Direct Lorentz force compensation flowmeter for electrolytes
NASA Astrophysics Data System (ADS)
Vasilyan, S.; Froehlich, Th.
2014-12-01
A simplified method of contactless Lorentz force (LF) measurements for flow meters on electrolytes is described and realized. Modification and comparative representation are discussed against recently well-developed methods. Based on the catapult effect, that current carrying conductor experiences a repulsive force in a magnetic field, we demonstrate force measurement method of LF velocimetry applications by commonly known "electromagnetic force" compensation principle. Measurement approach through zero point stability is considered to minimize mechanical influences and avoid gravimetric uncertainties. Here, the current carrying wires are static fixed in the vicinity of magnet system at zero point stable position, while occurring deflection of magnets by electrolyte flow is compensated by external applied current within wires. Measurements performed by developed servo-system which drives control loop by means of optical position sensor for simplified (i) single wire and (ii) coil-like extended compensation schemes. Guided by experiments on electrolyte flow, we demonstrate the applicability of adopted principle for conductivities ranging from 2 to 20 S/m. Further improvements are discussed in agreement with the parameters of demonstration setup, straightforward theory, and experimental results. We argue that this method is potentially suitable for: (a) applications with higher conductivity like molten metal (order of 106 S/m) assuming spatial configuration of setup and (b) for lower range of conductivity (below 1 S/m) while this is strongly subject to stiffness of system and noise mainly mechanical and thermal radiations.
Direct Lorentz force compensation flowmeter for electrolytes
Vasilyan, S. Froehlich, Th.
2014-12-01
A simplified method of contactless Lorentz force (LF) measurements for flow meters on electrolytes is described and realized. Modification and comparative representation are discussed against recently well-developed methods. Based on the catapult effect, that current carrying conductor experiences a repulsive force in a magnetic field, we demonstrate force measurement method of LF velocimetry applications by commonly known “electromagnetic force” compensation principle. Measurement approach through zero point stability is considered to minimize mechanical influences and avoid gravimetric uncertainties. Here, the current carrying wires are static fixed in the vicinity of magnet system at zero point stable position, while occurring deflection of magnets by electrolyte flow is compensated by external applied current within wires. Measurements performed by developed servo-system which drives control loop by means of optical position sensor for simplified (i) single wire and (ii) coil-like extended compensation schemes. Guided by experiments on electrolyte flow, we demonstrate the applicability of adopted principle for conductivities ranging from 2 to 20 S/m. Further improvements are discussed in agreement with the parameters of demonstration setup, straightforward theory, and experimental results. We argue that this method is potentially suitable for: (a) applications with higher conductivity like molten metal (order of 10{sup 6 }S/m) assuming spatial configuration of setup and (b) for lower range of conductivity (below 1 S/m) while this is strongly subject to stiffness of system and noise mainly mechanical and thermal radiations.
Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system
NASA Astrophysics Data System (ADS)
Ebert, R.; Leineweber, J.; Resagk, C.
2015-07-01
Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1 kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.
Lorentz force particle analyzer
NASA Astrophysics Data System (ADS)
Wang, Xiaodong; Thess, André; Moreau, René; Tan, Yanqing; Dai, Shangjun; Tao, Zhen; Yang, Wenzhi; Wang, Bo
2016-07-01
A new contactless technique is presented for the detection of micron-sized insulating particles in the flow of an electrically conducting fluid. A transverse magnetic field brakes this flow and tends to become entrained in the flow direction by a Lorentz force, whose reaction force on the magnetic-field-generating system can be measured. The presence of insulating particles suspended in the fluid produce changes in this Lorentz force, generating pulses in it; these pulses enable the particles to be counted and sized. A two-dimensional numerical model that employs a moving mesh method demonstrates the measurement principle when such a particle is present. Two prototypes and a three-dimensional numerical model are used to demonstrate the feasibility of a Lorentz force particle analyzer (LFPA). The findings of this study conclude that such an LFPA, which offers contactless and on-line quantitative measurements, can be applied to an extensive range of applications. These applications include measurements of the cleanliness of high-temperature and aggressive molten metal, such as aluminum and steel alloys, and the clean manufacturing of semiconductors.
Bhattacharyya, Sampriti; Pilipenko, Roman; /Fermilab
2010-01-01
Superconducting accelerators, such as the International Linear Collider (ILC), rely on very high Q accelerating cavities to achieve high electric fields at low RF power. Such cavities have very narrow resonances: a few kHz with a 1.3GHz resonance frequency for the ILC. Several mechanical factors cause tune shifts much larger than this: pressure variations in the liquid helium bath; microphonics from pumps and other mechanical devices; and for a pulsed machine such as the ILC, Lorentz force detuning (pressure from the contained RF field). Simple passive stiffening is limited by many manufacturing and material considerations. Therefore, active tuning using piezo actuators is needed. Here we study a supply for their operation. Since commercial power amplifiers are expensive, we analyzed the characteristics of four power amplifiers: (iPZD) built by Istituto Nazionale di Fisica Nucleare (Sezione di Pisa); and a DC-DC converter power supply built in Fermilab (Piezo Master); and two commercial amplifiers, Piezosystem jena and Piezomechanik. This paper presents an analysis and characterization of these amplifiers to understand the cost benefit and reliability when using in a large scale, pulsed beam accelerator like the ILC.
Lorentz force optical coherence elastography
NASA Astrophysics Data System (ADS)
Wu, Chen; Singh, Manmohan; Han, Zhaolong; Raghunathan, Raksha; Liu, Chih-Hao; Li, Jiasong; Schill, Alexander; Larin, Kirill V.
2016-09-01
Quantifying tissue biomechanical properties can assist in detection of abnormalities and monitoring disease progression and/or response to a therapy. Optical coherence elastography (OCE) has emerged as a promising technique for noninvasively characterizing tissue biomechanical properties. Several mechanical loading techniques have been proposed to induce static or transient deformations in tissues, but each has its own areas of applications and limitations. This study demonstrates the combination of Lorentz force excitation and phase-sensitive OCE at ˜1.5 million A-lines per second to quantify the elasticity of tissue by directly imaging Lorentz force-induced elastic waves. This method of tissue excitation opens the possibility of a wide range of investigations using tissue biocurrents and conductivity for biomechanical analysis.
Torsional Oscillations with Lorentz Force
ERIC Educational Resources Information Center
Gluck, Paul
2007-01-01
We have built a device that uses the Lorentz force on a current-carrying wire situated in a magnetic field, F = I L x B, in order to demonstrate a slowly varying alternating current by means of an optical lever. The apparatus consists of a horseshoe magnet, a length of thin enamel-coated wire (ours was 0.3 mm thick), a signal generator, a…
Lorentz force megahertz optical coherence elastography
NASA Astrophysics Data System (ADS)
Wu, Chen; Singh, Manmohan; Han, Zhaolong; Raghunathan, Raksha; Liu, Chih-Hao; Li, Jiasong; Schill, Alexander; Larin, Kirill V.
2016-03-01
Optical Coherence Elastography (OCE) is a rapidly developing technique for assessing tissue biomechanical properties. This study demonstrates the first use of the Lorentz force to induce elastic waves within tissue to quantify the elasticity of tissue in combination with a phase-sensitive OCE system at ~1.5 million A-scans per second. The feasibility of this technique was tested on tissue-mimicking agar phantoms of various concentrations. The results as assessed by OCE were in good agreement with standard mechanical testing of the samples. After the preliminary experiments, the stiffness of porcine liver was examined. The results demonstrate that Lorentz force MHz OCE can be applied to study the elasticity of biological tissue effectively and has the potential for clinical applications due to rapid excitation and imaging.
Lorentz Force Based Satellite Attitude Control
NASA Astrophysics Data System (ADS)
Giri, Dipak Kumar; Sinha, Manoranjan
2016-07-01
Since the inception of attitude control of a satellite, various active and passive control strategies have been developed. These include using thrusters, momentum wheels, control moment gyros and magnetic torquers. In this present work, a new technique named Lorentz force based Coulombic actuators for the active control is proposed. This method uses electrostatic charged shells, which interact with the time varying earth's magnetic field to establish a full three axes control of the satellite. It is shown that the proposed actuation mechanism is similar to a satellite actuated by magnetic coils except that the resultant magnetic moment vanishes under two different conditions. The equation for the required charges on the the Coulomb shells attached to the satellite body axes is derived, which is in turn used to find the available control torque for actuating the satellite along the orbit. Stability of the proposed system for very high initial angular velocity and exponential stability about the origin are proved for a proportional-differential control input. Simulations are carried out to show the efficacy of the proposed system for the attitude control of the earth-pointing satellite.
LORENTZ SELF-FORCE OF AN ELLIPSE CURRENT LOOP MODEL
Olmedo, Oscar; Zhang Jie; Kunkel, Valbona
2013-07-10
In this work, the Lorentz self-force of an ellipse current loop model is derived. We are motivated by the fact that it has been reported in the literature that coronal mass ejection morphology can resemble an ellipse in the field of view of coronagraph images. Deriving the Lorentz self-force using an ellipse geometry has the advantage of being able to be solved analytically, as opposed to other more complex geometries. The derived ellipse model is compared with the local curvature approximation, where the Lorentz self-force at the ellipse major/minor axis is compared with the Lorentz self-force of a torus with curvature equal to the local curvature at the ellipses major/minor axis. It is found that the local curvature approximation is valid for moderate values of eccentricity.
The competition between Lorentz and Coriolis forces in planetary dynamos
NASA Astrophysics Data System (ADS)
Soderlund, Krista M.; Sheyko, Andrey; King, Eric M.; Aurnou, Jonathan M.
2015-12-01
Fluid motions within planetary cores generate magnetic fields through dynamo action. These core processes are driven by thermo-compositional convection subject to the competing influences of rotation, which tends to organize the flow into axial columns, and the Lorentz force, which tends to inhibit the relative movement of the magnetic field and the fluid. It is often argued that these forces are predominant and approximately equal in planetary cores; we test this hypothesis using a suite of numerical geodynamo models to calculate the Lorentz to Coriolis force ratio directly. Our results show that this ratio can be estimated by ( Λ i is the traditionally defined Elsasser number for imposed magnetic fields and Rm is the system-scale ratio of magnetic induction to magnetic diffusion). Best estimates of core flow speeds and magnetic field strengths predict the geodynamo to be in magnetostrophic balance where the Lorentz and Coriolis forces are comparable. The Lorentz force may also be significant, i.e., within an order of magnitude of the Coriolis force, in the Jovian interior. In contrast, the Lorentz force is likely to be relatively weak in the cores of Saturn, Uranus, Neptune, Ganymede, and Mercury.
Lorentz Body Force Induced by Traveling Magnetic Fields
NASA Technical Reports Server (NTRS)
Volz, M. P.; Mazuruk, K.
2003-01-01
The Lorentz force induced by a traveling magnetic field (TMF) in a cylindrical container has been calculated. The force can be used to control flow in dectrically conducting melts and the direction of the magnetic field and resulting flow can be reversed. A TMF can be used to partially cancel flow driven by buoyancy. The penetration of the field into the cylinder decreases as the frequency increases, and there exists an optimal value of frequency for which the resulting force is a maximum. Expressions for the Lorentz force in the limiting cases of low frequency and infinite cylinder are also given and compared to the numerical calculations.
A theoretical model for the Lorentz force particle analyzer
NASA Astrophysics Data System (ADS)
Moreau, René; Tao, Zhen; Wang, Xiaodong
2016-07-01
In a previous paper [X. Wang et al., J. Appl. Phys. 120, 014903 (2016)], several experimental devices have been presented, which demonstrate the efficiency of electromagnetic techniques for detecting and sizing electrically insulating particles entrained in the flow of a molten metal. In each case, a non-uniform magnetic field is applied across the flow of the electrically conducting liquid, thereby generating a braking Lorentz force on this moving medium and a reaction force on the magnet, which tends to be entrained in the flow direction. The purpose of this letter is to derive scaling laws for this Lorentz force from an elementary theoretical model. For simplicity, as in the experiments, the flowing liquid is modeled as a solid body moving with a uniform velocity U. The eddy currents in the moving domain are derived from the classic induction equation and Ohm's law, and expressions for the Lorentz force density j ×B and for its integral over the entire moving domain follow. The insulating particles that are eventually present and entrained with this body are then treated as small disturbances in a classic perturbation analysis, thereby leading to scaling laws for the pulses they generate in the Lorentz force. The purpose of this letter is both to illustrate the eddy currents without and with insulating particles in the electrically conducting liquid and to derive a key relation between the pulses in the Lorentz force and the main parameters (particle volume and dimensions of the region subjected to the magnetic field).
Lorentz-force-induced motion in conductive media.
Basford, Alexandra T; Basford, Jeffrey R; Kugel, Jennifer; Ehman, Richard L
2005-06-01
This project was designed to assess whether MRI imaging could detect Lorentz-force-induced motion in conductive samples. Experiments were performed by applying alternating voltages across 2% agar and 18% bovine gels placed in the field of a 1.5-T MRI scanner. Motion-sensitized time-gated MRI images that were obtained and analyzed with custom-developed software used in previous studies revealed the production of movement in both agar and gel samples. Motion was most pronounced in the plane vertical to the sample and had the greatest amplitude when the current path was perpendicular to the scanner's magnetic field. These findings are compatible with the vector cross product nature of the Lorentz force and suggest that the imaging of Lorentz-force-induced motion in conductive samples is feasible. Whether this approach can be extended to study electrically active tissues such as the peripheral nerves, brain and heart remains to be seen.
Attitude dynamics and control of spacecraft using geomagnetic Lorentz force
NASA Astrophysics Data System (ADS)
Abdel-Aziz, Yehia A.; Shoaib, Muhammad
2015-01-01
Attitude stabilization of a charged rigid spacecraft in Low Earth Orbit using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth's magnetic field will be subject to perturbations from the Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft's orientation. We assume that the spacecraft is moving in the Earth's magnetic field in an elliptical orbit under the effects of gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole. A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to mass ratio (α*). Stable orbits are identified for various values of α*. The main parameters for stabilization of the spacecraft are α* and the difference between the components of the moment of inertia for the spacecraft.
NASA Astrophysics Data System (ADS)
Prokopidis, Konstantinos; Kalialakis, Christos
2014-10-01
It is proposed that a recently used ad hoc modified Lorentz dielectric function for metals can be physically interpreted via the Lorentz-Dirac force. The Lorentz-Dirac force considers the radiation reaction of electrons, an effect that is ignored in classical dispersion relationships. A suitable reduced order form of the Lorentz-Dirac force that does not suffer from pre-acceleration and runaway artifacts is employed in the derivation of the modified dispersion model. The frequency characteristics and the causality of the Lorentz-Dirac dielectric model are studied in detail. Furthermore, the superiority of the Lorentz-Dirac dielectric function as a means of improved fitting of experimental data is demonstrated for gold, silver, and silicon in the infrared and optical region.
Manipulating the Lorentz force via the chirality of nanoparticles
NASA Astrophysics Data System (ADS)
Wang, Maoyan; Li, Hailong; Dong, Yuliang; Zhang, Xiaochuan; Du, Ming; Wang, Rui; Xu, Tong; Wu, Jian
2016-12-01
We demonstrate that a single plane wave pulls a chiral nanoparticle toward the light source. The nanoparticle exhibits optical gain in a particular wavelength region. The equivalence of the generalized and alternative expressions of the Lorentz force density relating to bound charges for chiral media is numerically validated. By considering the two-dimensional electromagnetic problem of incident plane waves normally impinged on active chiral cylinders, it is shown that the gradient force is mainly contributed by the bound electric and magnetic current densities of the cross-polarized waves. We also investigate how the medium parameters and impedance mismatch can be used to manipulate the pulling or pushing Lorentz forces between two chiral cylinders. This finding may provide a recipe to understand the light interaction with multiple chiral nanoparticles of arbitrary shapes (in general) with the aid of the numerical approach. It could be a promising avenue in controlling the optical micromanipulation for chiral nanoparticles with mirroring asymmetry.
Control of heat transfer in engine coolers by Lorentz forces
NASA Astrophysics Data System (ADS)
Karcher, C.; Kühndel, J.
2016-09-01
In engine coolers of off-highway vehicles convective heat transfer at the coolant side is a limiting factor of both efficiency and performance density of the cooler. Here, due to design restrictions, backwater areas and stagnation regions appear that are caused by flow deflections and cross-sectional expansions. As appropriate coolants, mixtures of water and glysantine are commonly used. Such coolants are characterized by their electrical conductivity of some S/m. This gives rise to control coolant flow and therefore convective heat transfer by means of Lorentz forces. These body forces are generated within the weakly conducting fluid by the interactions of an electrical current density and a localized magnetic field both of which being externally superimposed. In application this may be achieved by inserting electrodes in the cooler wall and a corresponding arrangement of permanent magnets. In this paper we perform numerical simulations of such magnetohydrodynamic flow in three model geometries that are frequently apparent in engine cooling applications: Carnot-Borda diffusor, 90° bend, and 180° bend. The simulations are carried out using the software package ANSYS Fluent. The present study demonstrates that, depending on the electromagnetic interaction parameter and the specific geometric arrangement of electrodes and magnetic field, Lorentz forces are suitable to break up eddy waters and separation zones and are thus significantly increasing convective heat transfer in these areas. Furthermore, the results show that due to the action of the Lorentz forces the hydraulic pressure losses can be reduced.
Vacuum Plasma Spray Forming of Tungsten Lorentz Force Accelerator Components
NASA Technical Reports Server (NTRS)
Zimmerman, Frank R.
2001-01-01
The Vacuum Plasma Spray (VPS) Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using the VPS process to form anode sections for a Lorentz force accelerator from tungsten. Lorentz force accelerators are an attractive form of electric propulsion that provides continuous, high-efficiency propulsion at useful power levels for such applications as orbit transfers or deep space missions. The VPS process is used to deposit refractory metals such as tungsten onto a graphite mandrel of the desired shape. Because tungsten is reactive at high temperatures, it is thermally sprayed in an inert environment where the plasma gun melts and accelerates the metal powder onto the mandrel. A three-axis robot inside the chamber controls the motion of the plasma spray torch. A graphite mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the anode. This paper describes the processing techniques, design considerations, and process development associated with the VPS forming of the Lorentz force accelerator.
Vacuum Plasma Spray Forming of Tungsten Lorentz Force Accelerator Components
NASA Technical Reports Server (NTRS)
Zimmerman, Frank R.
2004-01-01
The Vacuum Plasma Spray (VPS) Laboratory at NASA's Marshall Space Flight Center, working with the Jet Propulsion Laboratory, has developed and demonstrated a fabrication technique using the VPS process to form anode and cathode sections for a Lorentz force accelerator made from tungsten. Lorentz force accelerators are an attractive form of electric propulsion that provides continuous, high-efficiency propulsion at useful power levels for such applications as orbit transfers or deep space missions. The VPS process is used to deposit refractory metals such as tungsten onto a graphite mandrel of the desired shape. Because tungsten is reactive at high temperatures, it is thermally sprayed in an inert environment where the plasma gun melts and deposits the molten metal powder onto a mandrel. A three-axis robot inside the chamber controls the motion of the plasma spray torch. A graphite mandrel acts as a male mold, forming the required contour and dimensions for the inside surface of the anode or cathode of the accelerator. This paper describes the processing techniques, design considerations, and process development associated with the VPS forming of Lorentz force accelerator components.
Parameterization of the Lorentz to Coriolis Force Ratio in Planetary Dynamos
NASA Astrophysics Data System (ADS)
Soderlund, K. M.; Sheyko, A. A.; King, E. M.; Aurnou, J. M.
2015-12-01
The Lorentz to Coriolis force ratio is an important parameter for the dynamics of planetary cores: it is expected that dynamos with dominant Coriolis forces will be driven by fundamentally different archetypes of fluid motions than those with co-dominant Lorentz forces. Using a suite of geodynamo simulations, we have tested several parameterizations of the Lorentz to Coriolis force ratio against direct calculations and developed a scaling estimate to predict this ratio for planetary cores. Our results suggest that the Earth's core is likely to be in magnetostrophic balance where the Lorentz and Coriolis forces are comparable. The Lorentz force may also be significant in Jupiter's core, where it is predicted to be approximately a factor of ten less than the Coriolis force. Magnetic fields become increasingly sub-dominant for the other planets: the Coriolis force is predicted to exceed the Lorentz force by at least two orders of magnitude within the cores of Saturn, Uranus/Neptune, Ganymede, and Mercury.
Lorentz-Dirac force from QED for linear acceleration
NASA Astrophysics Data System (ADS)
Higuchi, Atsushi; Martin, Giles D.
2004-10-01
We investigate the motion of a wave packet of a charged scalar particle linearly accelerated by a static potential in quantum electrodynamics. We calculate the expectation value of the position of the charged particle after the acceleration to first order in the fine structure constant in the ℏ→0 limit. We find that the change in the expectation value of the position (the position shift) due to radiation reaction agrees exactly with the result obtained using the Lorentz-Dirac force in classical electrodynamics. We also point out that the one-loop correction to the potential may contribute to the position change in this limit.
Amplitude modulated Lorentz force MEMS magnetometer with picotesla sensitivity
NASA Astrophysics Data System (ADS)
Kumar, Varun; Ramezany, Alireza; Mahdavi, Mohammad; Pourkamali, Siavash
2016-10-01
This paper demonstrates ultra-high sensitivities for a Lorentz force resonant MEMS magnetometer enabled by internal-thermal piezoresistive vibration amplification. A detailed model of the magneto-thermo-electro-mechanical internal amplification is described and is in good agreement with the experimental results. Internal amplification factors up to ~1620 times have been demonstrated by artificially boosting the effective quality factor of the resonator from 680 to 1.14 × 106 by tuning the bias current. The increase in the resonator bias current in addition to the improvement in the quality factor of the device led to a sensitivity enhancement by ~2400 times. For a bias current of 7.245 mA, where the effective quality factor of the device and consequently the sensitivity is maximum (2.107 mV nT-1), the noise floor is measured to be as low as 2.8 pT (√Hz)-1. This is by far the most sensitive Lorentz force MEMS magnetometer demonstrated to date.
Force-rebalanced Lorentz force magnetometer based on a micromachined oscillator
NASA Astrophysics Data System (ADS)
Sonmezoglu, S.; Li, M.; Horsley, D. A.
2015-03-01
This paper presents a 3-axis Lorentz force magnetometer based on an encapsulated micromechanical silicon resonator having three orthogonal vibration modes, each measuring one vector component of the external magnetic field. One mode, with natural frequency (fn) of 46.973 kHz and quality factor (Q) of 14 918, is operated as a closed-loop electrostatically excited oscillator to provide a frequency reference for 3-axis sensing and Lorentz force generation. Current, modulated at the reference frequency, is injected into the resonator, producing Lorentz force that is centered at the reference frequency. Lorentz force in the first axis is nulled by the oscillator loop, resulting in force-rebalanced operation. The bandwidth and scale-factor of this force-rebalanced axis are independent of resonator Q, improving the sensor's temperature coefficient from 20 841 ppm/ °C to 424 ppm/ °C. The frequencies of the other two modes are closely spaced to the first mode's reference frequency and are demonstrated to track this frequency over temperature within 1 ppm/K. Field measurements in these two axes are conducted open-loop and off-resonance, ensuring that the scale-factor is independent of Q to first order and producing a measurement bandwidth of over 40 Hz.
A novel reciprocating micropump based on Lorentz force
NASA Astrophysics Data System (ADS)
Salari, Alinaghi; Hakimsima, Abbas; Shafii, Mohammad Behshad
2015-03-01
Lorentz force is the pumping basis of many electromagnetic micropumps used in lab-on-a-chip. In this paper a novel reciprocating single-chamber micropump is proposed, in which the actuation technique is based on Lorentz force acting on an array of microwires attached on a membrane surface. An alternating current is applied through the microwires in the presence of a magnetic field. The resultant force causes the membrane to oscillate and pushes the fluid to flow through microchannel using a ball-valve. The pump chamber (3 mm depth) was fabricated on a Polymethylmethacrylate (PMMA) substrate using laser engraving technique. The chamber was covered by a 60 μm thick hyper-elastic latex rubber diaphragm. Two miniature permanent magnets capable of providing magnetic field of 0.09 T at the center of the diaphragm were mounted on each side of the chamber. Square wave electric current with low-frequencies was generated using a function generator. Cylindrical copper microwires (250 μm diameter and 5 mm length) were attached side-by-side on top surface of the diaphragm. Thin loosely attached wires were used as connectors to energize the electrodes. Due to large displacement length of the diaphragm (~3 mm) a high efficiency (~90%) ball valve (2 mm diameter stainless steel ball in a tapered tubing structure) was used in the pump outlet. The micropump exhibits a flow rate as high as 490 μl/s and pressure up to 1.5 kPa showing that the pump is categorized among high-flow-rate mechanical micropumps.
The electrodeless Lorentz force (ELF) thruster experimental facility.
Weber, T E; Slough, J T; Kirtley, D
2012-11-01
An innovative facility for testing high-power, pulsed plasmoid thrusters has been constructed to develop the electrodeless Lorentz force (ELF) thruster concept. It is equipped with a suite of diagnostics optimized to study the physical processes taking place within ELF and evaluate its propulsive utility including magnetic field, neutral gas, and plasma flux diagnostics, a method to determine energy flow into the plasma from the pulsed power systems, and a new type of ballistic pendulum, which enables thrust to be measured without the need for installing the entire propulsion system on a thrust stand. Variable magnetic fields allow controlled studies of plume expansion in a small-scale experiment and dielectric chamber walls reduce electromagnetic influences on plasma behavior and thruster operation. The unique capabilities of this facility enable novel concept development to take place at greatly reduced cost and increased accessibility compared to testing at large user-facilities.
Undulator with dynamic compensation of magnetic forces
Gluskin, Efim; Trakhtenberg, Emil; Xu, Joseph Z.
2016-05-31
A method and apparatus for implementing dynamic compensation of magnetic forces for undulators are provided. An undulator includes a respective set of magnet arrays, each attached to a strongback, and placed on horizontal slides and positioned parallel relative to each other with a predetermined gap. Magnetic forces are compensated by a set of compensation springs placed along the strongback. The compensation springs are conical springs having exponential-force characteristics that substantially match undulator magnetic forces independently of the predetermined gap. The conical springs are positioned along the length of the magnets.
Relative dynamics and control of spacecraft formations subject to lorentz force perturbations
NASA Astrophysics Data System (ADS)
Abdel-Aziz, Yehia; Shoaib, Muhammad
A spacecraft that generates an electrostatic charge on its surface in the Earth magnetic field will be subject to a perturbative Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft’s orbit. We develop Lorentz force as a function of the orbital elements. The orbital perturbations of a charged spacecraft by Lorentz force in the Earth’s magnetic field are investigated using the Gauss variation of the Lagrange planetary Equations. The Earth’s magnetic field is modeled as a tilted dipole. The perturbations in the orbital elements depend on the value of the charge to mass ratio (q/m). The dynamical model of relative motion developed leads to approximate analytical solutions for the motion of a charged spacecraft subject to Lorentz force. The chief spacecraft’s reference orbit is taken to be either circular or elliptical. The deputy spacecraft is capable of accumulating electrostatic charge. The numerical results show that Lorentz force can be used to change the in-track position and plane orbit of the spacecraft. The numerical analysis shows that the target trajectory of the Lorentz spacecraft can be reached by varying the ratio (q/m) in different Low Earth Orbits.
Optimal impedance on transmission of Lorentz force EMATs
NASA Astrophysics Data System (ADS)
Isla, Julio; Seher, Matthias; Challis, Richard; Cegla, Frederic
2016-02-01
Electromagnetic-acoustic transducers (EMATs) are attractive for non-destructive inspections because direct contact with the specimen under test is not required. This advantage comes at a high cost in sensitivity and therefore it is important to optimise every aspect of an EMAT. The signal strength produced by EMATs is in part determined by the coil impedance regardless of the transduction mechanism (e.g. Lorentz force, magnetostriction, etc.). There is very little literature on how to select the coil impedance that maximises the wave intensity; this paper addresses that gap. A transformer circuit is used to model the interaction between the EMAT coil and the eddy currents that are generated beneath the coil in the conducting specimen. Expressions for the coil impedances that satisfy the maximum efficiency and maximum power transfer conditions on transmission are presented. To support this analysis, a tunable coil that consists of stacked identical thin layers independently accessed is used so that the coil inductance can be modified while leaving the radiation pattern of the EMAT unaffected.
A study of dynamic Lorentz force detuning of 650 MHz βg=0.9 superconducting radiofrequency cavity
NASA Astrophysics Data System (ADS)
Kumar, Abhay; Ratan Jana, Arup; Kumar, Vinit
2014-06-01
The small bandwidth of superconducting cavities makes the study of dynamic Lorentz force detuning and its compensation indispensable in case of pulsed mode operation of high gradient accelerators. In this paper, we present the study of this detuning and also propose an optimized design for five cell 650 MHz βg=0.9 elliptic superconducting cavities, which will be used in the high energy section of the 1 GeV H- linear accelerator for the proposed Indian spallation neutron source project, by suitably inserting the inter-cell stiffeners. The paper presents a sequential design methodology which starts with study of static Lorentz force detuning and tunability; and progresses to find out the structural modes and related dynamic detuning values by performing transient structural dynamics calculations. The developed methodology is general in nature and can be used for a three dimensional model of any geometry. The work will be useful for optimizing the design against dynamic Lorentz force detuning of superconducting radiofrequency cavities of any shape.
