will be delayed because of the scattering.

  13. 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.

  14. Nonlinear harmonic generation in finite amplitude black hole oscillations

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Philippos

    2002-04-01

    The nonlinear generation of harmonics in gravitational perturbations of black holes is explored using numerical relativity based on an ingoing light-cone framework. Localized, finite, perturbations of an isolated black hole are parametrized by amplitude and angular harmonic form. The response of the black hole spacetime is monitored and its harmonic content analyzed to identify the strength of the nonlinear generation of harmonics as a function of the initial data amplitude. It is found that overwhelmingly the black hole responds at the harmonic mode perturbed, even for spacetimes with 10% of the black hole mass radiated. The coefficients for down and up scattering in harmonic space are computed for a range of couplings. Down scattering, leading to smoothing out of angular structure, is found to be equally as or more efficient than the up scatterings that would lead to increased rippling. The details of this nonlinear balance may form the quantitative mechanism by which black holes avoid fission even for arbitrary strong distortions.

  15. Two-photon exchange in electron-trinucleon elastic scattering

    NASA Astrophysics Data System (ADS)

    Kobushkin, A. P.; Timoshenko, Ju. V.

    2013-10-01

    We discuss two-photon exchange (TPE) in elastic electron scattering off the trinucleon systems, 3He and 3H. The calculations are done in the semirelativistic approximation with the trinucleon wave functions obtained with the Paris and CD-Bonn nucleon-nucleon potentials. An applicability area of the model is wide enough and includes the main part of kinematical domain where experimental data exist. All three TPE amplitudes (generalized form factors) for electron 3He elastic scattering are calculated. We find that the TPE amplitudes are a few times more significant in the scattering of electrons off 3He then in the electron-proton scattering.

  16. Unitarization and low-energy scattering data

    NASA Astrophysics Data System (ADS)

    Magalhães, P. C.; Robilotta, M. R.

    2014-07-01

    A procedure based on the well-known K-matrix formalism is presented, which makes patterns in inelastic regions of low-energy scattering data considerably more transparent. It relies on the use of an empirical kernel, obtained by eliminating elastic loops from the experimental amplitude. This allows structures associated with resonances, such as locations, widths, and heights, to become visible with the naked eye. The method is illustrated with a study of the P-wave Kπ amplitude.

  17. Large amplitude relativistic plasma waves

    SciTech Connect

    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.

  18. An optical model for composite nuclear scattering

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Townsend, L. W.

    1981-01-01

    The optical model of composite particle scattering is considered and compared to the accuracies of other models. A nonrelativistic Schroedinger equation with two-body potentials is used for the scattering of a single particle by an energy-dependent local potential. The potential for the elastic channel is composed of matrix elements of a single scattering operator taken between the ground states of the projectile and the target; the coherent amplitude is considered as dominating the scattering in the forward direction. A multiple scattering series is analytically explored and formally summed by the solution of an equivalent Schroedinger equation. Cross sections of nuclear scattering are then determined for He-4 and C-12 nuclei at 3.6 GeV/nucleus and O-16 projectiles at 2.1 GeV/nucleus, and the optical model approximations are found to be consistently lower and more accurate than approximations made by use of Glauber's theory.

  19. Hedgehog bases for A n cluster polylogarithms and an application to six-point amplitudes

    NASA Astrophysics Data System (ADS)

    Parker, Daniel E.; Scherlis, Adam; Spradlin, Marcus; Volovich, Anastasia

    2015-11-01

    Multi-loop scattering amplitudes in N=4 Yang-Mills theory possess cluster algebra structure. In order to develop a computational framework which exploits this connection, we show how to construct bases of Goncharov polylogarithm functions, at any weight, whose symbol alphabet consists of cluster coordinates on the A n cluster algebra. Using such a basis we present a new expression for the 2-loop 6-particle NMHV amplitude which makes some of its cluster structure manifest.

  20. Calculations of bar K-nuclear quasi-bound states using chiral bar KN amplitudes

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Barnea, N.; Cieplý, A.; Friedman, E.; Gal, A.; Gazda, D.

    2014-03-01

    We review our recent calculations of K- quasi-bound states in nuclear systems using subthreshold energy dependent chiral bar KN amplitudes. Strong energy dependence of the scattering amplitudes requires self-consistent evaluation of the involved bar KN interactions. In view of sizable widths predicted by our calculations, an unambiguous identification of K--nuclear quasi-bound states in ongoing experimental searches would be difficult.

  1. Constructing Amplitudes from Their Soft Limits

    SciTech Connect

    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.

  2. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude

    PubMed Central

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-01

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed. PMID:28054662

  3. Positroid stratification of orthogonal Grassmannian and ABJM amplitudes

    NASA Astrophysics Data System (ADS)

    Kim, Joonho; Lee, Sangmin

    2014-09-01

    A novel understanding of scattering amplitudes in terms of on-shell diagrams and positive Grassmannian has been recently established for four dimensional Yang-Mills theories and three dimensional Chern-Simons theories of ABJM type. We give a detailed construction of the positroid stratification of orthogonal Grassmannian relevant for ABJM amplitudes. On-shell diagrams are classified by pairing of external particles. We introduce a combinatorial aid called `OG tableaux' and map each equivalence class of on-shell diagrams to a unique tableau. The on-shell diagrams related to each other through BCFW bridging are naturally grouped by the OG tableaux. Introducing suitably ordered BCFW bridges and positive coordinates, we construct the complete coordinate charts to cover the entire positive orthogonal Grassmannian for arbitrary number of external particles. The graded counting of OG tableaux suggests that the positive orthogonal Grassmannian constitutes a combinatorial polytope.

  4. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude

    NASA Astrophysics Data System (ADS)

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-01

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed.

  5. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude.

    PubMed

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-05

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed.

  6. BPS amplitudes, helicity supertraces and membranes in M-theory

    NASA Astrophysics Data System (ADS)

    Wit, B. d.; Lüst, D.

    2000-03-01

    We study BPS dominated loop amplitudes in M-theory on T2. For this purpose we generalize the concept of helicity supertraces to nine spacetime dimensions. These traces distinguish between various massive supermultiplets and appear as coefficients in their one-loop contributions to n-graviton scattering amplitudes. This can be used to show that only ultrashort BPS multiplets contribute to the R4 term in the effective action, which was first computed by Green, Gutperle and Vanhove. There are two inequivalent ultrashort BPS multiplets which describe the Kaluza-Klein states and the wrapped membranes that cover the torus a number of times. From the perspective of the type-II strings they correspond to momentum and winding states and D0 or D1 branes.

  7. Integrable amplitude deformations for N =4 super Yang-Mills and ABJM theory

    NASA Astrophysics Data System (ADS)

    Bargheer, Till; Huang, Yu-Tin; Loebbert, Florian; Yamazaki, Masahito

    2015-01-01

    We study Yangian-invariant deformations of scattering amplitudes in 4d N =4 super Yang-Mills theory and 3d N =6 Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In particular, we obtain the deformed Graßmannian integral for 4d N =4 supersymmetric Yang-Mills theory, both in momentum and momentum-twistor space. For 3d ABJM theory, we initiate the study of deformed scattering amplitudes. We investigate general deformations of on-shell diagrams, and find the deformed Graßmannian integral for this theory. We furthermore introduce the algebraic R-matrix construction of deformed Yangian invariants for ABJM theory.

  8. Resonances in pi-K scattering

    SciTech Connect

    Wilson, David J.

    2014-06-23

    We have obtained clear signals of resonances in coupled-channel pi K - eta K scattering. Using distillation and a large basis of operators we are able to extract a precise spectrum of energy levels using the variational method. These energies are analysed using inelastic extensions of the Luescher method to obtain scattering amplitudes that clearly describe S, P and D wave resonances, corresponding to the physical K_0^*(1430), the K^*(892) and the K_2^*(1430).

  9. 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).

  10. Elliptic multiple zeta values and one-loop superstring amplitudes

    NASA Astrophysics Data System (ADS)

    Broedel, Johannes; Mafra, Carlos R.; Matthes, Nils; Schlotterer, Oliver

    2015-07-01

    We investigate iterated integrals on an elliptic curve, which are a natural genus-one generalization of multiple polylogarithms. These iterated integrals coincide with the multiple elliptic polylogarithms introduced by Brown and Levin when constrained to the real line. At unit argument they reduce to an elliptic analogue of multiple zeta values, whose network of relations we start to explore. A simple and natural application of this framework are one-loop scattering amplitudes in open superstring theory. In particular, elliptic multiple zeta values are a suitable language to express their low energy limit. Similar to the techniques available at tree-level, our formalism allows to completely automatize the calculation.

  11. Amplitude-masked photoacoustic wavefront shaping and application in flowmetry

    PubMed Central

    Tay, Jian Wei; Liang, Jinyang; Wang, Lihong V.

    2014-01-01

    Optical-resolution photoacoustic flowmetry allows non-invasive single-cell flow measurements. However, its operational depth is limited by optical diffusion, which prevents focusing beyond shallow depths in scattering media, as well as reducing the measurement signal-to-noise ratio (SNR). To overcome this limitation, we used binary-amplitude wavefront shaping to enhance light focusing in the presence of scattering. Here, the transmission modes that contributed constructively to the intensity at the optical focus were identified and selectively illuminated, resulting in a 14-fold intensity increase and a corresponding increase in SNR. This technique can potentially extend the operational depth of optical-resolution photoacoustic flowmetry beyond 1 mm in tissue. PMID:25360912

  12. Forward collisions and spin effects in evaluating amplitudes

    SciTech Connect

    Buttimore, N. H.

    2011-07-15

    Total cross sections and the phases of forward collision amplitudes form part of the early studies when a new energy window becomes available as is provided by the Large Hadron Collider. Enhancement of the forward elastic differential cross section above that expected from estimates of dispersion and optical theorem values may result from the presence of hadronic spin dependence in addition to effects induced by vacuum polarization contributions to the photon propagator. The elastic scattering of protons and ions at small angles is important in the evaluation of the luminosities of the corresponding incident beams and invites detailed examination. Polarization measurements taken at a number of high energies have yielded information on the extent of spin effects in hadronic scattering, particularly at the low momentum transfers related to diffraction.

  13. Modelling Broadband Scattering From Shelled Spheres in a Waveguide

    DTIC Science & Technology

    2007-10-01

    DRDC Atlantic TM 2007-270 17 0.12 0.14 0.16 0.18 Time(sec) Figure 11: The scattered Geld time series (amplitude) as a function of sphere depth. 0.5...discussed in Ref. 5. 20 DRDC Atlantic TM 2007-270 1.5 2 2.5 Frequency(kHz) Figure 15: The scattered Geld amplitude (scaled by 104j as function of

  14. Coherent backscattering of light with nonlinear atomic scatterers

    SciTech Connect

    Wellens, T.; Gremaud, B.; Delande, D.; Miniatura, C.

    2006-01-15

    We study coherent backscattering of a monochromatic laser by a dilute gas of cold two-level atoms in the weakly nonlinear regime. The nonlinear response of the atoms results in a modification of both the average field propagation (nonlinear refractive index) and the scattering events. Using a perturbative approach, the nonlinear effects arise from inelastic two-photon scattering processes. We present a detailed diagrammatic derivation of the elastic and inelastic components of the backscattering signal for both scalar and vectorial photons. In particular, we show that the coherent backscattering phenomenon originates in some cases from the interference between three different scattering amplitudes. This is in marked contrast with the linear regime where it is due to the interference between two different scattering amplitudes. In particular we show that, if elastically scattered photons are filtered out from the photodetection signal, the nonlinear backscattering enhancement factor exceeds the linear barrier of 2, consistently with a three-amplitude interference effect.

  15. The isomonodromy method for black hole scattering

    SciTech Connect

    Carneiro da Cunha, Bruno; Novaes, Fábio

    2015-12-17

    We summarize recent results by the authors [7, 8, 35] on the extraction of scattering amplitudes for scalar fields in Kerr/Kerr-de Sitter backgrounds. Analytical, closed forms are found in terms of the Painlevé V and VI transcendents for generic values of the physical parameters.

  16. Symmetry considerations in the scattering of identical composite bodies

    NASA Technical Reports Server (NTRS)

    Norbury, J. W.; Townsend, L. W.; Deutchman, P. A.

    1986-01-01

    Previous studies of the interactions between composite particles were extended to the case in which the composites are identical. The form of the total interaction potential matrix elements was obtained, and guidelines for their explicit evaluation were given. For the case of elastic scattering of identical composites, the matrix element approach was shown to be equivalent to the scattering amplitude method.

  17. Virasoro amplitude from theS N R24-orbifold sigma model

    NASA Astrophysics Data System (ADS)

    Arutyunov, G. E.; Frolov, S. A.

    1998-01-01

    Four tachyon scattering amplitude is derived from the $S^N\\R^{24}$ orbifold sigma model in the large $N$ limit. The closed string interaction is described by a vertex which is a bosonic analog of the supersymmetric one, recently proposed by Dijkgraaf, Verlinde and Verlinde.

  18. 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.

  19. Minimal Basis for Gauge Theory Amplitudes

    SciTech Connect

    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.

  20. Gravity and Yang-Mills amplitude relations

    SciTech Connect

    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.

  1. Three applications of a bonus relation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    Spradlin, Marcus; Volovich, Anastasia; Wen, Congkao

    2009-04-01

    Arkani-Hamed et al. have recently shown that all tree-level scattering amplitudes in maximal supergravity exhibit exceptionally soft behavior when two supermomenta are taken to infinity in a particular complex direction, and that this behavior implies new non-trivial relations amongst amplitudes in addition to the well-known on-shell recursion relations. We consider the application of these new 'bonus relations' to MHV amplitudes, showing that they can be used quite generally to relate (n - 2) !-term formulas typically obtained from recursion relations to (n - 3) !-term formulas related to the original BGK conjecture. Specifically we provide (1) a direct proof of a formula presented by Elvang and Freedman, (2) a new formula based on one due to Bedford et al., and (3) an alternate proof of a formula recently obtained by Mason and Skinner. Our results also provide the first direct proof that the conjectured BGK formula, only very recently proven via completely different methods, satisfies the on-shell recursion.

  2. Type I/heterotic duality and M-theory amplitudes

    NASA Astrophysics Data System (ADS)

    Green, Michael B.; Rudra, Arnab

    2016-12-01

    This paper investigates relationships between low-energy four-particle scattering amplitudes with external gauge particles and gravitons in the E 8 × E 8 and SO(32) heterotic string theories and the type I and type IA superstring theories by considering a variety of tree level and one-loop Feynman diagrams describing such amplitudes in eleven-dimensional supergravity in a Horava-Witten background compactified on a circle. This accounts for a number of perturbative and non-perturbative aspects of low order higher derivative terms in the low-energy expansion of string theory amplitudes, which are expected to be protected by half maximal supersymmetry from receiving corrections beyond one or two loops. It also suggests the manner in which type I/heterotic duality may be realised for certain higher derivative interactions that are not so obviously protected. For example, our considerations suggest that R 4 interactions (where R is the Riemann curvature) might receive no perturbative corrections beyond one loop by virtue of a conspiracy involving contributions from (non-BPS) {Z}_2 D-instantons in the type I and heterotic SO(32) theories.

  3. Light-like scattering in quantum gravity

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Donoghue, John F.; Holstein, Barry R.; Planté, Ludovic; Vanhove, Pierre

    2016-11-01

    We consider scattering in quantum gravity and derive long-range classical and quantum contributions to the scattering of light-like bosons and fermions (spin-0, spin- 1/2 , spin-1) from an external massive scalar field, such as the Sun or a black hole. This is achieved by treating general relativity as an effective field theory and identifying the non-analytic pieces of the one-loop gravitational scattering amplitude. It is emphasized throughout the paper how modern amplitude techniques, involving spinor-helicity variables, unitarity, and squaring relations in gravity enable much simplified computations. We directly verify, as predicted by general relativity, that all classical effects in our computation are universal (in the context of matter type and statistics). Using an eikonal procedure we confirm the post-Newtonian general relativity correction for light-like bending around large stellar objects. We also comment on treating effects from quantum ℏ dependent terms using the same eikonal method.

  4. 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).

  5. Amplitude image processing by diffractive optics.

    PubMed

    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.

  6. Thermal cracking and amplitude dependent attenuation

    SciTech Connect

    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.

  7. Landau retardation on the occurrence scattering time in quantum electron-hole plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2016-03-01

    The Landau damping effects on the occurrence scattering time in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Shukla-Stenflo-Bingham effective potential model is employed to obtain the occurrence scattering time in a quantum electron-hole plasma. The result shows that the influence of Landau damping produces the imaginary term in the scattering amplitude. It is then found that the Landau damping generates the retardation effect on the occurrence scattering time. It is found that the occurrence scattering time increases in forward scattering domains and decreases in backward scattering domains with an increase of the Landau parameter. It is also found that the occurrence scattering time decreases with increasing collision energy. In addition, it is found that the quantum shielding effect enhances the occurrence scattering time in the forward scattering and, however, suppresses the occurrence scattering time in the backward scattering.

  8. Hadron scattering, resonances, and QCD

    SciTech Connect

    Briceno, Raul

    2016-12-01

    The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.

  9. A Simple Discrete Model of Scattering in a Fluctuating Inhomogeneous Medium.

    ERIC Educational Resources Information Center

    West, Bruce J.

    1978-01-01

    Discusses scattering problems in continuous media, and presents a simple discrete model for scalar wave scattering from inhomogeneities on a lattice. Illustrates the relationships between the amplitude of the scattered wave and the characteristic function of the fluctuating motion of a point reflector in one dimension. (Author/GA)

  10. Discriminator amplitude walk correction in gamma-ray coincidence experiments using list-mode time-stamping data acquisition

    NASA Astrophysics Data System (ADS)

    Khamzin, Murat K.; Valentine, John D.

    2003-06-01

    When pulse amplitude and time stamp are recorded in list-mode time-stamping data acquisition, it is possible to correct for the system amplitude walk, typically observed as the time pickoff dependence on pulse amplitude. In this study, a method of correcting for amplitude walk during post-acquisition analysis of such list mode data is developed and demonstrated. The method is demonstrated using a simple two-channel system and a photon source capable of producing coincidence events ( 22Na). Two leading-edge discriminators, vulnerable to the amplitude walk, were used to produce the time pickoffs. The resulting corrected data show an amplitude walk less than the detector timing resolution. The method developed can be used in list-mode data acquisition systems such as medical imaging scanners or Compton scatter cameras.

  11. Deterministic forward scatter from surface gravity waves.

    PubMed

    Deane, Grant B; Preisig, James C; Tindle, Chris T; Lavery, Andone; Stokes, M Dale

    2012-12-01

    Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems. A stationary phase analysis of the Helmholtz-Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the surface wave field. Deterministic effects along paths up to 70 water depths long are observed in shallow water measurements of surface-scattered sound at the Martha's Vineyard Coastal Observatory. The arrival time and amplitude of surface-scattered pulses are reconciled with model calculations using measurements of surface waves made with an upward-looking sonar mounted mid-way along the propagation path. The root mean square difference between the modeled and observed pulse arrival amplitude and delay, respectively, normalized by the maximum range of amplitudes and delays, is found to be 0.2 or less for the observation periods analyzed. Cross-correlation coefficients for modeled and observed pulse arrival delays varied from 0.83 to 0.16 depending on surface conditions. Cross-correlation coefficients for normalized pulse energy for the same conditions were small and varied from 0.16 to 0.06. In contrast, the modeled and observed pulse arrival delay and amplitude statistics were in good agreement.

  12. 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.

  13. Amplitude- and rise-time-compensated filters

    DOEpatents

    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.

  14. 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.

  15. Nonlinear Aharonov-Bohm Scattering by Optical Vortices

    SciTech Connect

    Neshev, Dragomir; Nepomnyashchy, Alexander; Kivshar, Yuri S.

    2001-07-23

    We study linear and nonlinear wave scattering by an optical vortex in a self-defocusing nonlinear Kerr medium. In the linear case, we find a splitting of a plane-wave front at the vortex proportional to its circulation, similar to what occurs in the scattered wave of electrons for the Aharonov-Bohm effect. For larger wave amplitudes, we study analytically and numerically the scattering of a dark-soliton stripe (a nonlinear analog of a small-amplitude wave packet) by a vortex and observe a significant asymmetry of the scattered wave. Subsequently, a wave-front splitting of the scattered wave develops into transverse modulational instability, ''unzipping'' the stripe into trains of vortices with opposite charges.

  16. Conformal bootstrap, universality and gravitational scattering

    NASA Astrophysics Data System (ADS)

    Jackson, Steven; McGough, Lauren; Verlinde, Herman

    2015-12-01

    We use the conformal bootstrap equations to study the non-perturbative gravitational scattering between infalling and outgoing particles in the vicinity of a black hole horizon in AdS. We focus on irrational 2D CFTs with large c and only Virasoro symmetry. The scattering process is described by the matrix element of two light operators (particles) between two heavy states (BTZ black holes). We find that the operator algebra in this regime is (i) universal and identical to that of Liouville CFT, and (ii) takes the form of an exchange algebra, specified by an R-matrix that exactly matches the scattering amplitude of 2 + 1 gravity. The R-matrix is given by a quantum 6j-symbol and the scattering phase by the volume of a hyperbolic tetrahedron. We comment on the relevance of our results to scrambling and the holographic reconstruction of the bulk physics near black hole horizons.

  17. Amplitude dynamics favors synchronization in complex networks

    PubMed Central

    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

  18. 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.

  19. 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.

  20. Rayleigh scattering. [molecular scattering terminology redefined

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1981-01-01

    The physical phenomena of molecular scattering are examined with the objective of redefining the confusing terminology currently used. The following definitions are proposed: molecular scattering consists of Rayleigh and vibrational Raman scattering; the Rayleigh scattering consists of rotational Raman lines and the central Cabannes line; the Cabannes line is composed of the Brillouin doublet and the central Gross or Landau-Placzek line. The term 'Rayleigh line' should never be used.

  1. 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.

  2. Amplitude Metrics for Cellular Circadian Bioluminescence Reporters

    PubMed Central

    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

  3. Bootstrapping One-Loop QCD Amplitudes

    SciTech Connect

    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.

  4. Amplitude metrics for cellular circadian bioluminescence reporters.

    PubMed

    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

  5. 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.

  6. 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.

  7. Classical ultra-relativistic scattering in ADD

    NASA Astrophysics Data System (ADS)

    Gal'tsov, Dmitry V.; Kofinas, Georgios; Spirin, Pavel; Tomaras, Theodore N.

    2009-05-01

    The classical differential cross-section is calculated for high-energy small-angle gravitational scattering in the factorizable model with toroidal extra dimensions. The three main features of the classical computation are: (a) It involves summation over the infinite Kaluza-Klein towers but, contrary to the Born amplitude, it is finite with no need of an ultraviolet cutoff. (b) It is shown to correspond to the non-perturbative saddle-point approximation of the eikonal amplitude, obtained by the summation of an infinite number of ladder graphs of the quantum theory. (c) In the absence of extra dimensions it reproduces all previously known results.

  8. The integrated extinction for broadband scattering of acoustic waves.

    PubMed

    Sohl, Christian; Gustafsson, Mats; Kristensson, Gerhard

    2007-12-01

    In this paper, physical bounds on scattering of acoustic waves over a frequency interval are discussed based on the holomorphic properties of the scattering amplitude in the forward direction. The result is given by a dispersion relation for the extinction cross section which yields an upper bound on the product of the extinction cross section and the associated bandwidth of any frequency interval. The upper bound is shown to depend only on the geometry and the material properties of the scatterer in the static or low-frequency limit. The results are exemplified by permeable and impermeable scatterers with homogeneous and isotropic material properties.

  9. Renormalization-group evolution of the B-meson light-cone distribution amplitude.

    PubMed

    Lange, Björn O; Neubert, Matthias

    2003-09-05

    An integro-differential equation governing the evolution of the leading-order B-meson light-cone distribution amplitude is derived. The anomalous dimension in this equation contains a logarithm of the renormalization scale, whose coefficient is identified with the cusp anomalous dimension of Wilson loops. The exact solution of the evolution equation is obtained, from which the asymptotic behavior of the distribution amplitude is derived. These results can be used to resum Sudakov logarithms entering the hard-scattering kernels in QCD factorization theorems for exclusive B decays.

  10. Involution-dependent constants and the cancellation of divergences in the 1-loop open string amplitude

    SciTech Connect

    Nagao, G.

    1987-12-01

    We recalculate the bosonic 1-loop open string scattering amplitude using the results of the bosonic 1-loop closed string amplitude. The results show explicitly how the cancellation of divergences depends upon of a set of involution-dependent constants which relate the torus to the cylinder and Moebius strip. Such a set of involution-dependent constants exists at each loop level and thus provides a means with which to study the cancellation of divergences and the connection between the world-sheet and internal symmetries. 14 refs., 3 figs.

  11. The amplitude of auroral backscatter. I - Model estimates of the dependence on electron density

    NASA Astrophysics Data System (ADS)

    Uspenskii, M. V.; Williams, P. J. S.

    1988-01-01

    A model of the auroral backscatter amplitude, in the form discussed by Uspensky (1985) and Oksman et al. (1986), has been derived for the radar geometry appropriate to joint observations by the PGI auroral radars at Karmaselga and Essoyla and the EISCAT incoherent scatter radar. The model shows how refraction effects cause a strongly nonlinear dependence of backscatter amplitude on electron density in the E-region. It also explains why the macroaspect sensitivity for auroral radar operating at a frequency of about 45 MHz is only 1-2 dB per degree for aspect angles greater than 5 deg.

  12. 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

  13. Multichannel 1 → 2 transition amplitudes in a finite volume

    SciTech Connect

    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.

  14. Scattering States in AdS/CFT

    SciTech Connect

    Fitzpatrick, A.Liam; Kaplan, Jared; /SLAC

    2012-02-14

    We show that suitably regulated multi-trace primary states in large N CFTs behave like 'in' and 'out' scattering states in the flat-space limit of AdS. Their transition matrix elements approach the exact scattering amplitudes for the bulk theory, providing a natural CFT definition of the flat space S-Matrix. We study corrections resulting from the AdS curvature and particle propagation far from the center of AdS, and show that AdS simply provides an IR regulator that disappears in the flat space limit.

  15. Timelike Compton Scattering - A First Look (CLAS)

    SciTech Connect

    Pawel Nadel-Turonski

    2009-12-01

    A major goal of the 12 GeV upgrade at Jefferson Lab is to map out the Generalized Parton Distributions (GPDs) in the valence region. This is primarily done through Deeply Virtual Compton Scattering (DVCS), which provides the simplest and cleanest way of accessing the GPDs. However, the “inverse” process, Timelike Compton Scattering (TCS), can provide an important complement, in particular formeasuring the real part of the amplitude and understanding corrections at finite Q2. The first measurements of TCS have recently been carried out in Hall B at Jefferson Lab, using both tagged and untagged photon beams.

  16. On the frequency dependence and spatial coherence of PKP precursor amplitudes

    NASA Astrophysics Data System (ADS)

    Mancinelli, Nicholas; Shearer, Peter; Thomas, Christine

    2016-03-01

    Studies now agree that small-scale (˜10 km) weak (˜0.1%) velocity perturbations throughout the lowermost mantle generate the globally averaged amplitudes of 1 Hz precursors to the core phase, . The possible frequency dependence and spatial coherence of this scattered phase, however, has been given less attention. Using a large global data set of ˜150,000 PKP precursor recordings, we characterize the frequency dependence of PKP precursors at central frequencies ranging from 0.5 to 4 Hz. At greater frequencies, we observe more scattered energy (relative to the reference phase PKPdf), particularly at shorter ranges. We model this observation by invoking heterogeneity at length scales from 2 to 30 km. Amplitudes at 0.5 Hz, in particular, suggest the presence of more heterogeneity at scales >8 km than present in previously published models. Using a regional bootstrap approach, we identify large (>20°), spatially coherent regions of anomalously strong scattering beneath the West Pacific, Central/North America, and—to a lesser extent—East Africa. Finally, as proof of concept, we use array processing techniques to locate the origin of scattered energy observed in Southern California by the Anza and Southern California Seismic Networks. The energy appears to come primarily from out-of-plane scattering on the receiver side. We suggest that such improvised arrays can increase global coverage and may reveal whether a majority of precursor energy comes from localized heterogeneity in the lowermost mantle.

  17. Amplitude-masked photoacoustic wavefront shaping: theory and application in flowmetry

    NASA Astrophysics Data System (ADS)

    Liang, Jinyang; Tay, Jian Wei; Hemphill, Ashton S.; Wang, Lihong V.

    2015-03-01

    Optical diffusion in scattering media prevents focusing beyond shallow depths, causing optical imaging and sensing to suffer from low optical intensities, resulting in low signal-to-noise ratios (SNR). Here, we demonstrate focusing using a fast binary-amplitude digital micromirror device to characterize the transmission modes of the scattering medium. We then identify and selectively illuminate the transmission modes which contribute constructively to the intensity at the optical focus. Applying this method to photoacoustic flowmetry, we increased the optical intensity at the focus six-fold, and showed that the corresponding increase in SNR allows particle flow to be measured.

  18. Stress-dependent ultrasonic scattering in polycrystalline materials.

    PubMed

    Kube, Christopher M; Turner, Joseph A

    2016-02-01

    Stress-dependent elastic moduli of polycrystalline materials are used in a statistically based model for the scattering of ultrasonic waves from randomly oriented grains that are members of a stressed polycrystal. The stress is assumed to be homogeneous and can be either residual or generated from external loads. The stress-dependent elastic properties are incorporated into the definition of the differential scattering cross-section, which defines how strongly an incident wave is scattered into various directions. Nine stress-dependent differential scattering cross-sections or scattering coefficients are defined to include all possibilities of incident and scattered waves, which can be either longitudinal or (two) transverse wave types. The evaluation of the scattering coefficients considers polycrystalline aluminum that is uniaxially stressed. An analysis of the influence of incident wave propagation direction, scattering direction, frequency, and grain size on the stress-dependency of the scattering coefficients follows. Scattering coefficients for aluminum indicate that ultrasonic scattering is much more sensitive to a uniaxial stress than ultrasonic phase velocities. By developing the stress-dependent scattering properties of polycrystals, the influence of acoustoelasticity on the amplitudes of waves propagating in stressed polycrystalline materials can be better understood. This work supports the ongoing development of a technique for monitoring and measuring stresses in metallic materials.

  19. Low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}

  20. Low-energy pion-nucleon scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Ai, Li; Kaufmann, W. B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.

  1. Collinear limits beyond the leading order from the scattering equations

    NASA Astrophysics Data System (ADS)

    Nandan, Dhritiman; Plefka, Jan; Wormsbecher, Wadim

    2017-02-01

    The structure of tree-level scattering amplitudes for collinear massless bosons is studied beyond their leading splitting function behavior. These near-collinear limits at sub-leading order are best studied using the Cachazo-He-Yuan (CHY) formulation of the S-matrix based on the scattering equations. We compute the collinear limits for gluons, gravitons and scalars. It is shown that the CHY integrand for an n-particle gluon scattering amplitude in the collinear limit at sub-leading order is expressed as a convolution of an ( n - 1)-particle gluon integrand and a collinear kernel integrand, which is universal. Our representation is shown to obey recently proposed amplitude relations in which the collinear gluons of same helicity are replaced by a single graviton. Finally, we extend our analysis to effective field theories and study the collinear limit of the non-linear sigma model, Einstein-Maxwell-Scalar and Yang-Mills-Scalar theory.

  2. Differential cross sections for muonic atom scattering from hydrogenic molecules

    SciTech Connect

    Adamczak, Andrzej

    2006-10-15

    The differential cross sections for low-energy muonic hydrogen atom scattering from hydrogenic molecules are directly expressed by the corresponding amplitudes for muonic atom scattering from hydrogen-isotope nuclei. The energy and angular dependence of these three-body amplitudes is thus taken naturally into account in scattering from molecules, without involving any pseudopotentials. Effects of the internal motion of nuclei inside the target molecules are included for every initial rotational-vibrational state. These effects are very significant as the considered three-body amplitudes often vary strongly within the energy interval < or approx. 0.1 eV. The differential cross sections, calculated using the presented method, have been successfully used for planning and interpreting many experiments in low-energy muon physics. Studies of {mu}{sup -} nuclear capture in p{mu} and the measurement of the Lamb shift in p{mu} atoms created in H{sub 2} gaseous targets are recent examples.

  3. 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.

  4. Cut-constructible part of QCD amplitudes

    SciTech Connect

    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.

  5. 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.

  6. Kaonic atoms and in-medium K-N amplitudes II: Interplay between theory and phenomenology

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2013-02-01

    A microscopic kaonic-atom optical potential VK-(1) is constructed, using the Ikeda-Hyodo-Weise NLO chiral K-N subthreshold scattering amplitudes constrained by the kaonic hydrogen SIDDHARTA measurement, and incorporating Pauli correlations within the Waas-Rho-Weise generalization of the Ericson-Ericson multiple-scattering approach. Good fits to kaonic atom data over the entire periodic table require additionally sizable K-NN-motivated absorptive and dispersive phenomenological terms, in agreement with our former analysis based on a post-SIDDHARTA in-medium chirally-inspired NLO separable model by Cieplý and Smejkal. Such terms are included by introducing a phenomenological potential VK-(2) and coupling it self-consistently to VK-(1). Properties of resulting kaonic atom potentials are discussed with special attention paid to the role of K--nuclear absorption and to the extraction of density-dependent amplitudes representing K- multi-nucleon processes.

  7. Well Conditioned Formulations for Open Surface Scattering

    DTIC Science & Technology

    2008-08-01

    such as the MFIE and than with an integro - differential operator such as the EFIE. Current amplitudes on the circle-triangle target computed using the... equation (EFIE) is a first-kind integral equation formulation that is used to solve a wide variety of electromagnetic scattering problems in the...frequency domain. It is the only integral equation that can be applied to both open and closed targets. It is also a poorly conditioned integral equation

  8. 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.

  9. Topographic quantitative EEG amplitude in recovered alcoholics.

    PubMed

    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.

  10. Dual amplitude pulse generator for radiation detectors

    DOEpatents

    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.

  11. 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.

  12. 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.

  13. Statistical modeling of in situ hiss amplitudes using ground measurements

    NASA Astrophysics Data System (ADS)

    Golden, D. I.; Spasojevic, M.; Li, W.; Nishimura, Y.

    2012-05-01

    Plasmaspheric hiss is a naturally occurring extremely low frequency electromagnetic emission that is often observed within the Earth's plasmasphere. Plasmaspheric hiss plays a major role in the scattering and loss of electrons from the Earth's radiation belts, thereby contributing to the maintenance of the slot region between the inner and outer electron belt. Traditionally, in situ satellite observations have been the measurement modality of choice for studies of plasmaspheric hiss due to their ability to directly measure the hiss source region. However, satellite studies are relatively short-lived and very few satellite receivers remain operational for an entire 11-year solar cycle. Ground stations, in contrast, may collect multiple solar cycles' worth of data during their lifetime, yet they cannot directly measure the hiss source region. This study aims to determine the extent to which measurements of hiss at midlatitude ground stations may be used to predict the mean amplitude of in situ measurements of plasmaspheric hiss. We use coincident measurements between Palmer Station, Antarctica (L = 2.4, 50°S invariant latitude) and the THEMIS spacecraft from June 2008 through May 2010, during solar minimum. Using an autoregressive multiple regression model, we show that in the local time sector from 00 < MLT < 12, when the ionosphere above Palmer Station is in darkness and hiss is observed at Palmer, the amplitude of plasmaspheric hiss observed by the THEMIS spacecraft is 1.4 times higher than when hiss is not observed at Palmer. In the same local time sector when the ground station is in daylight and hiss is observed, the THEMIS observed amplitudes are not significantly different from those when hiss is not observed on the ground. A stronger relationship is found in the local time sector from 12 < MLT < 24 where, when Palmer is in daylight and hiss is observed, THEMIS plasmaspheric hiss amplitudes are 2 times higher compared to when hiss is not observed at Palmer

  14. Stimulated Brillouin scattering in the field of a two-dimensionally localized pumping wave

    NASA Astrophysics Data System (ADS)

    Solikhov, D. K.; Dvinin, S. A.

    2016-06-01

    Stimulated Brillouin scattering of electromagnetic waves in the field of a two-dimensionally localized pump wave at arbitrary scattering angles in the regime of forward scattering is analyzed. Spatial variations in the amplitudes of interacting waves are studied for different values of the pump field and different dimensions of the pump wave localization region. The intensity of scattered radiation is determined as a function of the scattering angle and the dimensions of the pump wave localization region. It is shown that the intensity increases with increasing scattering angle.

  15. QCD amplitudes with 2 initial spacelike legs via generalised BCFW recursion

    NASA Astrophysics Data System (ADS)

    Kutak, Krzysztof; van Hameren, Andreas; Serino, Mirko

    2017-02-01

    We complete the generalisation of the BCFW recursion relation to the off-shell case, allowing for the computation of tree level scattering amplitudes for full High Energy Factorisation (HEF), i.e. with both incoming partons having a non-vanishing transverse momentum. We provide explicit results for color-ordered amplitudes with two off-shell legs in massless QCD up to 4 point, continuing the program begun in two previous papers. For the 4-fermion amplitudes, which are not BCFW-recursible, we perform a diagrammatic computation, so as to offer a complete set of expressions. We explicitly show and discuss some plots of the squared 2 → 2 matrix elements as functions of the differences in rapidity and azimuthal angle of the final state particles.

  16. 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.

  17. 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.

  18. Travel-Time and Amplitude Sensitivity Kernels

    DTIC Science & Technology

    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

  19. 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…

  20. Realizing total reciprocity violation in the phase for photon scattering.

    PubMed

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-22

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

  1. Realizing total reciprocity violation in the phase for photon scattering

    PubMed Central

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-01-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices. PMID:28225031

  2. Realizing total reciprocity violation in the phase for photon scattering

    NASA Astrophysics Data System (ADS)

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

  3. Manifest Ultraviolet Behavior in the Three-Loop Four-Point Amplitude of N=8 Supergravity

    SciTech Connect

    Bern, Z.; Carrasco, J.J.M.; Dixon, L.J.; Johansson, H.; Roiban, R.; /Penn State U.

    2008-09-03

    Using the method of maximal cuts, we obtain a form of the three-loop four-point scattering amplitude of N = 8 supergravity in which all ultraviolet cancellations are made manifest. The Feynman loop integrals that appear have a graphical representation with only cubic vertices, and numerator factors that are quadratic in the loop momenta, rather than quartic as in the previous form. This quadratic behavior reflects cancellations beyond those required for finiteness, and matches the quadratic behavior of the three-loop four-point scattering amplitude in N = 4 super-Yang-Mills theory. By direct integration we confirm that no additional cancellations remain in the N = 8 supergravity amplitude, thus demonstrating that the critical dimension in which the first ultraviolet divergence occurs at three loops is D{sub c} = 6. We also give the values of the three-loop divergences in D = 7, 9, 11. In addition, we present the explicitly color-dressed three-loop four-point amplitude of N = 4 super-Yang-Mills theory.

  4. Roy-Steiner equations for πN scattering

    NASA Astrophysics Data System (ADS)

    de Elvira, J. Ruiz; Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.

    2015-10-01

    In this talk, we briefly review our ongoing collaboration to precisely determine the low-energy πN scattering amplitude by means of Roy-Steiner equations. After giving a brief overview of this system of dispersive equations and their application to πN scattering, we proceed to solve for the lower partial waves of the s-channel (πN → πN) and the t-channel l( {π π to bar NN} right) sub-problems.

  5. Photoacoustic Doppler flow measurement in optically scattering media

    NASA Astrophysics Data System (ADS)

    Fang, Hui; Maslov, Konstantin; Wang, Lihong V.

    2007-12-01

    We recently observed the photoacoustic Doppler effect from flowing small light-absorbing particles. Here, we apply the effect to measure blood-mimicking fluid flow in an optically scattering medium. The light scattering in the medium decreases the amplitude of the photoacoustic Doppler signal but does not affect either the magnitude or the directional discrimination of the photoacoustic Doppler shift. This technology may hold promise for a new Doppler method for measuring blood flow in microcirculation with high sensitivity.

  6. Strong WW scattering chiral lagrangians, unitarity and resonances

    SciTech Connect

    Pelaez, J.R.

    1996-08-01

    Chiral lagrangians provide a model independent description of the strongly interacting symmetry breaking sector. In this work, first we review the LHC sensitivity to the chiral parameters (in the hardest case of non-resonant low-energy WW scattering). Later we show how to reproduce or predict the resonance spectrum by means of dispersion theory and the inverse amplitude method. We present a parameter space scan that covers many different strong WW scattering scenarios.

  7. Speckle-learning-based object recognition through scattering media.

    PubMed

    Ando, Takamasa; Horisaki, Ryoichi; Tanida, Jun

    2015-12-28

    We experimentally demonstrated object recognition through scattering media based on direct machine learning of a number of speckle intensity images. In the experiments, speckle intensity images of amplitude or phase objects on a spatial light modulator between scattering plates were captured by a camera. We used the support vector machine for binary classification of the captured speckle intensity images of face and non-face data. The experimental results showed that speckles are sufficient for machine learning.

  8. Beam normal spin asymmetry in elastic lepton-nucleon scattering

    SciTech Connect

    M. Gorchtein; P.A.M. Guichon; M. Vanderhaeghen

    2004-04-01

    We discuss the two-photon exchange contribution to observables which involve lepton helicity flip in elastic lepton-nucleon scattering. This contribution is accessed through the spin asymmetry for a lepton beam polarized normal to the scattering plane. We estimate this beam normal spin asymmetry at large momentum transfer using a parton model and we express the corresponding amplitude in terms of generalized parton distributions.

  9. Effects of periodic forcing in chaotic scattering.

    PubMed

    Blesa, Fernando; Seoane, Jesús M; Barrio, Roberto; Sanjuán, Miguel A F

    2014-04-01

    The effects of a periodic forcing on chaotic scattering are relevant in certain situations of physical interest. We investigate the effects of the forcing amplitude and the external frequency in both the survival probability of the particles in the scattering region and the exit basins associated to phase space. We have found an exponential decay law for the survival probability of the particles in the scattering region. A resonant-like behavior is uncovered where the critical values of the frequencies ω≃1 and ω≃2 permit the particles to escape faster than for other different values. On the other hand, the computation of the exit basins in phase space reveals the existence of Wada basins depending of the frequency values. We provide some heuristic arguments that are in good agreement with the numerical results. Our results are expected to be relevant for physical phenomena such as the effect of companion galaxies, among others.

  10. Focusing of particles scattered by a surface

    NASA Astrophysics Data System (ADS)

    Babenko, P. Yu.; Zinov'ev, A. N.; Shergin, A. P.