Behavior of Boundary Layer in Supersonic Flow with Applied Lorentz Force
NASA Astrophysics Data System (ADS)
Udagawa, Keisuke; Saito, Shinya; Kawaguchi, Kenji; Tomioka, Sadatake; Yamasaki, Hiroyuki
Experimental study on behavior of boundary layer in supersonic flow with applied Lorentz force was carried out. In the experiment, Mach 1.5 supersonic wind tunnel driven by a shock-tube was used. At the test section, the current from the external DC power supply and the magnetic field of 2.4 Tesla were applied to the boundary layer developing on the bottom wall. Argon seeded with cesium was used as an electrically conducting gas. Effect of the direction of the Lorentz force on static pressure distribution was investigated, and the remarkable increase of static pressure at the test section was observed for the decelerating Lorentz force. It is noted that the acceleration of the flow inside the boundary layer was demonstrated for the first time without accelerating the main flow when the accelerating Lorentz force was applied. At the same time, the acceleration efficiency defined by a ratio of work done by the Lorentz force to energy input into the flow was found 54-61%. These results have suggested the possibility of the boundary layer separation control by applying the accelerating Lorentz force. In the case of the decelerating Lorentz force, the significant reduction of Mach number was observed not only inside the boundary layer but also in the main flow. The reduction of Mach number could be ascribed to the growth of the boundary layer due to gas heating inside the boundary layer. When the direction of the current was changed, the difference of light emission from the discharge inside the boundary layer was observed, and this was due to the difference of the electromotive force induced in the supersonic flow.
Lorentz force electrical impedance tomography using magnetic field measurements.
Zengin, Reyhan; Gençer, Nevzat Güneri
2016-08-21
In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from [Formula: see text] to [Formula: see text] at intervals of [Formula: see text]. The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 d
Lorentz force electrical impedance tomography using magnetic field measurements
NASA Astrophysics Data System (ADS)
Zengin, Reyhan; Güneri Gençer, Nevzat
2016-08-01
In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from -{{25}\\circ} to {{25}\\circ} at intervals of {{5}\\circ} . The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 dB. Simulation studies
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography.
Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy
2015-05-07
Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an 'acousto-electrical speckle' in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography
NASA Astrophysics Data System (ADS)
Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy
2015-05-01
Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.
Mansuripur, Masud
2012-05-11
The Lorentz law of force is the fifth pillar of classical electrodynamics, the other four being Maxwell's macroscopic equations. The Lorentz law is the universal expression of the force exerted by electromagnetic fields on a volume containing a distribution of electrical charges and currents. If electric and magnetic dipoles also happen to be present in a material medium, they are traditionally treated by expressing the corresponding polarization and magnetization distributions in terms of bound-charge and bound-current densities, which are subsequently added to free-charge and free-current densities, respectively. In this way, Maxwell's macroscopic equations are reduced to his microscopic equations, and the Lorentz law is expected to provide a precise expression of the electromagnetic force density on material bodies at all points in space and time. This Letter presents incontrovertible theoretical evidence of the incompatibility of the Lorentz law with the fundamental tenets of special relativity. We argue that the Lorentz law must be abandoned in favor of a more general expression of the electromagnetic force density, such as the one discovered by Einstein and Laub in 1908. Not only is the Einstein-Laub formula consistent with special relativity, it also solves the long-standing problem of "hidden momentum" in classical electrodynamics.
Imaging of Shear Waves Induced by Lorentz Force in Soft Tissues
NASA Astrophysics Data System (ADS)
Grasland-Mongrain, P.; Souchon, R.; Cartellier, F.; Zorgani, A.; Chapelon, J. Y.; Lafon, C.; Catheline, S.
2014-07-01
This study presents the first observation of elastic shear waves generated in soft solids using a dynamic electromagnetic field. The first and second experiments of this study showed that Lorentz force can induce a displacement in a soft phantom and that this displacement was detectable by an ultrasound scanner using speckle-tracking algorithms. For a 100 mT magnetic field and a 10 ms, 100 mA peak-to-peak electrical burst, the displacement reached a magnitude of 1 μm. In the third experiment, we showed that Lorentz force can induce shear waves in a phantom. A physical model using electromagnetic and elasticity equations was proposed. Computer simulations were in good agreement with experimental results. The shear waves induced by Lorentz force were used in the last experiment to estimate the elasticity of a swine liver sample.
Herrera-May, Agustín Leobardo; Soler-Balcazar, Juan Carlos; Vázquez-Leal, Héctor; Martínez-Castillo, Jaime; Vigueras-Zuñiga, Marco Osvaldo; Aguilera-Cortés, Luz Antonio
2016-01-01
Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate with Lorentz force. These sensors have a compact structure, wide measurement range, low energy consumption, high sensitivity and suitable performance. The design methodology, simulation tools, damping sources, sensing techniques and future applications of magnetic field sensors are discussed. The design process is fundamental in achieving correct selection of the operation principle, sensing technique, materials, fabrication process and readout systems of the sensors. In addition, the description of the main sensing systems and challenges of the MEMS sensors are discussed. To develop the best devices, researches of their mechanical reliability, vacuum packaging, design optimization and temperature compensation circuits are needed. Future applications will require multifunctional sensors for monitoring several physical parameters (e.g., magnetic field, acceleration, angular ratio, humidity, temperature and gases). PMID:27563912
Herrera-May, Agustín Leobardo; Soler-Balcazar, Juan Carlos; Vázquez-Leal, Héctor; Martínez-Castillo, Jaime; Vigueras-Zuñiga, Marco Osvaldo; Aguilera-Cortés, Luz Antonio
2016-08-24
Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate with Lorentz force. These sensors have a compact structure, wide measurement range, low energy consumption, high sensitivity and suitable performance. The design methodology, simulation tools, damping sources, sensing techniques and future applications of magnetic field sensors are discussed. The design process is fundamental in achieving correct selection of the operation principle, sensing technique, materials, fabrication process and readout systems of the sensors. In addition, the description of the main sensing systems and challenges of the MEMS sensors are discussed. To develop the best devices, researches of their mechanical reliability, vacuum packaging, design optimization and temperature compensation circuits are needed. Future applications will require multifunctional sensors for monitoring several physical parameters (e.g., magnetic field, acceleration, angular ratio, humidity, temperature and gases).
Numerical investigation on feedback control of flow around an oscillating hydrofoil by Lorentz force
NASA Astrophysics Data System (ADS)
Liu, Zong-Kai; Zhou, Ben-Mou; Liu, Hui-Xing; Ji, Yan-Liang; Huang, Ya-Dong
2013-06-01
In order to improve the hydrodynamic characteristics of a hydrofoil (NACA0012), this paper investigates an oscillating hydrofoil immersed in seawater (an electrically poorly conducting fluid) with feedback control of electromagnetic force (Lorentz force). This method is used in the iterative process, by forecasting the location of boundary layer separation points and attack angle at the next time step and figuring out the optimal force distribution function based on these parameters, then returns to the current time step and applies the optimal force onto the leeside to control the flow separation. Based on the basic flow governing equations, the flow field structures, lift evolutions and energy consumptions (the input impulse of Lorentz force) have been numerically investigated. Numerical results show that with this control, the flow separation could be fully suppressed. Meanwhile, the lift increases dramatically and oscillation is suppressed successfully. Furthermore, under similar lift improvement and control effects, the feedback control optimal ratio is 72.58%.
Experimental Demonstration of a Synthetic Lorentz Force by Using Radiation Pressure.
Šantić, N; Dubček, T; Aumiler, D; Buljan, H; Ban, T
2015-09-02
Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz force, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, radiation pressure - being one of the most common forces induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The force is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries.
Experimental Demonstration of a Synthetic Lorentz Force by Using Radiation Pressure
Šantić, N.; Dubček, T.; Aumiler, D.; Buljan, H.; Ban, T.
2015-01-01
Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz force, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, radiation pressure - being one of the most common forces induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The force is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries. PMID:26330327
NASA Astrophysics Data System (ADS)
Rouge, C.; Lhémery, A.; Aristégui, C.
2014-04-01
Magnetostriction arises in ferromagnetic materials subjected to magnetization, e.g., when an EMAT (Electro-Magnetic Acoustic Transducer) is used to generate ultrasonic waves. In such a case, the magnetostriction force must be taken into account as a transduction process that adds up to the Lorentz force. When the static magnetic field is high compared to the dynamic field, both forces are driven by the excitation frequency. For lower static relative values of the magnetic fields, the Lorentz force comprises both the excitation frequency and its first harmonic. In this work, a model is derived to predict the frequency content of the magnetostrictive force that comprises several harmonics. The discrete frequency spectrum strongly depends on both the static field and the relative amplitude of the dynamic field. The only material input data needed to predict it is the curve of macroscopic magnetostrictive strain that can be measured in the direction of an imposed magnetic field. Then, the various frequency-dependent distributions of Lorentz and magnetostriction body forces can be transformed into equivalent surface stresses. Examples of computation are given for different static and dynamic magnetic fields to study their influence on the frequency content of waves generated in ferromagnetic materials.
Galloway, Benjamin R; Popmintchev, Dimitar; Pisanty, Emilio; Hickstein, Daniel D; Murnane, Margaret M; Kapteyn, Henry C; Popmintchev, Tenio
2016-09-19
We present a semi-classical study of the effects of the Lorentz force on electrons during high harmonic generation in the soft and hard X-ray regions driven by near- and mid-infrared lasers with wavelengths from 0.8 to 20 μm, and at intensities below 10^{15} W/cm^{2}. The transverse extent of the longitudinal Lorentz drift is compared for both Gaussian focus and waveguide geometries. Both geometries exhibit a longitudinal electric field component that cancels the magnetic Lorentz drift in some regions of the focus, once each full optical cycle. We show that the Lorentz force contributes a super-Gaussian scaling which acts in addition to the dominant high harmonic flux scaling of λ^{-(5-6)} due to quantum diffusion. We predict that the high harmonic yield will be reduced for driving wavelengths > 6 μm, and that the presence of dynamic spatial mode asymmetries results in the generation of both even and odd harmonic orders. Remarkably, we show that under realistic conditions, the recollision process can be controlled and does not shut off completely even for wavelengths >10 μm and recollision energies greater than 15 keV.
Lorentz force and radiation pressure on a spherical cloak
Chen Hongsheng; Wu, B.-I.; Zhang Baile; Luo Yu; Zhang Jingjing; Ran Lixin; Kemp, Brandon A.
2009-07-15
The mechanical behavior of a transformation based spherical cloak under wave illumination is derived. We show that the equatorial region of the cloak is subject to much higher stress than the polar regions, where the polar axis is defined along the wave propagation direction. These forces do not exist before transformation but stem from the squeezed electromagnetic space. The trajectory of the ray can be interpreted as a result of the recoil force that the cloak exerts upon the ray. The total radiation pressure on an ideal cloak is shown to be exactly zero, effecting a stationary cloak.
NASA Astrophysics Data System (ADS)
Hernández, Daniel; Schleichert, Jan; Karcher, Christian; Fröhlich, Thomas; Wondrak, Thomas; Timmel, Klaus
2016-06-01
Lorentz force velocimetry is a non-invasive velocity measurement technique for electrical conductive liquids like molten steel. In this technique, the metal flow interacts with a static magnetic field generating eddy currents which, in turn, produce flow-braking Lorentz forces within the fluid. These forces are proportional to the electrical conductivity and to the velocity of the melt. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied static magnetic field which is in our case a permanent magnet. In this paper we will present a new multicomponent sensor for the local Lorentz force flowmeter (L2F2) which is able to measure simultaneously all three components of the force as well as all three components of the torque. Therefore, this new sensor is capable of accessing all three velocity components at the same time in the region near the wall. In order to demonstrate the potential of this new sensor, it is used to identify the 3-dimensional velocity field near the wide face of the mold of a continuous caster model available at the Helmholtz-Zentrum Dresden-Rossendorf. As model melt, the eutectic alloy GaInSn is used.
An Experimental Study of Electromagnetic Lorentz Force and Rail Recoil
2009-12-01
MOTIVATION For over 200 years, electromagnetic forces have been extensively researched. During 1802 , Gian Domenico Romagnosi noticed that a magnetic...C. Woods, “Comment: Origin, location, magnitude and consequences of recoil in the plasma armature railgun,” Inst. Elect. Eng. Proc. Sci. Meas...22, pp. 849-850, 1989. [26] A. E. Witalis, “Origin, location, magnitude and consequences of recoil in the plasma armature railgun,” Inst. Elect
Dynamics and control of spacecraft hovering using the geomagnetic Lorentz force
NASA Astrophysics Data System (ADS)
Huang, Xu; Yan, Ye; Zhou, Yang
2014-02-01
To achieve hovering, a spacecraft thrusts continuously to induce an equilibrium state at a desired position. Due to the constraints on the quantity of propellant onboard, long-time hovering around low-Earth orbits (LEO) is hardly achievable using traditional chemical propulsion. The Lorentz force, acting on an electrostatically charged spacecraft as it moves through a planetary magnetic field, provides a new propellantless method for orbital maneuvers. This paper investigates the feasibility of using the induced Lorentz force as an auxiliary means of propulsion for spacecraft hovering. Assuming that the Earth's magnetic field is a dipole that rotates with the Earth, a dynamical model that characterizes the relative motion of Lorentz spacecraft is derived to analyze the required open-loop control acceleration for hovering. Based on this dynamical model, we first present the hovering configurations that could achieve propellantless hovering and the corresponding required specific charge of a Lorentz spacecraft. For other configurations, optimal open-loop control laws that minimize the control energy consumption are designed. Likewise, the optimal trajectories of required specific charge and control acceleration are both presented. The effect of orbital inclination on the expenditure of control energy is also analyzed. Further, we also develop a closed-loop control approach for propellantless hovering. Numerical results prove the validity of proposed control methods for hovering and show that hovering around low-Earth orbits would be achievable if the required specific charge of a Lorentz spacecraft becomes feasible in the future. Typically, hovering radially several kilometers above a target in LEO requires specific charges on the order of 0.1 C/kg.
NASA Astrophysics Data System (ADS)
Essén, Hanno; Nordmark, Arne B.
2016-09-01
The canonical Poisson bracket algebra of four-dimensional relativistic mechanics is used to derive the equation of motion for a charged particle, with the Lorentz force, and the homogeneous Maxwell equations.
Fujii, Masafumi
2010-12-20
We analyze light-induced forces on metal nano-spheres by using the three-dimensional finite-difference time-domain method with the Lorentz force formulation. Convergent analysis of the force on metal nano-particle clusters has been achieved by integrating the Lorentz and the Coulomb forces over the volume of the metal particles. Comparison to the Mie theory of radiation pressure on metal spheres under a plane wave illumination has verified rigorously the accuracy of the numerical method. We also analyze separate two metal spheres in close proximity and the results of the induced forces are compared to those in previous publications. The present method allows analysis of forces on various irregular structures; we apply the method to touching metal spheres, forming a simple cluster with a slight deformation at the contact point, to analyze the forces induced by the plasmonic resonance of the clusters. We show that the fundamental resonance modes, which newly appear in an infrared range when spheres are touching, exhibit strong binding forces within the clusters. Based on the numerical analyses we identify the resonance modes and evaluate quantitatively the infrared-induced forces on metal nano-sphere clusters.
NASA Astrophysics Data System (ADS)
Weier, T.; Cierpka, C.; Huller, J.; Gerbeth, G.
2006-12-01
Velocity measurements and shadowgraph visualizations for copper electrolysis under the influence of a magnetic field are reported. Experiments in a rectangular cell show the expected strong correlation between flow features and limiting current density. The flow can be understood as driven by the interplay of Lorentz force and buoyancy. For a cylindrical cell with only slightly non-parallel electric and magnetic field lines, the presence and importance of the Lorentz force is demonstrated by velocity measurements. Figs 6, Refs 13.
Lorentz Force Flowmeter for Liquid Aluminum: Laboratory Experiments and Plant Tests
NASA Astrophysics Data System (ADS)
Kolesnikov, Yurii; Karcher, Christian; Thess, André
2011-06-01
This article aims to demonstrate that molten metal flow at a high temperature can be measured effectively in a contactless manner by using external direct current magnetic fields. The device applied in the present work is termed Lorentz force flowmeter (LFF) and is based on exposing the flow to a magnet system and measuring the drag force acting on it. Two series of measurements are reported. In the first series, we perform a model experiment in the laboratory using the eutectic alloy GaInSn, which is liquid at room temperature. The second series of measurements is devoted to two plant tests on flow measurement of a liquid aluminum alloy. In both tests, the force acting on the magnet system is measured that is equal to the Lorentz force acting on the flow. To generalize our results, we also derive the scaling law that relates the force acting on a localized magnet system to the flow rate of a fluid with arbitrary electrical conductivity. This law shows that LFF, if properly designed, has a wide range of potential applications in ferrous and nonferrous metallurgy.
Considerations against a force compensated coil
Hassenzahl, W.
1988-08-01
The cost of structural components in a large superconducting coil may well exceed the coil and cryostat cost. As a result, the idea of constructing a system composed of two different coil types assembled in such a way that the sources balance and reduce the total structural requirement is oft proposed. A suitable geometry has never been found for the fundamental reason that there can be no force compensated solution. In this paper, the general problem is presented and an analysis of the energy stored and stresses produced in the structure are described in a fundamental way. Finally, the relation between structural mass M and stored energy E, M greater than or equal to/rho/E/sigma/sub w/, that is valid for all magnetic systems is developed, where /rho/ is the density of the structure and sigma/sub w/ is the working stress in the structure. 12 refs., 2 figs.
Experimental Demonstration of Synthetic Lorentz Force on Cold Atoms by Using Radiation Pressure
NASA Astrophysics Data System (ADS)
Ban, Ticijana; Santic, Neven; Dubcek, Tena; Aumiler, Damir; Buljan, Hrvoje
2015-05-01
The quest for synthetic magnetism in quantum degenerate atomic gases is motivated by producing controllable quantum emulators, which could mimic complex quantum systems such as interacting electrons in magnetic fields. Experiments on synthetic magnetic fields for neutral atoms have enabled realization of the Hall effect, Harper and Haldane Hamiltonians, and other intriguing topological effects. Here we present the first demonstration of a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, in cold atomic gases captured in a Magneto-Optical Trap (MOT). Synthetic Lorentz force on cold atomic cloud is measured by recording the cloud trajectory. The observed force is perpendicular to the cloud velocity, and it is zero for the atomic cloud at rest. The proposed concept is straightforward to implement in a large volume and different geometries, it is applicable for a broad range of velocities, and it can be realized for different atomic species. The experiment is based on the theoretical proposal introduced in. This work was supported by the UKF Grant No. 5/13 and Croatian MZOS.
A simple levitation system using wireless power supply system and Lorentz force
NASA Astrophysics Data System (ADS)
Oka, Koichi; Tanaka, Masako
2016-09-01
A new type of magnetic levitation mechanism has been proposed. The feature of this mechanism is using wireless power supply system and Lorentz forces for levitation. The stability of levitation is performed by passive control by magnetic flux configuration between permanent magnets and active control of electromagnets. In this paper, the concept of levitation mechanism is introduced, FEM analyses for levitation force and wireless power supply performance is examined. In concept two types of levitation systems which are different on the point of active control directions are introduced. In FEM analyses, the required current for levitation and the directions of generating forces are calculated. In the study of wireless power supply system, the required voltage for the levitation is expected. Finally the feasibility of the proposed levitation system will be verified.
NASA Astrophysics Data System (ADS)
Wang, Shen; Huang, Songling; Zhang, Yu; Zhao, Wei
2016-12-01
The electromagnetic acoustic transducers (EMATs) are gaining much attention in recent years due to their non-contact operation in ultrasonic wave generation and reception in NDT field. Quite often the transduction efficiency of EMATs is low, so efforts are always necessary to gain a better understanding of their complex and multi-physics transduction mechanism. In this work, we focused on modeling of an omni-directional Lorentz force-based EMAT operating on an aluminum disk and containing a rounded meander coil to generate a pure Lamb wave mode. We introduced an approach to solve the underlying eddy current equations in cylindrical coordinates directly, and applied this approach to a multi-conductor electromagnetic model to investigate the skin and proximity effects. These effects existed both for the complete and incomplete equations. Then we built the omni-directional EMAT model composed of three sub-models and two geometries. The two-geometry structure made it possible to reduce the total number of elements. Time varying spatial distribution of the Lorentz force vector was plotted. Propagation velocity of the simulated wave packet was compared with the group velocity of desired S0 mode Lamb waves. Interaction of the waves with a slot defect with a depth of 50% thickness was studied. The response to high current excitation and dynamic magnetic field was also investigated.
Embbeded dipolar vortices driven by Lorentz forces in a shallow liquid metal layer
NASA Astrophysics Data System (ADS)
Lara, Cinthya G.; Cuevas, Sergio
2014-11-01
We present an experimental and numerical study of the vortex pattern that results from the action of a localized Lorentz force in a thin liquid metal layer (GaInSn) contained in a square box. The fluid motion is generated by the interaction of a uniform D.C. current and a non-uniform magnetic field produced by square-shaped permanent magnet much smaller that the container. Unlike the simple vortex dipole created by a localized Lorentz force in a layer of electrolyte, a more complex vortex pattern is formed in a liquid metal layer. Experiments show the appearance of two ``embedded'' vortex dipoles with a quasi-stagnat zone in the region of highest magnetic field intensity. The observed pattern can be explained by noticing that the localized magnetic field acts as a magnetic obstacle for the imposed flow. Using the Ultrasonic Doppler Velocimetry technique, we obtained the velocity profiles along the symmetry axis. We developed a quasi-two-dimensional numerical model that takes into account the effect of the boundary layers adhered to the bottom wall, the Hartmann friction and the induced effects. Numerical simulations show a satisfactory qualitative and quantitative agreement with the experimental results. Work supported by CONACYT, Mexico under Project 131399. C. G. Lara acknowledges a grant from CONACYT.
Self-similar expansion of solar coronal mass ejections: Implications for Lorentz self-force driving
Subramanian, Prasad; Arunbabu, K. P.; Mauriya, Adwiteey; Vourlidas, Angelos
2014-08-01
We examine the propagation of several coronal mass ejections (CMEs) with well-observed flux rope signatures in the field of view of the SECCHI coronagraphs on board the STEREO satellites using the graduated cylindrical shell fitting method of Thernisien et al. We find that the manner in which they propagate is approximately self-similar; i.e., the ratio (κ) of the flux rope minor radius to its major radius remains approximately constant with time. We use this observation of self-similarity to draw conclusions regarding the local pitch angle (γ) of the flux rope magnetic field and the misalignment angle (χ) between the current density J and the magnetic field B. Our results suggest that the magnetic field and current configurations inside flux ropes deviate substantially from a force-free state in typical coronagraph fields of view, validating the idea of CMEs being driven by Lorentz self-forces.
NASA Astrophysics Data System (ADS)
Vasilyan, Suren; Rivero, Michel; Schleichert, Jan; Halbedel, Bernd; Fröhlich, Thomas
2016-04-01
In this paper, we present an application for realizing high-precision horizontally directed force measurements in the order of several tens of nN in combination with high dead loads of about 10 N. The set-up is developed on the basis of two identical state-of-the-art electromagnetic force compensation (EMFC) high precision balances. The measurement resolution of horizontally directed single-axis quasi-dynamic forces is 20 nN over the working range of ±100 μN. The set-up operates in two different measurement modes: in the open-loop mode the mechanical deflection of the proportional lever is an indication of the acting force, whereas in the closed-loop mode it is the applied electric current to the coil inside the EMFC balance that compensates deflection of the lever to the offset zero position. The estimated loading frequency (cutoff frequency) of the set-up in the open-loop mode is about 0.18 Hz, in the closed-loop mode it is 0.7 Hz. One of the practical applications that the set-up is suitable for is the flow rate measurements of low electrically conducting electrolytes by applying the contactless technique of Lorentz force velocimetry. Based on a previously developed set-up which uses a single EMFC balance, experimental, theoretical and numerical analyses of the thermo-mechanical properties of the supporting structure are presented.
Hidden momentum in a hydrogen atom and the Lorentz-force law
NASA Astrophysics Data System (ADS)
Filho, J. S. Oliveira; Saldanha, Pablo L.
2015-11-01
By using perturbation theory, we show that a hydrogen atom with magnetic moment due to the orbital angular momentum of the electron has so-called hidden momentum in the presence of an external electric field. This means that the atomic electronic cloud has a nonzero linear momentum in its center-of-mass rest frame due to a relativistic effect. This is completely analogous to the hidden momentum that a classical current loop has in the presence of an external electric field. We discuss how this effect is essential for the validity of the Lorentz-force law in quantum systems. We also connect our results to the long-standing Abraham-Minkowski debate about the momentum of light in material media.
RAPID PENUMBRA AND LORENTZ FORCE CHANGES IN AN X1.0 SOLAR FLARE
Xu, Zhe; Jiang, Yunchun; Yang, Jiayang; Yang, Bo; Bi, Yi
2016-03-20
We present observations of the violent changes in photospheric magnetic structures associated with an X1.1 flare, which occurred in a compact δ-configuration region in the following part of AR 11890 on 2013 November 8. In both central and peripheral penumbra regions of the small δ sunspot, these changes took place abruptly and permanently in the reverse direction during the flare: the inner/outer penumbra darkened/disappeared, where the magnetic fields became more horizontal/vertical. Particularly, the Lorentz force (LF) changes in the central/peripheral region had a downward/upward and inward direction, meaning that the local pressure from the upper atmosphere was enhanced/released. It indicates that the LF changes might be responsible for the penumbra changes. These observations can be well explained as the photospheric response to the coronal field reconstruction within the framework of the magnetic implosion theory and the back reaction model of flares.
Light-induced dynamics in the Lorentz oscillator model with magnetic forces
Fisher, W. M.; Rand, S. C.
2010-07-15
The classical Lorentz oscillator model of bound electron motion ordinarily excludes magnetic forces at nonrelativistic intensities for the simple reason that their magnitude is small. However, perturbative and numerical results show that when the v-vectorxB-vector term is retained, dynamically enhanced terms give rise to large amplitude, magnetically induced charge displacements at zero frequency and at twice the driving frequency in the Cartesian laboratory frame. Numerical simulations of electron motion are in accord with the predictions of perturbative theory for steady-state motion in the classical picture. Direct integration shows that magnetic response which is comparable to electric dipole response can arise in transparent dielectrics at optical frequencies. Parametric instability in the equations of motion is implicated as the source of rapid energy transfer from electric to magnetic motions by reduction of the equations to a complex Mathieu equation.
Thermal and Lorentz force analysis of beryllium windows for a rectilinear muon cooling channel
Luo, T.; Stratakis, D.; Li, D.; Virostek, S.; Palmer, R. B.; Bowring, D.
2015-05-03
Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.
Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel
Luo, Tianhuan; Li, D.; Virostek, S.; Palmer, R.; Stratakis, Diktys; Bowring, D.
2015-06-01
Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.
Design and simulation of superconducting Lorentz Force Electrical Impedance Tomography (LFEIT)
NASA Astrophysics Data System (ADS)
Shen, Boyang; Fu, Lin; Geng, Jianzhao; Zhang, Xiuchang; Zhang, Heng; Dong, Qihuan; Li, Chao; Li, Jing; Coombs, T. A.
2016-05-01
Lorentz Force Electrical Impedance Tomography (LFEIT) is a hybrid diagnostic scanner with strong capability for biological imaging, particularly in cancer and haemorrhages detection. This paper presents the design and simulation of a novel combination: a superconducting magnet together with LFEIT system. Superconducting magnets can generate magnetic field with high intensity and homogeneity, which could significantly enhance the imaging performance. The modelling of superconducting magnets was carried out using Finite Element Method (FEM) package, COMSOL Multiphysics, which was based on Partial Differential Equation (PDE) model with H-formulation coupling B-dependent critical current density and bulk approximation. The mathematical model for LFEIT system was built based on the theory of magneto-acoustic effect. The magnetic field properties from magnet design were imported into the LFEIT model. The basic imaging of electrical signal was developed using MATLAB codes. The LFEIT model simulated two samples located in three different magnetic fields with varying magnetic strength and homogeneity.
A novel motion compensation algorithm for acoustic radiation force elastography.
Fahey, B J; Hsu, S J; Trahey, G E
2008-05-01
A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithmis evaluated in a series of clinically realistic imaging scenarios, and its performance is compared to that achieved with previously described motion compensation algorithms. Though not without limitations, the new model-based motion compensation algorithm performs favorably in many circumstances and may be a logical choice for use with in vivo abdominal imaging.