    2015-06-01

    It has been shown by computer simulation that the coefficient of reflection of argon atoms scattered by crystalline aluminum and germanium targets at glancing angles of less than 4° is close to unity and the beam of scattered particles exhibits focusing (the angular distributions of particles are strongly compressed). Whereas beam focusing with respect to the azimuth is well known and has already been studied, sharp focusing in the surface-normal direction at small glancing angles has not been studied so far. This effect is confirmed by the experimental results. It is associated with multiple scattering of incident particles by the atomic chain. The simulation results allowed finding quite accurately the amplitude of thermal vibrations of surface atoms ((0.123 ± 0.007) Å for aluminum), which agrees well with the experiment.

  11. Multipole radiation in charged-particle scattering

    NASA Technical Reports Server (NTRS)

    Gould, Robert J.

    1990-01-01

    This paper formulates the general problem of photon emission in particle scattering using a classical and quantum mechanical approach. The connection between the classical short collision time (SCT) and Born results is examined for various special classifications of problems. In the dipole case the two formulations yield results that can be expressed in the same form and for arbitrary scattering potential. For quadrupole emission the SCT and Born results are the same only for a short-range potential, however. The quadrupole problem is more sensitive to details in the process because the calculation requires an expansion of the total amplitude for the process to lowest order in the photon wave number or momentum. The special case of photon emission associated with spin-flip transitions during scattering is considered for spin-1/2 particles. Like classical magnetic dipole radiation, there is no infrared divergence feature for this type of emission.

  12. True and false symmetries in the classification of optical scatterers

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni F.; Videen, Gorden

    2014-05-01

    A plane wave is scattered by a potential of bounded support. Translation, rotation and reflection of the potential, q0 induce transformations of the scattered wave. The latter can be represented by means of Born sequences, where q0 appears under the integral sign: non-local formulas are thus derived, the properties of which are discussed. Next, the symmetries induced by the 1st BORN approximation are addressed. Invariance of the squared modulus of the scattering amplitude holds for translation and reflection. The transformation Tɛ := 13 +Σ3ℓ=1ɛℓAℓ, with {ɛℓ;} real and {Aℓ} the generators of rotations in IR3, is investigated. Conditions on the {ɛ ℓ} are derived, by which the scattering amplitude coming from the first BORN approximation is invariant to Tɛ. As an application, these "false symmetries" are compared to those induced by limited angular resolution of a detector in light scattering experiments. Namely, scattering patterns are made available by the TAOS (Two-dimensional Angle-resolved Optical Scattering) method, which consists of detecting single airborne aerosol particles and collecting the intensity of the light they scatter from a pulsed, monochromatic laser beam. The optics and the detector properties determine the resolution at which a pattern is saved. The implications on the performance of TAOS pattern analysis are briefly discussed.

  13. Resonances in Coupled πK-ηK Scattering from Quantum Chromodynamics

    DOE PAGES

    Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; ...

    2014-10-01

    Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled πK, ηK scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.

  14. Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy

    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.

  15. Aharonov-Bohm scattering in Chern-Simons theory of scalar particles

    SciTech Connect

    Boz, M.; Fainberg, V.; Pak, N.K.

    1996-03-15

    The S-matrix operator for relativistic theory of charged scalar particles interacting via Chern-Simon field is constructed and is shown to be formally the same as S-matrix in relativistic scalar quantum electrodynamics in which the Feynman diagrams with external photon lines are not considered and the propagators of the Chern-Simons particles are substituted in place of the ones for photons. All the one-loop Feynman diagrams for relativistic scattering amplitude of two charged particles are calculated. Due to the renormalizabilty of the theory only two diagrams have linear divergence, which are regularized. The nonrelativistic limit of the scattering amplitude is also finite, unlike the non-relativistic Chern-Simons scattering theory. It is found that for a certain value of the contact interaction, corresponding to the repulsive case, the scattering amplitude coincides with that of Aharonov-Bohm scattering, in the same approximation. 20 refs., 2 fig.

  16. Optics as Scattering

    ERIC Educational Resources Information Center

    di Francia, Giuliano Toraldo

    1973-01-01

    The art of deriving information about an object from the radiation it scatters was once limited to visible light. Now due to new techniques, much of the modern physical science research utilizes radiation scattering. (DF)

  17. Constructing QCD one-loop amplitudes

    SciTech Connect

    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

  18. 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.

  19. 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.

  20. High-amplitude, ultrashort strain solitons in solids

    NASA Astrophysics Data System (ADS)

    Muskens, O. L.

    2004-03-01

    In recent years, pressure pulses of very short (picosecond) time duration have found wide application as a diagnostic tool in the semiconductor industry and in fundamental condensed matter research. Next to their application in the studies of nanometer-sized structures, propagation of these short acoustic pulses over millimeter distances at low temperatures has revealed a new field of picosecond acoustics. It has been shown that, for very short strain pulses, phonon dispersion destroys the internal structure of the coherent wavepacket by pulling apart its different frequency components. However, when strain amplitudes are sufficiently increased, a nonlinear pulse-steepening mechanism emerges, that leads to the formation of shock waves. The combined action of the nonlinear and dispersive effects then results in the formation of stable, highly localized solitary waves. In this thesis, we study the development of picosecond pressure pulses into trains of ultrashort acoustic solitons in a bulk crystal. The high-amplitude, bipolar strain wavepackets are generated by femtosecond optical excitation of a thin chromium film evaporated onto the crystal, using high-power optical pulses from an amplified Ti:sapphire laser. Propagation over millimeter distances at low temperatures is studied by means of two complementary experimental methods. First, the development of low-frequency, gigahertz strain components is monitored using Brillouin light-scattering. By monitoring the scattered intensity against traveled distance of the packets, we demonstrate the breakup of the initial single-cycle pulse into an ultrashort acoustic soliton train, reaching transient pressures up to tens of kilobars and soliton widths less than 0.5 picoseconds, corresponding to only several nanometers in the crystal. Further, we show that the ultrashort strain solitons interact coherently with local electronic two-level systems at terahertz frequency, in optically excited ruby. The strain

  1. A method to measure the distance among scatters and the scatters' diameter in artificial composite materials.

    PubMed

    Sun, Li; Ji, Aiming; Hu, Jialing; Zhu, Canyan; Zhang, Lijun; Yang, Jianfeng; Liu, Yongsong; Mao, Ling-Feng

    2016-04-01

    A new method to measure the distance among scatters, the density of scatters, and the scatters' diameter in artificial composite materials has been proposed. This method is based on detecting the reflection amplitude change (amp) of the echo signal reflected from scatters. Simulation results show that such a method is valid for the distance less than four times of the acoustic wavelength, because the coupling between the scatters can be neglected for the distance larger than four times of the acoustic wavelength. Therefore, this new measure method can be always valid by choosing appropriate frequency according to the scaling rule discussed in this paper. At the same time, it is found that the diameter of scatters is the half of the wavelength where the curve peak of the amp vs frequency occurs. It implies that such a new method can also be used to measure the diameter of scatters in solids and liquids, and even in PM2.5 pollution particles in air.

  2. 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.

  3. 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.

  4. Photon Counting Chirped Amplitude Modulation Ladar

    DTIC Science & Technology

    2008-03-01

    22202-4302. Respondents should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to...135 S. Taylor Ave., Room 103, Louisville, CO 80027-3025 14. ABSTRACT This work developed a method using Geiger -mode avalanche photodiode (GM-APD...architecture are discussed. 15. SUBJECT TERMS laser radar, ladar, avalanche photo-detectors, Geiger mode detectors, chirped amplitude modulation

  5. Chiral extrapolation of SU(3) amplitudes

    SciTech Connect

    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}}.

  6. Understanding the amplitudes of noise correlation measurements

    USGS Publications Warehouse

    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.

  7. Scattering from binary optics

    NASA Technical Reports Server (NTRS)

    Ricks, Douglas W.

    1993-01-01

    There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

  8. Zeroing in on Supersymmetric Radiation Amplitude Zeros

    SciTech Connect

    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.

  9. 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.

  10. [Amplitude modulation in sound signals by mammals].

    PubMed

    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.

  11. Application of diffraction tomography theory to determine size and shape of spheroidal particles from light scattering

    NASA Astrophysics Data System (ADS)

    Ding, Chizhu; Yang, Kecheng; Li, Wei; Guo, Wenping; Zhang, Xiaohui; Xia, Min

    2014-10-01

    Discerning the geometry of spheroidal scatterers of micron order is an important topic in identifying marine microbes. Optical diffraction tomography theory indicates that under the first-order Born approximation for weak scattering, scattering amplitude in the far zone and scattering potential of the scatterer have a Fourier relationship. In this paper, we describe a method based on diffraction tomography theory and determine the size and the shape of spheroidal scatterers by reconstructing the distribution of scattering potential from angular resolved scattered field. As a demonstration of this method, the scattering from spheroidal particles with equal-volume-sphere radii of 0.5429, 1.00, and 2.00 μm and an aspect ratio that varies from 0.4 to 1.5 was modeled by using T-matrix theory and used as test data. Simulation results show that in the case of low contrast, size and shape determination can be achieved with sub-wavelength precision.

  12. New strings for old Veneziano amplitudes. II. Group-theoretic treatment

    NASA Astrophysics Data System (ADS)

    Kholodenko, A. L.

    2006-09-01

    In this part of our four parts work we use theory of polynomial invariants of finite pseudo-reflection groups in order to reconstruct both the Veneziano and Veneziano-like (tachyon-free) amplitudes and the generating function reproducing these amplitudes. We demonstrate that such generating function and amplitudes associated with it can be recovered with help of finite dimensional exactly solvableN=2 supersymmetric quantum mechanical model known earlier from works of Witten, Stone and others. Using the Lefschetz isomorphism theorem we replace traditional supersymmetric calculations by the group-theoretic thus solving the Veneziano model exactly using standard methods of representation theory. Mathematical correctness of our arguments relies on important theorems by Shepard and Todd, Serre and Solomon proven respectively in the early 50s and 60s and documented in the monograph by Bourbaki. Based on these theorems, we explain why the developed formalism leaves all known results of conformal field theories unchanged. We also explain why these theorems impose stringent requirements connecting analytical properties of scattering amplitudes with symmetries of space-time in which such amplitudes act.

  13. Amplitude Scintillation due to Atmospheric Turbulence for the Deep Space Network Ka-Band Downlink

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wheelon, A.

    2004-01-01

    Fast amplitude variations due to atmospheric scintillation are the main concerns for the Deep Space Network (DSN) Ka-band downlink under clear weather conditions. A theoretical study of the amplitude scintillation variances for a finite aperture antenna is presented. Amplitude variances for weak scattering scenarios are examined using turbulence theory to describe atmospheric irregularities. We first apply the Kolmogorov turbulent spectrum to a point receiver for three different turbulent profile models, especially for an exponential model varying with altitude. These analytic solutions then are extended to a receiver with a finite aperture antenna for the three profile models. Smoothing effects of antenna aperture are expressed by gain factors. A group of scaling factor relations is derived to show the dependences of amplitude variances on signal wavelength, antenna size, and elevation angle. Finally, we use these analytic solutions to estimate the scintillation intensity for a DSN Goldstone 34-m receiving station. We find that the (rms) amplitude fluctuation is 0.13 dB at 20-deg elevation angle for an exponential model, while the fluctuation is 0.05 dB at 90 deg. These results will aid us in telecommunication system design and signal-fading prediction. They also provide a theoretical basis for further comparison with other measurements at Ka-band.

  14. Scattered P'P' waves observed at short distances

    USGS Publications Warehouse

    Earle, Paul S.; Rost, Sebastian; Shearer, Peter M.; Thomas, Christine

    2011-01-01

    We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (ρt, ρr) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P′•d•P′, which can scatter from any depth, d, in the mantle.

  15. Isospin odd @pK scattering length [rapid communication

    NASA Astrophysics Data System (ADS)

    Schweizer, J.

    2005-10-01

    We make use of the chiral two-loop representation of the πK scattering amplitude [J. Bijnens, P. Dhonte, P. Talavera, JHEP 0405 (2004) 036] to investigate the isospin odd scattering length at next-to-next-to-leading order in the SU (3) expansion. This scattering length is protected against contributions of ms in the chiral expansion, in the sense that the corrections to the current algebra result are of order Mπ2. In view of the planned lifetime measurement on πK atoms at CERN it is important to understand the size of these corrections.

  16. Electromagnetic model based SAR ATR through attributed scatterers

    NASA Astrophysics Data System (ADS)

    Ma, Conghui; Wen, Gongjian; Gao, Feng; Huang, Xiaohong; Yang, Xiaoliang

    2016-10-01

    Electromagnetic model (em-model) provides a concise and physically relevant description of target through representative scatterers. In a forward built em-model, detailed information about each scatterer's position, scattering amplitude along with its provenance can be predicted. This makes em-model a good candidate for use in synthetic aperture radar (SAR) automatic target recognition (ATR). In this paper, we introduce scatterers' provenance as attributed information into target recognition, and an attributed em-model based target recognition method is proposed. Firstly, according to the purpose of ATR, each scatterer in em-model is endowed with an importance factor based on its provenance. Secondly, a detection is implemented to decide whether the em-model predicted scatterer has a corresponding scatterer in measured data. If the scatterer exist in measured target, evaluate how similar the scatterer pair resembled with each other. Next, similarities of all the scatterer pairs are synthesized as a whole match score between em-model and SAR data. In the synthesis, the importance factor servers as a weighting factor that scatterer with more attention will be more discriminative for recognition. In the end, target in measured SAR data is recognized as the model type or not based on the match score. The novelty of this method comes from taking into account of the provenance information of scatterers as attributed information and endowing the scatterers with different important factors according to their importance in recognition. This makes the attributed scatterer based recognition method pertinent to the purpose of ATR. Experiments on simulated Tank SAR data that produced by a high frequency electromagnetic simulation software verified the effectiveness of this method.

  17. Two-Photon Exchange in Elastic Electron-Proton Scattering: A QCD Factorization Approach

    SciTech Connect

    Kivel, Nikolai; Vanderhaeghen, Marc

    2009-08-28

    We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer Q{sup 2}. It is shown that the leading two-photon exchange amplitude behaves as 1/Q{sup 4}, and can be expressed in a model independent way in terms of the leading twist nucleon distribution amplitudes. Using several models for the nucleon distribution amplitudes, we provide estimates for existing data and for ongoing experiments.

  18. High energy parton-parton elastic scattering in QCD

    SciTech Connect

    Tang, W.K.

    1993-08-01

    We show that the high energy limit of quark-quark, or gluon-gluon, elastic scattering is calculable in terms of the BFKL pomeron when {minus}t {much_gt} {Lambda}{sub QCD}{sup 2}. Surprisingly, this on-shell amplitudes does not have infrared divergences in the high energy limit.

  19. Multiple scattering technique lidar

    NASA Technical Reports Server (NTRS)

    Bissonnette, Luc R.

    1992-01-01

    The Bernouilli-Ricatti equation is based on the single scattering description of the lidar backscatter return. In practice, especially in low visibility conditions, the effects of multiple scattering can be significant. Instead of considering these multiple scattering effects as a nuisance, we propose here to use them to help resolve the problems of having to assume a backscatter-to-extinction relation and specifying a boundary value for a position far remote from the lidar station. To this end, we have built a four-field-of-view lidar receiver to measure the multiple scattering contributions. The system has been described in a number of publications that also discuss preliminary results illustrating the multiple scattering effects for various environmental conditions. Reported here are recent advances made in the development of a method of inverting the multiple scattering data for the determination of the aerosol scattering coefficient.

  20. General solution of the scattering equations

    NASA Astrophysics Data System (ADS)

    Dolan, Louise; Goddard, Peter

    2016-10-01

    The scattering equations, originally introduced by Fairlie and Roberts in 1972 and more recently shown by Cachazo, He and Yuan to provide a kinematic basis for describing tree amplitudes for massless particles in arbitrary space-time dimension, have been reformulated in polynomial form. The scattering equations for N particles are equivalent to N - 3 polynomial equations h m = 0, 1 ≤ m ≤ N - 3, in N - 3 variables, where h m has degree m and is linear in the individual variables. Facilitated by this linearity, elimination theory is used to construct a single variable polynomial equation, Δ N = 0, of degree ( N - 3)! determining the solutions. Δ N is the sparse resultant of the system of polynomial scattering equations and it can be identified as the hyperdeterminant of a multidimensional matrix of border format within the terminology of Gel'fand, Kapranov and Zelevinsky. Macaulay's Unmixedness Theorem is used to show that the polynomials of the scattering equations constitute a regular sequence, enabling the Hilbert series of the variety determined by the scattering equations to be calculated, independently showing that they have ( N - 3)! solutions.

  1. Scattering theory without large-distance asymptotics

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Li, Wen-Du; Dai, Wu-Sheng

    2014-06-01

    In conventional scattering theory, to obtain an explicit result, one imposes a precondition that the distance between target and observer is infinite. With the help of this precondition, one can asymptotically replace the Hankel function and the Bessel function with the sine functions so that one can achieve an explicit result. Nevertheless, after such a treatment, the information of the distance between target and observer is inevitably lost. In this paper, we show that such a precondition is not necessary: without losing any information of distance, one can still obtain an explicit result of a scattering rigorously. In other words, we give an rigorous explicit scattering result which contains the information of distance between target and observer. We show that at a finite distance, a modification factor — the Bessel polynomial — appears in the scattering amplitude, and, consequently, the cross section depends on the distance, the outgoing wave-front surface is no longer a sphere, and, besides the phase shift, there is an additional phase (the argument of the Bessel polynomial) appears in the scattering wave function.

  2. Momentum space dipole amplitude for DIS and inclusive hadron production

    SciTech Connect

    Basso, E. A.; Gay Ducati, M. B.; De Oliveira, E. G.

    2013-03-25

    We show how the AGBS model, originally developed for deep inelastic scattering applied to HERA data on the proton structure function, can also describe the RHIC data on single inclusive hadron yield for d+Au and p+p collisions through a new simultaneous fit. The single inclusive hadron production is modeled through the color glass condensate, which uses the quark(and gluon) condensate amplitudes in momentum space. The AGBS model is also a momentum space model based on the asymptotic solutions of the BK equation, although a different definition of the Fourier transform is used. This description entirely in transverse momentum of both processes arises for the first time. The small difference between the simultaneous fit and the one for HERA data alone suggests that the AGBS model describes very well both kind of processes and thus emerges as a good tool to investigate the inclusive hadron production data. We use this model for predictions at LHC energies, which agree quite well with available experimental data.

  3. K-N amplitudes below threshold constrained by multinucleon absorption

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2017-03-01

    Six widely different subthreshold K- N scattering amplitudes obtained in SU(3) chiral-model EFT approaches by fitting to low-energy and threshold data are employed in optical-potential studies of kaonic atoms. Phenomenological terms representing K- multinucleon interactions are added to the EFT-inspired single-nucleon part of the K--nucleus optical potential in order to obtain good fits to kaonic-atom strong-interaction level shifts and widths across the periodic table. Introducing as a further constraint the fractions of single-nucleon K- absorption at rest from old bubble-chamber experiments, it is found that only two of the models considered here reproduce these absorption fractions. Within these two models, the interplay between single-nucleon and multinucleon K- interactions explains features observed previously with fully phenomenological optical potentials. Radial sensitivities of kaonic atom observables are re-examined, and remarks are made on the role of 'subthreshold kinematics' in absorption-at-rest calculations.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Loop-quantum-gravity vertex amplitude.

    PubMed

    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.

  9. Stochastic aspects of nuclear large amplitude motion

    SciTech Connect

    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.

  10. 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.

  11. Nonlinear Generation of Electromagnetic Waves through Induced Scattering by Thermal Plasma

    NASA Astrophysics Data System (ADS)

    Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.

    2015-12-01

    We demonstrate the conversion of electrostatic pump waves into electromagnetic waves through nonlinear induced scattering by thermal particles in a laboratory plasma. Electrostatic waves in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10-6 times the background magnetic field, wave power is scattered below the pump frequency with wave normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered wave has a perpendicular wavelength that is an order of magnitude larger than the pump wave and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered wave normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment.

  12. Nonlinear Generation of Electromagnetic Waves through Induced Scattering by Thermal Plasma

    PubMed Central

    Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.

    2015-01-01

    We demonstrate the conversion of electrostatic pump waves into electromagnetic waves through nonlinear induced scattering by thermal particles in a laboratory plasma. Electrostatic waves in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10−6 times the background magnetic field, wave power is scattered below the pump frequency with wave normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered wave has a perpendicular wavelength that is an order of magnitude larger than the pump wave and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered wave normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment. PMID:26647962

  13. Refraction and scattering of sound by a shear layer

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1980-01-01

    The angle and amplitude changes for acoustic waves refracted by a circular open jet shear layer were determined. The generalized refraction theory was assessed experimentally for on axis and off axis acoustic source locations as source frequency varied from 1 kHz to 10 kHz and free stream Mach number varied from 0.1 to 0.4. Angle and amplitude changes across the shear layer show good agreement with theory. Experiments confirm that the refraction theory is independent of shear layer thickness, acoustic source frequency, and source type. A generalized theory is, thus, available for correcting far field noise data acquired in open jet test facilities. The effect of discrete tone scattering by the open jet turbulent shear layer was also studied. Scattering effects were investigated over the same Mach number range as frequency varied from 5 kHz to 15 kHz. Attenuation of discrete tone amplitude and tone broadening were measured as a function of acoustic source position and radiation angle. Scattering was found to be stronger at angles close to the open jet axis than at 90 deg, and becomes stronger as the acoustic source position shifts downstream. A scattering analysis provided an estimate of the onset of discrete tone scattering.