Optical Characterization of Lorentz Force Based CMOS-MEMS Magnetic Field Sensor
Dennis, John Ojur; Ahmad, Farooq; Khir, M. Haris Bin Md; Hamid, Nor Hisham Bin
2015-01-01
Magnetic field sensors are becoming an essential part of everyday life due to the improvements in their sensitivities and resolutions, while at the same time they have become compact, smaller in size and economical. In the work presented herein a Lorentz force based CMOS-MEMS magnetic field sensor is designed, fabricated and optically characterized. The sensor is fabricated by using CMOS thin layers and dry post micromachining is used to release the device structure and finally the sensor chip is packaged in DIP. The sensor consists of a shuttle which is designed to resonate in the lateral direction (first mode of resonance). In the presence of an external magnetic field, the Lorentz force actuates the shuttle in the lateral direction and the amplitude of resonance is measured using an optical method. The differential change in the amplitude of the resonating shuttle shows the strength of the external magnetic field. The resonance frequency of the shuttle is determined to be 8164 Hz experimentally and from the resonance curve, the quality factor and damping ratio are obtained. In an open environment, the quality factor and damping ratio are found to be 51.34 and 0.00973 respectively. The sensitivity of the sensor is determined in static mode to be 0.034 µm/mT when a current of 10 mA passes through the shuttle, while it is found to be higher at resonance with a value of 1.35 µm/mT at 8 mA current. Finally, the resolution of the sensor is found to be 370.37 µT. PMID:26225972
Optical Characterization of Lorentz Force Based CMOS-MEMS Magnetic Field Sensor.
Dennis, John Ojur; Ahmad, Farooq; Khir, M Haris Bin Md; Bin Hamid, Nor Hisham
2015-07-27
Magnetic field sensors are becoming an essential part of everyday life due to the improvements in their sensitivities and resolutions, while at the same time they have become compact, smaller in size and economical. In the work presented herein a Lorentz force based CMOS-MEMS magnetic field sensor is designed, fabricated and optically characterized. The sensor is fabricated by using CMOS thin layers and dry post micromachining is used to release the device structure and finally the sensor chip is packaged in DIP. The sensor consists of a shuttle which is designed to resonate in the lateral direction (first mode of resonance). In the presence of an external magnetic field, the Lorentz force actuates the shuttle in the lateral direction and the amplitude of resonance is measured using an optical method. The differential change in the amplitude of the resonating shuttle shows the strength of the external magnetic field. The resonance frequency of the shuttle is determined to be 8164 Hz experimentally and from the resonance curve, the quality factor and damping ratio are obtained. In an open environment, the quality factor and damping ratio are found to be 51.34 and 0.00973 respectively. The sensitivity of the sensor is determined in static mode to be 0.034 µm/mT when a current of 10 mA passes through the shuttle, while it is found to be higher at resonance with a value of 1.35 µm/mT at 8 mA current. Finally, the resolution of the sensor is found to be 370.37 µT.
ERIC Educational Resources Information Center
De Luca, R.
2009-01-01
It is shown that, by applying elementary concepts in electromagnetism and electrochemistry to a system consisting of salt water flowing in a thin rectangular pipe at an average velocity v[subscript A] under the influence of a transverse magnetic field B[subscript 0], an electromotive force generator can be conceived. In fact, the Lorentz force…
NASA Astrophysics Data System (ADS)
Wiederhold, A.; Ebert, R.; Weidner, M.; Halbedel, B.; Fröhlich, T.; Resagk, C.
2016-12-01
The Lorentz force velocimetry (LFV) is a highly feasible contactless method for measuring flow rate in a pipe or in a channel. This method has been established for liquid metal flows but also for weakly conducting electrolytes where the Lorentz force amplitudes are typically six orders smaller than the ones from liquid metal flows. Due to an increased resolution of the Lorentz force measurements which was the main focus of research in the last years, now it is possible to investigate the influence of the flow profile on the amplitude of the Lorentz force. Even if there is a semi-theoretical approach an experimental validation is still outstanding. Therefore we have tested symmetric and asymmetric flow profiles to test the LFV for weakly conducting fluids for typical industrial flows. Salt water has been used as a test electrolyte with constant values of the electrical conductivity from 0.035 to 20 S m-1 and of the flow velocity in a range of 0.5-3 m s-1. We confirmed by extensive measurements that LFV is a suitable method for flow measurements even for different flow profiles within 5% measurement uncertainty. For a wide range of applications in research and industry the LFV should be not sensitive to various flow profiles.
ERIC Educational Resources Information Center
Abdul-Razzaq, Wathiq N.; Boehm, Manfred H.; Bushey, Ryan K.
2008-01-01
Introductory physics laboratories have been demonstrated in some instances to be difficult or uninteresting to students at the collegiate level. We have developed a laboratory that introduces the concept of the Lorentz force and allows students to build a non-traditional DC motor out of easily acquired materials. Basic electricity and magnetism…
Moradi, Hamed; Cally, Paul S.
2014-02-20
The rapid exponential increase in the Alfvén wave speed with height above the solar surface presents a serious challenge to physical modeling of the effects of magnetic fields on solar oscillations, as it introduces a significant Courant-Friedrichs-Lewy time-step constraint for explicit numerical codes. A common approach adopted in computational helioseismology, where long simulations in excess of 10 hr (hundreds of wave periods) are often required, is to cap the Alfvén wave speed by artificially modifying the momentum equation when the ratio between the Lorentz and hydrodynamic forces becomes too large. However, recent studies have demonstrated that the Alfvén wave speed plays a critical role in the MHD mode conversion process, particularly in determining the reflection height of the upwardly propagating helioseismic fast wave. Using numerical simulations of helioseismic wave propagation in constant inclined (relative to the vertical) magnetic fields we demonstrate that the imposition of such artificial limiters significantly affects time-distance travel times unless the Alfvén wave-speed cap is chosen comfortably in excess of the horizontal phase speeds under investigation.
Drain Current Modulation of a Single Drain MOSFET by Lorentz Force for Magnetic Sensing Application
Chatterjee, Prasenjit; Chow, Hwang-Cherng; Feng, Wu-Shiung
2016-01-01
This paper reports a detailed analysis of the drain current modulation of a single-drain normal-gate n channel metal-oxide semiconductor field effect transistor (n-MOSFET) under an on-chip magnetic field. A single-drain n-MOSFET has been fabricated and placed in the center of a square-shaped metal loop which generates the on-chip magnetic field. The proposed device designed is much smaller in size with respect to the metal loop, which ensures that the generated magnetic field is approximately uniform. The change of drain current and change of bulk current per micron device width has been measured. The result shows that the difference drain current is about 145 µA for the maximum applied magnetic field. Such changes occur from the applied Lorentz force to push out the carriers from the channel. Based on the drain current difference, the change in effective mobility has been detected up to 4.227%. Furthermore, a detailed investigation reveals that the device behavior is quite different in subthreshold and saturation region. A change of 50.24 µA bulk current has also been measured. Finally, the device has been verified for use as a magnetic sensor with sensitivity 4.084% (29.6 T−1), which is very effective as compared to other previously reported works for a single device. PMID:27589747
NASA Astrophysics Data System (ADS)
Yang, Xuegeng; Mühlenhoff, Sascha; Nikrityuk, Petr A.; Eckert, Kerstin
2013-03-01
Magnetic fields are well-established in electrochemistry as an attractive tool to improve both the quality of the deposit as well as the deposition rate. The key mechanism is a mass transfer enhancement by Lorentz-force-driven convection. However, during electrolysis this convection interacts with buoyancy-driven convection, which arises from concentration differences, in a sometimes intriguing way. In the case of a Lorentz force opposing buoyancy, this is due to the growth of a bubble-like zone of less-concentrated cupric ion solution at the lower part of the vertical cathode when copper electrolysis is performed. If buoyancy is strong enough to compete with the Lorentz force, this zone rises along the cathode and causes surprisingly unsteady initial transient behaviour. We explore this initial transient under galvanostatic conditions by analyzing the development of the concentration and velocity boundary layers obtained by Mach-Zehnder interferometry and particle image velocimetry. Particular attention is also paid to higher current densities above the limiting current, obtained from potentiodynamic measurements, at which a chaotic advection takes place. The results are compared by scaling analysis.
NASA Astrophysics Data System (ADS)
Wiederhold, Andreas; Ebert, Reschad; Resagk, Christian; Research Training Group: "Lorentz Force Velocimetry; Lorentz Force Eddy Current Testing" Team
2016-11-01
We report about the feasibility of Lorentz force velocimetry (LFV) for various flow profiles. LFV is a contactless non-invasive technique to measure flow velocity and has been developed in the last years in our institute. This method is advantageous if the fluid is hot, aggressive or opaque like glass melts or liquid metal flows. The conducted experiments shall prove an increased versatility for industrial applications of this method. For the force measurement we use an electromagnetic force compensation balance. As electrolyte salty water is used with an electrical conductivity in the range of 0.035 which corresponds to tap water up to 20 Sm-1. Because the conductivity is six orders less than that of liquid metals, here the challenging bottleneck is the resolution of the measurement system. The results show only a slight influence in the force signal at symmetric and strongly asymmetric flow profiles. Furthermore we report about the application of LFV to stratified two-phase flows. We show that it is possible to detect interface instabilities, which is important for the dimensioning of liquid metal batteries. Deutsche Forschungsgemeinschaft DFG.
Mechanical characterization and modelling of Lorentz force based MEMS magnetic field sensors
NASA Astrophysics Data System (ADS)
Gkotsis, P.; Lara-Castro, M.; López-Huerta, F.; Herrera-May, A. L.; Raskin, J.-P.
2015-10-01
In this work we present experimental results from dynamic and static tests on miniature magnetic field sensors which are based on Micro Electro Mechanical Systems (MEMS) technologies. These MEMS magnetometers were fabricated on SOI wafers using Si bulk micromachining techniques and they operate at the first resonant frequency under the action of the Lorentz force which arises when a current flows through them in the presence of an external magnetic field. Sensing is based on piezoresistive principles and high sensitivity is expected from devices that show high total quality factors Qtot. We investigate here the energy loss mechanisms and the temperature rise due to Joule heating effects in the resonators of the magnetometers by performing tests both in air and under vacuum conditions. Testing was performed using laser Doppler Vibrometry and white light interferometry. At each pressure different driving currents have been applied and Qtot was extracted. It is found that Qtot varies with pressure between two limiting values: a low one in air which was between 17 and 500 for the tested devices and a high one in vacuum which in the case of one of our devices was equal to 2800. The amplitude of the applied current is also affecting the Q value at a certain pressure due to the rise of thermal stress in the resonating structures. The sensitivity of the sensors in air was experimentally measured using a Helmholtz coil and an oscilloscope and values between 72 mV T-1 and 513 mV T-1 were obtained from the tested devices. We further attempt to estimate the temperature rise in the devices due to Joule heating effects by combining the topography scans which were experimentally obtained with results from thermomechanical analysis of the sensors using Finite Element Modelling.
NASA Astrophysics Data System (ADS)
Arkani-Hamed, Nima; Cheng, Hsin-Chia; Luty, Markus; Thaler, Jesse
2005-07-01
We study the universal low-energy dynamics associated with the spontaneous breaking of Lorentz invariance down to spatial rotations. The effective lagrangian for the associated Goldstone field can be uniquely determined by the non-linear realization of a broken time diffeomorphism symmetry, up to some overall mass scales. It has previously been shown that this symmetry breaking pattern gives rise to a Higgs phase of gravity, in which gravity is modified in the infrared. In this paper, we study the effects of direct couplings between the Goldstone boson and standard model fermions, which necessarily accompany Lorentz-violating terms in the theory. The leading interaction is the coupling to the axial vector current, which reduces to spin in the non-relativistic limit. A spin moving relative to the ``ether" rest frame will emit Goldstone Cerenkov radiation. The Goldstone also induces a long-range inverse-square law force between spin sources with a striking angular dependence, reflecting the underlying Goldstone shockwaves and providing a smoking gun for this theory. We discuss the regime of validity of the effective theory describing these phenomena, and the possibility of probing Lorentz violations through Goldstone boson signals in a way that is complementary to direct tests in some regions of parameter space.
Lim, Tau Meng; Zhang, Dongsheng
2006-05-01
A Lorentz force-type self-bearing motor was developed to provide delivery of both motoring torque and levitation force for an alternative axial flow blood pump design with an enclosed impeller. The axial flow pumps currently available introduce electromagnetic coupling from the motor's stator to the impeller by means of permanent magnets (PMs) embedded in the tips of the pump's blades. This design has distinct disadvantages, for example, pumping efficiency and electromagnetic coupling transmission are compromised by the constrained or poor geometry of the blades and limited pole width of the PMs, respectively. In this research, a Lorentz force-type self-bearing motor was developed. It is composed of (i) an eight-pole PM hollow-cylindrical rotor assembly supposedly to house and enclose the impeller of an axial flow blood pump, and (ii) a six-pole stator with two sets of copper wire and different winding configurations to provide the motoring torque and levitating force for the rotor assembly. MATLAB's xPC Target interface hardware was used as the rapid prototyping tool for the development of the controller for the self-bearing motor. Experimental results on a free/simply supported rotor assembly validated the design feasibility and control algorithm effectiveness in providing both the motoring torque and levitation force for the rotor. When levitated, a maximum orbital displacement of 0.3 mm corresponding to 1050 rpm of the rotor was measured by two eddy current probes placed in the orthogonal direction. This design has the advantage of eliminating the trade-off between motoring torques, levitating force, and pumping efficiency of previous studies. It also indicated the benefits of enclosed-impeller design as having good dynamic response, linearity, and better reliability. The nonmechanical contact feature between rotating and stationary parts will further reduce hemolysis and thromboembolitic tendencies in a typical blood pump application.
Force-Field Compensation in a Manual Tracking Task
Squeri, Valentina; Masia, Lorenzo; Casadio, Maura; Morasso, Pietro; Vergaro, Elena
2010-01-01
This study addresses force/movement control in a dynamic “hybrid” task: the master sub-task is continuous manual tracking of a target moving along an eight-shaped Lissajous figure, with the tracking error as the primary performance index; the slave sub-task is compensation of a disturbing curl viscous field, compatibly with the primary performance index. The two sub-tasks are correlated because the lateral force the subject must exert on the eight-shape must be proportional to the longitudinal movement speed in order to perform a good tracking. The results confirm that visuo-manual tracking is characterized by an intermittent control mechanism, in agreement with previous work; the novel finding is that the overall control patterns are not altered by the presence of a large deviating force field, if compared with the undisturbed condition. It is also found that the control of interaction-forces is achieved by a combination of arm stiffness properties and direct force control, as suggested by the systematic lateral deviation of the trajectories from the nominal path and the comparison between perturbed trials and catch trials. The coordination of the two sub-tasks is quickly learnt after the activation of the deviating force field and is achieved by a combination of force and the stiffness components (about 80% vs. 20%), which is a function of the implicit accuracy of the tracking task. PMID:20567516
26 CFR 1.112-1 - Combat zone compensation of members of the Armed Forces.
Code of Federal Regulations, 2010 CFR
2010-04-01
... (and members of the Armed Forces are described) in section 7701(a)(15). (4) Military compensation only... States or by an international organization to a member of the Armed Forces whose military active duty... supplement the member's military compensation or is labeled by the employer as compensation for...
26 CFR 1.112-1 - Combat zone compensation of members of the Armed Forces.
Code of Federal Regulations, 2013 CFR
2013-04-01
... (and members of the Armed Forces are described) in section 7701(a)(15). (4) Military compensation only... States or by an international organization to a member of the Armed Forces whose military active duty... supplement the member's military compensation or is labeled by the employer as compensation for...
26 CFR 1.112-1 - Combat zone compensation of members of the Armed Forces.
Code of Federal Regulations, 2012 CFR
2012-04-01
... (and members of the Armed Forces are described) in section 7701(a)(15). (4) Military compensation only... States or by an international organization to a member of the Armed Forces whose military active duty... supplement the member's military compensation or is labeled by the employer as compensation for...
26 CFR 1.112-1 - Combat zone compensation of members of the Armed Forces.
Code of Federal Regulations, 2014 CFR
2014-04-01
... (and members of the Armed Forces are described) in section 7701(a)(15). (4) Military compensation only... States or by an international organization to a member of the Armed Forces whose military active duty... supplement the member's military compensation or is labeled by the employer as compensation for...
26 CFR 1.112-1 - Combat zone compensation of members of the Armed Forces.
Code of Federal Regulations, 2011 CFR
2011-04-01
... (and members of the Armed Forces are described) in section 7701(a)(15). (4) Military compensation only... States or by an international organization to a member of the Armed Forces whose military active duty... supplement the member's military compensation or is labeled by the employer as compensation for...
Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes
NASA Astrophysics Data System (ADS)
Baczyzmalski, Dominik; Weier, Tom; Kähler, Christian J.; Cierpka, Christian
2015-08-01
Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode's surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.
Petrie, G. J. D.
2012-11-01
We analyze the spatial and temporal variations of the abrupt photospheric magnetic changes associated with six major flares using 12 minute, 0.''5 pixel{sup -1} vector magnetograms from NASA's Helioseismic and Magnetic Imager instrument on the Solar Dynamics Observatory satellite. The six major flares occurred near the main magnetic neutral lines of four active regions, NOAA 11158, 11166, 11283, and 11429. During all six flares the neutral-line field vectors became stronger and more horizontal, in each case almost entirely due to strengthening of the horizontal field components parallel to the neutral line. In all six cases the neutral-line pre-flare fields were more vertical than the reference potential fields, and collapsed abruptly and permanently closer to potential-field tilt angles during every flare, implying that the relaxation of magnetic stress associated with non-potential tilt angles plays a major role during major flares. The shear angle with respect to the reference potential field did not show such a pattern, demonstrating that flare processes do not generally relieve magnetic stresses associated with photospheric magnetic shear. The horizontal fields became significantly and permanently more aligned with the neutral line during the four largest flares, suggesting that the collapsing field is on average more aligned with the neutral line than the pre-flare neutral-line field. The vertical Lorentz force had a large, abrupt, permanent downward change during each of the flares, consistent with loop collapse. The horizontal Lorentz force changes acted mostly parallel to the neutral line in opposite directions on each side, a signature of the fields contracting during the flare, pulling the two sides of the neutral line toward each other. The greater effect of the flares on field tilt than on shear may be explained by photospheric line-tying.
Vertically polarizing undulator with dynamic compensation of magnetic forces
NASA Astrophysics Data System (ADS)
Strelnikov, N.; Vasserman, I.; Xu, J.; Jensen, D.; Schmidt, O.; Trakhtenberg, E.; Suthar, K.; Moog, E. R.; Pile, G.; Gluskin, E.
2017-01-01
As part of the R&D program of the LCLS-II project, a novel 3.4-meter-long undulator prototype with horizontal magnetic field and dynamic force compensation has recently been developed at the Advanced Photon Source (APS). Previous steps in this development were the shorter 0.8-meter-long and 2.8-meter-long prototypes. Extensive mechanical and magnetic testing were carried out for each prototype, and each prototype was magnetically tuned using magnetic shims. The resulting performance of the 3.4-meter-long undulator prototype meets all requirements for the LCLS-II insertion device, including limits on the field integrals, phase errors, higher-order magnetic moments, and electron-beam trajectory for all operational gaps, as well as the reproducibility and accuracy of the gap settings.
Chang, Jean H; Hogan, N Catherine; Hunter, Ian W
2015-08-10
We present a novel method of quickly acquiring dermal interstitial fluid (ISF) samples using a Lorentz-force actuated needle-free jet injector. The feasibility of the method is first demonstrated on post-mortem porcine tissue. The jet injector is used to first inject a small volume of physiological saline to breach the skin, and the back-drivability of the actuator is utilized to create negative pressure in the ampoule and collect ISF. The effect of the injection and extraction parameters on sample dilution and extracted volumes is investigated. A simple finite element model is developed to demonstrate why this acquisition method results in faster extractions than conventional sampling methods. Using this method, we are able to collect a sample that contains up to 3.5% ISF in 3.1s from post-mortem skin. The trends revealed from experimentation on post-mortem skin are then used to identify the parameters for a live animal study. The feasibility of the acquisition process is successfully demonstrated using live rats; the process is revealed to extract samples that have been diluted by a factor of 111-125.
Characterization of a high mechanical-Q fiber laser Lorentz force dc magnetometer.
Cranch, G A; Askins, C G; Miller, G A; Kirkendall, C K
2011-04-01
A magnetic field sensor is described based on coupling the field into a time varying strain in a fiber laser strain sensor, through the Lorentzian force. A conducting bridge carries an ac current and oscillates at resonance in the presence of a magnetic field. A fiber laser strain sensor attached to the ribbon measures the deflections. The quality factor is shown to be limited by air damping resulting in a measurement resolution of 704 pT/Hz(1/2)±10% at ambient pressure and 360 pT/Hz(1/2)±10% at a reduced pressure of 1700 Pa at 1 Hz and 75 mA (rms).
NASA Astrophysics Data System (ADS)
Sheikin, E. G.; Cheng, Wei Yang
2013-12-01
We obtain a solution to the equation for the electric potential in a locally ionized transverse magnetohydrodynamic flow past a circular cylinder in a nonuniform magnetic field produced by a linear conductor for various configurations of the ionization region. Analytical formulas are derived for the volume density of the Lorentz force acting on the flow in a locally ionized region. The effect of the Hall parameter and of the configuration of the region of the magnetohydrodynamic interaction on the Lorentz force is analyzed. It is shown that an increase in the Hall parameter leads to a decrease in the Lorentz force acting on the flow, and a change in the configuration of the locally ionized region makes it possible to suppress the effect of the Hall parameter on the Lorentz force.
Volegov, A I
2006-01-01
An idea has been advanced that inertial forces emerging during active movements are able to compensate for the deficiency of weight. The idea is based on the conception that these forces are by their effect on biological objects analogous to gravity forces. Training facilities have been developed, and tentative estimations have been made. The definition of "inertial massage" is introduced.
NASA Astrophysics Data System (ADS)
Kong, Xiangdong; Ba, Kaixian; Yu, Bin; Cao, Yuan; Zhu, Qixin; Zhao, Hualong
2016-05-01
Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit (HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this
Kim, Ji-Sik; Kim, Gi-Woo
2017-01-01
This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane) dispersed with carbon nanotubes (CNTs), to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor) for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS) as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied. PMID:28125046
Kim, Ji-Sik; Kim, Gi-Woo
2017-01-24
This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane) dispersed with carbon nanotubes (CNTs), to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor) for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS) as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied.
A temperature-compensated optical fiber force sensor for minimally invasive surgeries
NASA Astrophysics Data System (ADS)
Mo, Z.; Xu, W.; Broderick, N.; Chen, H.
2015-12-01
Force sensing in minimally invasive surgery (MIS) is a chronic problem since it has an intensive magnetic resonance (MR) operation environment, which causes a high influence to traditional electronic force sensors. Optical sensor is a promising choice in this area because it is immune to MR influence. However, the changing temperature introduces a lot of noise signals to them, which is the main obstacle for optical sensing applications in MIS. This paper proposes a miniature temperature-compensated optical force sensor by using Fabry-Perot interference (FPI) principle. It can be integrated into medical tools' tips and the temperature noise is decreased by using a reference FPI temperature sensor. An injection needle with embedded temperature-compensated FPI force sensor has been fabricated and tested. And the comparison between temperature-force simulation results and the temperature-force experiment results has been carried out.
NASA Astrophysics Data System (ADS)
Antunes, A.; Glover, P. M.; Li, Y.; Mian, O. S.; Day, B. L.
2012-07-01
Large static magnetic fields may be employed in magnetic resonance imaging (MRI). At high magnetic field strengths (usually from about 3 T and above) it is possible for humans to perceive a number of effects. One such effect is mild vertigo. Recently, Roberts et al (2011 Current Biology 21 1635-40) proposed a Lorentz-force mechanism resulting from the ionic currents occurring naturally in the endolymph of the vestibular system. In the present work a more detailed calculation of the forces and resulting pressures in the vestibular system is carried out using a numerical model. Firstly, realistic 3D finite element conductivity and fluid maps of the utricle and a single semi-circular canal containing the current sources (dark cells) and sinks (hair cells) of the utricle and ampulla were constructed. Secondly, the electrical current densities in the fluid are calculated. Thirdly, the developed Lorentz force is used directly in the Navier-Stokes equation and the trans-cupular pressure is computed. Since the driving force field is relatively large in comparison with the advective acceleration, we demonstrate that it is possible to perform an approximation in the Navier-Stokes equations that reduces the problem to solving a simpler Poisson equation. This simplification allows rapid and easy calculation for many different directions of applied magnetic field. At 7 T a maximum cupula pressure difference of 1.6 mPa was calculated for the combined ampullar (0.7 µA) and utricular (3.31 µA) distributed current sources, assuming a hair-cell resting current of 100 pA per unit. These pressure values are up to an order of magnitude lower than those proposed by Roberts et al using a simplistic model and calculation, and are in good agreement with the estimated pressure values for nystagmus velocities in caloric experiments. This modeling work supports the hypothesis that the Lorentz force mechanism is a significant contributor to the perception of magnetic field induced vertigo.
Bulanov, Sergei V; Esirkepov, Timur Zh; Kando, Masaki; Koga, James K; Bulanov, Stepan S
2011-11-01
When the parameters of electron-extreme power laser interaction enter the regime of dominated radiation reaction, the electron dynamics changes qualitatively. The adequate theoretical description of this regime becomes crucially important with the use of the radiation friction force either in the Lorentz-Abraham-Dirac form, which possesses unphysical runaway solutions, or in the Landau-Lifshitz form, which is a perturbation valid for relatively low electromagnetic wave amplitude. The goal of the present paper is to find the limits of the Landau-Lifshitz radiation force applicability in terms of the electromagnetic wave amplitude and frequency. For this, a class of the exact solutions to the nonlinear problems of charged particle motion in the time-varying electromagnetic field is used.
NASA Astrophysics Data System (ADS)
Bulanov, Sergei V.; Esirkepov, Timur Zh.; Kando, Masaki; Koga, James K.; Bulanov, Stepan S.
2011-11-01
When the parameters of electron-extreme power laser interaction enter the regime of dominated radiation reaction, the electron dynamics changes qualitatively. The adequate theoretical description of this regime becomes crucially important with the use of the radiation friction force either in the Lorentz-Abraham-Dirac form, which possesses unphysical runaway solutions, or in the Landau-Lifshitz form, which is a perturbation valid for relatively low electromagnetic wave amplitude. The goal of the present paper is to find the limits of the Landau-Lifshitz radiation force applicability in terms of the electromagnetic wave amplitude and frequency. For this, a class of the exact solutions to the nonlinear problems of charged particle motion in the time-varying electromagnetic field is used.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 45 Public Welfare 3 2013-10-01 2013-10-01 false Members of the Armed Forces of the United States... AMENDED ELIGIBILITY REQUIREMENTS FOR COMPENSATION Prisoners of War § 506.19 Members of the Armed Forces of the United States precluded from receiving award of compensation. Any member of the Armed Forces...
Code of Federal Regulations, 2012 CFR
2012-10-01
... 45 Public Welfare 3 2012-10-01 2012-10-01 false Members of the Armed Forces of the United States... AMENDED ELIGIBILITY REQUIREMENTS FOR COMPENSATION Prisoners of War § 506.19 Members of the Armed Forces of the United States precluded from receiving award of compensation. Any member of the Armed Forces...
Code of Federal Regulations, 2010 CFR
2010-10-01
... 45 Public Welfare 3 2010-10-01 2010-10-01 false Members of the Armed Forces of the United States... AMENDED ELIGIBILITY REQUIREMENTS FOR COMPENSATION Prisoners of War § 506.19 Members of the Armed Forces of the United States precluded from receiving award of compensation. Any member of the Armed Forces...
Code of Federal Regulations, 2011 CFR
2011-10-01
... 45 Public Welfare 3 2011-10-01 2011-10-01 false Members of the Armed Forces of the United States... AMENDED ELIGIBILITY REQUIREMENTS FOR COMPENSATION Prisoners of War § 506.19 Members of the Armed Forces of the United States precluded from receiving award of compensation. Any member of the Armed Forces...
Code of Federal Regulations, 2014 CFR
2014-10-01
... 45 Public Welfare 3 2014-10-01 2014-10-01 false Members of the Armed Forces of the United States... AMENDED ELIGIBILITY REQUIREMENTS FOR COMPENSATION Prisoners of War § 506.19 Members of the Armed Forces of the United States precluded from receiving award of compensation. Any member of the Armed Forces...
Alternative Compensation Plans for Improving Retention of Air Force Pilots
1989-08-01
paid to most pilots. These plans do tend, however, to provide equal pay for pilots with equal YOS. o Plans that avoid indexing flight pay to annual... equal YOS receive different amounts of pay . Despite precedents for such differences in the military pay system, the Air Force argues that pilots with... equal YOS should receive equal pay in order to maintain pilot morale. o Plans that emphasize across-the-board pay increases for pilots of all types
Moreira, Pedro; Zemiti, Nabil; Liu, Chao; Poignet, Philippe
2014-09-01
Controlling the interaction between robots and living soft tissues has become an important issue as the number of robotic systems inside the operating room increases. Many researches have been done on force control to help surgeons during medical procedures, such as physiological motion compensation and tele-operation systems with haptic feedback. In order to increase the performance of such controllers, this work presents a novel force control scheme using Active Observer (AOB) based on a viscoelastic interaction model. The control scheme has shown to be stable through theoretical analysis and its performance was evaluated by in vitro experiments. In order to evaluate how the force control scheme behaves under the presence of physiological motion, experiments considering breathing and beating heart disturbances are presented. The proposed control scheme presented a stable behavior in both static and moving environment. The viscoelastic AOB presented a compensation ratio of 87% for the breathing motion and 79% for the beating heart motion.
Magnetic field contribution to the Lorentz model.
Oughstun, Kurt E; Albanese, Richard A
2006-07-01
The classical Lorentz model of dielectric dispersion is based on the microscopic Lorentz force relation and Newton's second law of motion for an ensemble of harmonically bound electrons. The magnetic field contribution in the Lorentz force relation is neglected because it is typically small in comparison with the electric field contribution. Inclusion of this term leads to a microscopic polarization density that contains both perpendicular and parallel components relative to the plane wave propagation vector. The modified parallel and perpendicular polarizabilities are both nonlinear in the local electric field strength.
Driving forces behind the construction of an eco-compensation mechanism for wetlands in China
NASA Astrophysics Data System (ADS)
Wang, Changhai
2016-09-01
This research revealed important driving forces behind the construction of an eco-compensation mechanism for wetlands (DFEMW) in China. Using China's provincial panel data from 1978 to 2008, a fixed-effects model was used to analyze the impacts of agricultural production systems on wetlands. We identified three DFEMW as follows: the change of wetland resources and protection measures in China; declaration and implementation of the provincial Wetland Protection Ordinance; and wetland degradation by agricultural production systems, which necessitated the establishment of a wetland eco-compensation mechanism. In addition to the DFEMW, a significant positive correlation between wetland area and both rural population and gross agricultural production was identified, in addition to a negative correlation with chemical fertilizer usage, reservoir storage capacity, and irrigation area. The underlying reasons for the serious degradation and inadequate protection of wetlands were market failure and government failure; these were the driving forces behind the need to establish a wetland eco-compensation mechanism. From a governmental perspective, it has been difficult to rectify market failures in resource distribution and thus to prevent wetland degradation. Factors include conflicts of interest, lack of investment, effective special laws, a simple means to protect wetlands, and a multidisciplinary management system. Therefore, the key factor is the coordination of interest relationships between those who utilize wetlands and those who seek to minimize wetland degradation and effectively protect wetlands.
Reaching during virtual rotation: context specific compensations for expected coriolis forces
NASA Technical Reports Server (NTRS)
Cohn, J. V.; DiZio, P.; Lackner, J. R.
2000-01-01
Subjects who are in an enclosed chamber rotating at constant velocity feel physically stationary but make errors when pointing to targets. Reaching paths and endpoints are deviated in the direction of the transient inertial Coriolis forces generated by their arm movements. By contrast, reaching movements made during natural, voluntary torso rotation seem to be accurate, and subjects are unaware of the Coriolis forces generated by their movements. This pattern suggests that the motor plan for reaching movements uses a representation of body motion to prepare compensations for impending self-generated accelerative loads on the arm. If so, stationary subjects who are experiencing illusory self-rotation should make reaching errors when pointing to a target. These errors should be in the direction opposite the Coriolis accelerations their arm movements would generate if they were actually rotating. To determine whether such compensations exist, we had subjects in four experiments make visually open-loop reaches to targets while they were experiencing compelling illusory self-rotation and displacement induced by rotation of a complex, natural visual scene. The paths and endpoints of their initial reaching movements were significantly displaced leftward during counterclockwise illusory rotary displacement and rightward during clockwise illusory self-displacement. Subjects reached in a curvilinear path to the wrong place. These reaching errors were opposite in direction to the Coriolis forces that would have been generated by their arm movements during actual torso rotation. The magnitude of path curvature and endpoint errors increased as the speed of illusory self-rotation increased. In successive reaches, movement paths became straighter and endpoints more accurate despite the absence of visual error feedback or tactile feedback about target location. When subjects were again presented a stationary scene, their initial reaches were indistinguishable from pre
Reaching during virtual rotation: context specific compensations for expected coriolis forces.
Cohn, J V; DiZio, P; Lackner, J R
2000-06-01
Subjects who are in an enclosed chamber rotating at constant velocity feel physically stationary but make errors when pointing to targets. Reaching paths and endpoints are deviated in the direction of the transient inertial Coriolis forces generated by their arm movements. By contrast, reaching movements made during natural, voluntary torso rotation seem to be accurate, and subjects are unaware of the Coriolis forces generated by their movements. This pattern suggests that the motor plan for reaching movements uses a representation of body motion to prepare compensations for impending self-generated accelerative loads on the arm. If so, stationary subjects who are experiencing illusory self-rotation should make reaching errors when pointing to a target. These errors should be in the direction opposite the Coriolis accelerations their arm movements would generate if they were actually rotating. To determine whether such compensations exist, we had subjects in four experiments make visually open-loop reaches to targets while they were experiencing compelling illusory self-rotation and displacement induced by rotation of a complex, natural visual scene. The paths and endpoints of their initial reaching movements were significantly displaced leftward during counterclockwise illusory rotary displacement and rightward during clockwise illusory self-displacement. Subjects reached in a curvilinear path to the wrong place. These reaching errors were opposite in direction to the Coriolis forces that would have been generated by their arm movements during actual torso rotation. The magnitude of path curvature and endpoint errors increased as the speed of illusory self-rotation increased. In successive reaches, movement paths became straighter and endpoints more accurate despite the absence of visual error feedback or tactile feedback about target location. When subjects were again presented a stationary scene, their initial reaches were indistinguishable from pre
Local Lorentz transformations and Thomas effect in general relativity
NASA Astrophysics Data System (ADS)
Silenko, Alexander J.
2016-06-01
The tetrad method is used for an introduction of local Lorentz frames and a detailed analysis of local Lorentz transformations. A formulation of equations of motion in local Lorentz frames is based on the Pomeransky-Khriplovich gravitoelectromagnetic fields. These fields are calculated in the most important special cases and their local Lorentz transformations are determined. The local Lorentz transformations and the Pomeransky-Khriplovich gravitoelectromagnetic fields are applied for a rigorous derivation of a general equation for the Thomas effect in Riemannian spacetimes and for a consideration of Einstein's equivalence principle and the Mathisson force.
Lorentz Contraction and Current-Carrying Wires
ERIC Educational Resources Information Center
van Kampen, Paul
2008-01-01
The force between two parallel current-carrying wires is investigated in the rest frames of the ions and the electrons. A straightforward Lorentz transformation shows that what appears as a purely magnetostatic force in the ion frame appears as a combined magnetostatic and electrostatic force in the electron frame. The derivation makes use of a…
Lorentz Force Control of Turbulence
2005-01-01
Electrohydrodynamics 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE ABSTRACT OF...heating [6], piezo-electric flaps [7], oscillatory blowing [8], synthetic jets [9], surface motion [10] and plasma discharge [11]. Given the previous...interlaced with a commercially fabricated printed circuit board to generate the necessary fields. The segmentation of the electrodes in the spanwise
Temperature-Compensated Force/Pressure Sensor Based on Multi-Walled Carbon Nanotube Epoxy Composites
Dinh, Nghia Trong; Kanoun, Olfa
2015-01-01
In this study, we propose a multi-walled carbon nanotube epoxy composite sensor for force and pressure sensing in the range of 50 N–2 kN. A manufacturing procedure, including material preparation and deposition techniques, is proposed. The electrode dimensions and the layer thickness were optimized by the finite element method. Temperature compensation is realized by four nanocomposites elements, where only two elements are exposed to the measurand. In order to investigate the influence of the filler contents, samples with different compositions were prepared and investigated. Additionally, the specimens are characterized by cyclical and stepped force/pressure loads or at defined temperatures. The results show that the choice of the filler content should meet a compromise between sensitivity, temperature influence and noise behavior. At constant temperature, a force of at least 50 N can be resolved. The measurement error due to the temperature influence is 150 N in a temperature range of −20°C−50°C. PMID:25985160
Multifactorial determination of the electric drive for the force compensating manipulator
NASA Astrophysics Data System (ADS)
Pyatibratov, G. Ya; Danshina, A. A.
2017-02-01
The methodology of multifactorial determination of rational parameters of transmission gear and synchronous electric motor driving by permanent magnets for the system of the vertical freight movement of the force compensating manipulator is offered. An integrated approach to the selection of the power part of this manipulator takes into account: motor speed matching and an executive mechanism of the manipulator, operation of the electric drive with a minimum possible value of the maximum torque at the movement of freight with constant speed and with acceleration at different values of the freight mass. A reasonable radius of mechanism activation is determined from accepted values with application of the compromise approach enabling to consider at the same time the performance of all limiting conditions. The electromechanical module of the manipulator is selected when a value of the activation radius provides the minimum possible required motor torque.
Lorentz-violating gravitoelectromagnetism
Bailey, Quentin G.
2010-09-15
The well-known analogy between a special limit of general relativity and electromagnetism is explored in the context of the Lorentz-violating standard-model extension. An analogy is developed for the minimal standard-model extension that connects a limit of the CPT-even component of the electromagnetic sector to the gravitational sector. We show that components of the post-Newtonian metric can be directly obtained from solutions to the electromagnetic sector. The method is illustrated with specific examples including static and rotating sources. Some unconventional effects that arise for Lorentz-violating electrostatics and magnetostatics have an analog in Lorentz-violating post-Newtonian gravity. In particular, we show that even for static sources, gravitomagnetic fields arise in the presence of Lorentz violation.
Li, Katherine; Ackland, David C; McClelland, Jodie A; Webster, Kate E; Feller, Julian A; de Steiger, Richard; Pandy, Marcus G
2013-05-01
Patients with total knee arthroplasty (TKA) frequently exhibit changes in gait biomechanics post-surgery, including decreased ranges of joint motion and changes in joint loading; however, the actions of the lower-limb muscles in generating joint moments and accelerating the center of mass (COM) during walking are yet to be described. The aim of the present study was to evaluate differences in lower-limb joint kinematics, muscle-generated joint moments, and muscle contributions to COM accelerations in TKA patients and healthy age-matched controls when both groups walk at the same speed. Each TKA patient was fitted with a posterior-stabilized total knee replacement and underwent patellar resurfacing. Three-dimensional gait analysis and subject-specific musculoskeletal modeling were used to determine lower-limb and trunk muscle forces and muscle contributions to COM accelerations during the stance phase of gait. The TKA patients exhibited a 'quadriceps avoidance' gait pattern, with the vasti contributing significantly less to the extension moment developed about the knee during early stance (p=0.036). There was a significant decrease in the contribution of the vasti to the vertical acceleration (support) (p=0.022) and forward deceleration of the COM (braking) (p=0.049) during early stance; however, the TKA patients compensated for this deficiency by leaning their trunks forward. This significantly increased the contribution of the contralateral back extensor muscle (erector spinae) to support (p=0.030), and that of the contralateral back rotators (internal and external obliques) to braking (p=0.004). These findings provide insight into the biomechanical causes of post-operative gait adaptations such as 'quadriceps avoidance' observed in TKA patients.
Reuter, Eva-Maria; Cunnington, Ross; Mattingley, Jason B; Riek, Stephan; Carroll, Timothy J
2016-11-01
There are well-documented differences in the way that people typically perform identical motor tasks with their dominant and the nondominant arms. According to Yadav and Sainburg's (Neuroscience 196: 153-167, 2011) hybrid-control model, this is because the two arms rely to different degrees on impedance control versus predictive control processes. Here, we assessed whether differences in limb control mechanisms influence the rate of feedforward compensation to a novel dynamic environment. Seventy-five healthy, right-handed participants, divided into four subsamples depending on the arm (left, right) and direction of the force field (ipsilateral, contralateral), reached to central targets in velocity-dependent curl force fields. We assessed the rate at which participants developed predictive compensation for the force field using intermittent error-clamp trials and assessed both kinematic errors and initial aiming angles in the field trials. Participants who were exposed to fields that pushed the limb toward ipsilateral space reduced kinematic errors more slowly, built up less predictive field compensation, and relied more on strategic reaiming than those exposed to contralateral fields. However, there were no significant differences in predictive field compensation or kinematic errors between limbs, suggesting that participants using either the left or the right arm could adapt equally well to novel dynamics. It therefore appears that the distinct preferences in control mechanisms typically observed for the dominant and nondominant arms reflect a default mode that is based on habitual functional requirements rather than an absolute limit in capacity to access the controller specialized for the opposite limb.
Strelnikov, N.; Trakhtenberg, E.; Vasserman, I.; Xu, J.; Gluskin, E.
2014-11-15
A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID B{sub eff}, it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 μm. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R and D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS)
Love, LJL
2003-09-24
Learning Controller has little impact due to the variable nature of the wave period. We then introduce a new approach to HAT control, Ship Motion Compensation for Force Control Systems (SMCFCS). This basic approach uses inclinometer and acceleration information from the base of the robot to compensate for ship motion disturbances. Results of the simulation study show over an order of magnitude decrease in the disturbance force reflected back to the operator and an order of magnitude increase in positioning accuracy and resolution.
Massive photons and Lorentz violation
NASA Astrophysics Data System (ADS)
Cambiaso, Mauro; Lehnert, Ralf; Potting, Robertus
2012-04-01
All quadratic translation- and gauge-invariant photon operators for Lorentz breakdown are included into the Stueckelberg Lagrangian for massive photons in a generalized Rξ gauge. The corresponding dispersion relation and tree-level propagator are determined exactly, and some leading-order results are derived. The question of how to include such Lorentz-violating effects into a perturbative quantum-field expansion is addressed. Applications of these results within Lorentz-breaking quantum-field theories include the regularization of infrared divergences as well as the free propagation of massive vector bosons.
Search for anisotropic Lorentz invariance violation with γ -rays
NASA Astrophysics Data System (ADS)
Kislat, Fabian; Krawczynski, Henric
2015-08-01
While Lorentz invariance, the fundamental symmetry of Einstein's theory of general relativity, has been tested to a great level of detail, grand unified theories that combine gravity with the other three fundamental forces may result in a violation of Lorentz symmetry at the Planck scale. These energies are unattainable experimentally. However, minute deviations from Lorentz invariance may still be present at much lower energies. These deviations can accumulate over large distances, making astrophysical measurements the most sensitive tests of Lorentz symmetry. One effect of Lorentz invariance violation is an energy-dependent photon dispersion of the vacuum resulting in differences of the light travel time from distant objects. The Standard Model Extension (SME) is an effective theory to describe the low-energy behavior of a more fundamental grand unified theory, including Lorentz- and C P T -violating terms. In the SME the Lorentz-violating operators can in part be classified by their mass dimension d , with the lowest order being d =5 . However, measurements of photon polarization have constrained operators with d =5 setting lower limits on the energy at which they become dominant well beyond the Planck scale. On the other hand, these operators also violate C P T , and thus d =6 could be the leading order. In this paper we present constraints on all 25 real coefficients describing anisotropic nonbirefringent Lorentz invariance violation at mass dimension d =6 in the SME. We used Fermi-LAT observations of 25 active galactic nuclei to constrain photon dispersion and combined our results with previously published limits in order to simultaneously constrain all 25 coefficients. This represents the first set of constraints on these coefficients of mass dimension d =6 , whereas previous measurements were only able to constrain linear combinations of all 25 coefficients.
Generalization of the Lorentz-Dirac equation to include spin
NASA Astrophysics Data System (ADS)
Barut, A. O.; Unal, Nuri
1989-11-01
For the classical point electron with Zitterbewegung (hence spin) we derive, after regularization, the radiation reaction force and covariant equations for the dynamical variables (xμ, πμ, vμ, and Sμν), which reduce to the Lorentz-Dirac equation in the spinless limit.
Optimal Lorentz-augmented spacecraft formation flying in elliptic orbits
NASA Astrophysics Data System (ADS)
Huang, Xu; Yan, Ye; Zhou, Yang
2015-06-01
An electrostatically charged spacecraft accelerates as it moves through the Earth's magnetic field due to the induced Lorentz force, providing a new means of propellantless electromagnetic propulsion for orbital maneuvers. The feasibility of Lorentz-augmented spacecraft formation flying in elliptic orbits is investigated in this paper. Assuming the Earth's magnetic field as a tilted dipole corotating with Earth, a nonlinear dynamical model that characterizes the orbital motion of Lorentz spacecraft in the vicinity of arbitrary elliptic orbits is developed. To establish a predetermined formation configuration at given terminal time, pseudospectral method is used to solve the optimal open-loop trajectories of hybrid control inputs consisted of Lorentz acceleration and thruster-generated control acceleration. A nontilted dipole model is also introduced to analyze the effect of dipole tilt angle via comparisons with the tilted one. Meanwhile, to guarantee finite-time convergence and system robustness against external perturbations, a continuous fast nonsingular terminal sliding mode controller is designed and the closed-loop system stability is proved by Lyapunov theory. Numerical simulations substantiate the validity of proposed open-loop and closed-loop control schemes, and the results indicate that an almost propellantless formation establishment can be achieved by choosing appropriate objective function in the pseudospectral method. Furthermore, compared to the nonsingular terminal sliding mode controller, the closed-loop controller presents superior convergence rate with only a bit more control effort. And the proposed controller can be applied in other Lorentz-augmented relative orbital control problems.
Statistical mechanics and Lorentz violation
NASA Astrophysics Data System (ADS)
Colladay, Don; McDonald, Patrick
2004-12-01
The theory of statistical mechanics is studied in the presence of Lorentz-violating background fields. The analysis is performed using the Standard-Model Extension (SME) together with a Jaynesian formulation of statistical inference. Conventional laws of thermodynamics are obtained in the presence of a perturbed hamiltonian that contains the Lorentz-violating terms. As an example, properties of the nonrelativistic ideal gas are calculated in detail. To lowest order in Lorentz violation, the scalar thermodynamic variables are only corrected by a rotationally invariant combination of parameters that mimics a (frame dependent) effective mass. Spin-couplings can induce a temperature-independent polarization in the classical gas that is not present in the conventional case. Precision measurements in the residual expectation values of the magnetic moment of Fermi gases in the limit of high temperature may provide interesting limits on these parameters.
Fresnel formulas as Lorentz transformations
Monzon; Sanchez-Soto
2000-08-01
From a matrix formulation of the boundary conditions we obtain the fundamental invariant for an interface and a remarkably simple factorization of the interface matrix, which enables us to express the Fresnel coefficients in a new and compact form. This factorization allows us to recast the action of an interface between transparent media as a hyperbolic rotation. By exploiting the local isomorphism between SL(2, C) and the (3 + 1)-dimensional restricted Lorentz group SO(3, 1), we construct the equivalent Lorentz transformation that describes any interface.
On Lorentz Transformations in Symplectic Deformations
Cuesta, R.; Sabido, M.; Guzman, W.
2010-07-12
In this paper we study noncommutative Lorentz transformations using symplectic deformations. In this framework we define an infinitesimal line element that is invariant under this noncommutative Lorentz transformations. Using the symplectic geometry formalism, we find that noncommutative Lorentz transformations intertwine the canonical momentums with canonical position coordinates.
Reflection theorem for Lorentz-Minkowski spaces
NASA Astrophysics Data System (ADS)
Lee, Nam-Hoon
2016-07-01
We generalize the reflection theorem of the Lorentz-Minkowski plane to that of the Lorentz-Minkowski spaces of higher dimensions. As a result, we show that an isometry of the Lorentz-Minkowski spacetime is a composition of at most 5 reflections.
NASA Astrophysics Data System (ADS)
Mondragon, Antonio R.
Observations from the 1930s until the present have established the existence of dark matter with an abundance that is much larger than that of luminous matter. Because none of the known particles of nature have the correct properties to be identified as the dark matter, various exotic candidates have been proposed. The neutralino of supersymmetric theories is the most promising example. Such cold dark matter candidates, however, lead to a conflict between the standard simulations of the evolution of cosmic structure and observations. Simulations predict excessive structure formation on small scales, including density cusps at the centers of galaxies, that is not observed. This conflict still persists in early 2007, and it has not yet been convincingly resolved by attempted explanations that invoke astrophysical phenomena, which would destroy or broaden all small scale structure. We have investigated another candidate that is perhaps more exotic: Lorentz-violating dark matter, which was originally motivated by an unconventional fundamental theory, but which in this dissertation is defined as matter which has a nonzero minimum velocity. Furthermore, the present investigation evolved into the broader goal of exploring the properties of Lorentz-violating matter and the astrophysical consequences-a subject which to our knowledge has not been previously studied. Our preliminary investigations indicated that this form of matter might have less tendency to form small-scale structure. These preliminary calculations certainly established that Lorentz-violating matter which always moves at an appreciable fraction of the speed of light will bind less strongly. However, the much more thorough set of studies reported here lead to the conclusion that, although the binding energy is reduced, the small-scale structure problem is not solved by Lorentz-violating dark matter. On the other hand, when we compare the predictions of Lorentz-violating dynamics with those of classical
An Involution of Lorentz Transformations
NASA Astrophysics Data System (ADS)
Lubkin, Elihu
2000-04-01
Quadrilateral(axis, joystick) creates a proper Lorentz transformation dual to Quadrilateral(joystick, axis). The joystick is a line through axis and coaxis, selecting on them the intrinsic velocity and the intrinsic angle, respectively.(E. Lubkin, ``Reversed 3velocities'', APR99.) (Thing and co-thing are skew perpendicular with inverse nearest points.) This involution may be interesting: axis, coaxis, joystick, and cojoystick indeed do close in a quadrilateral. And this came up in multiplying coaxial Lorentz transformations A and B to get C. When result C is surprisingly not coaxial with A and B---this happens when A, B are improper of opposite types---the result is an (intrinsic) aboutface whose new axis is of old joystick form.
Lorentz transformation of blackbody radiation.
Ford, G W; O'Connell, R F
2013-10-01
We present a simple calculation of the Lorentz transformation of the spectral distribution of blackbody radiation at temperature T. Here we emphasize that T is the temperature in the blackbody rest frame and does not change. We thus avoid the confused and confusing question of how temperature transforms. We show by explicit calculation that at zero temperature the spectral distribution is invariant. At finite temperature we find the well-known result familiar in discussions of the 2.7 K cosmic radiation.
Lorentz violation and Faddeev-Popov ghosts
Altschul, B.
2006-02-15
We consider how Lorentz-violating interactions in the Faddeev-Popov ghost sector will affect scalar QED. The behavior depends sensitively on whether the gauge symmetry is spontaneously broken. If the symmetry is not broken, Lorentz violations in the ghost sector are unphysical, but if there is spontaneous breaking, radiative corrections will induce Lorentz-violating and gauge-dependent terms in other sectors of the theory.
Renormalization of Lorentz violating theories
Anselmi, Damiano; Halat, Milenko
2007-12-15
We classify the unitary, renormalizable, Lorentz violating quantum field theories of interacting scalars and fermions, obtained improving the behavior of Feynman diagrams by means of higher space derivatives. Higher time derivatives are not generated by renormalization. Renormalizability is ensured by a ''weighted power-counting'' criterion. The theories contain a dimensionful parameter {lambda}{sub L}, yet a set of models are classically invariant under a weighted scale transformation, which is anomalous at the quantum level. Formulas for the weighted trace anomaly are derived. The renormalization-group properties are studied.
South Pole Lorentz Invariance Test
NASA Astrophysics Data System (ADS)
Hedges, Morgan; Smiciklas, Marc; Romalis, Michael
2014-05-01
Atomic spin co-magnetometers are among the most sensitive instruments to test for violations of CPT and Lorentz symmetry. Our rotating co-magnetometer has, in recent years, set the most stringent limits for such violations in fermions with measurements conducted in Princeton. In order to eliminate the gyroscopic pickup of Earth's rotation as a major limiting background, we now operate a Rb-21Ne co-magnetometer at the Amundsen-Scott South Pole Station. We discuss the current status of our ongoing South Pole experiment along with the latest results. This research is funded by NSF grant #PLR-1142032.
South Pole Lorentz Invariance Test
NASA Astrophysics Data System (ADS)
Hedges, Morgan; Smiciklas, Marc; Romalis, Michael
2015-05-01
Searches for Lorentz and CPT violation play an important role in testing current theories of space-time. To test one of the consequences of local Lorentz invariance we have performed a precision test of spatial isotropy at the Amundsen-Scott station near the geographic South Pole. This location provides the most isotropic environment available on Earth. The experiment is a rotating atomic-spin co-magnetometer which compares energy levels of 21Ne and Rubidium atoms as a function of direction. The experimental sensitivity obtained is more than an order of magnitude better than in previous such measurements, known as Hughes-Drever experiments. By operating the experiment at the Pole we are able to eliminate background signals due to the gyroscopic interactions of spins with Earth's rotation as well as diurnal environmental effects. Here we will present final results from the experiment's 2-year data collection period. This is the first precision atomic physics experiment performed at the Pole, and we will discuss the potential for future such measurements.
South Pole Lorentz Invariance Test
NASA Astrophysics Data System (ADS)
Hedges, Morgan; Smiciklas, Marc; Romalis, Michael
2015-04-01
Tests of Lorentz and CPT symmetries are important because they form a cornerstone of quantum field theory and general relativity. To test one of the consequences of local Lorentz invariance we have performed a precision test of spatial isotropy at the Amundsen-Scott station near the geographic South Pole. This location provides the most isotropic environment available on Earth. We use an atomic spin co-magnetometer to compare energy levels in 21 Ne and Rubidium atoms as the apparatus rotates with respect to the cosmos. Our experimental sensitivity is more than an order of magnitude greater than in previous such measurements, known as Hughes-Drever experiments. By operating at the South Pole we eliminate background signals due to the gyroscopic interactions of spins with Earth's rotation as well as diurnal environmental effects. The experiment has finished a 2-year data collection period and we expect to present the final results at the meeting. This is the first precision atomic physics experiment performed at the Pole and we will discuss the potential for future such measurements.
NASA Astrophysics Data System (ADS)
Borges, L. H. C.; Ferrari, A. F.; Barone, F. A.
2016-11-01
This paper is dedicated to the study of interactions between external sources for the electromagnetic field in the presence of Lorentz symmetry breaking. We focus on a higher derivative, Lorentz violating interaction that arises from a specific model that was argued to lead to interesting effects in the low energy phenomenology of light pseudoscalars interacting with photons. The kind of higher derivative Lorentz violating interaction we discuss are called nonminimal. They are usually expected to be relevant only at very high energies, but we argue they might also induce relevant effects in low energy phenomena. Indeed, we show that the Lorentz violating background considered by us leads to several phenomena that have no counterpart in Maxwell theory, such as nontrivial torques on isolated electric dipoles, as well as nontrivial forces and torques between line currents and point like charges, as well as among Dirac strings and other electromagnetic sources.
Enhanced sensitivity to Lorentz invariance violations in short-range gravity experiments
NASA Astrophysics Data System (ADS)
Shao, Cheng-Gang; Chen, Ya-Fen; Tan, Yu-Jie; Luo, Jun; Yang, Shan-Qing; Tobar, Michael Edmund
2016-11-01
Recently, first limits on putative Lorentz invariance violation coefficients in the pure gravity sector were determined by the reanalysis of short-range gravity experiments. Such experiments search for new physics at sidereal frequencies. They are not, however, designed to optimize the signal strength of a Lorentz invariance violation force; in fact the Lorentz violating signal is suppressed in the planar test mass geometry employed in those experiments. We describe a short-range torsion pendulum experiment with enhanced sensitivity to possible Lorentz violating signals. A periodic, striped test mass geometry is used to augment the signal. Careful arrangement of the phases of the striped patterns on opposite ends of the pendulum further enhances the signal while simultaneously suppressing the Newtonian background.
CPT violation implies violation of Lorentz invariance.
Greenberg, O W
2002-12-02
A interacting theory that violates CPT invariance necessarily violates Lorentz invariance. On the other hand, CPT invariance is not sufficient for out-of-cone Lorentz invariance. Theories that violate CPT by having different particle and antiparticle masses must be nonlocal.
Neutrinos as Probes of Lorentz Invariance
Díaz, Jorge S.
2014-01-01
Neutrinos can be used to search for deviations from exact Lorentz invariance. The worldwide experimental program in neutrino physics makes these particles a remarkable tool to search for a variety of signals that could reveal minute relativity violations. This paper reviews the generic experimental signatures of the breakdown of Lorentz symmetry in the neutrino sector.
Lorentz Covariant Distributions with Spectral Conditions
Zinoviev, Yury M.
2007-11-14
The properties of the vacuum expectation values of products of the quantum fields are formulated in the book [1]. The vacuum expectation values of quantum fields products would be the Fourier transforms of the Lorentz covariant tempered distributions with supports in the product of the closed upper light cones. Lorentz invariant distributions are studied in the papers [2]--[4]. The authors of these papers wanted to describe Lorentz invariant distributions in terms of distributions given on the Lorentz group orbit space. This orbit space has a complicated structure. It is noted [5] that a tempered distribution with support in the closed upper light cone may be represented as the action of the wave operator in some power on a differentiable function with support in the closed upper light cone. For the description of the Lorentz covariant differentiable functions the boundary of the closed upper light cone is not important. The measure of this boundary is zero.