  14. Investigation of scattering in lunar seismic coda

    NASA Astrophysics Data System (ADS)

    Blanchette-Guertin, J.-F.; Johnson, C. L.; Lawrence, J. F.

    2012-06-01

    We investigate the intrinsic attenuation and scattering properties of the Moon by parameterizing the coda decay of 369 higher-quality lunar seismograms from 72 events via their characteristic rise and decay times. We investigate any dependence of the decay times on source type, frequency, and epicentral distance. Intrinsic attenuation, scattering, and possible focusing of energy in a near-surface, low-velocity layer all contribute to the coda decay. Although it is not possible to quantify the exact contribution of each of these effects in the seismograms, results suggest that scattering in a near-surface global layer dominates the records of shallow events (˜0-200 km depth), particularly at frequencies above 2 Hz, and for increasing epicentral distance. We propose that the scattering layer is the megaregolith and that energy from shallow sources encounters more scatterers as it travels longer distances in the layer, increasing the coda decay times. A size distribution of ejecta blocks that has more small-scale than large-scale scatterers intensifies this effect for increasing frequencies. Deep moonquakes (700-1100 km depth) exhibit no dependence of the decay time on epicentral distance. We suggest that because of their large depths and small amplitudes, deep moonquakes from any distance sample a similar region near a given receiver. Near-station structure and geology may also control the decay times of local events, as evidenced by two natural impact records. This study provides constraints and testable hypotheses for waveform modeling of the lunar interior that includes the effects of intense scattering and shallow, low-velocity layers.

  15. Wrist Proprioception: Amplitude or Position Coding?

    PubMed Central

    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

  16. Small-amplitude synchrotron tune near transition

    SciTech Connect

    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.

  17. 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.

  18. Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

    NASA Technical Reports Server (NTRS)

    Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

    2012-01-01

    One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

  19. Halo-independent methods for inelastic dark matter scattering

    SciTech Connect

    Bozorgnia, Nassim; Schwetz, Thomas; Herrero-Garcia, Juan; Zupan, Jure E-mail: juan.a.herrero@uv.es E-mail: jure.zupan@cern.ch

    2013-07-01

    We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo.

  20. Theory of direct scattering of neutral and charged atoms

    NASA Technical Reports Server (NTRS)

    Franco, V.

    1979-01-01

    The theory for direct elastic and inelastic collisions between composite atomic systems formulated within the framework of the Glauber approximation is presented. It is shown that the phase-shift function is the sum of a point Coulomb contribution and of an expression in terms of the known electron-hydrogen-atom and proton-hydrogen-atom phase shift function. The scattering amplitude is reexpressed, the pure Coulomb scattering in the case of elastic collisions between ions is isolated, and the exact optical profile function is approximated by a first-order expansion in Glauber theory which takes into account some multiple collisions. The approximate optical profile function terms corresponding to interactions involving one and two electrons are obtained in forms of Meijer G functions and as a one-dimensional integral, and for collisions involving one or two neutral atoms, the scattering amplitude is further reduced to a simple closed-form expression.

  1. Scattering process in the Scalar Duffin-Kemmer-Petiau gauge theory

    NASA Astrophysics Data System (ADS)

    Beltran, J.; Pimentel, B. M.; Soto, D. E.

    2016-04-01

    In this work we calculate the cross section of the scattering process of the Duffin-Kemmer-Petiau theory coupling with the Maxwell’s electromagnetic field. Specifically, we find the propagator of the free theory, the scattering amplitudes and cross sections at Born level for the Moeller and Compton scattering process of this model. For this purpose we use the analytic representation for free propagators and take account the framework of the Causal Perturbation Theory of Epstein and Glaser.

  2. Resonance scattering by fish schools: A comparison of two models.

    PubMed

    Raveau, M; Feuillade, C

    2016-01-01

    The effective medium method is used to investigate resonance scattering from schools of fish with gas-filled swim bladders, as a function of frequency and azimuth. Calculations are also performed with a coupled differential equation model, which incorporates both multiple scattering between fish and wave interference interactions of their scattered fields [Feuillade, Nero, and Love, J. Acoust. Soc. Am. 99, 196-208 (1996)]. A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect. Good agreement is also seen in back scattering at low frequencies, where the wavelength λ≥4s, and s is the average nearest neighbor fish separation. If λ<4s, the models diverge in back scattering, and the effective medium method fails. This can be critically important when migrations of schools to deeper water cause the collective resonance frequency to increase. Multiple scattering interactions are negligible when |4πnf(b)(2)/k|⪅0.01, where n is the fish number density, f(b) is the individual fish scattering amplitude, and k=2π/λ. A comparison with forward scattering data shows very good agreement for both models, and indicates a method for estimating fish abundance. For back scattering data, the effective medium method diverges strongly when λ<4s.

  3. 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.

  4. 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.

  5. Multigluon scattering in open superstring theory

    SciTech Connect

    Stieberger, Stephan; Taylor, Tomasz R.

    2006-12-15

    We discuss the amplitudes describing N-gluon scattering in type I superstring theory, on a disk world sheet. After reviewing the general structure of amplitudes and the complications created by the presence of a large number of vertices at the boundary, we focus on the most promising case of maximally helicity violating (MHV) configurations because in this case, the zero Regge slope limit ({alpha}{sup '}{yields}0) is particularly simple. We obtain the full-fledged MHV disk amplitudes for N=4, 5, and N=6 gluons, expressed in terms of one, two and six functions of kinematic invariants, respectively. These functions represent certain boundary integrals--generalized Euler integrals--which for N{>=}6 correspond to multiple hypergeometric series (generalized Kampe de Feriet functions). Their {alpha}{sup '} expansions lead to Euler-Zagier sums. For arbitrary N, we show that the leading string corrections to the Yang-Mills amplitude, of order O({alpha}{sup '2}), originate from the well-known {alpha}{sup '2} TrF{sup 4} effective interactions of four gauge field strength tensors. By using iteration based on the soft gluon limit, we derive a simple formula valid to that order for arbitrary N. We argue that such a procedure can be extended to all orders in {alpha}{sup '}. If nature gracefully picked a sufficiently low string mass scale, our results would be important for studying string effects in multijet production at the Large Hadron Collider (LHC)

  6. Partially strong WW scattering

    SciTech Connect

    Cheung Kingman; Chiang Chengwei; Yuan Tzuchiang

    2008-09-01

    What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the WW scattering. After partial unitarization by the light Higgs boson, the WW scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong WW scattering.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Presynaptic spike broadening reduces junctional potential amplitude.

    PubMed

    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.

  12. Analytic Form of the Two-Loop Planar Five-Gluon All-Plus-Helicity Amplitude in QCD.

    PubMed

    Gehrmann, T; Henn, J M; Lo Presti, N A

    2016-02-12

    Virtual two-loop corrections to scattering amplitudes are a key ingredient to precision physics at collider experiments. We compute the full set of planar master integrals relevant to five-point functions in massless QCD, and use these to derive an analytical expression for the two-loop five-gluon all-plus-helicity amplitude. After subtracting terms that are related to the universal infrared and ultraviolet pole structure, we obtain a remarkably simple and compact finite remainder function, consisting only of dilogarithms.

  13. Involution-dependent constants and the cancellation of divergences in the one-loop open-string amplitude

    SciTech Connect

    Nagao, G.

    1988-07-15

    We recalculate the bosonic one-loop open-string scattering amplitude using the results of the bosonic one-loop closed-string amplitude. The results show explicitly how the cancellation of divergences depends upon a set of involution-dependent constants which relate the torus to the cylinder and Moebius strip. Such a set of involution-dependent constants exists at each loop level and thus provides a means with which to study the cancellation of divergences and the connection between the world sheet and internal symmetries.

  14. Focusing through a turbid medium by amplitude modulation with genetic algorithm

    NASA Astrophysics Data System (ADS)

    Dai, Weijia; Peng, Ligen; Shao, Xiaopeng

    2014-05-01

    Multiple scattering of light in opaque materials such as white paint and human tissue forms a volume speckle field, will greatly reduce the imaging depth and degrade the imaging quality. A novel approach is proposed to focus light through a turbid medium using amplitude modulation with genetic algorithm (GA) from speckle patterns. Compared with phase modulation method, amplitude modulation approach, in which the each element of spatial light modulator (SLM) is either zero or one, is much easier to achieve. Theoretical and experimental results show that, the advantage of GA is more suitable for low the signal to noise ratio (SNR) environments in comparison to the existing amplitude control algorithms such as binary amplitude modulation. The circular Gaussian distribution model and Rayleigh Sommerfeld diffraction theory are employed in our simulations to describe the turbid medium and light propagation between optical devices, respectively. It is demonstrated that the GA technique can achieve a higher overall enhancement, and converge much faster than others, and outperform all algorithms at high noise. Focusing through a turbid medium has potential in the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  15. Two-pion-exchange potential and the {pi}{ital N} amplitude

    SciTech Connect

    Pena, M.T.; Gross, F.; Surya, Y.

    1996-11-01

    We discuss the two-pion-exchange (TPE) potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant {pi}{ital N} scattering amplitude which includes {Delta}, Roper, and {ital D}{sub 13} isobars, as well as contact terms and off-shell (nonpole) dressed nucleon terms. The {pi}{ital N} amplitude satisfies chiral symmetry constraints and fits {pi}{ital N} data below {approximately} 700 MeV pion energy. We find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit {ital NN} data below the pion production threshold. {copyright} {ital 1996 The American Physical Society.}

  16. Tissue characterization of skin ulcer for bacterial infection by multiple statistical analysis of echo amplitude envelope

    NASA Astrophysics Data System (ADS)

    Omura, Masaaki; Yoshida, Kenji; Kohta, Masushi; Kubo, Takabumi; Ishiguro, Toshimichi; Kobayashi, Kazuto; Hozumi, Naohiro; Yamaguchi, Tadashi

    2016-07-01

    To characterize skin ulcers for bacterial infection, quantitative ultrasound (QUS) parameters were estimated by the multiple statistical analysis of the echo amplitude envelope based on both Weibull and generalized gamma distributions and the ratio of mean to standard deviation of the echo amplitude envelope. Measurement objects were three rat models (noninfection, critical colonization, and infection models). Ultrasound data were acquired using a modified ultrasonic diagnosis system with a center frequency of 11 MHz. In parallel, histopathological images and two-dimensional map of speed of sound (SoS) were observed. It was possible to detect typical tissue characteristics such as infection by focusing on the relationship of QUS parameters and to indicate the characteristic differences that were consistent with the scatterer structure. Additionally, the histopathological characteristics and SoS of noninfected and infected tissues were matched to the characteristics of QUS parameters in each rat model.

  17. Two-pion exchange potential and the {pi}N amplitude

    SciTech Connect

    M. T. Pena; Franz Gross; Yohanes Surya

    1996-05-01

    The authors discuss the two-pion exchange potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant {pi}N scattering amplitude which includes {Delta}, Roper, and D{sub 13} isobars, as well as contact terms and off-shell (non-pole) dressed nucleon terms. The {pi}N amplitude satisfies chiral symmetry constraints and fits {pi}N data below {approximately} 700 MeV pion energy. They find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit NN data below the pion production threshold.

  18. Reconstruction of Rain Microstructure From Spectrum of Scattering Light

    NASA Astrophysics Data System (ADS)

    Sterlyadkin, V.; Gluschenko, A.

    Night photoregistration of light, scattered by drops had proved that practically all drops oscillate as they fall. As drop oscillation frequency W monotony diminish with drop volume V rise, so different fractions of rain form different parts of spectrum. Thereby it is possible to reconstruct rain microstructure from remote optical measure- ments. In common case the form of spectrum depends not only on drop size distri- bution N(V) but also on oscillation amplitudes function, scattering phase function for oscillating drops and on frequency dependence W(V). The statistical treatment of our field data had shown that average oscillation amplitude rise with drop volume V as , where A is a some constant. This result allows to solve the inverse problem: to re- construct drop size distribution N(V) from the power spectrum of light, scattering by rain. Scattering phase function for nonspherical and oscillating drops was calculated in straight-line approximation. Analysis of optical properties of oscillating water drop had shown some optimal measurement geometry for registration of rain microstruc- ture. For low intensity rains it is reasonable to use the effect of abnormal high modu- lation of light scattered by oscillating drops, which we discovered earlier in laboratory condition and under field measurements. (The effect of abnormal high modulation al- lows us to detect 2-3 mm raindrop deformations from 5 m distance). The results of reconstruction of drop size distributions from spectra of light, scattered by rains are presented and discussed.

  19. Two space scatterer formalism calculation of bulk parameters of thunderclouds

    NASA Technical Reports Server (NTRS)

    Phanord, Dieudonne D.

    1994-01-01

    In a previous study, we used a modified two-space scatterer formalism of Twersky to establish for a cloud modeled as a statistically homogeneous distribution of spherical water droplets, the dispersion relations that determine its bulk propagation numbers and bulk indexes of refraction in terms of the vector equivalent scattering amplitude and the dyadic scattering amplitude of the single water droplet in isolation. The results were specialized to the forward direction of scattering while demanding that the scatterers preserve the incident polarization. We apply this approach to obtain specific numerical values for the macroscopic parameters of the cloud. We work with a cloud of density rho = 100 cm(exp -3), a wavelength lambda = 0.7774 microns, and with spherical water droplets of common radius alpha = 10 microns. In addition, the scattering medium is divided into three parts, the medium outside the cloud, moist air (the medium inside the cloud but outside the droplets), and the medium inside the spherical water droplets. The results of this report are applicable to a cloud of any geometry since the boundary does not interfere with the calculations. Also, it is important to notice the plane wave nature of the incidence wave in the moist atmosphere.

  20. Low energy neutron deuteron scattering to N3LO

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Vanasse, Jared; Springer, Roxanne

    2015-10-01

    We calculate the next-to-next-to-next-to-leading order (N3LO) nd scattering amplitude in the framework of nonrelativistic pionless effective field theory (EFTπ/). This theory is only valid when the typical momentum exchange in the scattering is smaller then the mass of the pion. The power counting parameter for EFTπ/ is the ratio Q/Λπ /, where Q is the typical momentum exchange in the scattering and Λπ / is the EFTπ/ breakdown scale, Λπ / amplitude for nd scattering at leading order requires summing an infinite set of diagrams. The first nonzero polarization-dependent observables occur at N2LO. At N3LO new 2-body forces appear, which introduce four new EFTπ/ coefficients. These coefficients are fixed by the 3PJ and 1P1 phase shifts of NN scattering. We find that these terms have an important impact. The results of this calculation at N3LO will be important for understanding spin polarization observables in nd scattering, in particular the longstanding Ay puzzle. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics, under Award Number DE-FG02-05ER41368.

  1. Scattering of matter waves in spatially inhomogeneous environments

    SciTech Connect

    Tsitoura, F.; Krüger, P.; Kevrekidis, P. G.; Frantzeskakis, D. J.

    2015-03-30

    In this article, we study scattering of quasi-one-dimensional matter waves at an interface of two spatial domains, one with repulsive and one with attractive interatomic interactions. It is shown that the incidence of a Gaussian wave packet from the repulsive to the attractive region gives rise to generation of a soliton train. More specifically, the number of emergent solitons can be controlled, e.g., by the variation of the amplitude or the width of the incoming wave packet. Furthermore, we study the reflectivity of a soliton incident from the attractive region to the repulsive one. We find the reflection coefficient numerically and employ analytical methods, which treat the soliton as a particle (for moderate and large amplitudes) or a quasilinear wave packet (for small amplitudes), to determine the critical soliton momentum (as a function of the soliton amplitude) for which total reflection is observed.

  2. Scattering of matter waves in spatially inhomogeneous environments

    DOE PAGES

    Tsitoura, F.; Krüger, P.; Kevrekidis, P. G.; ...

    2015-03-30

    In this article, we study scattering of quasi-one-dimensional matter waves at an interface of two spatial domains, one with repulsive and one with attractive interatomic interactions. It is shown that the incidence of a Gaussian wave packet from the repulsive to the attractive region gives rise to generation of a soliton train. More specifically, the number of emergent solitons can be controlled, e.g., by the variation of the amplitude or the width of the incoming wave packet. Furthermore, we study the reflectivity of a soliton incident from the attractive region to the repulsive one. We find the reflection coefficient numericallymore » and employ analytical methods, which treat the soliton as a particle (for moderate and large amplitudes) or a quasilinear wave packet (for small amplitudes), to determine the critical soliton momentum (as a function of the soliton amplitude) for which total reflection is observed.« less

  3. Quadratic electroweak corrections for polarized Moller scattering

    SciTech Connect

    A. Aleksejevs, S. Barkanova, Y. Kolomensky, E. Kuraev, V. Zykunov

    2012-01-01

    The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity violating electron-electron scattering asymmetry induced by squaring one-loop diagrams. The calculations are relevant for the ultra-precise 11 GeV MOLLER experiment planned at Jefferson Laboratory and experiments at high-energy future electron colliders. The imaginary parts of the amplitudes are taken into consideration consistently in both the infrared-finite and divergent terms. The size of the obtained partial correction is significant, which indicates a need for a complete study of the two-loop electroweak radiative corrections in order to meet the precision goals of future experiments.

  4. Systematics of meson-Skyrmion scattering

    SciTech Connect

    Mattis, M.P.

    1986-02-01

    The S-matrix characterizing the scattering of pions from nucleons is calculated in the context of skyrmion models of the nucleon. These are models in which the nucleon is considered a soliton in the field of pions. The spectrum of nucleon and delta resonances in the Skyrme model is calculated and found to be in overall good agreement with Nature. Model-independent sum rules between amplitudes in the same partial wave are derived and examined. An extension of the formalism to the case of three light flavors is presented. 31 refs., 26 figs., 6 tabs.

  5. Deeply Virtual Compton Scattering off the Neutron

    SciTech Connect

    Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E.

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e{sup '}{gamma})X cross section measured at Q{sup 2}=1.9 GeV{sup 2} and x{sub B}=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E{sub q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  6. Optical scatter: an overview

    NASA Astrophysics Data System (ADS)

    Stover, John C.

    1991-12-01

    Optical scatter is a bothersome source of optical noise, limits resolution and reduces system throughput. However, it is also an extremely sensitive metrology tool. It is employed in a wide variety of applications in the optics industry (where direct scatter measurement is of concern) and is becoming a popular indirect measurement in other industries where its measurement in some form is an indicator of another component property - like roughness, contamination or position. This paper presents a brief review of the current state of this technology as it emerges from university and government laboratories into more general industry use. The bidirectional scatter distribution function (or BSDF) has become the common format for expressing scatter data and is now used almost universally. Measurements made at dozens of laboratories around the country cover the spectrum from the uv to the mid- IR. Data analysis of optical component scatter has progressed to the point where a variety of analysis tools are becoming available for discriminating between the various sources of scatter. Work has progressed on the analysis of rough surface scatter and the application of these techniques to some challenging problems outside the optical industry. Scatter metrology is acquiring standards and formal test procedures. The available scatter data base is rapidly expanding as the number and sophistication of measurement facilities increases. Scatter from contaminants is continuing to be a major area of work as scatterometers appear in vacuum chambers at various laboratories across the country. Another area of research driven by space applications is understanding the non-topographic sources of mid-IR scatter that are associated with Beryllium and other materials. The current flurry of work in this growing area of metrology can be expected to continue for several more years and to further expand to applications in other industries.

  7. Characterization of Source and Wave Propagation Effects of Volcano-seismic Events and Tremor Using the Amplitude Source Location Method

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Londono, J. M.; López, C. M.; Ruiz, M. C.; Mothes, P. A.; Maeda, Y.

    2015-12-01

    We propose application of the amplitude source location (ASL) method to characterize source and wave propagation effects of volcano-seismic events and tremor observed at different volcanoes. We used this method to estimate the source location and source amplitude from high-frequency (5-10 Hz) seismic amplitudes under the assumption of isotropic S-wave radiation. We estimated the cumulative source amplitude (Is) as the offset value of the time-integrated envelope of the vertical seismogram corrected for geometrical spreading and medium attenuation in the 5-10 Hz band. We studied these parameters of tremor signals associated with eruptions and explosion events at Tungurahua volcano, Ecuador; long-period (LP) events at Cotopaxi volcano, Ecuador; and LP events at Nevado del Ruiz volcano, Colombia. We identified two types of eruption tremor at Tungurahua; noise-like inharmonic waveforms and harmonic oscillatory signals. We found that Is increased linearly with increasing source amplitude for explosion events and LP events, and that Is increased exponentially with increasing source amplitude for inharmonic eruption tremor signals. The source characteristics of harmonic eruption tremor signals differed from those of inharmonic tremor signals. The Is values we estimated for inharmonic eruption tremor were consistent with previous estimates of volumes of tephra fallout. The linear relationship between the source amplitude and Is for LP events can be explained by the wave propagation effects in the diffusion model for multiple scattering assuming a diffusion coefficient of 105 m2/s and an intrinsic Q factor of around 50. The resultant mean free path is approximately 100 m. Our results suggest that Cotopaxi and Nevado del Ruiz volcanoes have similar highly scattering and attenuating structures. Our approach provides a systematic way to compare the size of volcano-seismic signals observed at different volcanoes. The scaling relations among source parameters that we identified

  8. Multiphoton Amplitudes and Generalized LKF Transformation in Scalar QED Using the Worldline Formalism

    NASA Astrophysics Data System (ADS)

    Ahmadiniaz, N.; Bashir, A.; Schubert, C.