Lorentz violation and perpetual motion
Eling, Christopher; Foster, Brendan Z.; Jacobson, Ted; Wall, Aron C.
2007-05-15
We show that any Lorentz-violating theory with two or more propagation speeds is in conflict with the generalized second law of black hole thermodynamics. We do this by identifying a classical energy-extraction method, analogous to the Penrose process, which would decrease the black hole entropy. Although the usual definitions of black hole entropy are ambiguous in this context, we require only very mild assumptions about its dependence on the mass. This extends the result found by Dubovsky and Sibiryakov, which uses the Hawking effect and applies only if the fields with different propagation speeds interact just through gravity. We also point out instabilities that could interfere with their black hole perpetuum mobile, but argue that these can be neglected if the black hole mass is sufficiently large.
Lorentz violation and perpetual motion
NASA Astrophysics Data System (ADS)
Eling, Christopher; Foster, Brendan Z.; Jacobson, Ted; Wall, Aron C.
2007-05-01
We show that any Lorentz-violating theory with two or more propagation speeds is in conflict with the generalized second law of black hole thermodynamics. We do this by identifying a classical energy-extraction method, analogous to the Penrose process, which would decrease the black hole entropy. Although the usual definitions of black hole entropy are ambiguous in this context, we require only very mild assumptions about its dependence on the mass. This extends the result found by Dubovsky and Sibiryakov, which uses the Hawking effect and applies only if the fields with different propagation speeds interact just through gravity. We also point out instabilities that could interfere with their black hole perpetuum mobile, but argue that these can be neglected if the black hole mass is sufficiently large.
Light-bending tests of Lorentz invariance
Tso, Rhondale; Bailey, Quentin G.
2011-10-15
Classical light-bending is investigated for weak gravitational fields in the presence of hypothetical local Lorentz violation. Using an effective field theory framework that describes general deviations from local Lorentz invariance, we derive a modified deflection angle for light passing near a massive body. The results include anisotropic effects not present for spherical sources in General Relativity as well as Weak Equivalence Principle violation. We develop an expression for the relative deflection of two distant stars that can be used to analyze data in past and future solar-system observations. The measurement sensitivities of such tests to coefficients for Lorentz violation are discussed.
Lorentz covariant {kappa}-Minkowski spacetime
DaPbrowski, Ludwik; Godlinski, Michal; Piacitelli, Gherardo
2010-06-15
In recent years, different views on the interpretation of Lorentz covariance of noncommuting coordinates have been discussed. By a general procedure, we construct the minimal canonical central covariantization of the {kappa}-Minkowski spacetime. Here, undeformed Lorentz covariance is implemented by unitary operators, in the presence of two dimensionful parameters. We then show that, though the usual {kappa}-Minkowski spacetime is covariant under deformed (or twisted) Lorentz action, the resulting framework is equivalent to taking a noncovariant restriction of the covariantized model. We conclude with some general comments on the approach of deformed covariance.
Nonrelativisitic Ideal Gases and Lorentz Violations
NASA Astrophysics Data System (ADS)
Colladay, D.; McDonald, P.
2005-04-01
We develop statistical mechanics for a nonrelativisitic ideal gas in the presence of Lorentz violating background fields. The analysis is performed using the Standard-Model Extension (SME). We derive the corresponding laws of thermodynamics and find that, to lowest order in Lorentz violation, the scalar thermodynamic variables are corrected by a rotationally invariant combination of the Lorentz terms which can be interpreted in terms of a (frame dependent) effective mass. We find that spin couplings can induce a temperature independent polarization in the gas that is not present in the conventional case.
Alternative theories of gravity and Lorentz violation
NASA Astrophysics Data System (ADS)
Xu, Rui; Foster, Joshua; Kostelecky, V. Alan
2017-01-01
General relativity has achieved many successes, including the prediction of experimental results. However, its incompatibility with quantum theory remains an obstacle. By extending the foundational properties of general relativity, alternative theories of gravity can be constructed. In this talk, we focus on fermion couplings in the weak-gravity limit of certain alternative theories of gravity. Under suitable experimental circumstances, some of these couplings match terms appearing in the gravitational SME, which is a general framework describing violations of local Lorentz invariance. Existing limits on Lorentz violation can therefore be used to constrain certain Lorentz-invariant alternative theories of gravity.
Abraham-Lorentz versus Landau-Lifshitz
NASA Astrophysics Data System (ADS)
Griffiths, David J.; Proctor, Thomas C.; Schroeter, Darrell F.
2010-04-01
The classical Abraham-Lorentz formula for the radiation reaction on a point charge suffers from two notorious defects: runaways and preacceleration. Recently, several authors have advocated as an alternative the Landau-Lifshitz formula, which has neither fault. The latter formula is often presented as an approximation to Abraham-Lorentz, raising the delicate question of how an approximation can be considered more accurate than the original. For a spherical shell of finite size, the equation for the radiation reaction is noncontroversial. We begin there, obtain the Abraham-Lorentz and Landau-Lifshitz expressions as limiting cases, and undertake some numerical studies to determine which is superior.
Projected constraints on Lorentz-violating gravity with gravitational waves
NASA Astrophysics Data System (ADS)
Hansen, Devin; Yunes, Nicolás; Yagi, Kent
2015-04-01
Gravitational waves are excellent tools to probe the foundations of general relativity in the strongly dynamical and nonlinear regime. One such foundation is Lorentz symmetry, which can be broken in the gravitational sector by the existence of a preferred time direction and, thus, a preferred frame at each spacetime point. This leads to a modification in the orbital decay rate of binary systems, and also in the generation and chirping of their associated gravitational waves. Here we study whether waves emitted in the late, quasicircular inspiral of nonspinning, neutron star binaries can place competitive constraints on two proxies of gravitational Lorentz violation: Einstein-Æther theory and khronometric gravity. We model the waves in the small-coupling (or decoupling) limit and in the post-Newtonian approximation, by perturbatively solving the field equations in small deformations from general relativity and in the small-velocity or weak-gravity approximation. We assume that a gravitational wave consistent with general relativity has been detected with second- and third-generation, ground-based detectors, and with the proposed space-based mission DECIGO, with and without coincident electromagnetic counterparts. Without a counterpart, a detection consistent with general relativity can only place competitive constraints on gravitational Lorentz violation when using future, third-generation or space-based instruments. On the other hand, a single counterpart is enough to place constraints that are 10 orders of magnitude more stringent than current binary pulsar bounds, even when using second-generation detectors. This is because Lorentz violation forces the group velocity of gravitational waves to be different from that of light, and this difference can be very accurately constrained with coincident observations.
LORENTZ PHASE IMAGING AND IN-SITU LORENTZ MICROSCOPY OF PATTERNED CO-ARRAYS.
VOLKOV,V.V.ZHU,Y.
2003-08-03
Understanding magnetic structures and properties of patterned and ordinary magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The key feature to such success is the ability to achieve visual quantitative information on domain configurations with a maximum ''magnetic'' resolution. Several methods have been developed to meet these demands (Kerr and Faraday effects, differential phase contrast microscopy, magnetic force microscopy, SEMPA etc.). In particular, the modern off-axis electron holography allows retrieval of the electron-wave phase shifts down to 2{pi}/N (with typical N = 10-20, approaching in the limit N {approx} 100) in TEM equipped with field emission gun, which is already successfully employed for studies of magnetic materials at nanometer scale. However, it remains technically demanding, sensitive to noise and needs highly coherent electron sources. As possible alternative we developed a new method of Lorentz phase microscopy [1,2] based on the Fourier solution [3] of magnetic transport-of-intensity (MTIE) equation. This approach has certain advantages, since it is less sensitive to noise and does not need high coherence of the source required by the holography. In addition, it can be realized in any TEM without basic hardware changes. Our approach considers the electron-wave refraction in magnetic materials (magnetic refraction) and became possible due to general progress in understanding of noninterferometric phase retrieval [4-6] dealing with optical refraction. This approach can also be treated as further development of Fresnel microscopy, used so far for imaging of in-situ magnetization process in magnetic materials studied by TEM. Figs. 1-3 show some examples of what kind information can be retrieved from the conventional Fresnel images using the new approach. Most of these results can be compared with electron-holographic data. Using this approach we can shed more light on fine
ERIC Educational Resources Information Center
Gamble, Reed
1989-01-01
Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)
Lorentz invariance in chiral kinetic theory.
Chen, Jing-Yuan; Son, Dam T; Stephanov, Mikhail A; Yee, Ho-Ung; Yin, Yi
2014-10-31
We show that Lorentz invariance is realized nontrivially in the classical action of a massless spin-1/2 particle with definite helicity. We find that the ordinary Lorentz transformation is modified by a shift orthogonal to the boost vector and the particle momentum. The shift ensures angular momentum conservation in particle collisions and implies a nonlocality of the collision term in the Lorentz-invariant kinetic theory due to side jumps. We show that 2/3 of the chiral-vortical effect for a uniformly rotating particle distribution can be attributed to the magnetic moment coupling required by the Lorentz invariance. We also show how the classical action can be obtained by taking the classical limit of the path integral for a Weyl particle.
Testing Lorentz invariance of dark matter
Blas, Diego; Ivanov, Mikhail M.; Sibiryakov, Sergey E-mail: mm.ivanov@physics.msu.ru
2012-10-01
We study the possibility to constrain deviations from Lorentz invariance in dark matter (DM) with cosmological observations. Breaking of Lorentz invariance generically introduces new light gravitational degrees of freedom, which we represent through a dynamical timelike vector field. If DM does not obey Lorentz invariance, it couples to this vector field. We find that this coupling affects the inertial mass of small DM halos which no longer satisfy the equivalence principle. For large enough lumps of DM we identify a (chameleon) mechanism that restores the inertial mass to its standard value. As a consequence, the dynamics of gravitational clustering are modified. Two prominent effects are a scale dependent enhancement in the growth of large scale structure and a scale dependent bias between DM and baryon density perturbations. The comparison with the measured linear matter power spectrum in principle allows to bound the departure from Lorentz invariance of DM at the per cent level.
Kim, Yongdae; Park, Kyihwan; Kim, Sangyoo
2009-04-15
A six-axis active vibration isolation system (AVIS) is developed using voice coil actuators. Point contact configuration is employed to have an easy assembly of eight voice coil actuators to an upper and a base plates. The velocity sensor, using an electromagnetic principle that is commonly used in the vibration control, is investigated since its phase lead characteristic causes an instability problem for a low frequency vibration. The performances of the AVIS are investigated in the frequency domain and finally validated by comparing with the passive isolation system using the atomic force microscope images.
Lorentz Transformation from Symmetry of Reference Principle
Petre, M.; Dima, M.; Dima, A.; Petre, C.; Precup, I.
2010-01-21
The Lorentz Transformation is traditionally derived requiring the Principle of Relativity and light-speed universality. While the latter can be relaxed, the Principle of Relativity is seen as core to the transformation. The present letter relaxes both statements to the weaker, Symmetry of Reference Principle. Thus the resulting Lorentz transformation and its consequences (time dilatation, length contraction) are, in turn, effects of how we manage space and time.
Lorentz violation in simple QED processes
NASA Astrophysics Data System (ADS)
de Brito, G. P.; Guaitolini Junior, J. T.; Kroff, D.; Malta, P. C.; Marques, C.
2016-09-01
We determine the effect of a C P T -even and Lorentz violating nonminimal coupling on the differential cross sections for some of the most important tree-level processes in QED, namely, Compton and Bhabha scatterings, as well as electron-positron annihilation. Experimental limits constraining the allowed deviation of the differential cross sections relative to pure QED allow us to place upper bounds on the Lorentz violating parameters. A constraint based on the decay rate of parapositronium is also obtained.
Gauge anomalies in Lorentz-violating QED
NASA Astrophysics Data System (ADS)
Santos, Tiago R. S.; Sobreiro, Rodrigo F.
2016-12-01
In this work we study the issue of gauge anomalies in Lorentz-violating QED. To do so, we opt to use the Becchi-Rouet-Stora-Tyutin formalism within the algebraic renormalization approach, reducing our study to a cohomology problem. Since this approach is independent of the renormalization scheme, the results obtained here are expected to be general. We find that the Lorentz-violating QED is free of gauge anomalies to all orders in perturbation theory.
Supersymmetry and Lorentz Violation in 5D
Garcia-Aguilar, J. D.; Perez-Lorenzana, A.; Pedraza-Ortega, O.
2011-10-14
We present a study for a Supersymmetric field theory with Lorentz-Violation terms in 5D. We perform the analysis in the context of the Berger-Kostelecky model (BK), adding one compactified dimension that explicitly breaks the Lorentz invariance. We introduce terms that encode this breaking, and find non trivial restrictions over boundary conditions of fields that one needs to close the supersymmetric algebra.
Supersymmetry and Lorentz Violation in 5D
NASA Astrophysics Data System (ADS)
García-Aguilar, J. D.; Pérez-Lorenzana, A.; Pedraza-Ortega, O.
2011-10-01
We present a study for a Supersymmetric field theory with Lorentz-Violation terms in 5D. We perform the analysis in the context of the Berger-Kostelecky model (BK), adding one compactified dimension that explicitly breaks the Lorentz invariance. We introduce terms that encode this breaking, and find non trivial restrictions over boundary conditions of fields that one needs to close the supersymmetric algebra.
NASA Astrophysics Data System (ADS)
Kumar, A. S.; Isobe, Syuzo
1992-03-01
An analysis is presented of the charging processes for the dust particles in the circumsolar dust band at 4 solar radii, as well as the effects of the interactions between these charged particles and the magnetized ambient solar wind plasma on the evolution of their orbits. It is concluded that due to the higher values of the potential on the dust particle and the ambient solar wind magnetic field, the Lorentz force affects a much wider size range of particles in the near-solar regions. Since the magnitude of the Lorentz force is much higher and its characteristic time to affect the particle's orbit is much lower than those for the Poynting-Robertson drag force, the Lorentz force is a major perturbing force for dust particles in the circumsolar dust band at 4 solar radii.
Lorentz covariance of loop quantum gravity
NASA Astrophysics Data System (ADS)
Rovelli, Carlo; Speziale, Simone
2011-05-01
The kinematics of loop gravity can be given a manifestly Lorentz-covariant formulation: the conventional SU(2)-spin-network Hilbert space can be mapped to a space K of SL(2,C) functions, where Lorentz covariance is manifest. K can be described in terms of a certain subset of the projected spin networks studied by Livine, Alexandrov and Dupuis. It is formed by SL(2,C) functions completely determined by their restriction on SU(2). These are square-integrable in the SU(2) scalar product, but not in the SL(2,C) one. Thus, SU(2)-spin-network states can be represented by Lorentz-covariant SL(2,C) functions, as two-component photons can be described in the Lorentz-covariant Gupta-Bleuler formalism. As shown by Wolfgang Wieland in a related paper, this manifestly Lorentz-covariant formulation can also be directly obtained from canonical quantization. We show that the spinfoam dynamics of loop quantum gravity is locally SL(2,C)-invariant in the bulk, and yields states that are precisely in K on the boundary. This clarifies how the SL(2,C) spinfoam formalism yields an SU(2) theory on the boundary. These structures define a tidy Lorentz-covariant formalism for loop gravity.
Hadronic Lorentz violation in chiral perturbation theory
NASA Astrophysics Data System (ADS)
Kamand, Rasha; Altschul, Brett; Schindler, Matthias R.
2017-03-01
Any possible Lorentz violation in the hadron sector must be tied to Lorentz violation at the underlying quark level. The relationships between the theories at these two levels are studied using chiral perturbation theory. Starting from a two-flavor quark theory that includes dimension-4 Lorentz-violation operators, the effective Lagrangians are derived for both pions and nucleons, with novel terms appearing in both sectors. Since the Lorentz-violation coefficients for nucleons and pions are all related to a single set of underlying quark coefficients, one can compare the sensitivity of different types of experiments. Our analysis shows that atomic physics experiments currently provide constraints on the quark parameters that are stronger by about 10 orders of magnitude than astrophysical experiments with relativistic pions. Alternatively, it is possible to place approximate bounds on pion Lorentz violation using only proton and neutron observations. Under the assumption that the Lorentz-violating operators considered here are the only ones contributing to the relevant observables and taking the currently unknown hadronic low-energy constants to be of natural size, the resulting estimated bounds on four pion parameters are at the 10-23 level, representing improvements of 10 orders of magnitude.
Test of Lorentz symmetry with trapped ions
NASA Astrophysics Data System (ADS)
Pruttivarasin, Thaned
2016-05-01
The outcome of an experiment should not depend on the orientation of the apparatus in space. This important cornerstone of physics is deeply engrained into the Standard Model of Physics by requiring that all fields must be Lorentz invariant. However, it is well-known that the Standard Model is incomplete. Some theories conjecture that at the Planck scale Lorentz symmetry might be broken and measurable at experimentally accessible energy scales. Therefore, a search for violation of Lorentz symmetry directly probes physics beyond the Standard model. We present a novel experiment utilizing trapped calcium ions as a direct probe of Lorentz-violation in the electron-photon sector. We monitor the energy between atomic states with different orientations of the electronic wave-functions as they rotate together with the motion of the Earth. This is analogous to the famous Michelson-Morley experiment. To remove magnetic field noise, we perform the experiment with the ions prepared in the decoherence-free states. Our result improves on the most stringent bounds on Lorentz symmetry for electrons by 100 times. The experimental scheme is readily applicable to many ion species, hence opening up paths toward much improved test of Lorentz symmetry in the future. (Ph. D. Advisor: Hartmut Haeffner, University of California, Berkeley).
A technique for monitoring fast tuner piezoactuator preload forces for superconducting rf cavities
Pischalnikov, Y.; Branlard, J.; Carcagno, R.; Chase, B.; Edwards, H.; Orris, D.; Makulski, A.; McGee, M.; Nehring, R.; Poloubotko, V.; Sylvester, C.; /Fermilab
2007-06-01
The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII)[2] tested at FNAL are presented. These results include measurements during cool-down, warmup, and cavity tuning along with dynamic Lorentz force compensation.
Fluctuation theorem applied to the Nosé-Hoover thermostated Lorentz gas.
Gilbert, Thomas
2006-03-01
We present numerical evidence supporting the validity of the Gallavotti-Cohen fluctuation theorem applied to the driven Lorentz gas with Nosé-Hoover thermostating. It is moreover argued that the asymptotic form of the fluctuation formula is independent of the amplitude of the driving force in the limit where it is small.
Fluctuation theorem applied to the Nosé-Hoover thermostated Lorentz gas
NASA Astrophysics Data System (ADS)
Gilbert, Thomas
2006-03-01
We present numerical evidence supporting the validity of the Gallavotti-Cohen fluctuation theorem applied to the driven Lorentz gas with Nosé-Hoover thermostating. It is moreover argued that the asymptotic form of the fluctuation formula is independent of the amplitude of the driving force in the limit where it is small.
A test of Lorentz-Dirac and Lienard-Wiechert equations
NASA Astrophysics Data System (ADS)
Comay, E.
1987-12-01
Gedanken experiments of two charges moving uniformly along a circle are used for testing both the Lorentz-Dirac radiation reaction force and the Lienard-Wiechert formulas of retarted potentials. It is shown that if some additional postulates hold then these expressions are acceptable only as low order approximations.
NASA Astrophysics Data System (ADS)
Barut, A. O.
1990-04-01
By exact explicit solution it is shown that the Lorentz-Dirac equation with radiation reaction and proper initial conditions does not violate causality, even if the force is nonanalytic. We also show that if the equation is correctly renormalized there are no runaway solutions.
Generalized Lorentz-Dirac equation for a strongly coupled gauge theory.
Chernicoff, Mariano; García, J Antonio; Güijosa, Alberto
2009-06-19
We derive a semiclassical equation of motion for a "composite" quark in strongly coupled large-N_{c} N = 4 super Yang-Mills theory, making use of the anti-de Sitter space/conformal field theory correspondence. The resulting nonlinear equation incorporates radiation damping, and reduces to the standard Lorentz-Dirac equation for external forces that are small on the scale of the quark Compton wavelength, but has no self-accelerating or preaccelerating solutions. From this equation one can read off a nonstandard dispersion relation for the quark, as well as a Lorentz-covariant formula for its radiation rate.
Magnetic Susceptibility Effects and Lorentz Damping in Diamagnetic Fluids
NASA Technical Reports Server (NTRS)
Ramachandran, Narayanan; Leslie, Fred W.
2000-01-01
A great number of crystals (semi-conductor and protein) grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity and g-jitter. Both static and dynamic (rotating or travelling wave) magnetic fields can be used to reduce the effects of convection in materials processing. In semi-conductor melts, due to their relatively high electrical conductivity, the induced Lorentz force can be effectively used to curtail convective effects. In melts/solutions with reduced electrical conductivity, such as aqueous solutions used in solution crystal growth, protein crystal growth and/or model fluid experiments for simulating melt growth, however, the variation of the magnetic susceptibility with temperature and/or concentration can be utilized to better damp fluid convection than the Lorentz force method. This paper presents a comprehensive, comparative numerical study of the relative damping effects using static magnetic fields and gradients in a simple geometry subjected to a thermal gradient. The governing equations are formulated in general terms and then simplified for the numerical calculations. Operational regimes, based on the best damping technique for different melts/solutions are identified based on fluid properties. Comparisons are provided between the numerical results and available results from experiments in surveyed literature.
Maps for Lorentz transformations of spin
Jordan, Thomas F.; Shaji, Anil; Sudarshan, E. C. G.
2006-03-15
Lorentz transformations of spin density matrices for a particle with positive mass and spin 1/2 are described by maps of the kind used in open quantum dynamics. They show how the Lorentz transformations of the spin depend on the momentum. Since the spin and momentum generally are not independent, the maps generally are not completely positive and act in limited domains. States with two momentum values are considered, so the maps are for the spin qubit correlated with the qubit made from the two momentum values, and results from the open quantum dynamics of two coupled qubits can be applied. Inverses are used to show that every Lorentz transformation completely removes the spin polarization, and so completely removes the information, from a number of spin density matrices. The size of the spin polarization that is removed is calculated for particular cases.
Theoretical Studies of Lorentz and CPT Symmetry
NASA Technical Reports Server (NTRS)
Kostelecky, V. Alan
2005-01-01
The fundamental symmetries studied here are Lorentz and CPT invariance, which form a cornerstone of the relativistic quantum theories used in modern descriptions of nature. The results obtained during the reporting period focus on the idea, originally suggested by the P.I. and his group in the late 1980s, that observable CPT and Lorentz violation in nature might emerge from the qualitatively new physics expected to hold at the Planck scale. What follows is a summary of results obtained during the period of this grant.
Imperfect fluids, Lorentz violations, and Finsler cosmology
Kouretsis, A. P.; Stathakopoulos, M.; Stavrinos, P. C.
2010-09-15
We construct a cosmological toy model based on a Finslerian structure of space-time. In particular, we are interested in a specific Finslerian Lorentz violating theory based on a curved version of Cohen and Glashow's very special relativity. The osculation of a Finslerian manifold to a Riemannian manifold leads to the limit of relativistic cosmology, for a specified observer. A modified flat Friedmann-Robertson-Walker cosmology is produced. The analogue of a zero energy particle unfolds some special properties of the dynamics. The kinematical equations of motion are affected by local anisotropies. Seeds of Lorentz violations may trigger density inhomogeneities to the cosmological fluid.
Aberration corrected Lorentz scanning transmission electron microscopy.
McVitie, S; McGrouther, D; McFadzean, S; MacLaren, D A; O'Shea, K J; Benitez, M J
2015-05-01
We present results from an aberration corrected scanning transmission electron microscope which has been customised for high resolution quantitative Lorentz microscopy with the sample located in a magnetic field free or low field environment. We discuss the innovations in microscope instrumentation and additional hardware that underpin the imaging improvements in resolution and detection with a focus on developments in differential phase contrast microscopy. Examples from materials possessing nanometre scale variations in magnetisation illustrate the potential for aberration corrected Lorentz imaging as a tool to further our understanding of magnetism on this lengthscale.
Black Hole Thermodynamics and Lorentz Symmetry
NASA Astrophysics Data System (ADS)
Jacobson, Ted; Wall, Aron C.
2010-08-01
Recent developments point to a breakdown in the generalized second law of thermodynamics for theories with Lorentz symmetry violation. It appears possible to construct a perpetual motion machine of the second kind in such theories, using a black hole to catalyze the conversion of heat to work. Here we describe and extend the arguments leading to that conclusion. We suggest the inference that local Lorentz symmetry may be an emergent property of the macroscopic world with origins in a microscopic second law of causal horizon thermodynamics.
38 CFR 3.708 - Federal Employees' Compensation.
Code of Federal Regulations, 2010 CFR
2010-07-01
...' Compensation Act (FECA) based upon disability or death due to service in the Armed Forces and is also entitled based upon service in the Armed Forces to pension, compensation or dependency and indemnity compensation..., hospitalization or hospital care, training, or compensated work therapy program. See §§ 3.358 and 3.361....
The Lorentz Theory of Electrons and Einstein's Theory of Relativity
ERIC Educational Resources Information Center
Goldberg, Stanley
1969-01-01
Traces the development of Lorentz's theory of electrons as applied to the problem of the electrodynamics of moving bodies. Presents evidence that the principle of relativity did not play an important role in Lorentz's theory, and that though Lorentz eventually acknowledged Einstein's work, he was unwilling to completely embrace the Einstein…
Lorentz-covariant dissipative Lagrangian systems
NASA Technical Reports Server (NTRS)
Kaufman, A. N.
1985-01-01
The concept of dissipative Hamiltonian system is converted to Lorentz-covariant form, with evolution generated jointly by two scalar functionals, the Lagrangian action and the global entropy. A bracket formulation yields the local covariant laws of energy-momentum conservation and of entropy production. The formalism is illustrated by a derivation of the covariant Landau kinetic equation.
Another route to the Lorentz transformations
NASA Astrophysics Data System (ADS)
Bessonov, E. G.
2016-05-01
This paper uses the Galilean relativity principle and the dependence of the rate of a clock on its velocity to derive the Lorentz transformations (LTs). Analyzing different ways of deriving the LTs provides different perspectives on them and their implications, as well as making them more accessible to a wide range of readers with an interest in relativistic physics.
Gravity, Lorentz violation, and the standard model
NASA Astrophysics Data System (ADS)
Kostelecký, V. Alan
2004-05-01
The role of the gravitational sector in the Lorentz- and CPT-violating standard-model extension (SME) is studied. A framework is developed for addressing this topic in the context of Riemann-Cartan spacetimes, which include as limiting cases the usual Riemann and Minkowski geometries. The methodology is first illustrated in the context of the QED extension in a Riemann-Cartan background. The full SME in this background is then considered, and the leading-order terms in the SME action involving operators of mass dimension three and four are constructed. The incorporation of arbitrary Lorentz and CPT violation into general relativity and other theories of gravity based on Riemann-Cartan geometries is discussed. The dominant terms in the effective low-energy action for the gravitational sector are provided, thereby completing the formulation of the leading-order terms in the SME with gravity. Explicit Lorentz symmetry breaking is found to be incompatible with generic Riemann-Cartan geometries, but spontaneous Lorentz breaking evades this difficulty.
ERIC Educational Resources Information Center
Minnesota State Office of the Legislative Auditor, St. Paul. Program Evaluation Div.
Minnesota state policy makers are concerned about teacher compensation because it constitutes a major category of state and local spending and can affect education results. This report examines compensation issues by describing the pay structure of Minnesota's K-12 public school teachers, making pay comparisons with other professionals, and…
ERIC Educational Resources Information Center
Roady, Celia
2008-01-01
Congress, the news media, and the Internal Revenue Service (IRS) continue to cast a wary eye on the compensation of nonprofit leaders. Hence, any college or university board that falls short of IRS expectations in its procedures for setting the president's compensation is putting the president, other senior officials, and board members at…
Transforming to Lorentz gauge on de Sitter
Miao, S. P.; Tsamis, N. C.; Woodard, R. P.
2009-12-15
We demonstrate that certain gauge fixing functionals cannot be added to the action on backgrounds such as de Sitter, in which a linearization instability is present. We also construct the field-dependent gauge transformation that carries the electromagnetic vector potential from a convenient, non-de Sitter invariant gauge to the de Sitter invariant, Lorentz gauge. The transformed propagator agrees with the de Sitter invariant result previously found by solving the propagator equation in Lorentz gauge. This shows that the gauge transformation technique will eliminate unphysical breaking of de Sitter invariance introduced by a gauge condition. It is suggested that the same technique can be used to finally resolve the issue of whether or not free gravitons are de Sitter invariant.
Remarks on holography with broken Lorentz invariance
NASA Astrophysics Data System (ADS)
Gordeli, Ivan; Koroteev, Peter
2009-12-01
Recently a family of solutions of Einstein equations in backgrounds with broken Lorentz invariance was found. We show that the gravitational solution recently obtained by Kachru et al. is a part of the former solution which was derived earlier in the framework of extra-dimensional theories. We show how the energy-momentum and Einstein tensors are related and establish a correspondence between parameters which govern Lorentz invariance violation. Then we demonstrate that scaling behavior of two point correlation functions of local operators in scalar field theory is reproduced correctly for two cases with critical values of scaling parameters. Therefore, we complete the dictionary of “tree-level” duality for all known solutions of the bulk theory. In the end we speculate on relations between renormalization group flow of a boundary theory and asymptotic behavior of gravitational solutions in the bulk.
Mr. Tompkins in Java: Interactive Lorentz transformations
NASA Astrophysics Data System (ADS)
Saha, Prasenjit
2003-12-01
This paper describes a simple applet for illustrating Lorentz transformations. The user specifies stationary and moving objects and light pulses, and sees animations of two reference frames. Even with minimal graphics (the objects are colored dots and the light flashes are expanding circles), such animations can make the concepts of redshift, length contraction, time dilation, and non-simultaneity more intuitive than traditional spacetime diagrams.
Neutrino velocity and local Lorentz invariance
NASA Astrophysics Data System (ADS)
Cardone, Fabio; Mignani, Roberto; Petrucci, Andrea
2015-09-01
We discuss the possible violation of local Lorentz invariance (LLI) arising from a faster-than-light neutrino speed. A toy calculation of the LLI violation parameter δ, based on the (disclaimed) OPERA data, suggests that the values of δ are determined by the interaction involved, and not by the energy range. This hypothesis is further corroborated by the analysis of the more recent results of the BOREXINO, LVD and ICARUS experiments.
The Lorentz anomaly via operator product expansion
Fredenhagen, Stefan; Hoppe, Jens Hynek, Mariusz
2015-10-15
The emergence of a critical dimension is one of the most striking features of string theory. One way to obtain it is by demanding closure of the Lorentz algebra in the light-cone gauge quantisation, as discovered for bosonic strings more than forty years ago. We give a detailed derivation of this classical result based on the operator product expansion on the Lorentzian world-sheet.
NASA Technical Reports Server (NTRS)
Schaffer, L.; Burns, J. A.
1995-01-01
Dust grains in planetary rings acquire stochastically fluctuating electric charges as they orbit through any corotating magnetospheric plasma. Here we investigate the nature of this stochastic charging and calculate its effect on the Lorentz resonance (LR). First we model grain charging as a Markov process, where the transition probabilities are identified as the ensemble-averaged charging fluxes due to plasma pickup and photoemission. We determine the distribution function P(t;N), giving the probability that a grain has N excess charges at time t. The autocorrelation function tau(sub q) for the strochastic charge process can be approximated by a Fokker-Planck treatment of the evolution equations for P(t; N). We calculate the mean square response to the stochastic fluctuations in the Lorentz force. We find that transport in phase space is very small compared to the resonant increase in amplitudes due to the mean charge, over the timescale that the oscillator is resonantly pumped up. Therefore the stochastic charge variations cannot break the resonant interaction; locally, the Lorentz resonance is a robust mechanism for the shaping of etheral dust ring systems. Slightly stronger bounds on plasma parameters are required when we consider the longer transit times between Lorentz resonances.
Lorentz force effects for graphene Aharonov-Bohm interferometers
NASA Astrophysics Data System (ADS)
Mreńca-Kolasińska, A.; Szafran, B.
2016-11-01
We investigate magnetic deflection of currents that flow across the Aharonov-Bohm interferometers defined in graphene. We consider devices induced by closed n -p junctions in nanoribbons as well as etched quantum rings. The deflection effects on conductance are strictly correlated with the properties of the ring-localized quasibound states. The energy of these states, their lifetime, and the periodicity of the conductance oscillations are determined by orientation of the current circulating within the interferometer. The formation of high harmonics of conductance at high magnetic field and the role of intervalley scattering are discussed.
Far-field intensity of Lorentz related beams
NASA Astrophysics Data System (ADS)
Peng, Xi; Chen, Chidao; Chen, Bo; Peng, Yulian; Zhou, Meiling; Zhang, Liping; Li, Dongdong; Deng, Dongmei
2016-12-01
We introduce a sufficient condition under which the Lorentz beam convolution with other beams constitutes valid cross-spectral densities. Two examples are given to show how the Lorentz related beam can be used for generation of a far field being a modulated version of another one. The far-field intensity patterns in the Cartesian symmetries by the convolution operation of the Lorentz beams with multi-sinc beams, and the convolution operation of the Lorentz beams with multi-sinc Gaussian beams, are shown respectively. We find that different beam order can result distinct far field changes.
Fractional Fourier transform of Lorentz-Gauss beams.
Zhou, Guoquan
2009-02-01
Lorentz-Gauss beams are introduced to describe certain laser sources that produce highly divergent beams. The fractional Fourier transform (FRFT) is applied to treat the propagation of Lorentz-Gauss beams. Based on the definition of convolution and the convolution theorem of the Fourier transform, an analytical expression for a Lorentz-Gauss beam passing through an FRFT system has been derived. By using the derived expression, the properties of a Lorentz-Gauss beam in the FRFT plane are graphically illustrated with numerical examples.
Extending the Lorentz transformation by characteristic coordinates
NASA Technical Reports Server (NTRS)
Jones, R. T.
1976-01-01
The problem considered is that of rectilinear motion with variable velocity. The paper gives, by an elementary construction, a system of coordinates which is conformal in a restricted region near the axis of the motion. In such coordinates the velocity of light remains invariant even for observers moving with variable velocity. By a particular choice of the scale relation the restricted conformal transformations can be made to reduce to the Lorentz transformation everywhere in the case of constant velocity and locally in the case of variable velocity.
Optical finite representation of the Lorentz group
NASA Astrophysics Data System (ADS)
Rodríguez-Lara, B. M.; Guerrero, J.
2015-12-01
We present a class of photonic lattices with an underlying symmetry given by a finite-dimensional representation of the 2+1D Lorentz group. In order to construct such a finite-dimensional representation of a non-compact group, we have to design a $\\mathcal{PT}$-symmetric optical structure. Thus, the array of coupled waveguides may keep or break $\\mathcal{PT}$-symmetry, leading to a device that behaves like an oscillator or directional amplifier, respectively. We show that the so-called linear $\\mathcal{PT}$-symmetric dimer belongs to this class of photonic lattices.
Fermi acceleration in the randomized driven Lorentz gas and the Fermi-Ulam model.
Karlis, A K; Papachristou, P K; Diakonos, F K; Constantoudis, V; Schmelcher, P
2007-07-01
Fermi acceleration of an ensemble of noninteracting particles evolving in a stochastic two-moving wall variant of the Fermi-Ulam model (FUM) and the phase randomized harmonically driven periodic Lorentz gas is investigated. As shown in [A. K. Karlis, P. K. Papachristou, F. K. Diakonos, V. Constantoudis, and P. Schmelcher, Phys. Rev. Lett. 97, 194102 (2006)], the static wall approximation, which ignores scatterer displacement upon collision, leads to a substantial underestimation of the mean energy gain per collision. In this paper, we clarify the mechanism leading to the increased acceleration. Furthermore, the recently introduced hopping wall approximation is generalized for application in the randomized driven Lorentz gas. Utilizing the hopping approximation the asymptotic probability distribution function of the particle velocity is derived. Moreover, it is shown that, for harmonic driving, scatterer displacement upon collision increases the acceleration in both the driven Lorentz gas and the FUM by the same amount. On the other hand, the investigation of a randomized FUM, comprising one fixed and one moving wall driven by a sawtooth force function, reveals that the presence of a particular asymmetry of the driving function leads to an increase of acceleration that is different from that gained when symmetrical force functions are considered, for all finite number of collisions. This fact helps open up the prospect of designing accelerator devices by combining driving laws with specific symmetries to acquire a desired acceleration behavior for the ensemble of particles.
NASA Astrophysics Data System (ADS)
Hnizdo, V.
1988-06-01
Refutation is given of a recent claim that both the Lorentz-Dirac radiation reaction force and Lienard-Wiechert retarded potentials satisfy energy conservation only to a low order of approximation in a system of two charges which move uniformly along a circle. When correctly calculated, the power radiated by such a system equals exactly the rate at which work is done on the system by external forces.
Testing Lorentz Symmetry with Lunar Laser Ranging
NASA Astrophysics Data System (ADS)
Bourgoin, A.; Hees, A.; Bouquillon, S.; Le Poncin-Lafitte, C.; Francou, G.; Angonin, M.-C.
2016-12-01
Lorentz symmetry violations can be parametrized by an effective field theory framework that contains both general relativity and the standard model of particle physics called the standard-model extension (SME). We present new constraints on pure gravity SME coefficients obtained by analyzing lunar laser ranging (LLR) observations. We use a new numerical lunar ephemeris computed in the SME framework and we perform a LLR data analysis using a set of 20 721 normal points covering the period of August, 1969 to December, 2013. We emphasize that linear combination of SME coefficients to which LLR data are sensitive and not the same as those fitted in previous postfit residuals analysis using LLR observations and based on theoretical grounds. We found no evidence for Lorentz violation at the level of 10-8 for s¯T X, 10-12 for s¯X Y and s¯X Z, 10-11 for s¯X X-s¯Y Y and s¯X X+s¯Y Y-2 s¯Z Z-4.5 s¯Y Z, and 10-9 for s¯T Y+0.43 s¯T Z. We improve previous constraints on SME coefficient by a factor up to 5 and 800 compared to postfit residuals analysis of respectively binary pulsars and LLR observations.
The Superluminal Neutrinos from Deformed Lorentz Invariance
NASA Astrophysics Data System (ADS)
Huo, Yunjie; Li, Tianjun; Liao, Yi; Nanopoulos, Dimitri V.; Qi, Yonghui; Wang, Fei
2012-10-01
We study two superluminal neutrino scenarios where δ v≡ (v-c)/(c) is a constant. To be consistent with the OPERA, Borexino and ICARUS experiments and with the SN1987a observations, we assume that δvν on the Earth is about three-order larger than that on the interstellar scale. To explain the theoretical challenges from the Bremsstrahlung effects and pion decays, we consider the deformed Lorentz invariance, and show that the superluminal neutrino dispersion relations can be realized properly while the modifications to the dispersion relations of the other Standard Model particles can be negligible. In addition, we propose the deformed energy and momentum conservation laws for a generic physical process. In Scenario I the momentum conservation law is preserved while the energy conservation law is deformed. In Scenario II the energy conservation law is preserved while the momentum conservation law is deformed. We present the energy and momentum conservation laws in terms of neutrino momentum in Scenario I and in terms of neutrino energy in Scenario II. In such formats, the energy and momentum conservation laws are exactly the same as those in the traditional quantum field theory with Lorentz symmetry. Thus, all the above theoretical challenges can be automatically solved. We show explicitly that the Bremsstrahlung processes are forbidden and there is no problem for pion decays.
Planar factors of proper homogeneous Lorentz transformations
Fahnline, D.E.
1985-02-01
This article discusses two constructions factoring proper homogeneous Lorentz transformations H into the product of two planar transformations. A planar transformation is a proper homogeneous Lorentz transformation changing vectors in a two-flat through the origin, called the transformation two-flat, into new vectors in the same two-flat and which leaves unchanged vectors in the orthogonal two-flat, called the pointwise invariant two-flat. The first construction provides two planar factors such that a given timelike vector lies in the transformation two-flat of one and in the pointwise invariant two-flat of the other; it leads to several basic conditions on the trace of H and to necessary and sufficient conditions for H to be planar. The second construction yields explicit formulas for the orthogonal factors of H when they exist and are unique, where two planar transformations are orthogonal if the transformation two-flat of one is the pointwise invariant two-flat of the other.
Testing Lorentz Symmetry with Lunar Laser Ranging.
Bourgoin, A; Hees, A; Bouquillon, S; Le Poncin-Lafitte, C; Francou, G; Angonin, M-C
2016-12-09
Lorentz symmetry violations can be parametrized by an effective field theory framework that contains both general relativity and the standard model of particle physics called the standard-model extension (SME). We present new constraints on pure gravity SME coefficients obtained by analyzing lunar laser ranging (LLR) observations. We use a new numerical lunar ephemeris computed in the SME framework and we perform a LLR data analysis using a set of 20 721 normal points covering the period of August, 1969 to December, 2013. We emphasize that linear combination of SME coefficients to which LLR data are sensitive and not the same as those fitted in previous postfit residuals analysis using LLR observations and based on theoretical grounds. We found no evidence for Lorentz violation at the level of 10^{-8} for s[over ¯]^{TX}, 10^{-12} for s[over ¯]^{XY} and s[over ¯]^{XZ}, 10^{-11} for s[over ¯]^{XX}-s[over ¯]^{YY} and s[over ¯]^{XX}+s[over ¯]^{YY}-2s[over ¯]^{ZZ}-4.5s[over ¯]^{YZ}, and 10^{-9} for s[over ¯]^{TY}+0.43s[over ¯]^{TZ}. We improve previous constraints on SME coefficient by a factor up to 5 and 800 compared to postfit residuals analysis of respectively binary pulsars and LLR observations.
Testing local Lorentz invariance with short-range gravity
NASA Astrophysics Data System (ADS)
Kostelecký, V. Alan; Mewes, Matthew
2017-03-01
The Newton limit of gravity is studied in the presence of Lorentz-violating gravitational operators of arbitrary mass dimension. The linearized modified Einstein equations are obtained and the perturbative solutions are constructed and characterized. We develop a formalism for data analysis in laboratory experiments testing gravity at short range and demonstrate that these tests provide unique sensitivity to deviations from local Lorentz invariance.
Lorentz and CPT Tests with Spin-Polarized Solids
Bluhm, Robert; Kostelecky, V. Alan
2000-02-14
Experiments using macroscopic samples of spin-polarized matter offer exceptional sensitivity to Lorentz and CPT violation in the electron sector. Data from existing experiments with a spin-polarized torsion pendulum provide sensitivity in this sector rivaling that of all other existing experiments and could reveal spontaneous violation of Lorentz symmetry at the Planck scale. (c) 2000 The American Physical Society.
Lorentz-Dirac equation and circularly moving charges
NASA Astrophysics Data System (ADS)
Comay, E.
1987-09-01
The Lorentz-Dirac equation of radiation reaction is tested in a system of circularly moving changes. It is shown that this equation together with the Lienard-Wiechert retarded fields is consistent with energy conservation. Therefore, in this particular experiment, any alternative expression of radiation reaction must agree with the Lorentz-Dirac equation.
Supersymmetric Lorentz Chern-Simons terms coupled to supergravity
Nishino, Hitoshi; Rajpoot, Subhash
2010-04-15
We present supersymmetric Lorentz Chern-Simons terms coupled to anti-de Sitter supergravity in three dimensions with an arbitrary number of supersymmetries. As an application to higher dimensions, we present analogous supersymmetric Lorentz Chern-Simons terms coupled to N=1 supergravity in 11 dimensions.
ERIC Educational Resources Information Center
Kim, Y. S.; And Others
1979-01-01
Using covarient harmonic oscillator formalism as an illustrative example, a method is proposed for illustrating the difference between the Poincare (inhomogeneous Lorentz) and homogeneous Lorentz groups. (BT)
Dynamical properties of the Lorentz gas
NASA Astrophysics Data System (ADS)
Sharma, K. C.; Ranganathan, S.; Egelstaff, P. A.; Soper, A. K.
1987-07-01
A Lorentz gas interacting with a Lennard-Jones (LJ) potential and obeying classical equations of motion has been simulated by the molecular-dynamics method. A system of 255 Ar particles and one H2 molecule at a reduced Ar density 0.413 and temperature 2.475 is simplified by allowing the ``argon'' to have infinite mass, and the hydrogen molecule interacts with Ar atoms via the LJ potential. The simulated incoherent dynamic structure factor Ss(Q,ω) for the hydrogen molecule, which is corrected for the rotational states, is found to be in reasonable agreement with the experimental data of Egelstaff et al. (unpublished). One-parameter phenomenological model calculations are also compared to these data.
Cosmology of a Lorentz violating Galileon theory
Haghani, Zahra; Shahidi, Shahab; Harko, Tiberiu; Sepangi, Hamid Reza E-mail: t.harko@ucl.ac.uk E-mail: s.shahidi@du.ac.ir
2015-05-01
We modify the scalar Einstein-aether theory by breaking the Lorentz invariance of a gravitational theory coupled to a Galileon type scalar field. This is done by introducing a Lagrange multiplier term into the action, thus ensuring that the gradient of the scalar field is time-like, with unit norm. The theory can also be considered as an extension to the mimetic dark matter theory, by adding some derivative self interactions to the action, which keeps the equation of motion at most second order in time derivatives. The cosmological implications of the model are discussed in detail. In particular, for pressure-less baryonic matter, we show that the universe experiences a late time acceleration. The cosmological implications of a special coupling between the scalar field and the trace of the energy-momentum tensor are also explored.
Living with ghosts in Lorentz invariant theories
Garriga, Jaume; Vilenkin, Alexander E-mail: vilenkin@cosmos.phy.tufts.edu
2013-01-01
We argue that theories with ghosts may have a long lived vacuum state even if all interactions are Lorentz preserving. In space-time dimension D = 2, we consider the tree level decay rate of the vacuum into ghosts and ordinary particles mediated by non-derivative interactions, showing that this is finite and logarithmically growing in time. For D > 2, the decay rate is divergent unless we assume that the interaction between ordinary matter and the ghost sector is soft in the UV, so that it can be described in terms of non-local form factors rather than point-like vertices. We provide an example of a nonlocal gravitational-strength interaction between the two sectors, which appears to satisfy all observational constraints.
Testing Lorentz symmetry with planetary orbital dynamics
NASA Astrophysics Data System (ADS)
Hees, A.; Bailey, Q. G.; Le Poncin-Lafitte, C.; Bourgoin, A.; Rivoldini, A.; Lamine, B.; Meynadier, F.; Guerlin, C.; Wolf, P.
2015-09-01
Planetary ephemerides are a very powerful tool to constrain deviations from the theory of general relativity (GR) using orbital dynamics. The effective field theory framework called the Standard-Model Extension (SME) has been developed in order to systematically parametrize hypothetical violations of Lorentz symmetry (in the Standard Model and in the gravitational sector). In this communication, we use the latest determinations of the supplementary advances of the perihelia and of the nodes obtained by planetary ephemerides analysis to constrain SME coefficients from the pure gravity sector and also from gravity-matter couplings. Our results do not show any deviation from GR and they improve current constraints. Moreover, combinations with existing constraints from Lunar Laser Ranging and from atom interferometry gravimetry allow us to disentangle contributions from the pure gravity sector from the gravity-matter couplings.
Lorentz invariance violation and generalized uncertainty principle
NASA Astrophysics Data System (ADS)
Tawfik, Abdel Nasser; Magdy, H.; Ali, A. Farag
2016-01-01
There are several theoretical indications that the quantum gravity approaches may have predictions for a minimal measurable length, and a maximal observable momentum and throughout a generalization for Heisenberg uncertainty principle. The generalized uncertainty principle (GUP) is based on a momentum-dependent modification in the standard dispersion relation which is conjectured to violate the principle of Lorentz invariance. From the resulting Hamiltonian, the velocity and time of flight of relativistic distant particles at Planck energy can be derived. A first comparison is made with recent observations for Hubble parameter in redshift-dependence in early-type galaxies. We find that LIV has two types of contributions to the time of flight delay Δ t comparable with that observations. Although the wrong OPERA measurement on faster-than-light muon neutrino anomaly, Δ t, and the relative change in the speed of muon neutrino Δ v in dependence on redshift z turn to be wrong, we utilize its main features to estimate Δ v. Accordingly, the results could not be interpreted as LIV. A third comparison is made with the ultra high-energy cosmic rays (UHECR). It is found that an essential ingredient of the approach combining string theory, loop quantum gravity, black hole physics and doubly spacial relativity and the one assuming a perturbative departure from exact Lorentz invariance. Fixing the sensitivity factor and its energy dependence are essential inputs for a reliable confronting of our calculations to UHECR. The sensitivity factor is related to the special time of flight delay and the time structure of the signal. Furthermore, the upper and lower bounds to the parameter, a that characterizes the generalized uncertainly principle, have to be fixed in related physical systems such as the gamma rays bursts.
NASA Astrophysics Data System (ADS)
Chamseddine, Riad
2016-04-01
A new vectorial representation for the successive Lorentz transformations (SLT) has recently been proved very convenient to achieve a straightforward treatment of the Thomas rotation effect. Such a representation rests on equivalent forms for the pure Lorentz transformation (PLT) and SLT whose physical meaning escaped us. The present paper fills this gap in by showing that those equivalent forms could represent appropriate world lines, lines and planes of simultaneity. Those geometric elements are particularly convenient to build up two new graphical representations for the SLT: the first rests on that equivalent form for the SLT, while the second takes the SLT as a PLT preceded or followed by a Thomas rotation and uses the equivalent form for the PLT. As an application, the SLT Lorentz contraction (SLTLC) formulas are derived for the first time. The dependence of the SLTLC on the Thomas rotation is put in evidence. The SLTLC along directions transverse and parallel to the composite velocity is studied. Original SLT Minkowski diagrams are given for the first time.
An implicit δf particle-in-cell method with sub-cycling and orbit averaging for Lorentz ions
NASA Astrophysics Data System (ADS)
Sturdevant, Benjamin J.; Parker, Scott E.; Chen, Yang; Hause, Benjamin B.
2016-07-01
A second order implicit δf Lorentz ion hybrid model with sub-cycling and orbit averaging has been developed to study low-frequency, quasi-neutral plasmas. Models using the full Lorentz force equations of motion for ions may be useful for verifying gyrokinetic ion simulation models in applications where higher order terms may be important. In the presence of a strong external magnetic field, previous Lorentz ion models are limited to simulating very short time scales due to the small time step required for resolving the ion gyromotion. Here, we use a simplified model for ion Landau damped ion acoustic waves in a uniform magnetic field as a test bed for developing efficient time stepping methods to be used with the Lorentz ion hybrid model. A detailed linear analysis of the model is derived to validate simulations and to examine the significance of ion Bernstein waves in the Lorentz ion model. Linear analysis of a gyrokinetic ion model is also performed, and excellent agreement with the dispersion results from the Lorentz ion model is demonstrated for the ion acoustic wave. The sub-cycling/orbit averaging algorithm is shown to produce accurate finite-Larmor-radius effects using large macro-time steps sizes, and numerical damping of high frequency fluctuations can be achieved by formulating the field model in terms of the perturbed flux density. Furthermore, a CPU-GPU implementation of the sub-cycling/orbit averaging is presented and is shown to achieve a significant speedup over an equivalent serial code.
Relativistic integro-differential form of the Lorentz-Dirac equation in 3D without runaways
NASA Astrophysics Data System (ADS)
Ibison, Michael; Puthoff, Harold E.
2001-04-01
It is well known that the third-order Lorentz-Dirac equation admits runaway solutions wherein the energy of the particle grows without limit, even when there is no external force. These solutions can be denied simply on physical grounds, and on the basis of careful analysis of the correspondence between classical and quantum theory. Nonetheless, one would prefer an equation that did not admit unphysical behavior at the outset. Such an equation - an integro-differential version of the Lorentz-Dirac equation - is currently available either in 1 dimension only, or in 3 dimensions only in the non-relativistic limit. It is shown herein how the Lorentz-Dirac equation may be integrated without approximation, and is thereby converted to a second-order integro-differential equation in 3D satisfying the above requirement. I.E., as a result, no additional constraints on the solutions are required because runaway solutions are intrinsically absent. The derivation is placed within the historical context established by standard works on classical electrodynamics by Rohrlich, and by Jackson.
Disentangling forms of Lorentz violation with complementary clock comparison experiments
Altschul, Brett
2009-03-15
Atomic clock comparisons provide some of the most precise tests of Lorentz and CPT symmetries in the laboratory. With data from multiple such experiments using different nuclei, it is possible to constrain new regions of the parameter space for Lorentz violation. Relativistic effects in the nuclei allow us to disentangle forms of Lorentz violation which could not be separately measured in purely nonrelativistic experiments. The disentangled bounds in the neutron sectors are at the 10{sup -28} GeV level, far better than could be obtained with any other current technique.
Ultrarelativistic Bose-Einstein gas on Lorentz symmetry violation
NASA Astrophysics Data System (ADS)
de Sales, J. A.; Costa-Soares, T.; Vasquez Otoya, V. J.
2012-11-01
In this paper, we study the effects of Lorentz Symmetry Breaking on the thermodynamic properties of ideal gases. Inspired by the dispersion relation coming from the Carroll-Field-Jackiw model for Electrodynamics with Lorentz and CPT violation term, we compute the thermodynamics quantities for a Boltzmann, Fermi-Dirac and Bose-Einstein distributions. Two regimes are analyzed: the large and the small Lorentz violation. In the first case, we show that the topological mass induced by the Chern-Simons term behaves as a chemical potential. For Bose-Einstein gases, a condensation in both regimes can be found.
Strong binary pulsar constraints on Lorentz violation in gravity.
Yagi, Kent; Blas, Diego; Yunes, Nicolás; Barausse, Enrico
2014-04-25
Binary pulsars are excellent laboratories to test the building blocks of Einstein's theory of general relativity. One of these is Lorentz symmetry, which states that physical phenomena appear the same for all inertially moving observers. We study the effect of violations of Lorentz symmetry in the orbital evolution of binary pulsars and find that it induces a much more rapid decay of the binary's orbital period due to the emission of dipolar radiation. The absence of such behavior in recent observations allows us to place the most stringent constraints on Lorentz violation in gravity, thus verifying one of the cornerstones of Einstein's theory much more accurately than any previous gravitational observation.
Combined Search for Lorentz Violation in Short-Range Gravity.
Shao, Cheng-Gang; Tan, Yu-Jie; Tan, Wen-Hai; Yang, Shan-Qing; Luo, Jun; Tobar, Michael Edmund; Bailey, Quentin G; Long, J C; Weisman, E; Xu, Rui; Kostelecký, V Alan
2016-08-12
Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of 10^{-9} m^{2}, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings.
Neutrino beam constraints on flavor-diagonal Lorentz violation
NASA Astrophysics Data System (ADS)
Altschul, Brett
2013-05-01
Breaking of isotropy and Lorentz boost invariance in the dynamics of second-generation leptons would lead to direction-dependent changes in the lifetimes of charged pions. This would make the intensity of a neutrino beam produced via pion decay a function of the beam orientation. The experimental signature of this phenomenon—sidereal variations in the event rate at a downstream neutrino detector—has already been studied, in searches for Lorentz-violating neutrino oscillations. Existing analyses of MINOS near detector data can be used to constrain the flavor-diagonal Lorentz violation coefficients affecting muon neutrino speeds at roughly the 10-5 level.
Pathology-Free Modification of the Lorentz-Dirac Equation
NASA Astrophysics Data System (ADS)
Blinder, S. M.
2001-04-01
The Lorentz-Dirac equation for the force on an accelerating electron is conventionally written in covariant form F_ext^λ=ma^λ-2 e^2\\over 3 c^3(dot a^λ+1\\over c^2 a^2 v^λ) However, this equation has fallen into disfavor in recent years because it admits pathological solutions representing runaway behavior or preacceleration violating classical causality. For example, force-free motion can exhibit unphysical runaway solutions of the form a(t)= a(0)exp(t/ τ_0), where τ_0≡ 2e^2/3mc^3≈ 6.26× 10-24 sec. Note that the first two terms of the L-D equation could originate from expansion of ma^λ(τ-τ_0) in powers of τ_0. We propose the following differential-difference equation as a compact non-pathologial alternative to the L-D equation: F^λ_ext(τ)=m [a^λ β^μ -a^μ β^λ]_τ-τ0 β_μ(τ) where β^λ=v^λ/c. Expansion of the bracketed quantity reacquires the conventional equation, apart from higher-order terms in τ_0. It can be demonstrated that F=0 unambiguously implies a=0. Moreover the occurrence of the retarded time variable τ-τ0 precludes any solutions with preacceleration. A more detailed derivation is given in a forthcoming paper [S. M. Blinder, ``Classical electrodynamics with vacuum polarization: electron self-energy and radiation reaction," Repts. Math. Phys., in press].
Probes of Lorentz violation in neutrino propagation
NASA Astrophysics Data System (ADS)
Ellis, John; Harries, Nicholas; Meregaglia, Anselmo; Rubbia, André; Sakharov, Alexander S.