    2017-03-01

    We apply the worldline formalism to scalar quantum electrodynamics (QED) to find a Bern-Kosower type master formula for generalized Compton scattering, on-shell and off-shell. Moreover, we use it to study the non-perturbative gauge parameter dependence of amplitudes in scalar QED and, as our main result, find a simple non-perturbative transformation rule under changes of this parameter in x-space in terms of conformal cross ratios. This generalizes the well-known Landau-Khalatnikov-Fradkin transformation (LKFT). We also exemplify how this generilized LKFT works in perturbation theory.

  9. Bubble nonlinear dynamics and stimulated scattering process

    NASA Astrophysics Data System (ADS)

    Jie, Shi; De-Sen, Yang; Sheng-Guo, Shi; Bo, Hu; Hao-Yang, Zhang; Shi-Yong, Hu

    2016-02-01

    A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller-Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition. Project supported by the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1228) and the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 11204050 and 11204049).

  10. A scattering model for forested area

    NASA Technical Reports Server (NTRS)

    Karam, M. A.; Fung, A. K.

    1988-01-01

    A forested area is modeled as a volume of randomly oriented and distributed disc-shaped, or needle-shaped leaves shading a distribution of branches modeled as randomly oriented finite-length, dielectric cylinders above an irregular soil surface. Since the radii of branches have a wide range of sizes, the model only requires the length of a branch to be large compared with its radius which may be any size relative to the incident wavelength. In addition, the model also assumes the thickness of a disc-shaped leaf or the radius of a needle-shaped leaf is much smaller than the electromagnetic wavelength. The scattering phase matrices for disc, needle, and cylinder are developed in terms of the scattering amplitudes of the corresponding fields which are computed by the forward scattering theorem. These quantities along with the Kirchoff scattering model for a randomly rough surface are used in the standard radiative transfer formulation to compute the backscattering coefficient. Numerical illustrations for the backscattering coefficient are given as a function of the shading factor, incidence angle, leaf orientation distribution, branch orientation distribution, and the number density of leaves. Also illustrated are the properties of the extinction coefficient as a function of leaf and branch orientation distributions. Comparisons are made with measured backscattering coefficients from forested areas reported in the literature.

  11. 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

  12. Feed-forward digital phase and amplitude correction system

    DOEpatents

    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.

  13. Feed-forward digital phase and amplitude correction system

    DOEpatents

    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.

  14. Amplitude interpretation and visualization of three-dimensional reflection data

    SciTech Connect

    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.

  15. Bit-string scattering theory

    SciTech Connect

    Noyes, H.P.

    1990-01-29

    We construct discrete space-time coordinates separated by the Lorentz-invariant intervals h/mc in space and h/mc{sup 2} in time using discrimination (XOR) between pairs of independently generated bit-strings; we prove that if this space is homogeneous and isotropic, it can have only 1, 2 or 3 spacial dimensions once we have related time to a global ordering operator. On this space we construct exact combinatorial expressions for free particle wave functions taking proper account of the interference between indistinguishable alternative paths created by the construction. Because the end-points of the paths are fixed, they specify completed processes; our wave functions are born collapsed''. A convenient way to represent this model is in terms of complex amplitudes whose squares give the probability for a particular set of observable processes to be completed. For distances much greater than h/mc and times much greater than h/mc{sup 2} our wave functions can be approximated by solutions of the free particle Dirac and Klein-Gordon equations. Using a eight-counter paradigm we relate this construction to scattering experiments involving four distinguishable particles, and indicate how this can be used to calculate electromagnetic and weak scattering processes. We derive a non-perturbative formula relating relativistic bound and resonant state energies to mass ratios and coupling constants, equivalent to our earlier derivation of the Bohr relativistic formula for hydrogen. Using the Fermi-Yang model of the pion as a relativistic bound state containing a nucleon-antinucleon pair, we find that (G{sub {pi}N}{sup 2}){sup 2} = (2m{sub N}/m{sub {pi}}){sup 2} {minus} 1. 21 refs., 1 fig.

  16. Scattering characteristics of Lamb waves from debondings at structural features in composite laminates.

    PubMed

    Ng, Ching-Tai; Veidt, Martin

    2012-07-01

    This article investigates the scattering characteristics of Lamb waves from a debonding at a structural feature in a composite laminate. This study specifically focuses on the use of the low frequency fundamental antisymmetric (A(0)) Lamb wave as the incident wave for debonding detection. Three-dimensional finite element (FE) simulations and experimental measurements are used to investigate the scattering phenomena. Good agreement is obtained between the FE simulations and experimental results. Detailed parameter studies are carried out to further investigate the relationship between the scattering amplitudes and debonding sizes. The results show that the amplitude of the scattered A(0) Lamb wave is sensitive to the debonding size, which indicates the potential of using the low frequency A(0) Lamb wave as the interrogating wave for debonding detection and monitoring. The findings of the study provide improved physical insights into the scattering phenomena, which are important to further advance damage detection techniques and optimize transducer networks.

  17. Effect of an electron scattering cloud on X-ray oscillations produced by beaming

    NASA Technical Reports Server (NTRS)

    Brainerd, J.; Lamb, F. K.

    1987-01-01

    The effect of a scattering cloud on the amplitude of oscillations produced by a rotating beam of X-rays is investigated using analytical and Monte Carlo methods. The scattering cloud was modeled as a uniform density sphere, and the source was represented as an anistropic distribution of radiation emerging from a point at the center of the scattering cloud. The intensity distribution produced by the source beam is examined as a function of optical depth. The relation between electron scattering optical depth and the forward-backward ratio is studied. It is observed that the scattering in a central corona of various optical depths reduces the amplitude of the oscillation. The data suggest that the quasi-periodic oscillations observed in the X-ray intensities of some luminous low-mass X-ray binaries are caused by oscillations in the luminosity of the X-ray star.

  18. 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.

  19. Baseline blood oxygenation modulates response amplitude

    PubMed Central

    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

  20. Nonlinear amplitude dynamics in flagellar beating

    PubMed Central

    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.

  1. 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'').

  2. The pulsed amplitude unit for the SLC

    SciTech Connect

    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.

  3. A Rayleigh-Brillouin scattering spectrometer for ultraviolet wavelengths.

    PubMed

    Gu, Ziyu; Vieitez, M Ofelia; van Duijn, Eric-Jan; Ubachs, Wim

    2012-05-01

    A spectrometer for the measurement of spontaneous Rayleigh-Brillouin (RB) scattering line profiles at ultraviolet wavelengths from gas phase molecules has been developed, employing a high-power frequency-stabilized UV-laser with narrow bandwidth (2 MHz). The UV-light from a frequency-doubled titanium:sapphire laser is further amplified in an enhancement cavity, delivering a 5 W UV-beam propagating through the interaction region inside a scattering cell. The design of the RB-scattering cell allows for measurements at gas pressures in the range 0-4 bars and at stably controlled temperatures from -30 °C to 70 °C. A scannable Fabry-Perot analyzer with instrument resolution of 232 MHz probes the RB profiles. Measurements on N(2) and SF(6) gases demonstrate that the high signal-to-noise ratio is achievable with the instrument at the 1% level at the peak amplitude of the scattering profile.

  4. Learning from the scatter in type ia supernovae

    SciTech Connect

    Dodelson, Scott; Vallinotto, Alberto; /Fermilab /Chicago U.

    2005-11-01

    Type Ia Supernovae are standard candles so their mean apparent magnitude has been exploited to learn about the redshift-distance relationship. Besides intrinsic scatter in this standard candle, additional scatter is caused by gravitational magnification by large scale structure. Here they probe the dependence of this dispersion on cosmological parameters and show that information about the amplitude of clustering, {sigma}{sub s}, is contained in the scatter. In principle, it will be possible to constrain {sigma}{sub s} to within 5% with observations of 2000 Type Ia Supernovae. They identify three sources of systematic error--evolution of intrinsic scatter, baryon contributions to lensing, and non-Gaussianity of lensing--which will make this measurement difficult.

  5. Nonreciprocal wave scattering on nonlinear string-coupled oscillators

    SciTech Connect

    Lepri, Stefano; Pikovsky, Arkady

    2014-12-01

    We study scattering of a periodic wave in a string on two lumped oscillators attached to it. The equations can be represented as a driven (by the incident wave) dissipative (due to radiation losses) system of delay differential equations of neutral type. Nonlinearity of oscillators makes the scattering non-reciprocal: The same wave is transmitted differently in two directions. Periodic regimes of scattering are analyzed approximately, using amplitude equation approach. We show that this setup can act as a nonreciprocal modulator via Hopf bifurcations of the steady solutions. Numerical simulations of the full system reveal nontrivial regimes of quasiperiodic and chaotic scattering. Moreover, a regime of a “chaotic diode,” where transmission is periodic in one direction and chaotic in the opposite one, is reported.

  6. Progress in three-particle scattering from LQCD

    NASA Astrophysics Data System (ADS)

    Briceño, Raúl A.; Hansen, Maxwell T.; Sharpe, Stephen R.

    2017-03-01

    We present the status of our formalism for extracting three-particle scattering observables from lattice QCD (LQCD). The method relies on relating the discrete finitevolume energy spectrum of a quantum field theory with its scattering amplitudes. As the finite-volume spectrum can be directly determined in LQCD, this provides a method for determining scattering observables, and associated resonance properties, from the underlying theory. In a pair of papers published over the last two years, two of us have extended this approach to apply to relativistic three-particle scattering states. In this talk we summarize recent progress in checking and further extending this result. We describe an extension of the formalism to include systems in which two-to-three transitions can occur. We then present a check of the previously published formalism, in which we reproduce the known finite-volume energy shift of a three-particle bound state.

  7. Path integral approach to electron scattering in classical electromagnetic potential

    NASA Astrophysics Data System (ADS)

    Chuang, Xu; Feng, Feng; Ying-Jun, Li

    2016-05-01

    As is known to all, the electron scattering in classical electromagnetic potential is one of the most widespread applications of quantum theory. Nevertheless, many discussions about electron scattering are based upon single-particle Schrodinger equation or Dirac equation in quantum mechanics rather than the method of quantum field theory. In this paper, by using the path integral approach of quantum field theory, we perturbatively evaluate the scattering amplitude up to the second order for the electron scattering by the classical electromagnetic potential. The results we derive are convenient to apply to all sorts of potential forms. Furthermore, by means of the obtained results, we give explicit calculations for the one-dimensional electric potential. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374360, 11405266, and 11505285) and the National Basic Research Program of China (Grant No. 2013CBA01504).

  8. Scattering Matrix for the Interaction between Solar Acoustic Waves and Sunspots. I. Measurements

    NASA Astrophysics Data System (ADS)

    Yang, Ming-Hsu; Chou, Dean-Yi; Zhao, Hui

    2017-01-01

    Assessing the interaction between solar acoustic waves and sunspots is a scattering problem. The scattering matrix elements are the most commonly used measured quantities to describe scattering problems. We use the wavefunctions of scattered waves of NOAAs 11084 and 11092 measured in the previous study to compute the scattering matrix elements, with plane waves as the basis. The measured scattered wavefunction is from the incident wave of radial order n to the wave of another radial order n‧, for n=0{--}5. For a time-independent sunspot, there is no mode mixing between different frequencies. An incident mode is scattered into various modes with different wavenumbers but the same frequency. Working in the frequency domain, we have the individual incident plane-wave mode, which is scattered into various plane-wave modes with the same frequency. This allows us to compute the scattering matrix element between two plane-wave modes for each frequency. Each scattering matrix element is a complex number, representing the transition from the incident mode to another mode. The amplitudes of diagonal elements are larger than those of the off-diagonal elements. The amplitude and phase of the off-diagonal elements are detectable only for n-1≤slant n\\prime ≤slant n+1 and -3{{Δ }}k≤slant δ {k}x≤slant 3{{Δ }}k, where δ {k}x is the change in the transverse component of the wavenumber and Δk = 0.035 rad Mm‑1.

  9. Thomas double scattering in electron capture from oriented molecular hydrogen

    SciTech Connect

    Alston, S.; Brennan, T.; Bannon, F.

    1995-11-01

    Electron capture from hydrogen molecules by protons is treated using the second-order Born approximation. Differential cross sections in an adiabatic-nuclei approximation for specific molecular orientations and for an equally weighted averaging over all orientations are presented for incident energies of 2.5 and 10 MeV. A Hartree-Fock molecular wave function and linearized-propagator approximation are employed to evaluate the amplitude. An approximate factoring of the amplitude into double scattering and diffraction (arising from the two target nuclei) components is shown to give a poor description of high-velocity molecular capture.

  10. Few-body multiple scattering calculations for {sup 6}He on protons

    SciTech Connect

    Al-Khalili, J. S.; Johnson, R. C.; Thompson, I. J.; Crespo, R.; Moro, A. M.

    2007-02-15

    The elastic scattering of the halo nucleus {sup 6}He from a proton target at 717 MeV/nucleon is investigated within three different multiple-scattering formulations of the total transition amplitude. The factorized impulse approximation (FIA) and the fixed scatterer approximation (FSA) of the multiple-scattering expansion are used to evaluate accurately the single-scattering terms and to test the validity of a few-body Glauber approach. The latter also includes terms beyond single scattering and the importance of these terms is investigated. The differential cross section is calculated for proton scattering from {sup 6}He at 717 MeV in inverse kinematics and compared with recent data.

  11. The polynomial form of the scattering equations

    NASA Astrophysics Data System (ADS)

    Dolan, Louise; Goddard, Peter

    2014-07-01

    The scattering equations, recently proposed by Cachazo, He and Yuan as providing a kinematic basis for describing tree amplitudes for massless particles in arbitrary space-time dimension (including scalars, gauge bosons and gravitons), are reformulated in polynomial form. The scattering equations for N particles are shown to be equivalent to a Möbius invariant system of N - 3 equations, m = 0, 2 ≤ m ≤ N - 2, in N variables, where m is a homogeneous polynomial of degree m, with the exceptional property of being linear in each variable taken separately. Fixing the Möbius invariance appropriately, yields polynomial equations h m = 0, 1 ≤ m ≤ N - 3, in N - 3 variables, where h m has degree m. The linearity of the equations in the individual variables facilitates computation, e.g. the elimination of variables to obtain single variable equations determining the solutions. Expressions are given for the tree amplitudes in terms of the m and h m . The extension to the massive case for scalar particles is described and the special case of four dimensional space-time is discussed.

  12. Elastic Compton Scattering from 3He

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Griesshammer, Harald W.; Phillips, Daniel R.; Strandberg, Bruno; McGovern, Judith A.; Shukla, Deepshikha

    2017-01-01

    We study elastic Compton scattering on 3He using chiral effective field theory (χEFT) at photon energies from 60 MeV to approximately 120 MeV. Experiments to measure this process have been proposed for both MAMI at Mainz and the HI γS facility at TUNL. I will present the revised results of a full calculation at third order in the expansion (O (Q3)). The amplitude involves a sum of both one- and two-nucleon Compton-scattering mechanisms. We have recently computed the fourth-order two-nucleon diagrams. The numerical impact they have on the cross-section results will be discussed. I will also present results in which amplitudes used so far are augmented by the leading effects from Δ (1232) degrees of freedom, a step which has already been performed for the proton and deuteron processes. Both cross sections and doubly-polarized asymmetries will be presented, and the sensitivity of these observables to the values of neutron scalar and spin polarizabilities will be assessed. This material is based upon work supported in part by DOE and George Washington University.

  13. On Aharonov-Casher scattering in a CPT-odd Lorentz-violating background

    NASA Astrophysics Data System (ADS)

    Andrade, F. M.; Silva, E. O.; Prudêncio, T.; Filgueiras, C.

    2013-07-01

    The effects of a Lorentz symmetry-violating background vector on Aharonov-Casher scattering in the nonrelativistic limit are considered. Using the self-adjoint extension method, we find that there is additional scattering for any value of the self-adjoint extension parameter and non-zero energy bound states for negative values of this parameter. Expressions for the energy bound states, phase-shift and scattering matrix are explicitly determined in terms of the self-adjoint extension parameter. The expression obtained for the scattering amplitude reveals that the helicity is not conserved in this scenario.

  14. Light scattering by radially inhomogeneous fuel droplets in a high-temperature environment

    NASA Astrophysics Data System (ADS)

    Schneider, Michael; Hirleman, E. Dan; Saleheen, Hasan I.; Chowdhury, Dipakbin Q.; Hill, Steven C.

    1993-05-01

    Light scattering by radially inhomogeneous fuel droplets has been calculated using both geometrical optics (GO) and the exact separation of variables (SV) solutions. The refractive index profiles of the fuel droplets were those calculated by Kneer et al. The GO and SV solutions agree very well in the forward direction (for scattering angles between 30 and 60 degrees), and less well in the backward direction (for scattering angles between 140 and 170 degrees). Both amplitudes and phases of the scattered light are compared. The agreement in the backward direction is much better for 40 micrometers diameter droplets than for 20 micrometers diameter droplets.

  15. Scattering of spin-polarized electron in an Aharonov-Bohm potential

    SciTech Connect

    Khalilov, V.R.; Ho, C.-L.

    2008-05-15

    The scattering of spin-polarized electrons in an Aharonov-Bohm vector potential is considered. We solve the Pauli equation in 3 + 1 dimensions taking into account explicitly the interaction between the three-dimensional spin magnetic moment of electron and magnetic field. Expressions for the scattering amplitude and the cross section are obtained for spin-polarized electron scattered off a flux tube of small radius. It is also shown that bound electron states cannot occur in this quantum system. The scattering problem for the model of a flux tube of zero radius in the Born approximation is briefly discussed.

  16. Scattering state solutions of the Duffin-Kemmer-Petiau equation with the Varshni potential model

    NASA Astrophysics Data System (ADS)

    Oluwadare, O. J.; Oyewumi, K. J.

    2017-02-01

    The scattering state of the Duffin-Kemmer-Petiau equation with the Varshni potential was studied. The asymptotic wave function, the scattering phase shift and normalization constant were obtained for any J states by dealing with the centrifugal term using a suitable approximation. The analytical properties of the scattering amplitude and the bound state energy were obtained and discussed. Our numerical and graphical results indicate that the scattering phase shift depends largely on total angular momentum J , screening parameter β and potential strengths a and b.

  17. Environment scattering in GADRAS.

    SciTech Connect

    Thoreson, Gregory G.; Mitchell, Dean J; Theisen, Lisa Anne; Harding, Lee T.

    2013-09-01

    Radiation transport calculations were performed to compute the angular tallies for scattered gamma-rays as a function of distance, height, and environment. Greens Functions were then used to encapsulate the results a reusable transformation function. The calculations represent the transport of photons throughout scattering surfaces that surround sources and detectors, such as the ground and walls. Utilization of these calculations in GADRAS (Gamma Detector Response and Analysis Software) enables accurate computation of environmental scattering for a variety of environments and source configurations. This capability, which agrees well with numerous experimental benchmark measurements, is now deployed with GADRAS Version 18.2 as the basis for the computation of scattered radiation.

  18. Rayleigh Scattering Diagnostics Workshop

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard (Compiler)

    1996-01-01

    The Rayleigh Scattering Diagnostics Workshop was held July 25-26, 1995 at the NASA Lewis Research Center in Cleveland, Ohio. The purpose of the workshop was to foster timely exchange of information and expertise acquired by researchers and users of laser based Rayleigh scattering diagnostics for aerospace flow facilities and other applications. This Conference Publication includes the 12 technical presentations and transcriptions of the two panel discussions. The first panel was made up of 'users' of optical diagnostics, mainly in aerospace test facilities, and its purpose was to assess areas of potential applications of Rayleigh scattering diagnostics. The second panel was made up of active researchers in Rayleigh scattering diagnostics, and its purpose was to discuss the direction of future work.

  19. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength

    NASA Astrophysics Data System (ADS)

    Lee, Victor; Hawa, Takumi

    2013-09-01

    The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, dm, affects both qdip and qpeak of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the qdip of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized qpeak ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

  20. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength

    SciTech Connect

    Lee, Victor; Hawa, Takumi

    2013-09-28

    The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, d{sub m}, affects both q{sub dip} and q{sub peak} of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the q{sub dip} of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized q{sub peak} ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

  1. Sound scattering in shallow water in presence of internal solitons

    NASA Astrophysics Data System (ADS)

    Katsnelson, Boris G.; Pereselkov, Serguey A.; Petnikov, Valery G.

    2002-05-01

    Sound scattering by localized inhomogeneity (object) in a shallow-water waveguide is studied. Influence of internal solitons (IS) traveling in the sea, on the scattered field is considered. The problem is analyzed within the framework of theory of the sound scattering in the waveguide developed by the authors, where the scattering matrix is expressed through modal decomposition including the scattering amplitude of the object in free space. The peculiarity of the given work is the taking into account of additional modes conversion due to IS. The waveguide and IS are modeled on the basis of experimental data (sound-speed profile, bottom relief, IS parameters, etc.) collected in the Japan Sea. The inhomogeneity is selected in the form of soft spheroids with dimensions characteristic of gray whales (eschrichtius). Calculations of amplitude fluctuations of the low-frequency sound field at the receiving point are carried out for moving spheroid and different orientations of acoustic track with respect to direction of propagation of IS. It is shown that sound fluctuations have essentially different characteristics for longitudinal and transversal propagation of IS. [Work supported by RFBR, Grant No. 00-05-64752.

  2. Positron-rubidium scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.

    1990-01-01

    A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements.

  3. CONTINUOUS ROTATION SCATTERING CHAMBER

    DOEpatents

    Verba, J.W.; Hawrylak, R.A.