2008-08-01
It has been suggested that the interactions of energetic particles with the foamy structure of space-time thought to be generated by quantum-gravitational (QG) effects might violate Lorentz invariance, so that they do not propagate at a universal speed of light. We consider the limits that may be set on a linear or quadratic violation of Lorentz invariance in the propagation of energetic neutrinos, v/c=[1±(E/MνQG1)] or [1±(E/MνQG2)2], using data from supernova explosions and the OPERA long-baseline neutrino experiment. Using the SN1987a neutrino data from the Kamioka II, IMB, and Baksan experiments, we set the limits MνQG1>2.7(2.5)×1010GeV for subluminal (superluminal) propagation and MνQG2>4.6(4.1)×104GeV at the 95% confidence level. A future galactic supernova at a distance of 10 kpc would have sensitivity to MνQG1>2(4)×1011GeV for subluminal (superluminal) propagation and MνQG2>2(4)×105GeV. With the current CERN neutrinos to Gran Sasso extraction spill length of 10.5μs and with standard clock synchronization techniques, the sensitivity of the OPERA experiment would reach MνQG1˜7×105GeV (MνQG2˜8×103GeV) after 5 years of nominal running. If the time structure of the super proton synchrotron radio frequency bunches within the extracted CERN neutrinos to Gran Sasso spills could be exploited, these figures would be significantly improved to MνQG1˜5×107GeV (MνQG2˜4×104GeV). These results can be improved further if a similar time resolution can be achieved with neutrino events occurring in the rock upstream of the OPERA detector: we find potential sensitivities to MνQG1˜4×108GeV and MνQG2˜7×105GeV.
Probes of Lorentz violation in neutrino propagation
Ellis, John; Harries, Nicholas; Meregaglia, Anselmo; Sakharov, Alexander S.
2008-08-01
It has been suggested that the interactions of energetic particles with the foamy structure of space-time thought to be generated by quantum-gravitational (QG) effects might violate Lorentz invariance, so that they do not propagate at a universal speed of light. We consider the limits that may be set on a linear or quadratic violation of Lorentz invariance in the propagation of energetic neutrinos, v/c=[1{+-}(E/M{sub {nu}}{sub QG1})] or [1{+-}(E/M{sub {nu}}{sub QG2}){sup 2}], using data from supernova explosions and the OPERA long-baseline neutrino experiment. Using the SN1987a neutrino data from the Kamioka II, IMB, and Baksan experiments, we set the limits M{sub {nu}}{sub QG1}>2.7(2.5)x10{sup 10} GeV for subluminal (superluminal) propagation and M{sub {nu}}{sub QG2}>4.6(4.1)x10{sup 4} GeV at the 95% confidence level. A future galactic supernova at a distance of 10 kpc would have sensitivity to M{sub {nu}}{sub QG1}>2(4)x10{sup 11} GeV for subluminal (superluminal) propagation and M{sub {nu}}{sub QG2}>2(4)x10{sup 5} GeV. With the current CERN neutrinos to Gran Sasso extraction spill length of 10.5 {mu}s and with standard clock synchronization techniques, the sensitivity of the OPERA experiment would reach M{sub {nu}}{sub QG1}{approx}7x10{sup 5} GeV (M{sub {nu}}{sub QG2}{approx}8x10{sup 3} GeV) after 5 years of nominal running. If the time structure of the super proton synchrotron radio frequency bunches within the extracted CERN neutrinos to Gran Sasso spills could be exploited, these figures would be significantly improved to M{sub {nu}}{sub QG1}{approx}5x10{sup 7} GeV (M{sub {nu}}{sub QG2}{approx}4x10{sup 4} GeV). These results can be improved further if a similar time resolution can be achieved with neutrino events occurring in the rock upstream of the OPERA detector: we find potential sensitivities to M{sub {nu}}{sub QG1}{approx}4x10{sup 8} GeV and M{sub {nu}}{sub QG2}{approx}7x10{sup 5} GeV.
Larmor and the Prehistory of the Lorentz Transformations
ERIC Educational Resources Information Center
Kittel, C.
1974-01-01
A historical analysis is given of the development in 1900 of the Lorentz transformation of coordinates and time, and of electric and magnetic field components. The earlier work of Voight is discussed. (RH)
Comment on ‘Lorentz transformations and the wave equation’
NASA Astrophysics Data System (ADS)
Di Rocco, Héctor O.
2017-01-01
In this comment we make some clarifications with respect to certain asumptions and demands required by Ricardo Heras in his paper entitled ‘Lorentz transformations and the wave equation’ (2016 Eur. J. Phys. 37 025603).
Traveling solitons in Lorentz and CPT breaking systems
Souza Dutra, A. de; Correa, R. A. C.
2011-05-15
In this work we present a class of traveling solitons in Lorentz and CPT breaking systems. In the case of Lorentz violating scenarios, as far as we know, only static solitonic configurations were analyzed up to now in the literature. Here it is shown that it is possible to construct some traveling solitons which cannot be mapped into static configurations by means of Lorentz boosts due to explicit breaking. In fact, the traveling solutions cannot be reached from the static ones by using something similar to a Lorentz boost in those cases. Furthermore, in the model studied, a complete set of exact solutions is obtained. The solutions present a critical behavior controlled by the choice of an arbitrary integration constant.
Limits on neutron Lorentz violation from pulsar timing
Altschul, Brett
2007-01-15
Pulsars are the most accurate naturally occurring clocks, and data about them can be used to set bounds on neutron-sector Lorentz violations. If SO(3) rotation symmetry is completely broken for neutrons, then pulsars' rotation speeds will vary periodically. Pulsar timing data limits the relevant Lorentz-violating coefficients to be smaller than 1.7x10{sup -8} at at least 90% confidence.
Cavity tests of parity-odd Lorentz violations in electrodynamics
NASA Astrophysics Data System (ADS)
Mewes, Matthew; Petroff, Alexander
2007-03-01
Electromagnetic resonant cavities form the basis for a number modern tests of Lorentz invariance. The geometry of most of these experiments implies unsuppressed sensitivities to parity-even Lorentz violations only. Parity-odd violations typically enter through suppressed boost effects, causing a reduction in sensitivity by roughly 4 orders of magnitude. Here we discuss possible techniques for achieving unsuppressed sensitivities to parity-odd violations using asymmetric resonators.
Lorentz-breaking theory with higher derivatives in spinor sector
NASA Astrophysics Data System (ADS)
Nascimento, J. R.; Petrov, A. Yu.; Reyes, C. Marat
2015-08-01
We consider the two-point function of the gauge field in Lorentz-breaking theories with higher-derivative extension of the Dirac Lagrangian. We show that the Carroll-Field-Jackiw term naturally arises in this theory as a quantum correction being perfectly finite and thus displaying no ambiguities. Also, the finiteness of this term at the low energy limit and the absence of large Lorentz violating corrections allows to avoid the fine-tuning problem.
Letter: On the Solutions of the Lorentz-Dirac Equation
NASA Astrophysics Data System (ADS)
Vogt, D.; Letelier, P. S.
2003-12-01
We discuss the unstable character of the solutions of the Lorentz-Dirac equation and stress the need of methods like order reduction to derive a physically acceptable equation of motion. The discussion is illustrated with the paradigmatic example of the non-relativistic harmonic oscillator with radiation reaction. We also illustrate the removal of the noncausal pre-acceleration with the introduction of a small correction in the Lorentz-Dirac equation.
Local effects of the quantum vacuum in Lorentz-violating electrodynamics
NASA Astrophysics Data System (ADS)
Martín-Ruiz, A.; Escobar, C. A.
2017-02-01
The Casimir effect is one of the most remarkable consequences of the nonzero vacuum energy predicted by quantum field theory. In this paper we use a local approach to study the Lorentz violation effects of the minimal standard model extension on the Casimir force between two parallel conducting plates in the vacuum. Using a perturbative method similar to that used for obtaining the Born series for the scattering amplitudes in quantum mechanics, we compute, at leading order in the Lorentz-violating coefficients, the relevant Green's function which satisfies given boundary conditions. The standard point-splitting technique allow us to express the vacuum expectation value of the stress-energy tensor in terms of the Green's function. We discuss its structure in the region between the plates. We compute the renormalized vacuum stress, which is obtained as the difference between the vacuum stress in the presence of the plates and that of the vacuum. The Casimir force is evaluated in an analytical fashion by two methods: by differentiating the renormalized global energy density and by computing the normal-normal component of the renormalized vacuum stress. We compute the local Casimir energy, which is found to diverge as approaching the plates, and we demonstrate that it does not contribute to the observable force.
ICECUBE NEUTRINOS AND LORENTZ INVARIANCE VIOLATION
Amelino-Camelia, Giovanni; Guetta, D.; Piran, Tsvi
2015-06-20
The IceCube neutrino telescope has found so far no evidence of gamma-ray burst (GRB) neutrinos. We here notice that these results assume the same travel times from source to telescope for neutrinos and photons, an assumption that is challenged by some much-studied pictures of spacetime quantization. We briefly review previous results suggesting that limits on quantum-spacetime effects obtained for photons might not be applicable to neutrinos, and we then observe that the outcome of GRB-neutrino searches could depend strongly on whether one allows for neutrinos to be affected by the minute effects of Lorentz invariance violation (LIV) predicted by some relevant quantum-spacetime models. We discuss some relevant issues using as an illustrative example three neutrinos that were detected by IceCube in good spatial coincidence with GRBs, but hours before the corresponding gamma rays. In general, this could happen if the earlier arrival reflects quantum-spacetime-induced LIV, but, as we stress, some consistency criteria must be enforced in order to properly test such a hypothesis. Our analysis sets the stage for future GRB-neutrino searches that could systematically test the possibility of quantum-spacetime-induced LIV.
Lorentz symmetry and very long baseline interferometry
NASA Astrophysics Data System (ADS)
Le Poncin-Lafitte, C.; Hees, A.; Lambert, S.
2016-12-01
Lorentz symmetry violations can be described by an effective field theory framework that contains both general relativity and the Standard Model of particle physics called the Standard Model extension (SME). Recently, postfit analysis of Gravity Probe B and binary pulsars led to an upper limit at the 10-4 level on the time-time coefficient s¯T T of the pure-gravity sector of the minimal SME. In this work, we derive the observable of very long baseline interferometry (VLBI) in SME and then implement it into a real data analysis code of geodetic VLBI observations. Analyzing all available observations recorded since 1979, we compare estimates of s¯T T and errors obtained with various analysis schemes, including global estimations over several time spans, and with various Sun elongation cutoff angles, and by analysis of radio source coordinate time series. We obtain a constraint on s¯ T T=(-5 ±8 )×10-5 , directly fitted to the observations and improving by a factor of 5 previous postfit analysis estimates.
Hendrik Antoon Lorentz: his role in physics and society.
Berends, Frits
2009-04-22
Hendrik Antoon Lorentz (1853-1928) was appointed in 1878 to a chair of theoretical physics at the University of Leiden, one of the first of such chairs in the world. A few years later Heike Kamerlingh Onnes became his experimental colleague, after vehement discussions in the faculty. Lorentz strongly supported Kamerlingh Onnes then, and proved subsequently to be an ideal colleague. With Lorentz's electron theory the classical theory of electromagnetism obtained its final form, at the time often called the Maxwell-Lorentz theory. In this theory the Zeeman effect could be explained: the first glimpse of the electron. The Nobel Prize followed in 1902. The Lorentz transformation, established in 1904, preceded the special theory of relativity. Later on, Lorentz played a much admired role in the debate on the new developments in physics, in particular as chairman of a series of Solvay conferences. Gradually his stature outside of physics grew, both nationally as chairman of the Zuiderzee committee and internationally as president of the International Commission on Intellectual Cooperation of the League of Nations. At his funeral the overwhelming tribute was the recognition of his unique greatness. Einstein said about him 'He meant more to me personally than anyone else I have met on my life's journey'.
A new look at Lorentz-covariant loop quantum gravity
NASA Astrophysics Data System (ADS)
Geiller, Marc; Lachièze-Rey, Marc; Noui, Karim
2011-08-01
In this work, we study the classical and quantum properties of the unique commutative Lorentz-covariant connection for loop quantum gravity. This connection has been found after solving the second-class constraints inherited from the canonical analysis of the Holst action without the time gauge. We show that it has the property of lying in the conjugacy class of a pure su(2) connection, a result which enables one to construct the kinematical Hilbert space of the Lorentz-covariant theory in terms of the usual SU(2) spin-network states. Furthermore, we show that there is a unique Lorentz-covariant electric field, up to trivial and natural equivalence relations. The Lorentz-covariant electric field transforms under the adjoint action of the Lorentz group, and the associated Casimir operators are shown to be proportional to the area density. This gives a very interesting algebraic interpretation of the area. Finally, we show that the action of the surface operator on the Lorentz-covariant holonomies reproduces exactly the usual discrete SU(2) spectrum of time-gauge loop quantum gravity. In other words, the use of the time gauge does not introduce anomalies in the quantum theory.
Lorentz, the Solvay Councils and the Physics Institute
NASA Astrophysics Data System (ADS)
Berends, Frits A.
2015-09-01
This paper describes the crucial role which Lorentz played in shaping and continuing the Solvay Councils and the Physics Institute. At the same time it will become clear that Lorentz* intensive involvement in these activities added significantly to his influence on, and recognition in, the international physics community. The first Solvay Council in 1911 was an initiative of the German physical chemist Walther Nernst. It was generously supported by the wealthy industrialist and philantropist Ernest Solvay. About five months before the Council*s start Nernst invited Lorentz to chair the meeting. That was no simple task in view of the fundamental problem of the quanta and the practical problem of communication in different languages. Lorentz*s way of presiding the conference impressed all participants. When, after the meeting, Solvay was willing to support research in the field, it was only natural to ask Lorentz for a plan. Within two months Lorentz provided Solvay with a draft which would serve as an outline for the statutes of an institute. The international Solvay Institute of Physics was founded on 1 May 1912. It would support research proposals in a specified field and would regularly organize Councils. An international scientific committee would decide on grants which could be requested from everywhere. Between the Institute*s beginnings and the outbreak of WWI, 97 requests were considered and 40 proposals - originating from 7 countries - were accepted. A second Council took place in 1913. Lorentz was given the possibility to spend considerable time on chairing the scientific committee when in 1912 his full time professorship in Leiden was changed into a part-time one. During WWI Lorentz maintained contacts with Solvay and with several of his foreign colleagues in the countries at war. He tried to remain objective, impartial and helpful, and did not lose hope that pre-war international scientific relations would eventually be re-established. After the war he
Michelson-Morley analogue for electrons using trapped ions to test Lorentz symmetry
NASA Astrophysics Data System (ADS)
Pruttivarasin, T.; Ramm, M.; Porsev, S. G.; Tupitsyn, I. I.; Safronova, M. S.; Hohensee, M. A.; Häffner, H.
2015-01-01
All evidence so far suggests that the absolute spatial orientation of an experiment never affects its outcome. This is reflected in the standard model of particle physics by requiring all particles and fields to be invariant under Lorentz transformations. The best-known tests of this important cornerstone of physics are Michelson-Morley-type experiments verifying the isotropy of the speed of light. For matter, Hughes-Drever-type experiments test whether the kinetic energy of particles is independent of the direction of their velocity, that is, whether their dispersion relations are isotropic. To provide more guidance for physics beyond the standard model, refined experimental verifications of Lorentz symmetry are desirable. Here we search for violation of Lorentz symmetry for electrons by performing an electronic analogue of a Michelson-Morley experiment. We split an electron wave packet bound inside a calcium ion into two parts with different orientations and recombine them after a time evolution of 95 milliseconds. As the Earth rotates, the absolute spatial orientation of the two parts of the wave packet changes, and anisotropies in the electron dispersion will modify the phase of the interference signal. To remove noise, we prepare a pair of calcium ions in a superposition of two decoherence-free states, thereby rejecting magnetic field fluctuations common to both ions. After a 23-hour measurement, we find a limit of h × 11 millihertz (h is Planck's constant) on the energy variations, verifying the isotropy of the electron's dispersion relation at the level of one part in 1018, a 100-fold improvement on previous work. Alternatively, we can interpret our result as testing the rotational invariance of the Coulomb potential. Assuming that Lorentz symmetry holds for electrons and that the photon dispersion relation governs the Coulomb force, we obtain a fivefold-improved limit on anisotropies in the speed of light. Our result probes Lorentz symmetry violation at
Michelson-Morley analogue for electrons using trapped ions to test Lorentz symmetry.
Pruttivarasin, T; Ramm, M; Porsev, S G; Tupitsyn, I I; Safronova, M S; Hohensee, M A; Häffner, H
2015-01-29
All evidence so far suggests that the absolute spatial orientation of an experiment never affects its outcome. This is reflected in the standard model of particle physics by requiring all particles and fields to be invariant under Lorentz transformations. The best-known tests of this important cornerstone of physics are Michelson-Morley-type experiments verifying the isotropy of the speed of light. For matter, Hughes-Drever-type experiments test whether the kinetic energy of particles is independent of the direction of their velocity, that is, whether their dispersion relations are isotropic. To provide more guidance for physics beyond the standard model, refined experimental verifications of Lorentz symmetry are desirable. Here we search for violation of Lorentz symmetry for electrons by performing an electronic analogue of a Michelson-Morley experiment. We split an electron wave packet bound inside a calcium ion into two parts with different orientations and recombine them after a time evolution of 95 milliseconds. As the Earth rotates, the absolute spatial orientation of the two parts of the wave packet changes, and anisotropies in the electron dispersion will modify the phase of the interference signal. To remove noise, we prepare a pair of calcium ions in a superposition of two decoherence-free states, thereby rejecting magnetic field fluctuations common to both ions. After a 23-hour measurement, we find a limit of h × 11 millihertz (h is Planck's constant) on the energy variations, verifying the isotropy of the electron's dispersion relation at the level of one part in 10(18), a 100-fold improvement on previous work. Alternatively, we can interpret our result as testing the rotational invariance of the Coulomb potential. Assuming that Lorentz symmetry holds for electrons and that the photon dispersion relation governs the Coulomb force, we obtain a fivefold-improved limit on anisotropies in the speed of light. Our result probes Lorentz symmetry violation
A Real Lorentz-FitzGerald Contraction
NASA Astrophysics Data System (ADS)
Barceló, Carlos; Jannes, Gil
2008-02-01
Many condensed matter systems are such that their collective excitations at low energies can be described by fields satisfying equations of motion formally indistinguishable from those of relativistic field theory. The finite speed of propagation of the disturbances in the effective fields (in the simplest models, the speed of sound) plays here the role of the speed of light in fundamental physics. However, these apparently relativistic fields are immersed in an external Newtonian world (the condensed matter system itself and the laboratory can be considered Newtonian, since all the velocities involved are much smaller than the velocity of light) which provides a privileged coordinate system and therefore seems to destroy the possibility of having a perfectly defined relativistic emergent world. In this essay we ask ourselves the following question: In a homogeneous condensed matter medium, is there a way for internal observers, dealing exclusively with the low-energy collective phenomena, to detect their state of uniform motion with respect to the medium? By proposing a thought experiment based on the construction of a Michelson-Morley interferometer made of quasi-particles, we show that a real Lorentz-FitzGerald contraction takes place, so that internal observers are unable to find out anything about their ‘absolute’ state of motion. Therefore, we also show that an effective but perfectly defined relativistic world can emerge in a fishbowl world situated inside a Newtonian (laboratory) system. This leads us to reflect on the various levels of description in physics, in particular regarding the quest towards a theory of quantum gravity.
Reactive power compensating system
Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.
1987-01-01
The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.
Faculty Compensation Policies.
ERIC Educational Resources Information Center
Silander, Fred
1983-01-01
Faculty compensation policy is seen as one means by which an institution influences the faculty to work toward institutional goals. Among the broad criteria for compensation are worth, equity, need, and market measures. Benefits and issues in compensation including differentials in compensation, merit, part-time instruction, etc. are discussed.…
Energy Loss by Radiation in Many-Particle Numerical Simulation With Lorentz-Dirac Equation
NASA Astrophysics Data System (ADS)
Žáček, Martin
2006-01-01
We studied the possibilities for numerical integration of Lorentz-Dirac equation that is the equation describing the motion of a charged point particle when radiation reaction is taken into account. In numerical modelling based on particle models usually the equations of motion without radiation force are used and the corrections for radiation are used consequently, expressed by laws given by averaged particle parameters as the temperature or particle density. If the complete equation of motion concluding the radiation would be used, the corrections for radiation reaction force could be used for every charged particle individually from more fundamental laws. Thus the model could be able to describe more physical phenomena. However from theory of Lorentz-Dirac equation there are known various problems with non-physical solutions and nonuniqueness that are often solved and tested by various methods. One way to eliminate the non-physical solutions is to use integro-differential equation, which is used here. The leap-frog method is used for numerical integrating and accuracy is verified for electron in magnetic field. This approach is proposed to be used for PIC (particle-in-cell) integration method, which is often used as an effective method of simulation in plasma physics for many charged particles interactinge with electromagnetic field.
Energy Loss by Radiation in Many-Particle Numerical Simulation With Lorentz-Dirac Equation
Zacek, Martin
2006-01-15
We studied the possibilities for numerical integration of Lorentz-Dirac equation that is the equation describing the motion of a charged point particle when radiation reaction is taken into account. In numerical modelling based on particle models usually the equations of motion without radiation force are used and the corrections for radiation are used consequently, expressed by laws given by averaged particle parameters as the temperature or particle density. If the complete equation of motion concluding the radiation would be used, the corrections for radiation reaction force could be used for every charged particle individually from more fundamental laws. Thus the model could be able to describe more physical phenomena. However from theory of Lorentz-Dirac equation there are known various problems with non-physical solutions and nonuniqueness that are often solved and tested by various methods. One way to eliminate the non-physical solutions is to use integro-differential equation, which is used here. The leap-frog method is used for numerical integrating and accuracy is verified for electron in magnetic field. This approach is proposed to be used for PIC (particle-in-cell) integration method, which is often used as an effective method of simulation in plasma physics for many charged particles interactinge with electromagnetic field.
EMITTANCE COMPENSATION FOR MAGNETIZED BEAMS
KEWISCH,J.; CHANG, X.
2007-06-25
Emittance compensation is a well established technique for minimizing the emittance of an electron beam from a RF photo-cathode gun. Longitudinal slices of a bunch have a small emittance, but due to the longitudinal charge distribution of the bunch and time dependent RF fields they are not focused in the same way, so that the direction of their phase ellipses diverges in phase space and the projected emittance is much larger. Emittance compensation reverses the divergence. At the location where the slopes of the phase ellipses coincide the beam is accelerated, so that the space charge forces are reduced. A recipe for emittance compensation is given in. For magnetized beams (where the angular momentum is non-zero) such emittance compensation is not sufficient because variations in the slice radius lead to variations in the angular speed and therefore to an increase of emittance in the rotating game. We describe a method and tools for a compensation that includes the beam magnetization.
Black hole dynamical evolution in a Lorentz-violating spacetime
Esposito, S.; Salesi, G.
2011-04-15
We consider the black hole dynamical evolution in the framework of a Lorentz-violating spacetime endowed with a Schwarzchild-like momentum-dependent metric. Large deviations from the Hawking-Bekenstein predictions are obtained, depending on the values of the Lorentz-violating parameter {lambda} introduced. A nontrivial evolution comes out, following mainly from the existence of a nonvanishing minimum mass: for large Lorentz violations, most of the black hole evaporation takes place in the initial stage, which is then followed by a stationary stage (whose duration depends on the value of {lambda}) where the mass does not change appreciably. Furthermore, for the final stage of evolution, our model predicts a sweet slow death of the black hole, whose ''slowness'' again depends on {lambda}, in contrast with the violent final explosion predicted by the standard theory.
Dynamical ambiguities in models with spontaneous Lorentz violation
NASA Astrophysics Data System (ADS)
Bonder, Yuri; Escobar, Carlos A.
2016-01-01
Spontaneous Lorentz violation is a viable mechanism to look for Planck scale physics. In this work, we study spontaneous Lorentz violation models, in flat spacetime, where a vector field produces such a violation and matter is modeled by a complex scalar field. We show that it is possible to construct a Hamilton density for which the evolution respects the dynamical constraints. However, we also find that the initial data, as required by standard field theory, does not determine the fields evolution in a unique way. In addition, we present some examples where the physical effects of such ambiguities can be recognized. As a consequence, the proposals in which the electromagnetic and gravitational interactions emerge from spontaneous Lorentz violation are challenged.
Restrictions from Lorentz invariance violation on cosmic ray propagation
NASA Astrophysics Data System (ADS)
Martínez-Huerta, H.; Pérez-Lorenzana, A.
2017-03-01
Lorentz invariance violation introduced as a generic modification to particle dispersion relations is used to study high energy cosmic ray attenuation processes. It is shown to reproduce the same physical effects for vacuum Cherenkov radiation, as in some particular models with spontaneous breaking of Lorentz symmetry. This approximation is also implemented for the study of photon decay in vacuum, where stringent limits to the violation scale are derived from the direct observation of very high energy cosmic ray photon events on gamma telescopes. Photo production processes by cosmic ray primaries on photon background are also addressed, to show that Lorentz violation may turn off this attenuation process at energies above a well-defined secondary threshold.
A Lorentz-Covariant Connection for Canonical Gravity
NASA Astrophysics Data System (ADS)
Geiller, Marc; Lachièze-Rey, Marc; Noui, Karim; Sardelli, Francesco
2011-08-01
We construct a Lorentz-covariant connection in the context of first order canonical gravity with non-vanishing Barbero-Immirzi parameter. To do so, we start with the phase space formulation derived from the canonical analysis of the Holst action in which the second class constraints have been solved explicitly. This allows us to avoid the use of Dirac brackets. In this context, we show that there is a ''unique'' Lorentz-covariant connection which is commutative in the sense of the Poisson bracket, and which furthermore agrees with the connection found by Alexandrov using the Dirac bracket. This result opens a new way toward the understanding of Lorentz-covariant loop quantum gravity.
Classical kinematics for isotropic, minimal Lorentz-violating fermion operators
NASA Astrophysics Data System (ADS)
Schreck, M.
2015-05-01
In this article a particular classical, relativistic Lagrangian based on the isotropic fermion sector of the Lorentz-violating (minimal) Standard Model extension is considered. The motion of the associated classical particle in an external electromagnetic field is studied, and the evolution of its spin, which is introduced by hand, is investigated. It is shown that the particle travels along trajectories that are scaled versions of the standard ones. Furthermore there is no spin precession due to Lorentz violation, but the rate is modified at which the longitudinal and transverse spin components transform into each other. This demonstrates that it is practical to consider classical physics within such an isotropic Lorentz-violating framework and it opens the pathway to study a curved background in that context.
Convexity and concavity constants in Lorentz and Marcinkiewicz spaces
NASA Astrophysics Data System (ADS)
Kaminska, Anna; Parrish, Anca M.
2008-07-01
We provide here the formulas for the q-convexity and q-concavity constants for function and sequence Lorentz spaces associated to either decreasing or increasing weights. It yields also the formula for the q-convexity constants in function and sequence Marcinkiewicz spaces. In this paper we extent and enhance the results from [G.J.O. Jameson, The q-concavity constants of Lorentz sequence spaces and related inequalities, Math. Z. 227 (1998) 129-142] and [A. Kaminska, A.M. Parrish, The q-concavity and q-convexity constants in Lorentz spaces, in: Banach Spaces and Their Applications in Analysis, Conference in Honor of Nigel Kalton, May 2006, Walter de Gruyter, Berlin, 2007, pp. 357-373].
Special Relativity in Week One: 3) Introducing the Lorentz Contraction
NASA Astrophysics Data System (ADS)
Huggins, Elisha
2011-05-01
This is the third of four articles on teaching special relativity in the first week of an introductory physics course.1,2 With Einstein's second postulate that the speed of light is the same to all observers, we could use the light pulse clock to introduce time dilation. But we had difficulty introducing the Lorentz contraction until we saw the movie "Time Dilation, an Experiment with Mu-Mesons" by David Frisch and James Smith.3,4 The movie demonstrates that time dilation and the Lorentz contraction are essentially two sides of the same coin. Here we take the muon's point of view for a more intuitive understanding of the Lorentz contraction, and use the results of the movie to provide an insight into the way we interpret experimental results involving special relativity.
Spontaneous breaking of Lorentz symmetry with an antisymmetric tensor
NASA Astrophysics Data System (ADS)
Hernaski, C. A.
2016-11-01
This paper considers the spontaneous violation of Lorentz symmetry by the vacuum condensation of an antisymmetric two-tensor. The coset construction for nonlinear realization of spacetime symmetries is employed to build the most general low-energy effective action for the Goldstone modes interacting with photons. We analyze the model within the context of the Standard-Model extension and noncommutative QED. Experimental bounds for some parameters of the model are discussed, and we readdress the subtle issues of stability and causality in Lorentz-noninvariant scenarios. To set a sensible low-energy effective model, in addition to the two photon polarizations only one Goldstone mode must be dynamical, and the enhancement of the stability by accounting for interaction terms points to a protection against observational Lorentz violation.