    1963-08-01

    An evacuated scattering chamber for use in observing nuclear reaction products produced therein over a wide range of scattering angles from an incoming horizontal beam that bombards a target in the chamber is described. A helically moving member that couples the chamber to a detector permits a rapid and broad change of observation angles without breaching the vacuum in the chamber. Also, small inlet and outlet openings are provided whose size remains substantially constant. (auth)

  4. Microcavity Enhanced Raman Scattering

    NASA Astrophysics Data System (ADS)

    Petrak, Benjamin J.

    Raman scattering can accurately identify molecules by their intrinsic vibrational frequencies, but its notoriously weak scattering efficiency for gases presents a major obstacle to its practical application in gas sensing and analysis. This work explores the use of high finesse (≈50 000) Fabry-Perot microcavities as a means to enhance Raman scattering from gases. A recently demonstrated laser ablation method, which carves out a micromirror template on fused silica--either on a fiber tip or bulk substrates-- was implemented, characterized, and optimized to fabricate concave micromirror templates ˜10 mum diameter and radius of curvature. The fabricated templates were coated with a high-reflectivity dielectric coating by ion-beam sputtering and were assembled into microcavities ˜10 mum long and with a mode volume ˜100 mum 3. A novel gas sensing technique that we refer to as Purcell enhanced Raman scattering (PERS) was demonstrated using the assembled microcavities. PERS works by enhancing the pump laser's intensity through resonant recirculation at one longitudinal mode, while simultaneously, at a second mode at the Stokes frequency, the Purcell effect increases the rate of spontaneous Raman scattering by a change to the intra-cavity photon density of states. PERS was shown to enhance the rate of spontaneous Raman scattering by a factor of 107 compared to the same volume of sample gas in free space scattered into the same solid angle subtended by the cavity. PERS was also shown capable of resolving several Raman bands from different isotopes of CO2 gas for application to isotopic analysis. Finally, the use of the microcavity to enhance coherent anti-Stokes Raman scattering (CARS) from CO2 gas was demonstrated.

  5. High energy bounds on soft mathcal{N} = 4 SYM amplitudes from AdS/CFT

    NASA Astrophysics Data System (ADS)

    Giordano, M.; Peschanski, R.

    2010-05-01

    Using the AdS/CFT correspondence, we study the high-energy behavior of colorless dipole elastic scattering amplitudes in mathcal{N} = 4 SYM gauge theory through the Wilson loop correlator formalism and Euclidean to Minkowskian analytic continuation. The purely elastic behavior obtained at large impact-parameter L, through duality from disconnected AdS 5 minimal surfaces beyond the Gross-Ooguri transition point, is combined with unitarity and analyticity constraints in the central region. In this way we obtain an absolute bound on the high-energy behavior of the forward scattering amplitude due to the graviton interaction between minimal surfaces in the bulk. The dominant “Pomeron” intercept is bounded by α ≤ 11=7 using the AdS/CFT constraint of a weak gravitational field in the bulk. Assuming the elastic eikonal approximation in a larger impact-parameter range gives 4/3 ≤ α ≤ 11/7: The actual intercept becomes 4/3 if one assumes the elastic eikonal approximation within its maximally allowed range L ≳ exp Y/3; where Y is the total rapidity. Subleading AdS/CFT contributions at large impact-parameter due to the other d = 10 supergravity fields are obtained. A divergence in the real part of the tachyonic KK scalar is cured by analyticity but signals the need for a theoretical completion of the AdS/CFT scheme.

  6. E710, Proton, Antiproton Elastic Scattering at Tevatron Energies

    NASA Astrophysics Data System (ADS)

    Sadr, Sasan

    Experiment E710, located at site E0 of the Tevatron collider at Fermilab, was conceived in order to measure pp elastic scattering. The measured parameters were: the total cross section sigma_{t }, the ratio of the real to the imaginary part of the forward scattering amplitude rho, the nuclear slope parameter B, the nuclear curvature parameter C, the total elastic cross section sigma _{el}, and the single diffractive cross section sigma_{sd} . These measurements were taken at center-of-mass energies of sqrt{s}=1.02 and 1.8 TeV.

  7. Partial Wave Dispersion Relations: Application to Electron-Atom Scattering

    NASA Technical Reports Server (NTRS)

    Temkin, A.; Drachman, Richard J.

    1999-01-01

    In this Letter we propose the use of partial wave dispersion relations (DR's) as the way of solving the long-standing problem of correctly incorporating exchange in a valid DR for electron-atom scattering. In particular a method is given for effectively calculating the contribution of the discontinuity and/or poles of the partial wave amplitude which occur in the negative E plane. The method is successfully tested in three cases: (i) the analytically solvable exponential potential, (ii) the Hartree potential, and (iii) the S-wave exchange approximation for electron-hydrogen scattering.

  8. Potential scattering of electrons in a quantized radiation field

    NASA Astrophysics Data System (ADS)

    Bergou, J.; Ehlotzky, F.

    1986-05-01

    Potential scattering of electrons in a strong laser field is reconsidered. The laser beam is described by a quantized single-mode plane-wave field with a finite number of quanta in the mode. The scattering amplitude is expanded in powers of the potential, and the first two Born terms are considered. It is shown that in the limit of an infinite number of field quanta, the Kroll-Watson approximation is recovered. Additional insight is gained into the validity of this low-frequency theorem. The approach rests on the introduction of electron-dressed quantized-field states. Relations to earlier work are indicated.

  9. Spin observables in neutron-proton elastic scattering

    SciTech Connect

    Ahmidouch, A.; Arnold, J.; van den Brandt, B.; Daum, M.; Demierre, P.; Drevenak, R.; Finger, M. |; Finger, M. Jr.; Franz, J.; Goujon, N.; Hautle, P.; Janout, Z. Jr.; Hajdas, W.; Heer, E.; Hess, R.; Koger, R.; Konter, J.A.; Lacker, H.; Lechanoine-LeLuc, C.; Lehar, F.; Mango, S.; Mascarini, C.; Rapin, D.; Roessle, E.; Schmelzbach, P.A.; Schmitt, H.; Sereni, P.; Slunecka, M.

    1995-07-15

    We describe here two experiments presently running at PSI using the NA2 polarized neutron beam. They are devoted to the measurement of 2- and 3-spin observables in {ital np} elastic scattering for kinetic energies from 230 to 590 MeV with a center of mass angular range from 60 to 180 degrees. The goal is to determine the five {ital NN} scattering amplitudes for isospin 0 in a model independent way. Preliminary results for {ital K}{sub {ital OSKO}} and {ital K}{sub {ital OSSO}} spin-transfers are presented.

  10. Molecular alignment and orientation with a hybrid Raman scattering technique

    NASA Astrophysics Data System (ADS)

    Bustard, Philip J.; Lausten, R.; Sussman, Benjamin J.

    2012-11-01

    We demonstrate a scheme for the preparation of molecular alignment and angular momentum orientation using a hybrid combination of two limits of Raman scattering. First a weak, impulsive pump pulse initializes the system via the nonresonant dynamic Stark effect. Then, having overcome the influence of the vacuum fluctuations, an amplification pulse selectively enhances the initial coherences by transient stimulated Raman scattering, generating alignment and angular momentum orientation of molecular hydrogen. The amplitude and phase of the resulting coherent dynamics are experimentally probed, indicating an amplification factor of 4.5. An analytic theory is developed to model the dynamics.

  11. 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.

  12. Detection of combined frequency and amplitude modulation.

    PubMed

    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

  13. Wave scattering from encapsulated microbubbles subject to high-frequency ultrasound: contribution of higher-order scattering modes.

    PubMed

    Chen, Jiusheng; Hunter, Kendall S; Shandas, Robin

    2009-10-01

    The theoretical understanding of encapsulated microbubble response to high-frequency ultrasound (HFUS) excitation is still limited although some novel experimental HFUS contrast imaging techniques have been well developed. In this paper, the higher-order modal (HOM) contributions to the scattered field are studied for such microbubbles driven by 1-100 MHz ultrasound. An exact solution of all small-amplitude vibrational modes of a single encapsulated microbubble in water is given by the wave scattering theory (WST) method and compared to results obtained from Church's Rayleigh-Plesset-like model for the small-amplitude radial oscillation of a microbubble in an incompressible fluid. From numerical results, we show that the HOM field contribution is significant for scattering properties from individual Nycomed microbubbles with normalized frequency > or = 0.2. It is also shown that the multiple scattering is strengthened for monodispersed Definity microbubbles of 3 microm radius at frequencies >40 MHz. However, comparisons between the authors' analyses and known experimental data for polydispersed Definity microbubbles indicate that the HOM contributions are insignificant in attenuation estimation at frequencies <50 MHz. In conclusion, the WST model analysis suggests that HOM scattering is an important consideration for single bubbles but may be less critical in the modeling of polydispersed Definity bubbles at high frequencies.

  14. Experimental Studies of Multiple Scattering by Rough Surfaces.

    NASA Astrophysics Data System (ADS)

    Knotts, Michael Eugene

    Experimental investigations were conducted to study the optical scattering properties of metallic rough surfaces with steep slopes and wavelength-sized structures that exhibit backscattering enhancement. Particular emphasis was placed on two kinds of surface with strictly one-dimensional roughness: random surfaces with Gaussian statistics and gratings consisting of deep, regularly spaced grooves that have been subjected to a random, groove-to-groove depth fluctuation. Methods for the fabrication of surfaces in photoresist and techniques for their characterization using a Talystep mechanical profilometer were developed. Normalized measurements of the angular dependence of the mean diffusely scattered intensities were obtained with the plane of incidence parallel to the axis of the surface height fluctuations. Using an incident wave polarized at 45^circ with respect to the plane of incidence, the Mueller matrix describing the complete polarization dependence of the mean scattered intensity was determined. It was shown that this matrix contains four distinct quantities corresponding to the second moments of scattered amplitudes, and that previous work presenting only the p- and s-polarized scattered intensities is therefore incomplete. Furthermore, it was shown that the four additional measured intensities required to determine the matrix elements can be used to isolate the backscattering enhancement and yield valuable physical insight. The results conclusively demonstrate that contributions arising from waves multiply scattered within valleys of the surface significantly affect the polarization dependence of the far-field scattered intensity and give rise to the observed backscattering enhancement.

  15. Angular scattering of sound from solid particles in turbulent suspension.

    PubMed

    Moore, Stephanie A; Hay, Alex E

    2009-09-01

    Sound scattering by solid particles suspended in a turbulent jet is investigated. Measurements of the scattered amplitude were made in a bistatic geometry at frequencies between 1.5 and 4.0 MHz, and at scattering angles from 95 degrees to 165 degrees relative to the forward direction. Two types of particle were used: nearly spherical lead-glass beads and aspherical natural sand grains. For each particle type, experiments were carried out using approximately 200 and approximately 500 microm median diameter grain sizes, corresponding to 0.7 < or approximately ka < or approximately 4. The sphericity of the sand grains, defined as the ratio of projected perimeter size to projected area size, was 1.08. The lead-glass bead results are consistent with an elastic sphere model. A rigid movable sphere model provides the best fit to the sand data, and the best-fit diameter is within 4% of the equivalent volume size. However, the scattering pattern for sand is systematically smoother than predicted: that is, the undulations in the angular scattering pattern predicted by spherical scatterer theory are present, but muted. This observed departure from spherical scatterer theory is attributed to disruption of the interference among creeping waves by the irregular surfaces of natural sand grains.

  16. Amplitude-modulated circular-harmonic filter for pattern recognition.

    PubMed

    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.

  17. N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop

    SciTech Connect

    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.

  18. 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.

  19. Calculation and modular properties of multiloop superstring amplitudes

    SciTech Connect

    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.

  20. 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.

  1. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    Dimsdle, Jeffrey William

    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.

  2. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  3. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  4. Method of differential-phase/absolute-amplitude QAM

    SciTech Connect

    Dimsdle, Jeffrey William

    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.

  5. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  6. Phase and amplitude control system for Stanford Linear Accelerator

    SciTech Connect

    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.

  7. MODE CONVERSION BETWEEN DIFFERENT RADIAL ORDERS FOR SOLAR ACOUSTIC WAVES SCATTERED BY SUNSPOTS

    SciTech Connect

    Zhao, Hui; Chou, Dean-Yi

    2013-11-20

    We study the mode conversion between different radial orders for solar acoustic waves interacting with sunspots. Solar acoustic waves are modified in the presence of sunspots. The modification in the wave can be viewed as that the sunspot, excited by the incident wave, generates the scattered wave, and the scattered wave is added to the incident wave to form the total wave inside and around the sunspot. The wavefunction of the acoustic wave on the solar surface is computed from the cross-correlation function. The wavefunction of the scattered wave is obtained by subtracting the wavefunction of the incident wave from that of the total wave. We use the incident waves of radial order n = 0-5 to measure the scattered wavefunctions from n to another radial order n' for NOAAs 11084 and 11092. The strength of scattered waves decreases rapidly with |Δn|, where Δn ≡ n' – n. The scattered waves of Δn = ±1 are visible for n ≤ 1, and significant for n ≥ 2. For the scattered wave of Δn = ±2, only few cases are visible. None of the scattered waves of Δn = ±3 are visible. The properties of scattered waves for Δn = 0 and Δn ≠ 0 are different. The scattered wave amplitude relative to the incident wave amplitude decreases with n for Δn = 0, while it increases with n for Δn ≠ 0. The scattered wave amplitudes of Δn = 0 are greater for the larger sunspot, while those of Δn ≠ 0 are insensitive to the sunspot size.

  8. The amplitudes and the structure of the charge density wave in YBCO.

    PubMed

    Kharkov, Y A; Sushkov, O P

    2016-10-10

    We find unknown s- and d-wave amplitudes of the recently discovered charge density wave (CDW) in underdoped cuprates. To do so we perform a combined analysis of experimental data for ortho-II YBa2Cu3Oy. The analysis includes data on nuclear magnetic resonance, resonant inelastic X-ray scattering, and hard X-ray diffraction. The amplitude of doping modulation found in our analysis is 3.5 · 10(-3) in a low magnetic field and T = 60 K, the amplitude is 6.5 · 10(-3) in a magnetic field of 30T and T = 1.3 K. The values are in units of elementary charge per unit cell of a CuO2 plane. We show that the data rule out a checkerboard pattern, and we also show that the data might rule out mechanisms of the CDW which do not include phonons.

  9. Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope

    NASA Astrophysics Data System (ADS)

    Kotko, P.; Serino, M.; Stasto, A. M.

    2016-08-01

    One of the methods to calculate tree-level multi-gluon scattering amplitudes is to use the Berends-Giele recursion relation involving off-shell currents or off-shell amplitudes, if working in the light cone gauge. As shown in recent works using the light-front perturbation theory, solutions to these recursions naturally collapse into gauge invariant and gauge-dependent components, at least for some helicity configurations. In this work, we show that such structure is helicity independent and emerges from analytic properties of matrix elements of Wilson line operators, where the slope of the straight gauge path is shifted in a certain complex direction. This is similar to the procedure leading to the Britto-Cachazo-Feng-Witten (BCFW) recursion, however we apply a complex shift to the Wilson line slope instead of the external momenta. While in the original BCFW procedure the boundary integrals over the complex shift vanish for certain deformations, here they are non-zero and are equal to the off-shell amplitudes. The main result can thus be summarized as follows: we derive a decomposition of a helicity-fixed off-shell current into gauge invariant component given by a matrix element of a straight Wilson line plus a reminder given by a sum of products of gauge invariant and gauge dependent quantities. We give several examples realizing this relation, including the five-point next-to-MHV helicity configuration.

  10. The amplitudes and the structure of the charge density wave in YBCO

    NASA Astrophysics Data System (ADS)

    Kharkov, Y. A.; Sushkov, O. P.

    2016-10-01

    We find unknown s- and d-wave amplitudes of the recently discovered charge density wave (CDW) in underdoped cuprates. To do so we perform a combined analysis of experimental data for ortho-II YBa2Cu3Oy. The analysis includes data on nuclear magnetic resonance, resonant inelastic X-ray scattering, and hard X-ray diffraction. The amplitude of doping modulation found in our analysis is 3.5 · 10‑3 in a low magnetic field and T = 60 K, the amplitude is 6.5 · 10‑3 in a magnetic field of 30T and T = 1.3 K. The values are in units of elementary charge per unit cell of a CuO2 plane. We show that the data rule out a checkerboard pattern, and we also show that the data might rule out mechanisms of the CDW which do not include phonons.

  11. The amplitudes and the structure of the charge density wave in YBCO

    PubMed Central

    Kharkov, Y. A.; Sushkov, O. P.

    2016-01-01

    We find unknown s- and d-wave amplitudes of the recently discovered charge density wave (CDW) in underdoped cuprates. To do so we perform a combined analysis of experimental data for ortho-II YBa2Cu3Oy. The analysis includes data on nuclear magnetic resonance, resonant inelastic X-ray scattering, and hard X-ray diffraction. The amplitude of doping modulation found in our analysis is 3.5 · 10−3 in a low magnetic field and T = 60 K, the amplitude is 6.5 · 10−3 in a magnetic field of 30T and T = 1.3 K. The values are in units of elementary charge per unit cell of a CuO2 plane. We show that the data rule out a checkerboard pattern, and we also show that the data might rule out mechanisms of the CDW which do not include phonons. PMID:27721385

  12. Parity-Violating Electron Scattering: New Results and Future Prospects

    SciTech Connect

    Krishna S. Kumar

    2006-11-01

    We discuss the status and prospects of an experimental program of parity-violating asymmetry measurements in the scattering of longitudinally polarized electrons off unpolarized fixed targets. One thrust is the measurements of nucleon neutral weak form factors at intermediate four-momentum transfer (0.1 < Q2 < 1) (GeV/c)2 which provide information about the role of virtual strange quarks on the charge and current distributions inside nucleons. A new topic is the elastic neutral weak amplitude from scattering off a heavy spinless nucleus, which is sensitive to the presence of a neutron skin. Finally, we discuss the neutral current elastic amplitude at very low Q2, which allows precision measurements of the weak mixing angle at low energy and is thus sensitive to new physics at the TeV scale. The physics implications of recent results, potential measurements from experiments under construction as well as new ideas at future facilities are discussed.

  13. Parity-Violating Electron Scattering: New Results and Future Prospects

    SciTech Connect

    Kumar, Krishna S.

    2006-11-17

    We discuss the status and prospects of an experimental program of parity-violating asymmetry measurements in the scattering of longitudinally polarized electrons off unpolarized fixed targets. One thrust is the measurements of nucleon neutral weak form factors at intermediate four-momentum transfer (0.1 < Q2 < 1) (GeV/c)2 which provide information about the role of virtual strange quarks on the charge and current distributions inside nucleons. A new topic is the elastic neutral weak amplitude from scattering off a heavy spinless nucleus, which is sensitive to the presence of a neutron skin. Finally, we discuss the neutral current elastic amplitude at very low Q2, which allows precision measurements of the weak mixing angle at low energy and is thus sensitive to new physics at the TeV scale. The physics implications of recent results, potential measurements from experiments under construction as well as new ideas at future facilities are discussed.

  14. Suppression of Rayleigh-scattering-induced noise in OEOs.

    PubMed

    Okusaga, Olukayode; Cahill, James P; Docherty, Andrew; Menyuk, Curtis R; Zhou, Weimin; Carter, Gary M

    2013-09-23

    Optoelectronic oscillators (OEOs) are hybrid RF-photonic devices that promise to be environmentally robust high-frequency RF sources with very low phase noise. Previously, we showed that Rayleigh-scattering-induced noise in optical fibers coupled with amplitude-to-phase noise conversion in photodetectors and amplifiers leads to fiber-length-dependent noise in OEOs. In this work, we report on two methods for the suppression of this fiber-length-dependent noise: altering the amplitude-dependent phase delay of the OEO loops and suppressing the Rayleigh-scattering-induced noise in optical fibers. We report a 20 dB reduction in the flicker phase noise of a 6 km OEO via these suppression techniques.

  15. SCRIT electron scattering facility

    NASA Astrophysics Data System (ADS)

    Tsukada, Kyo

    2014-09-01

    Electron scattering is the most powerful and reliable tool to investigate the nuclear structure because this reaction has the great advantage that the electron is structureless particle and its interaction is well described by the quantum electrodynamics. As is well known, the charge density distributions of many stable nuclei were determined by elastic electron scattering. Recently, many efforts for studies of unstable nuclei have been made, and the precise information of the structure of unstabe nuclei have been strongly desired. However, due to the difficulty of preparing a short-lived unstable nuclear target, there is no electron scattering on unstable nuclei with a few important exceptions, such as on 3H, 14C and so on. Under these circumstances, we have established a completely new target-forming technique, namely SCRIT (Self-Confining Radioactive isotope Ion Target) which makes electron scattering on unstable nuclei possible. A Dedicated electron scattering facility at RIKEN consists of an electron accelerator with the SCRIT system, an ERIS (Electron-beam-driven RI separator for SCRIT), and a WiSES (Window-frame Spectrometer for Electron Scattering). Feasibility test of the SCRIT and ERIS system have been successfully carried out using the stable nuclei, and more than 1026 [cm-2s-1] luminosity was already achieved. Furthermore, 132Sn, which is one of the important target at the beginning of this project, was also successfully separated in the ERIS. The WiSES with momentum resolution of Δp/p ~ 10-3 consisting of the wide acceptance dipole magnet, two set of drift chambers together with trigger scintillation hodoscope is under construction. Electron scattering on unstable nuclei will start within a year. In this talk, the introduction of our project and the progress of the preparation status will be presented.

  16. Test of 600 and 750 MeV NN matrix on elastic scattering Glauber model calculations

    NASA Astrophysics Data System (ADS)

    Brissaud, I.

    1980-09-01

    The 600 and 750 MeV proton nucleus elastic scattering cross section and polarization calculations have been performed in the framework of the Glauber model to test the pp and pn scattering amplitudes deduced from a phase shift analysis by Bystricky, Lechanoine and Lehar. It is well known that up to now we do not possess a non-phenomenological NN scattering matrix at intermediate energies. However proton-nucleus scattering analyses are used to extract information about short range correlations1), Δ resonance2) or pion condensation presences)... etc. Most scattering calculations made at these energies have been done with phenomenological NN amplitudes having a gaussian q-dependence 10050_2005_Article_BF01438168_TeX2GIFE1.gif A(q) = {kσ }/{4π }(α + i) e^{ - β ^2 q^2 /2} and 10050_2005_Article_BF01438168_TeX2GIFE2.gif C(q) = {kσ }/{4π }iq(α + i) D_e - β ^2 q^2 /2 K and σ being respectively the projectile momentum and the total pN total cross section. The parameters α, β and D are badly known and are adjusted by fitting some specific reactions as p+4He elastic scattering4). Even when these amplitudes provide good fits to the data, our understanding of the dynamics of the scattering remains obscure.

  17. Source-Space Cross-Frequency Amplitude-Amplitude Coupling in Tinnitus

    PubMed Central

    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

  18. Eikonal particle scattering and dilaton gravity

    SciTech Connect

    Das, S.; Majumdar, P.

    1997-02-01

    Approximating light charged pointlike particles in terms of (nonextremal) dilatonic black holes is shown to lead to certain pathologies in Planckian scattering in the eikonal approximation, which are traced to the presence of a (naked) curvature singularity in the metric of these black holes. The existence of such pathologies is confirmed by analyzing the problem in an {open_quotes}external metric{close_quote}{close_quote} formulation where an ultrarelativistic point particle scatters off a dilatonic black hole geometry at large impact parameters. The maladies disappear almost trivially upon imposing the extremal limit. Attempts to derive an effective three-dimensional {open_quotes}boundary{close_quote}{close_quote} field theory in the eikonal limit are stymied by four-dimensional (bulk) terms proportional to the light-cone derivatives of the dilaton field, leading to nontrivial mixing of electromagnetic and gravitational effects, in contrast with the case of general relativity. An eikonal scattering amplitude, showing decoupling of these effects, is shown to be derivable by resummation of graviton, dilaton, and photon exchange ladder diagrams in a linearized version of the theory for an asymptotic value of the dilaton field which makes the string coupling constant nonperturbative. {copyright} {ital 1997} {ital The American Physical Society}

  19. Deeply virtual Compton scattering at 6 GeV

    SciTech Connect

    Jian-ping Chen; Eugene Chudakov; Cornelis De Jager; Javier Gomez; Jens-ole Hansen; John Lerose; Robert Michaels; Joseph Mitchell; Arunava Saha; Bogdan Wojtsekhowski; J. Berthot; Pierre Bertin; Alexandre Deur; Rachele Di Salvo; Lawrence Weinstein; Werner Boeglin; Pete Markowitz; Jeffrey Templon; Paul Gueye; Ting Chang; Alan Nathan; Raffaele De Leo; Luigi Lagamba; Moskov Amarian; Evaristo Cisbani; Salvatore Frullani; Franco Garibaldi; R. Iommi; Mauro Iodice; Guido Urciuoli; Marc Vanderhaeghen; Douglas Higinbotham; Xiaodong Jiang; Pierre Guichon; Yves Roblin; Gail Dodge; Christophe Jutier; Charles Hyde-wright; Franck Sabatie; Luminita Todor; Paul Ulmer

    2000-06-01

    The authors propose a measurement of the Deep Virtual Compton Scattering process (DVCS) ep {yields} ep{gamma} in Hall A at Jefferson Lab with a 6 GeV beam. The authors are able to explore the onset of Q{sup 2} scaling, by measuring a beam helicity asymmetry for Q{sup 2} ranging from 1.5 to 2.5 GeV{sup 2} at x{sub B} {approx} 0.35. At this kinematics, the asymmetry is dominated by the DVCS Bethe-Heitler (BH) interference, which is proportional to the imaginary part of the DVCS amplitude amplified by the full magnitude of the BH amplitude. The imaginary part of the DVCS amplitude is expected to scale early. Indeed, the imaginary part of the forward Compton amplitude measured in deep inelastic scattering (via the optical theorem) scales at Q{sup 2} as low as 1 GeV{sup 2}. If the scaling regime is reached, they make an 8% measurement of the skewed parton distributions (SPD) contributing to the DVCS amplitude. Also, this experiment allows them to separately estimate the size of the higher-twist effects, since they are only suppressed by an additional factor 1/Q compared to the leading-twist term, and have a different angular dependence. They use a polarized electron beam and detect the scattered electron in the HRSe, the real photon in an electromagnetic calorimeter (under construction) and the recoil proton in a shielded scintillator array (to be constructed). This allows them to determine the difference in cross-sections for electrons of opposite helicities. This observable is directly linked to the SPD's. The authors estimate that 25 days of beam (600 hours) are needed to achieve this goal.

  20. Laser light scattering review

    NASA Technical Reports Server (NTRS)

    Schaetzel, Klaus

    1989-01-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  1. Numerical Simulations of High-Amplitude Delta Scuti Star Pulsations

    NASA Astrophysics Data System (ADS)

    Templeton, M. R.

    1999-12-01

    We present the results of a theoretical program to model high-amplitude delta Scuti (HADS) stars. We base this study on field HADS, and on the MACHO Project delta Scuti stars. We have generated a grid of evolution models with (X,Y,Z) = (0.76,0.24,0.0001) to (0.58,0.36,0.06) covering the delta Scuti/SX Phoenicis region of the instability strip. Linear pulsation tests were done to make theoretical Petersen diagrams for the double-mode pulsators, and to make period-luminosity relations. Petersen diagrams are consistent with previous observational and theoretical work, with all fundamental-first overtone pulsators having period ratios around 0.77. For a single metallicity, stars with masses separated by 0.1 Msun have distinct tracks in the Petersen diagram, which permits mass and age estimates for stars of known abundance. We also find that period ratios drop rapidly as these stars evolve toward the red giant branch. The two MACHO delta Scuti stars with period ratios around 0.75 may be highly evolved, cool (T = 6700 K) delta Scuti stars. Period-luminosity relations for stars of different masses but the same abundances have a large intrinsic scatter, indicating that a color term must be included in the P-L relation for delta Scuti stars. Hydrodynamic models of HADS have also been tested, using a variant of the Los Alamos DYNSTAR code (Ostlie and Cox, 1993, Astrophys. Space Sci 210, 311), modified to include the OPAL96 tabular opacities. We have obtained light curves that are similar to those of observed HADS, over a range of temperatures and masses. Our results are consistent with those of Bono et al. (1997; ApJ 477, 346) in that the light curves of fundamental mode pulsators are more sinusoidal than those of overtone pulsators. Work on the hydrodynamic models is being expanded to test the effects of helium enrichment on light curve shape, and to include convection in cooler HADS to better model the red edge of the instability strip.

  2. The soft-collinear bootstrap: mathcal{N} = {4} Yang-Mills amplitudes at six- and seven-loops

    NASA Astrophysics Data System (ADS)

    Bourjaily, J. L.; DiRe, A.; Shaikh, A.; Spradlin, M.; Volovich, A.

    2012-03-01

    Infrared divergences in scattering amplitudes arise when a loop momentum ℓ becomes collinear with a massless external momentum p. In gauge theories, it is known that the L-loop logarithm of a planar amplitude has much softer infrared singularities than the L-loop amplitude itself. We argue that planar amplitudes in mathcal{N} = {4} super-Yang-Mills theory enjoy softer than expected behavior as ℓ ∥ p already at the level of the integrand. Moreover, we conjecture that the four-point integrand can be uniquely determined, to any loop-order, by imposing the correct soft-behavior of the logarithm together with dual conformal invariance and dihedral symmetry. We use these simple criteria to determine explicit formulae for the four-point integrand through seven-loops, finding perfect agreement with previously known results through five-loops. As an input to this calculation, we enumerate all four-point dual conformally invariant (DCI) integrands through seven-loops, an analysis which is aided by several graph-theoretic theorems we prove about general DCI integrands at arbitrary loop-order. The six- and seven-loop amplitudes receive non-zero contributions from 229 and 1873 individual DCI diagrams respectively. PDF and Mathematica files with all of our results are provided at http://goo.gl/qIKe8 .

  3. Pion-eta scalar-isovector 3-coupled channel amplitude fitted to branching ratios and threshold plus subthreshold parameters

    NASA Astrophysics Data System (ADS)

    Kamiński, Robert; Bibrzycki, Łukasz

    2017-03-01

    The low energy (below 2 GeV) πη channel interaction amplitude becomes an object of interest mainly because of the search for exotic mesons in just beginning to collect data detector GlueX in JLab. Finding and interpretation of expected weak signals from these states require a comparison with a very accurate amplitude containing standard (qq¯) states i.e. a0(980) and a0(1450). The main problem in the determination of such amplitude is a total absence of data about the phases and inelasticities in the elastic and inelastic region. In addition, it is necessary to take into account the next two coupled higher channels - KK¯ and πη'. Presented here amplitude is based on separable potential model (working very well for the scalar-isoscalar ππ interactions) with only 9 free parameters. To determine such 3-coupled channel amplitude, the following information has been taken into account: experimental branching ratios and positions of both a0 resonances, theoretical couplings, scattering length from ChPT and value of squared radius of the πη form factor. Phase shifts, inelasticities and cross sections in all single and crossed channels are presented.

  4. 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…

  5. 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.

  6. Electromagnetic scattering theory

    NASA Technical Reports Server (NTRS)

    Bird, J. F.; Farrell, R. A.

    1986-01-01

    Electromagnetic scattering theory is discussed with emphasis on the general stochastic variational principle (SVP) and its applications. The stochastic version of the Schwinger-type variational principle is presented, and explicit expressions for its integrals are considered. Results are summarized for scalar wave scattering from a classic rough-surface model and for vector wave scattering from a random dielectric-body model. Also considered are the selection of trial functions and the variational improvement of the Kirchhoff short-wave approximation appropriate to large size-parameters. Other applications of vector field theory discussed include a general vision theory and the analysis of hydromagnetism induced by ocean motion across the geomagnetic field. Levitational force-torque in the magnetic suspension of the disturbance compensation system (DISCOS), now deployed in NOVA satellites, is also analyzed using the developed theory.

  7. Dynamic Scattering Mode LCDs

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

  8. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

    ZALIZNYAK,I.A.; LEE,S.H.

    2004-07-30

    Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science

  9. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  10. 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.

  11. 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.

  12. Microstructure and nonlinear signatures of yielding in a heterogeneous colloidal gel under large amplitude oscillatory shear

    SciTech Connect

    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.

  13. Correlations in alpha-alpha scattering and semi-classical optical models.

    PubMed

    Cucinotta, F A; Khandelwal, G S; Townsend, L W; Wilson, J W

    1989-06-08

    We show the equivalence of semi-classical solutions to optical model coupled-channel equations derived from Watson's form of the nucleus-nucleus multiple-scattering series to the Glauber multiple-scattering series. A second-order solution to the semi-classical coupled-channel elastic amplitude is shown to be nearly equivalent to a second-order optical-phase-shift approximation to the Glauber amplitude if the densities of all nuclear excited states are approximated by the ground-state density. Using the Jastrow method to model the two-body density we find an average excited-state density to be of negligible importance in the double-scattering region of alpha-alpha scattering.

  14. Correlations in alpha-alpha scattering and semi-classical optical models

    NASA Technical Reports Server (NTRS)

    Cucinotta, F. A.; Khandelwal, G. S.; Townsend, L. W.; Wilson, J. W.

    1989-01-01

    We show the equivalence of semi-classical solutions to optical model coupled-channel equations derived from Watson's form of the nucleus-nucleus multiple-scattering series to the Glauber multiple-scattering series. A second-order solution to the semi-classical coupled-channel elastic amplitude is shown to be nearly equivalent to a second-order optical-phase-shift approximation to the Glauber amplitude if the densities of all nuclear excited states are approximated by the ground-state density. Using the Jastrow method to model the two-body density we find an average excited-state density to be of negligible importance in the double-scattering region of alpha-alpha scattering.

  15. On the multiple scattering of VHF/UHF waves in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Vats, H. O.

    1981-01-01

    Using amplitude data of radio beacons at 40, 140, and 360 MHz from ATS 6 (phase II), an attempt has been made to study scattering of these waves in the equatorial ionosphere. A comparison of observed scintillation index S sub 4 with the theoretical results of the multiple scattering approach and variation of autocorrelation time with frequency indicates that this theory explains the results to a large extent. A comparison of power spectra of amplitude records with the ionograms of a nearby equatorial station has led to the following conclusions: the change from a weak scattering regime to a strong scattering regime is gradual and occurs because of the gradual decrease in the scale size of the irregularities (i.e., broadening of the spectra) and the gradual increase in the thickness of the irregular region.

  16. Scattering compensation by focus scanning holographic aberration probing (F-SHARP)

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Ioannis N.; Jouhanneau, Jean-Sébastien; Poulet, James F. A.; Judkewitz, Benjamin

    2016-12-01

    A long-standing goal in biomedical imaging, the control of light inside turbid media, requires knowledge of how the phase and amplitude of an illuminating wavefront are transformed as the electric field propagates inside a scattering sample onto a target plane. So far, it has proved challenging to non-invasively characterize the scattered optical wavefront inside a disordered medium. Here, we present a non-invasive scattering compensation method, termed F-SHARP, which allows us to measure the scattered electric-field point spread function (E-field PSF) in three dimensions. Knowledge of the phase and amplitude of the E-field PSF makes it possible to optically cancel sample turbulence. We demonstrate the imaging capabilities of this technique on a variety of samples and notably through vertebrate brains and across thinned skull in vivo.

  17. Resonance estimates for single spin asymmetries in elastic electron-nucleon scattering

    SciTech Connect

    Barbara Pasquini; Marc Vanderhaeghen

    2004-07-01

    We discuss the target and beam normal spin asymmetries in elastic electron-nucleon scattering which depend on the imaginary part of two-photon exchange processes between electron and nucleon. We express this imaginary part as a phase space integral over the doubly virtual Compton scattering tensor on the nucleon. We use unitarity to model the doubly virtual Compton scattering tensor in the resonance region in terms of {gamma}* N {yields} {pi} N electroabsorption amplitudes. Taking those amplitudes from a phenomenological analysis of pion electroproduction observables, we present results for beam and target normal single spin asymmetries for elastic electron-nucleon scattering for beam energies below 1 GeV and in the 1-3 GeV region, where several experiments are performed or are in progress.

  18. Effect of the third π ∗ resonance on the angular distributions for electron-pyrimidine scattering

    NASA Astrophysics Data System (ADS)

    Mašín, Zdeněk; Gorfinkiel, Jimena D.

    2016-07-01

    We present a detailed analysis of the effect of the well known third π∗ resonance on the angular behaviour of the elastic cross section in electron scattering from pyrimidine. This resonance, occurring approximately at 4.7 eV, is of mixed shape and core-excited character. Experimental and theoretical results show the presence of a peak/dip behaviour in this energy range, that is absent for other resonances. Our investigations show that the cause of the peak/dip is an interference of background p-wave to p-wave scattering amplitudes with the amplitudes for resonant scattering. The equivalent resonance in pyrazine shows the same behaviour and the effect is therefore likely to appear in other benzene-like molecules. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  19. The Use of Scattering Matrix to Model Multi-Modal Array Inspection with the Tfm

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.

    2009-03-01

    The scattering coefficient matrix describes the far field amplitude of scattered signals from a scatterer as a function of incident and scattering angles. In this paper an FE model is used to predict scattering matrices. By combining the predicted scattering coefficient matrix with a ray tracing model to predict the full matrix of array data, an efficient forward model of the complete array inspection process is presented. Longitudinal wave, shear waves and wave mode conversions are considered in the model. The TFM images for various wave mode combination cases from a weld sample are predicted and measured. Results show that by selecting the optimum array mode combination a good image for a given defect in the weld sample can be produced using an array. It is also shown how the model can be used to optimize the array inspection configuration.

  20. REGIONAL SEISMIC AMPLITUDE MODELING AND TOMOGRAPHY FOR EARTHQUAKE-EXPLOSION DISCRIMINATION

    SciTech Connect

    Walter, W R; Pasyanos, M E; Matzel, E; Gok, R; Sweeney, J; Ford, S R; Rodgers, A J

    2008-07-08

    events and discriminating between natural and man-made seismic events, such as earthquakes and mining activities, and nuclear weapons testing. We continue developing, testing, and refining size-, distance-, and location-based regional seismic amplitude corrections to facilitate the comparison of all events that are recorded at a particular seismic station. These corrections, calibrated for each station, reduce amplitude measurement scatter and improve discrimination performance. We test the methods on well-known (ground truth) datasets in the U.S. and then apply them to the uncalibrated stations in Eurasia, Africa, and other regions of interest to improve underground nuclear test monitoring capability.

  1. Application and development of the Schwinger multichannel scattering theory and the partial differential equation theory of electron-molecule scattering

    NASA Technical Reports Server (NTRS)

    Weatherford, Charles A.

    1993-01-01

    One version of the multichannel theory for electron-target scattering based on the Schwinger variational principle, the SMC method, requires the introduction of a projection parameter. The role of the projection parameter a is investigated and it is shown that the principal-value operator in the SMC equation is Hermitian regardless of the value of a as long as it is real and nonzero. In a basis that is properly orthonormalizable, the matrix representation of this operator is also Hermitian. The use of such basis is consistent with the Schwinger variational principle because the Lippmann-Schwinger equation automatically builds in the correct boundary conditions. Otherwise, an auxiliary condition needs to be introduced, and Takatsuka and McKoy's original value of a is one of the three possible ways to achieve Hermiticity. In all cases but one, a can be uncoupled from the Hermiticity condition and becomes a free parameter. An equation for a based on the variational stability of the scattering amplitude is derived; its solution has an interesting property that the scattering amplitude from a converged SMC calculation is independent of the choice of a even though the SMC operator itself is a-dependent. This property provides a sensitive test of the convergence of the calculation. For a static-exchange calculation, the convergence requirement only depends on the completeness of the one-electron basis, but for a general multichannel case, the a-invariance in the scattering amplitude requires both the one-electron basis and the N plus 1-electron basis to be complete. The role of a in the SMC equation and the convergence property are illustrated using two examples: e-CO elastic scattering in the static-exchange approximation, and a two-state treatment of the e-H2 Chi(sup 1)Sigma(sub g)(+) yields b(sup 3)Sigma(sub u)(+) excitation.

  2. Deep inelastic scattering in conformal QCD

    NASA Astrophysics Data System (ADS)

    Cornalba, Lorenzo; Costa, Miguel S.; Penedones, João

    2010-03-01

    We consider the Regge limit of a CFT correlation function of two vector and two scalar operators, as appropriate to study small-x deep inelastic scattering in mathcal{N} = 4 SYM or in QCD assuming approximate conformal symmetry. After clarifying the nature of the Regge limit for a CFT correlator, we use its conformal partial wave expansion to obtain an impact parameter representation encoding the exchange of a spin j Reggeon for any value of the coupling constant. The CFT impact parameter space is the three-dimensional hyperbolic space H 3, which is the impact parameter space for high energy scattering in the dual AdS space. We determine the small-x structure functions associated to the exchange of a Reggeon. We discuss unitarization from the point of view of scattering in AdS and comment on the validity of the eikonal approximation. We then focus on the weak coupling limit of the theory where the amplitude is dominated by the exchange of the BFKL pomeron. Conformal invariance fixes the form of the vector impact factor and its decomposition in transverse spin 0 and spin 2 components. Our formalism reproduces exactly the general results predict by the Regge theory, both for a scalar target and for γ* - γ* scattering. We compute current impact factors for the specific examples of mathcal{N} = 4 SYM and QCD, obtaining very simple results. In the case of the R-current of mathcal{N} = 4 SYM, we show that the transverse spin 2 component vanishes. We conjecture that the impact factors of all chiral primary operators of mathcal{N} = 4 SYM only have components with 0 transverse spin.

  3. High Frequency Scattering from Arbitrarily Oriented Dielectric Disks

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Meneghini, R.; Lang, R. H.; Seker, S. S.

    1982-01-01

    Calculations have been made of electromagnetic wave scattering from dielectric disks of arbitrary shape and orientation in the high frequency (physical optics) regime. The solution is obtained by approximating the fields inside the disk with the fields induced inside an identically oriented slab (i.e. infinite parallel planes) with the same thickness and dielectric properties. The fields inside the disk excite conduction and polarization currents which are used to calculate the scattered fields by integrating the radiation from these sources over the volume of the disk. This computation has been executed for observers in the far field of the disk in the case of disks with arbitrary orientation and for arbitrary polarization of the incident radiation. The results have been expressed in the form of a dyadic scattering amplitude for the disk. The results apply to disks whose diameter is large compared to wavelength and whose thickness is small compared to diameter, but the thickness need not be small compared to wavelength. Examples of the dependence of the scattering amplitude on frequency, dielectric properties of the disk and disk orientation are presented for disks of circular cross section.

  4. Elastic scattering, polarization and absorption of relativistic antiprotons on nuclei

    NASA Astrophysics Data System (ADS)

    Larionov, A. B.; Lenske, H.

    2017-01-01

    We perform Glauber model calculations of the antiproton-nucleus elastic and quasielastic scattering and absorption in the beam momentum range ∼ 0.5 ÷ 10 GeV / c. A good agreement of our calculations with available LEAR data and with earlier Glauber model studies of the p bar A elastic scattering allows us to make predictions at the beam momenta of ∼10 GeV/c, i.e. at the regime of the PANDA experiment at FAIR. The comparison with the proton-nucleus elastic scattering cross sections shows that the diffractive minima are much deeper in the p bar A case due to smaller absolute value of the ratio of the real-to-imaginary part of the elementary elastic amplitude. Significant polarization signal for p bar A elastic scattering at 10 GeV/c is expected. We have also revealed a strong dependence of the p bar A absorption cross section on the slope parameter of the transverse momentum dependence of the elementary p bar N amplitude. The p bar A optical potential is discussed.

  5. Detecting quantum coherence of Bose gases in optical lattices by scattering light intensity in cavity.

    PubMed

    Zhou, Xiaoji; Xu, Xu; Yin, Lan; Liu, W M; Chen, Xuzong

    2010-07-19

    We propose a new method of detecting quantum coherence of a Bose gas trapped in a one-dimensional optical lattice by measuring the light intensity from Raman scattering in cavity. After pump and displacement process, the intensity or amplitude of scattering light is different for different quantum states of a Bose gas, such as superfluid and Mott-Insulator states. This method can also be useful to detect quantum states of atoms with two components in an optical lattice.

  6. Measurements of near forward scattered laser light in a large ICF plasma

    SciTech Connect

    Moody, J.D., LLNL

    1998-06-02

    We describe an instrument which measures the angular spread and spectrum of near forward scattered laser light from a probe beam in a long scalelength laser-plasma. The instrument consists of a combination of time integrating and time resolving detectors which measure the scattered light amplitude over four orders of magnitude for a range of angles. These measurements allow us to study the beam spray resulting from various laser and plasma conditions and determine the density fluctuations associated with this beam spray.

  7. Laser Thomson scattering in a pulsed atmospheric arc discharge

    NASA Astrophysics Data System (ADS)

    Sommers, Bradley; Adams, Steven

    2015-09-01

    Laser scattering measurements, including Rayleigh, Raman, and Thomson scattering have been performed on an atmospheric pulsed arc discharge. Such laser scattering techniques offer a non-invasive diagnostic to measure gas temperature, electron temperature, and electron density in atmospheric plasma sources, particularly those with feature sizes approaching 1 mm. The pulsed discharge is ignited in a pin to pin electrode geometry using a 6 kV pulse with 10 ns duration. The electrodes are housed in a glass vacuum chamber filled with argon gas. The laser signal is produced by a Nd:Yag laser supply, repetitively pulsed at 10 Hz and frequency quadrupled to operate at 266 nm. The scattered laser signal is imaged onto a triple grating spectrometer, which is used to suppress the Rayleigh scatter signal in order to measure the low amplitude Thomson and Raman signals. Preliminary results include measurements of electron temperature and electron density in the plasma column taken during the evolution of the discharge. The laser system is also used to measure the Rayleigh scattering signal, which provides space and time resolved measurements of gas temperature in the arc discharge.

  8. The contribution of scattering to near-surface attenuation

    NASA Astrophysics Data System (ADS)

    Pilz, Marco; Fäh, Donat

    2017-01-01

    The rapid decrease of the acceleration spectral amplitude at high frequencies has widely been modeled by the spectral decay factor kappa (κ). Usually, the path-corrected component of κ, often called κ0, is believed to be a local and frequency-independent site characteristic, in turn representing attenuation related to waves propagating vertically through the very shallow layers beneath the study site. Despite the known relevance of κ0 in a wide range of seismological applications, most methods for its calculation do not fully consider the influence of the scattering component. To account for the scattering component, we present a summary of statistical observations of the seismic wavefield at sites of the Swiss seismic networks. The intrinsic properties of the wavefield show a clear dependency on the local shallow subsoil conditions with differences in the structural heterogeneity of the shallow subsoil layers producing different scattering regimes. Such deviations from the ballistic behavior (i.e., direct waves that sample only distinct directions) are indicative for local structural heterogeneities and the associated level of scatter. Albeit the attenuation term related to scattering depends nonlinearly on the intrinsic term, the results indicate that the commonly used explanation for the high-frequency decay spectrum might not be appropriate but involving the amount of scattering might allow better constrained estimates of κ0.

  9. Small Angle Neutron Scattering

    SciTech Connect

    Urban, Volker S

    2012-01-01

    Small Angle Neutron Scattering (SANS) probes structural details at the nanometer scale in a non-destructive way. This article gives an introduction to scientists who have no prior small-angle scattering knowledge, but who seek a technique that allows elucidating structural information in challenging situations that thwart approaches by other methods. SANS is applicable to a wide variety of materials including metals and alloys, ceramics, concrete, glasses, polymers, composites and biological materials. Isotope and magnetic interactions provide unique methods for labeling and contrast variation to highlight specific structural features of interest. In situ studies of a material s responses to temperature, pressure, shear, magnetic and electric fields, etc., are feasible as a result of the high penetrating power of neutrons. SANS provides statistical information on significant structural features averaged over the probed sample volume, and one can use SANS to quantify with high precision the structural details that are observed, for example, in electron microscopy. Neutron scattering is non-destructive; there is no need to cut specimens into thin sections, and neutrons penetrate deeply, providing information on the bulk material, free from surface effects. The basic principles of a SANS experiment are fairly simple, but the measurement, analysis and interpretation of small angle scattering data involves theoretical concepts that are unique to the technique and that are not widely known. This article includes a concise description of the basics, as well as practical know-how that is essential for a successful SANS experiment.

  10. Nanowire electron scattering spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D. (Inventor); Bronikowski, Michael (Inventor); Wong, Eric W. (Inventor); von Allmen, Paul (Inventor); Oyafuso, Fabiano A. (Inventor)

    2009-01-01

    Methods and devices for spectroscopic identification of molecules using nanoscale wires are disclosed. According to one of the methods, nanoscale wires are provided, electrons are injected into the nanoscale wire; and inelastic electron scattering is measured via excitation of low-lying vibrational energy levels of molecules bound to the nanoscale wire.

  11. Fluorescence and Light Scattering

    ERIC Educational Resources Information Center

    Clarke, Ronald J.; Oprysa, Anna

    2004-01-01

    The aim of the mentioned experiment is to aid students in developing tactics for distinguishing between signals originating from fluorescence and light scattering. Also, the experiment provides students with a deeper understanding of the physicochemical bases of each phenomenon and shows that the techniques are actually related.

  12. Modeling of the Bistatic Scattering by a Group of Cylinders

    NASA Astrophysics Data System (ADS)

    Thirion-Lefevre, L.; Dahon, C.

    2007-03-01

    We propose in this communication to study the scattering of a group of cylinders at P-band in bistatic configurations. The goal is to determine which radar configurations can be of interest for FOliage PENetration (FOPEN) studies on a first hand, and which radar configurations maximise the difference between the amplitude of the cross-polarized scattering coefficients, when we analyzed a forested area. To achieve this study, we analyse the scattering by a group of cylinders at P-band, whose locations and orientations are either random or deterministic. The receiver is located at a constant place and the receiver moves around a square scene of about 400m by 400m, so that the aspect angle varies between 0 and π /2 and the squint angle is in [0, π ].

  13. Modelling of classical ghost images obtained using scattered light

    NASA Astrophysics Data System (ADS)

    Crosby, S.; Castelletto, S.; Aruldoss, C.; Scholten, R. E.; Roberts, A.

    2007-08-01

    The images obtained in ghost imaging with pseudo-thermal light sources are highly dependent on the spatial coherence properties of the incident light. Pseudo-thermal light is often created by reducing the coherence length of a coherent source by passing it through a turbid mixture of scattering spheres. We describe a model for simulating ghost images obtained with such partially coherent light, using a wave-transport model to calculate the influence of the scattering on initially coherent light. The model is able to predict important properties of the pseudo-thermal source, such as the coherence length and the amplitude of the residual unscattered component of the light which influence the resolution and visibility of the final ghost image. We show that the residual ballistic component introduces an additional background in the reconstructed image, and the spatial resolution obtainable depends on the size of the scattering spheres.

  14. Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves.

    PubMed

    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.

  15. 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.

  16. Broadband metasurface holograms: toward complete phase and amplitude engineering

    PubMed Central

    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

  17. Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra

    PubMed Central

    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

  18. Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves

    PubMed Central

    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

  19. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  20. A Discrete Scatterer Technique for Evaluating Electromagnetic Scattering from Trees

    DTIC Science & Technology

    2016-09-01

    ARL-TR-7799 ● SEP 2016 US Army Research Laboratory A Discrete Scatterer Technique for Evaluating Electromagnetic Scattering from...longer needed. Do not return it to the originator. ARL-TR-7799 ● SEP 2016 US Army Research Laboratory A Discrete Scatterer Technique ... Technique for Evaluating Electromagnetic Scattering from Trees 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  1. The Classical Scattering of Waves: Some Analogies with Quantum Scattering

    DTIC Science & Technology

    1992-01-01

    Code . Approved for public release; distribution is unlimited. 13. Abstract (Maximum 200 words). The scattering of waves in classical physics and quantum...both areas. 92-235222’ 14. Subject Terms. IS. Number of Page. Acoustic scattering , shallow water, waveguide propagation . 27 16. Price Code . 17. Security...Numbers. The Classical Scattering of Waves: Some Analogies with Quantum Scattering Contract ,~~ ~ -V ,~Pom Element NO- 0601153N 6. Author(s). t

  2. 3D Finite-Difference Modeling of Scattered Teleseismic Wavefields in a Subduction Zone

    NASA Astrophysics Data System (ADS)

    Morozov, I. B.; Zheng, H.

    2005-12-01

    For a teleseismic array targeting subducting crust in a zone of active subduction, scattering from the zone underlying the trench result in subhorizontally-propagating waves that could be difficult to distinguish from converted P- and S- wave backscattered from the surface. Because back-scattered modes often provide the most spectacular images of subducting slabs, it is important to understand their differences from the arrivals scattered from the trench zone. To investigate the detailed teleseismic wavefield in a subduction zone environment, we performed a full-waveform, 3-D visco-elastic finite-difference modeling of teleseismic wave propagation using a Beowulf cluster. The synthetics show strong scattering from the trench zone, dominated by the mantle and crustal P-waves propagating at 6.2-8.1.km/s and slower. These scattered waves occupy the same time and moveout intervals as the backscattered modes, and also have similar amplitudes. Although their amplitude decay characters are different, with the uncertainties in the velocity and density structure of the subduction zone, unambiguous distinguishing of these modes appears difficult. However, under minimal assumptions (in particular, without invoking slab dehydration), recent observations of receiver function amplitudes decreasing away from the trench favor the interpretation of trench-zone scattering.

  3. One-loop amplitudes of gluons in supersymmetric QCD

    SciTech Connect

    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.

  4. 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 .

  5. 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.

  6. 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.

  7. 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.

  8. 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).

  9. 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.

  10. Resonances in Coupled πK-ηK Scattering from Quantum Chromodynamics

    SciTech Connect

    Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; Wilson, David J.

    2014-10-01

    Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled πK, ηK scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.

  11. FDTD scattered field formulation for scatterers in stratified dispersive media.

    PubMed

    Olkkonen, Juuso

    2010-03-01

    We introduce a simple scattered field (SF) technique that enables finite difference time domain (FDTD) modeling of light scattering from dispersive objects residing in stratified dispersive media. The introduced SF technique is verified against the total field scattered field (TFSF) technique. As an application example, we study surface plasmon polariton enhanced light transmission through a 100 nm wide slit in a silver film.

  12. Angle resolved scatter measurement of bulk scattering in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Sharma, Saurabh; Miller, J. Keith; Shori, Ramesh K.; Goorsky, Mark S.

    2015-02-01

    Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. Angle Resolved Scatter (ARS) measurement allows for the spatial mapping of scattered light at all possible angles about a sample, mapping the intensity for both forward scatter and back-scatter regions. The cumulative scattered light intensity, in the forward scatter direction, away from the specular beam is used for the comparison of bulk scattering between samples. This technique employ the detection of scattered light at all angles away from the specular beam directions and represented as a 2-D polar map. The high sensitivity of the ARS technique allows us to compare bulk scattering in different PLM samples which otherwise had similar transmitted beam wavefront distortions.

  13. Scattering on two Aharonov-Bohm vortices

    NASA Astrophysics Data System (ADS)

    Bogomolny, E.

    2016-12-01

    The problem of two Aharonov-Bohm (AB) vortices for the Helmholtz equation is examined in detail. It is demonstrated that the method proposed by Myers (1963 J. Math. Phys. 6 1839) for slit diffraction can be generalised to obtain an explicit solution for AB vortices. Due to the singular nature of AB interaction the Green function and scattering amplitude for two AB vortices obey a series of partial differential equations. Coefficients entering these equations, fulfil ordinary non-linear differential equations whose solutions can be obtained by solving the Painlevé III equation. The asymptotics of necessary functions for very large and very small vortex separations are calculated explicitly. Taken together, this means that the problem of two AB vortices is exactly solvable.

  14. Interface scattering in polycrystalline thermoelectrics

    SciTech Connect

    Popescu, Adrian; Haney, Paul M.

    2014-03-28

    We study the effect of electron and phonon interface scattering on the thermoelectric properties of disordered, polycrystalline materials (with grain sizes larger than electron and phonons' mean free path). Interface scattering of electrons is treated with a Landauer approach, while that of phonons is treated with the diffuse mismatch model. The interface scattering is embedded within a diffusive model of bulk transport, and we show that, for randomly arranged interfaces, the overall system is well described by effective medium theory. Using bulk parameters similar to those of PbTe and a square barrier potential for the interface electron scattering, we identify the interface scattering parameters for which the figure of merit ZT is increased. We find the electronic scattering is generally detrimental due to a reduction in electrical conductivity; however, for sufficiently weak electronic interface scattering, ZT is enhanced due to phonon interface scattering.

  15. Seismic inversion with generalized Radon transform based on local second-order approximation of scattered field in acoustic media

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Mao, Weijian; Li, Xuelei; Li, Wuqun

    2014-08-01

    Sound velocity inversion problem based on scattering theory is formulated in terms of a nonlinear integral equation associated with scattered field. Because of its nonlinearity, in practice, linearization algorisms (Born/single scattering approximation) are widely used to obtain an approximate inversion solution. However, the linearized strategy is not congruent with seismic wave propagation mechanics in strong perturbation (heterogeneous) medium. In order to partially dispense with the weak perturbation assumption of the Born approximation, we present a new approach from the following two steps: firstly, to handle the forward scattering by taking into account the second-order Born approximation, which is related to generalized Radon transform (GRT) about quadratic scattering potential; then to derive a nonlinear quadratic inversion formula by resorting to inverse GRT. In our formulation, there is a significant quadratic term regarding scattering potential, and it can provide an amplitude correction for inversion results beyond standard linear inversion. The numerical experiments demonstrate that the linear single scattering inversion is only good in amplitude for relative velocity perturbation () of background media up to 10 %, and its inversion errors are unacceptable for the perturbation beyond 10 %. In contrast, the quadratic inversion can give more accurate amplitude-preserved recovery for the perturbation up to 40 %. Our inversion scheme is able to manage double scattering effects by estimating a transmission factor from an integral over a small area, and therefore, only a small portion of computational time is added to the original linear migration/inversion process.

  16. The amplitude of the cross-covariance function of solar oscillations as a diagnostic tool for wave attenuation and geometrical spreading

    NASA Astrophysics Data System (ADS)

    Nagashima, Kaori; Fournier, Damien; Birch, Aaron C.; Gizon, Laurent

    2017-03-01

    Context. In time-distance helioseismology, wave travel times are measured from the two-point cross-covariance function of solar oscillations and are used to image the solar convection zone in three dimensions. There is, however, also information in the amplitude of the cross-covariance function, for example, about seismic wave attenuation. Aims: We develop a convenient procedure to measure the amplitude of the cross-covariance function of solar oscillations. Methods: In this procedure, the amplitude of the cross-covariance function is linearly related to the cross-covariance function and can be measured even for high levels of noise. Results: As an example application, we measure the amplitude perturbations of the seismic waves that propagate through the sunspot in active region NOAA 9787. We can recover the amplitude variations due to the scattering and attenuation of the waves by the sunspot and associated finite-wavelength effects. Conclusions: The proposed definition of cross-covariance amplitude is robust to noise, can be used to relate measured amplitudes to 3D perturbations in the solar interior under the Born approximation, and provides independent information from the travel times.

  17. Laser beam complex amplitude measurement by phase diversity.

    PubMed

    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.

  18. 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

  19. Amplitude sorting of oscillatory burst signals by sampling

    DOEpatents

    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.

  20. Amplitude-modulation detection by gerbils in reverberant sound fields.

    PubMed

    Lingner, Andrea; Kugler, Kathrin; Grothe, Benedikt; Wiegrebe, Lutz

    2013-08-01

    Reverberation can dramatically reduce the depth of amplitude modulations which are critical for speech intelligibility. Psychophysical experiments indicate that humans' sensitivity to amplitude modulation in reverberation is better than predicted from the acoustic modulation depth at the receiver position. Electrophysiological studies on reverberation in rabbits highlight the contribution of neurons sensitive to interaural correlation. Here, we use a prepulse-inhibition paradigm to quantify the gerbils' amplitude modulation threshold in both anechoic and reverberant virtual environments. Data show that prepulse inhibition provides a reliable method for determining the gerbils' AM sensitivity. However, we find no evidence for perceptual restoration of amplitude modulation in reverberation. Instead, the deterioration of AM sensitivity in reverberant conditions can be quantitatively explained by the reduced modulation depth at the receiver position. We suggest that the lack of perceptual restoration is related to physical properties of the gerbil's ear input signals and inner-ear processing as opposed to shortcomings of their binaural neural processing.

  1. Non-perturbative QCD amplitudes in quenched and eikonal approximations

    SciTech Connect

    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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. High Amplitude (delta)-Scutis in the Large Magellanic Cloud

    SciTech Connect

    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).

  8. Bekki-Nozaki Amplitude Holes in Hydrothermal Nonlinear Waves

    NASA Astrophysics Data System (ADS)

    Burguete, Javier; Chaté, Hugues; Daviaud, François; Mukolobwiez, Nathalie

    1999-04-01

    We present and analyze experimental results on the dynamics of hydrothermal waves occurring in a laterally heated fluid layer. We argue that the large-scale modulations of the waves are governed by a one-dimensional complex Ginzburg-Landau equation (CGLE). We determine quantitatively all the coefficients of this amplitude equation using the localized amplitude holes observed in the experiment, which we show to be well described as Bekki-Nozaki hole solutions of the CGLE.

  9. 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.

  10. 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).

  11. A Pn Spreading Model Constrained with Observed Amplitudes in Asia

    DTIC Science & Technology

    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

  12. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers.

    PubMed

    Sell, J F; Gulyuz, K; Sprouse, G D

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized (208-210)Fr ion beams at beam energies of 5 keV and intensities of 10(5) s(-1). Efficient neutralization (> or = 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  13. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    NASA Astrophysics Data System (ADS)

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized F208-210r ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (≥80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  14. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    SciTech Connect

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-15

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized {sup 208-210}Fr ion beams at beam energies of 5 keV and intensities of 10{sup 5} s{sup -1}. Efficient neutralization ({>=}80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  15. Nonlinear damping of a finite amplitude whistler wave due to modified two stream instability

    SciTech Connect

    Saito, Shinji; Nariyuki, Yasuhiro; Umeda, Takayuki

    2015-07-15

    A two-dimensional, fully kinetic, particle-in-cell simulation is used to investigate the nonlinear development of a parallel propagating finite amplitude whistler wave (parent wave) with a wavelength longer than an ion inertial length. The cross field current of the parent wave generates short-scale whistler waves propagating highly oblique directions to the ambient magnetic field through the modified two-stream instability (MTSI) which scatters electrons and ions parallel and perpendicular to the magnetic field, respectively. The parent wave is largely damped during a time comparable to the wave period. The MTSI-driven damping process is proposed as a cause of nonlinear dissipation of kinetic turbulence in the solar wind.

  16. Scalar-particle self-energy amplitudes and confinement in Minkowski space

    SciTech Connect

    Elmar P. Biernat, Franz Gross, Teresa Pena, Alfred Stadler

    2012-09-01

    We analyze the analytic structure of the Covariant Spectator Theory (CST) contribution to the self-energy amplitude for a scalar particle in a {phi}{sup 2}{chi} theory. To this end we derive dispersion relations in 1+1 and in 3+1 dimensional Minkowski space. The divergent loop integrals in 3+1 dimensions are regularized using dimensional regularization. We find that the CST dispersion relations exhibit, in addition to the usual right-hand branch cut, also a left-hand cut. The origin of this "spectator" left-hand cut can be understood in the context of scattering for a scalar {phi}{sup 2}{chi}{sup 2}-type theory. If the interaction kernel contains a linear confining component, its contribution to the self-energy vanishes exactly.

  17. Coherent Scatter Imaging Measurements

    NASA Astrophysics Data System (ADS)

    Ur Rehman, Mahboob

    In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.

  18. Magnetic diffuse scattering

    SciTech Connect

    Cable, J.W.

    1987-01-01

    The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recent neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs.

  19. 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.

  20. 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.