Electrodynamics with Lorentz-violating operators of arbitrary dimension
Kostelecky, V. Alan; Mewes, Matthew
2009-07-01
The behavior of photons in the presence of Lorentz and CPT violation is studied. Allowing for operators of arbitrary mass dimension, we classify all gauge-invariant Lorentz- and CPT-violating terms in the quadratic Lagrange density associated with the effective photon propagator. The covariant dispersion relation is obtained, and conditions for birefringence are discussed. We provide a complete characterization of the coefficients for Lorentz violation for all mass dimensions via a decomposition using spin-weighted spherical harmonics. The resulting nine independent sets of spherical coefficients control birefringence, dispersion, and anisotropy in the photon propagator. We discuss the restriction of the general theory to various special models, including among others the minimal standard-model extension, the isotropic limit, the case of vacuum propagation, the nonbirefringent limit, and the vacuum-orthogonal model. The transformation of the spherical coefficients for Lorentz violation between the laboratory frame and the standard Sun-centered frame is provided. We apply the results to various astrophysical observations and laboratory experiments. Astrophysical searches of relevance include studies of birefringence and of dispersion. We use polarimetric and dispersive data from gamma-ray bursts to set constraints on coefficients for Lorentz violation involving operators of dimensions four through nine, and we describe the mixing of polarizations induced by Lorentz and CPT violation in the cosmic-microwave background. Laboratory searches of interest include cavity experiments. We present the general theory for searches with cavities, derive the experiment-dependent factors for coefficients in the vacuum-orthogonal model, and predict the corresponding frequency shift for a circular-cylindrical cavity.
How is Lorentz invariance encoded in the Hamiltonian?
NASA Astrophysics Data System (ADS)
Kajuri, Nirmalya
2016-07-01
One of the disadvantages of the Hamiltonian formulation is that Lorentz invariance is not manifest in the former. Given a Hamiltonian, there is no simple way to check whether it is relativistic or not. One would either have to solve for the equations of motion or calculate the Poisson brackets of the Noether charges to perform such a check. In this paper we show that, for a class of Hamiltonians, it is possible to check Lorentz invariance directly from the Hamiltonian. Our work is particularly useful for theories where the other methods may not be readily available.
On the anomalies in Lorentz-breaking theories
NASA Astrophysics Data System (ADS)
Baêta Scarpelli, A. P.; Mariz, T.; Nascimento, J. R.; Yu. Petrov, A.
2016-04-01
In this paper, we discuss the chiral anomaly in a Lorentz-breaking extension of QED which, besides the common terms that are present in the Standard Model Extension, includes some dimension-five nonminimal couplings. We find, using the Fujikawa formalism, that these nonminimal couplings induce new terms in the anomaly which depend on the Lorentz-violating parameters. Perturbative calculations are also carried out in order to investigate whether new ambiguous Carroll-Field-Jackiw terms are induced in the effective action.
Global defects in theories with Lorentz symmetry violation
NASA Astrophysics Data System (ADS)
Lubo, Musongela
2005-02-01
We study global topological defects in the Jacobson-Corley model which breaks Lorentz symmetry and involves up to fourth order derivatives. There is a window in the parameter space in which no solution exists. Otherwise, different profiles are allowed for the same values of the parameters. For a scale of Lorentz violation much higher than the scale of gauge symmetry breaking, the energy densities are higher, of the same order or smaller than in the usual case for domain walls, cosmic strings, and hedgehogs, respectively. Possible cosmological implications are suggested.
Global defects in theories with Lorentz symmetry violation
Lubo, Musongela
2005-02-15
We study global topological defects in the Jacobson-Corley model which breaks Lorentz symmetry and involves up to fourth order derivatives. There is a window in the parameter space in which no solution exists. Otherwise, different profiles are allowed for the same values of the parameters. For a scale of Lorentz violation much higher than the scale of gauge symmetry breaking, the energy densities are higher, of the same order or smaller than in the usual case for domain walls, cosmic strings, and hedgehogs, respectively. Possible cosmological implications are suggested.
The 1895 Lorentz transformations: historical issues and present teaching
NASA Astrophysics Data System (ADS)
Provost, Jean-Pierre; Bracco, Christian
2016-07-01
We present the pedagogical interest for the teaching of special relativity of the 1895 Lorentz transformations, which are a simple modification of the Galilean ones, satisfying the invariance of light velocity at first order in V/c. Since they are also the infinitesimal version of the better known but more complicated 1904 Lorentz ones, they allow us to address the main topics of this teaching (time dilatation, length contraction, relativistic dynamics, invariance of electromagnetism) and to recover standard results through simple integrations or the use of invariants. In addition, they are directly related to important historical issues, including Einstein’s 1911 relativistic approach to gravitation.
Bernardini, A. E.; Rocha, R. da
2007-03-15
We work on some general extensions of the formalism for theories which preserve the relativity of inertial frames with a nonlinear action of the Lorentz transformations on momentum space. Relativistic particle models invariant under the corresponding deformed symmetries are presented with particular emphasis on deformed dilatation transformations. The algebraic transformations relating the deformed symmetries with the usual (undeformed) ones are provided in order to preserve the Lorentz algebra. Two distinct cases are considered: a deformed dilatation transformation with a spacelike preferred direction and a very special relativity embedding with a lightlike preferred direction. In both analysis we consider the possibility of introducing quantum deformations of the corresponding symmetries such that the spacetime coordinates can be reconstructed and the particular form of the real space-momentum commutator remains covariant. Eventually feasible experiments, for which the nonlinear Lorentz dilatation effects here pointed out may be detectable, are suggested.
2003-06-03
COMPERA is a decision support system designed to facilitate the compensation review process. With parameters provided by the user(s), the system generates recommendations for base increases and nonbase compensation that strives to align total compensation with performance compensation targets. The user(s) prescribe(s) compensation targets according to performance (or value of contribution) designators. These targets are presented in look-up tables, which are then used by embedded formulas in the worksheet to determine the recommended compensation for each individual.
NASA Astrophysics Data System (ADS)
Heras, Ricardo
2017-01-01
In this paper I briefly discuss and compare four easy derivations of the Lorentz transformations. Two of these derivations assume the invariance of the Minkowski spacetime interval in inertial frames and the other two assume the invariance of the d’Alembert operator in these frames. These derivations are suitable for a first view of special relativity. Finally, I discuss the comment made by Di Rocco on my original paper, ‘Lorentz transformations and the wave equation’ (2016 Eur. J. Phys. 37 025603).
NASA Astrophysics Data System (ADS)
Compère, Geoffrey; Gralla, Samuel E.; Lupsasca, Alexandru
2016-12-01
Electromagnetic field configurations with vanishing Lorentz force density are known as force-free and appear in terrestrial, space, and astrophysical plasmas. We explore a general method for finding such configurations based on formulating equations for the field lines rather than the field itself. The basic object becomes a foliation of spacetime or, in the stationary axisymmetric case, of the half-plane. We use this approach to find some new stationary and axisymmetric solutions, one of which could represent a rotating plasma vortex near a magnetic null point.
Spontaneous Lorentz violation: the case of infrared QED
NASA Astrophysics Data System (ADS)
Balachandran, A. P.; Kürkçüoǧlu, S.; de Queiroz, A. R.; Vaidya, S.
2015-02-01
It is by now clear that the infrared sector of quantum electrodynamics (QED) has an intriguingly complex structure. Based on earlier pioneering work on this subject, two of us recently proposed a simple modification of QED by constructing a generalization of the charge group of QED to the "Sky" group incorporating the well-known spontaneous Lorentz violation due to infrared photons, but still compatible in particular with locality (Balachandran and Vaidya, Eur Phys J Plus 128:118, 2013). It was shown that the "Sky" group is generated by the algebra of angle-dependent charges and a study of its superselection sectors has revealed a manifest description of spontaneous breaking of the Lorentz symmetry. We further elaborate this approach here and investigate in some detail the properties of charged particles dressed by the infrared photons. We find that Lorentz violation due to soft photons may be manifestly codified in an angle-dependent fermion mass, modifying therefore the fermion dispersion relations. The fact that the masses of the charged particles are not Lorentz invariant affects their spin content, and time dilation formulas for decays should also get corrections.
Lorentz transformations in the presence of a uniform gravitational field.
NASA Technical Reports Server (NTRS)
Broucke, R.
1971-01-01
This article describes a Lorentz-like transformation between a fixed frame and an inertial frame that is free falling due to the presence of a uniform gravitation field. The application to the clock paradox problem and some connections with similar works are also discussed.
Lorentz Transformation Derived from First-Order Experiments
ERIC Educational Resources Information Center
Pfleiderer, J.
1969-01-01
Suggests a first-order experiment that can be used to establish the Lorentz transformation without considering the constancy of light velocity or the full set of Maxwell's equations. Involves the use of a long solenoid to create an electric field in a moving magnetic field. (LC)
A Useful Device for Illustrating the Lorentz Transformations
ERIC Educational Resources Information Center
Cortini, Giulio
1972-01-01
A graphical representation is proposed as a teaching device which can be useful in order to obtain a good intuitive grasp of the physical meaning of the Lorentz transformations. The connection between the time dilation and the desynchronization of clocks is particularly discussed. (Author/PR)
The Lorentz extension as consequence of the family symmetry
Wang Haijun
2008-05-15
In this paper, we postulate an algebraic model to explain how the symmetry of three lepton species plays its role in the Lorentz extension. Inspired by the two-to-one mapping between the SL(2,C) group and the Lorentz group, we design a mapping between the SL(3,C) group, which displays the family symmetry, and a generalized Lorentz group. Following the conventional method, we apply the mapping results to the Dirac equation to discuss its transformation invariance, and it turns out that only when the vertex matrix {gamma}{sub {mu}} is extended to the combination c{sub 1}{gamma}{sub {mu}}+c{sub 2}{gamma}{sub 5}{gamma}{sub {mu}} can the Dirac-equation form be reserved. At the same time, we find that the Lorentz group has to be extended with an additional generator {gamma}{sub 5}. The generalized vertex matrix is helpful in understanding the axial-like form of weak interaction and the neutrino oscillations.
On the conformal geometry of transverse Riemann Lorentz manifolds
NASA Astrophysics Data System (ADS)
Aguirre, E.; Fernández, V.; Lafuente, J.
2007-06-01
Physical reasons suggested in [J.B. Hartle, S.W. Hawking, Wave function of the universe, Phys. Rev. D41 (1990) 1815-1834] for the Quantum Gravity Problem lead us to study type-changing metrics on a manifold. The most interesting cases are Transverse Riemann-Lorentz Manifolds. Here we study the conformal geometry of such manifolds.
Lorentz- and CPT-symmetry studies in subatomic physics
NASA Astrophysics Data System (ADS)
Lehnert, Ralf
2016-12-01
Subatomic systems provide an exquisite test bench for spacetime symmetries. This work motivates such measurements, reviews the effective field theory test framework for the description of Lorentz and CPT violation, and employs this framework to study the phenomenology of spacetime-symmetry breaking in various subatomic systems.
Noncommutative spaces, the quantum of time, and Lorentz symmetry
Romero, Juan M.; Vergara, J. D.; Santiago, J. A.
2007-03-15
We introduce three space-times that are discrete in time and compatible with the Lorentz symmetry. We show that these spaces are not commutative, with commutation relations similar to the relations of the Snyder and Yang spaces. Furthermore, using a reparametrized relativistic particle we obtain a realization of the Snyder type spaces and we construct an action for them.
Tests of Lorentz and CPT Invariance in Space
NASA Technical Reports Server (NTRS)
Mewes, Matthew
2003-01-01
I give a brief overview of recent work concerning possible signals of Lorentz violation in sensitive clock-based experiments in space. The systems under consideration include atomic clocks and electromagnetic resonators of the type planned for flight on the International Space Station.
Lorentz estimates for degenerate and singular evolutionary systems
NASA Astrophysics Data System (ADS)
Baroni, Paolo
We prove estimates of Calderón-Zygmund type for evolutionary p-Laplacian systems in the setting of Lorentz spaces. We suppose the coefficients of the system to satisfy only a VMO condition with respect to the space variable. Our results hold true, mutatis mutandis, also for stationary p-Laplacian systems.
A More Intuitive Version of the Lorentz Velocity Addition Formula
ERIC Educational Resources Information Center
Devlin, John F.
2009-01-01
The Lorentz velocity addition formula for one-dimensional motion presents a number of problems for beginning students of special relativity. In this paper we suggest a simple rewrite of the formula that is easier for students to memorize and manipulate, and furthermore is more intuitive in understanding the correction necessary when adding…
Special Relativity in Week One: 3) Introducing the Lorentz Contraction
ERIC Educational Resources Information Center
Huggins, Elisha
2011-01-01
This is the third of four articles on teaching special relativity in the first week of an introductory physics course. With Einstein's second postulate that the speed of light is the same to all observers, we could use the light pulse clock to introduce time dilation. But we had difficulty introducing the Lorentz contraction until we saw the movie…
Round Table Discussion at the Lorentz Workshop "beyond the Quantum"
NASA Astrophysics Data System (ADS)
Cetto, A. M.; Balian, R.; 't Hooft, G.; Khrennikov, A. Yu.; Nieuwenhuizen, Th. M.
2007-09-01
This is a transcript of the round table discussion, moderated by G. 't Hooft, that took place at the end of the workshop "Beyond The Quantum" in the Lorentz Center of the University of Leiden, the Netherlands, 29 May - 2 June 2006. It displays current views on foundations of quantum mechanics.
Lorentz-violating effects in three-dimensional QED
NASA Astrophysics Data System (ADS)
Bufalo, R.
2014-08-01
Inspired in discussions presented lately regarding Lorentz-violating interaction terms in B. Charneski, M. Gomes, R. V. Maluf and A. J. da Silva, Phys. Rev. D86, 045003 (2012); R. Casana, M. M. Ferreira Jr., R. V. Maluf and F. E. P. dos Santos, Phys. Lett. B726, 815 (2013); R. Casana, M. M. Ferreira Jr., E. Passos, F. E. P. dos Santos and E. O. Silva, Phys. Rev. D87, 047701 (2013), we propose here a slightly different version for the coupling term. We will consider a modified quantum electrodynamics with violation of Lorentz symmetry defined in a (2+1)-dimensional space-time. We define the Lagrangian density with a Lorentz-violating interaction, where the space-time dimensionality is explicitly taken into account in its definition. The work encompasses an analysis of this model at both zero and finite-temperature, where very interesting features are known to occur due to the space-time dimensionality. With that in mind, we expect that the space-time dimensionality may provide new insights about the radiative generation of higher-derivative terms into the action, implying in a new Lorentz-violating electrodynamics, as well the nonminimal coupling may provide interesting implications on the thermodynamical quantities.
Relativity and electromagnetism: The force on a magnetic monopole
NASA Astrophysics Data System (ADS)
Rindler, Wolfgang
1989-11-01
On the occasion of the 100th anniversary of the first publication, by Oliver Heaviside, of what is now known as the Lorentz force law in electromagnetic theory, the analogous force law for magnetic monopoles is examined. Its relevance and limitations in calculating the force and torque on small current loops are discussed, and both its heuristic and practical uses are demonstrated.
Transverse forces on a vortex in lattice models of superfluids
NASA Astrophysics Data System (ADS)
Sonin, E. B.
2013-12-01
The paper derives the transverse forces (the Magnus and the Lorentz forces) in the lattice models of superfluids in the continuous approximation. The continuous approximation restores translational invariance absent in the original lattice model, but the theory is not Galilean invariant. As a result, calculation of the two transverse forces on the vortex, Magnus force and Lorentz force, requires the analysis of two balances, for the true momentum of particles in the lattice (Magnus force) and for the quasimomentum (Lorentz force) known from the Bloch theory of particles in the periodic potential. While the developed theory yields the same Lorentz force, which was well known before, a new general expression for the Magnus force was obtained. The theory demonstrates how a small Magnus force emerges in the Josephson-junction array if the particle-hole symmetry is broken. The continuous approximation for the Bose-Hubbard model close to the superfluid-insulator transition was developed, which was used for calculation of the Magnus force. The theory shows that there is an area in the phase diagram for the Bose-Hubbard model, where the Magnus force has an inverse sign with respect to that which is expected from the sign of velocity circulation.
2011-08-01
Leader iii Executive Summary The Eleventh Quadrennial Review of Military Compensation (11th QRMC) was chartered to review four areas of the military...compensation is an important element in the remuneration of military personnel. The principal justification for combat compensation is to recognize...combat zone received at least $4,660 in federal tax savings and benefits. One unexpected aspect of CZTE-related compensation is that senior officers
Further evaluation of the constrained least squares electromagnetic compensation method
NASA Technical Reports Server (NTRS)
Smith, William T.
1991-01-01
Technologies exist for construction of antennas with adaptive surfaces that can compensate for many of the larger distortions caused by thermal and gravitational forces. However, as the frequency and size of reflectors increase, the subtle surface errors become significant and degrade the overall electromagnetic performance. Electromagnetic (EM) compensation through an adaptive feed array offers means for mitigation of surface distortion effects. Implementation of EM compensation is investigated with the measured surface errors of the NASA 15 meter hoop/column reflector antenna. Computer simulations are presented for: (1) a hybrid EM compensation technique, and (2) evaluating the performance of a given EM compensation method when implemented with discretized weights.
Approaching a realistic force balance in geodynamo simulations
NASA Astrophysics Data System (ADS)
Yadav, Rakesh K.; Gastine, Thomas; Christensen, Ulrich R.; Wolk, Scott J.; Poppenhaeger, Katja
2016-10-01
Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints. In typical geodynamo models, viscous and inertial forces are not much smaller than the Coriolis force, and the Lorentz force plays a subdominant role; this has led to conclusions that these simulations are viscously controlled and do not represent the physics of the geodynamo. Here we show, by a direct analysis of the relevant forces, that a MAC balance can be achieved when the viscosity is reduced to values close to the current practical limit. Lorentz force, buoyancy, and the uncompensated (by pressure) part of the Coriolis force are of very similar strength, whereas viscous and inertial forces are smaller by a factor of at least 20 in the bulk of the fluid volume. Compared with nonmagnetic convection at otherwise identical parameters, the dynamo flow is of larger scale and is less invariant parallel to the rotation axis (less geostrophic), and convection transports twice as much heat, all of which is expected when the Lorentz force strongly influences the convection properties.
Approaching a realistic force balance in geodynamo simulations.
Yadav, Rakesh K; Gastine, Thomas; Christensen, Ulrich R; Wolk, Scott J; Poppenhaeger, Katja
2016-10-25
Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints. In typical geodynamo models, viscous and inertial forces are not much smaller than the Coriolis force, and the Lorentz force plays a subdominant role; this has led to conclusions that these simulations are viscously controlled and do not represent the physics of the geodynamo. Here we show, by a direct analysis of the relevant forces, that a MAC balance can be achieved when the viscosity is reduced to values close to the current practical limit. Lorentz force, buoyancy, and the uncompensated (by pressure) part of the Coriolis force are of very similar strength, whereas viscous and inertial forces are smaller by a factor of at least 20 in the bulk of the fluid volume. Compared with nonmagnetic convection at otherwise identical parameters, the dynamo flow is of larger scale and is less invariant parallel to the rotation axis (less geostrophic), and convection transports twice as much heat, all of which is expected when the Lorentz force strongly influences the convection properties.
Average intensity and spreading of a Lorentz-Gauss beam in turbulent atmosphere.
Zhou, Guoquan; Chu, Xiuxiang
2010-01-18
The propagation of a Lorentz-Gauss beam in turbulent atmosphere is investigated. Based on the extended Huygens-Fresnel integral and the Hermite-Gaussian expansion of a Lorentz function, analytical formulae for the average intensity and the effective beam size of a Lorentz-Gauss beam are derived in turbulent atmosphere. The average intensity distribution and the spreading properties of a Lorentz-Gauss beam in turbulent atmosphere are numerically demonstrated. The influences of the beam parameters and the structure constant of the atmospheric turbulence on the propagation of a Lorentz-Gauss beam in turbulent atmosphere are also discussed in detail.
Phenomenologically viable Lorentz-violating quantum gravity.
Sotiriou, Thomas P; Visser, Matt; Weinfurtner, Silke
2009-06-26
Horava's "Lifschitz point gravity" has many desirable features, but in its original incarnation one is forced to accept a nonzero cosmological constant of the wrong sign to be compatible with observation. We develop an extension of Horava's model that abandons "detailed balance" and regains parity invariance, and in 3+1 dimensions exhibit all five marginal (renormalizable) and four relevant (super-renormalizable) operators, as determined by power counting. We also consider the classical limit of this theory, evaluate the Hamiltonian and supermomentum constraints, and extract the classical equations of motion in a form similar to the Arnowitt-Deser-Misner formulation of general relativity. This puts the model in a framework amenable to developing detailed precision tests.
Reduced-order Abraham-Lorentz-Dirac equation and the consistency of classical electromagnetism
NASA Astrophysics Data System (ADS)
Steane, Andrew M.
2015-03-01
It is widely believed that classical electromagnetism is either unphysical or inconsistent, owing to pathological behavior when self-force and radiation reaction are non-negligible. We argue that there is no inconsistency as long as it is recognized that certain types of charge distribution are simply impossible, such as, for example, a point particle with finite charge and finite inertia. This is owing to the fact that negative inertial mass is an unphysical concept in classical physics. It remains useful to obtain an equation of motion for small charged objects that describes their motion to good approximation without requiring knowledge of the charge distribution within the object. We give a simple method to achieve this, leading to a reduced-order form of the Abraham-Lorentz-Dirac equation, essentially as proposed by Eliezer, Landau, and Lifshitz and derived by Ford and O'Connell.
Friction Compensation for Enhancing Transparency of a Teleoperator with Compliant Transmission
Mahvash, Mohsen; Okamura, Allison
2009-01-01
This article presents a model-based compensator for canceling friction in the tendon-driven joints of a haptic-feedback teleoperator. Unlike position-tracking systems, a teleoperator involves an unknown environment force that prevents the use of tracking position error as a feedback to the compensator. Thus, we use a model-based feedforward friction compensator to cancel the friction forces. We provide conditions for selecting compensator parameters to ensure passivity of the teleoperator and demonstrate performance experimentally. PMID:20514151
Anterior Cruciate Ligament Injury: Compensation during Gait using Hamstring Muscle Activity.
Catalfamo, Paola Formento; Aguiar, Gerardo; Curi, Jorge; Braidot, Ariel
2010-06-10
Previous research has shown that an increase in hamstring activation may compensate for anterior tibial transalation (ATT) in patients with anterior cruciate ligament deficient knee (ACLd); however, the effects of this compensation still remain unclear. The goals of this study were to quantify the activation of the hamstring muscles needed to compensate the ATT in ACLd knee during the complete gait cycle and to evaluate the effect of this compensation on quadriceps activation and joint contact forces. A two dimensional model of the knee was used, which included the tibiofemoral and patellofemoral joints, knee ligaments, the medial capsule and two muscles units. Simulations were conducted to determine the ATT in healthy and ACLd knee and the hamstring activation needed to correct the abnormal ATT to normal levels (100% compensation) and to 50% compensation. Then, the quadriceps activation and the joint contact forces were calculated. Results showed that 100% compensation would require hamstring and quadriceps activations larger than their maximum isometric force, and would generate an increment in the peak contact force at the tibiofemoral (115%) and patellofemoral (48%) joint with respect to the healthy knee. On the other hand, 50% compensation would require less force generated by the muscles (less than 0.85 of maximum isometric force) and smaller contact forces (peak tibiofemoral contact force increased 23% and peak patellofemoral contact force decreased 7.5% with respect to the healthy knee). Total compensation of ATT by means of increased hamstring activity is possible; however, partial compensation represents a less deleterious strategy.
A multiportal compensator system for IMRT delivery.
Yoda, Kiyoshi; Aoki, Yukimasa
2003-05-01
We have developed a multiportal compensator system for IMRT delivery, comprising a rotational compensator mount for a linac head, cylindrical compensator enclosures positioned in the mount, a vacuum-formed thermoplastic sheet with heavy alloy granules inside the enclosure, and a vacuum thermoforming device. The mount rotates like a revolver by a stepping motor, thus allowing automatic multiportal IMRT without exchanging compensators by human operators during treatment. The thermoforming device has servo-motor-driven 10 x 10 metal rod elements to actualize an arbitrary intensity profile. The thermoplastic sheet is preheated by a built-in biplanar heater and then it is placed over the rod elements. Subsequently, vacuum forming is performed through corner cutouts of the rod elements. After forced cooling down, the heavy alloy granules are fed into the formed sheet. Preliminary experiment using solid water phantoms and an x-ray film has shown that the intensity profile on the film agrees reasonably well with the desired profile.
The local geometry of compact homogeneous Lorentz spaces
NASA Astrophysics Data System (ADS)
Günther, Felix
2015-03-01
In 1995, S. Adams and G. Stuck as well as A. Zeghib independently provided a classification of non-compact Lie groups which can act isometrically and locally effectively on compact Lorentzian manifolds. In the case that the corresponding Lie algebra contains a direct summand isomorphic to the two-dimensional special linear algebra or to a twisted Heisenberg algebra, Zeghib also described the geometric structure of the manifolds. Using these results, we investigate the local geometry of compact homogeneous Lorentz spaces whose isometry groups have non-compact connected components. It turns out that they all are reductive. We investigate the isotropy representation and curvatures. In particular, we obtain that any Ricci-flat compact homogeneous Lorentz space is flat or has compact isometry group.
Quantum gravity and Lorentz invariance violation in the standard model.
Alfaro, Jorge
2005-06-10
The most important problem of fundamental physics is the quantization of the gravitational field. A main difficulty is the lack of available experimental tests that discriminate among the theories proposed to quantize gravity. Recently, Lorentz invariance violation by quantum gravity (QG) has been the source of growing interest. However, the predictions depend on an ad hoc hypothesis and too many arbitrary parameters. Here we show that the standard model itself contains tiny Lorentz invariance violation terms coming from QG. All terms depend on one arbitrary parameter alpha that sets the scale of QG effects. This parameter can be estimated using data from the ultrahigh energy cosmic ray spectrum to be |alpha|< approximately 10(-22)-10(-23).
Impossibility of superluminal travel in Lorentz violating theories
NASA Astrophysics Data System (ADS)
Coutant, Antonin; Finazzi, Stefano; Liberati, Stefano; Parentani, Renaud
2012-03-01
Warp drives are space-times allowing for superluminal travel. However, they are quantum mechanically unstable because they produce a Hawking-like radiation which is blue shifted at their front wall without any bound. We reexamine this instability when local Lorentz invariance is violated at ultrahigh energy by dispersion, as in some theories of quantum gravity. Interestingly, even though the ultraviolet divergence is now regulated, warp drives are still unstable. Moreover the type of instability is different whether one uses a subluminal or a superluminal dispersion relation. In the first case, a black-hole laser yields an exponential amplification of the emitted flux whereas, in the second, infrared effects produce a linear growth of that flux. These results suggest that chronology could still be protected when violating Lorentz invariance.
Extending the Lorentz Transformation to Motion with Variable Velocity
NASA Technical Reports Server (NTRS)
Jones, Robert T.
1959-01-01
The problem considered is that of rectilinear motion with variable velocity. The paper gives, by an elementary construction, a system of coordinates which is conformal in the vicinity of the axis of motion. By a particular choice of the scale relation, such restricted conformal transformations can be made to reduce to the Lorentz transformation everywhere in the case of uniform velocity and locally in the case of variable velocity.
Shape of solitons in classically forbidden states - 'Lorentz expansion'
NASA Technical Reports Server (NTRS)
Guinea, F.; Peierls, R. E.; Schrieffer, R.
1986-01-01
The shape of extended objects in classically forbidden regions is shown to undergo expansion analogous to Lorentz contraction of a relativistic body of finite velocities. The problem of two interacting Dirac particles moving in one dimension is solved explicitly and the results are generalized to soliton solutions of field theories. An estimate of the effect on tunneling rates is also given, including solitons in (CH)z.
Two field BPS solutions for generalized Lorentz breaking models
Souza Dutra, A. de; Hott, M.; Barone, F. A.
2006-10-15
In this work we present nonlinear models in two-dimensional space-time of two interacting scalar fields in the Lorentz and CPT violating scenarios. We discuss the soliton solutions for these models as well as the question of stability for them. This is done by generalizing a model recently published by Barreto and collaborators and also by getting new solutions for the model introduced by them.
Einstein and Lorentz: The structure of a scientific revolution
NASA Astrophysics Data System (ADS)
Brouwer, W.
1980-06-01
In a course entitled ''Revolutions in Physics'' a number of episodes in the history of physics are examined, in order to test the theories of Kuhn, Popper, Lakatos, and others, with regard to any common structure exhibited by the various revolutions that physics has undergone. The conflict between Lorentz's Electron Theory and Einstein's Special Relativity becomes a major focal point in the second half of the course for the models of scientific revolutions that are studied.
Anderson, R.C.
1985-10-01
Congress has demonstrated interest in toxic compensation legislation, but not enough agreement to make significant progress. Advocates of reform claim that the legal system is heavily weighed against victims who seek compensation through the courts. Proposed reforms include a compensation fund and a cause of action in federal court. Critics have questioned whether these changes in the law would represent an improvement. Existing income replacement, medical cost reimbursement, and survivor insurance programs largely cover the losses of individuals with chronic disease. Thus, the need for an additional compensation is not clear. Furthermore, experience with compensation funds such as the Black Lung Fund suggests that political rather than scientific criteria may be used to determine eligibility. Finally, under the proposed financing mechanisms the compensation funds that are being debated would not increase incentives for care in the handling of hazardous wastes or toxic substances.
Anderson, R C
1985-01-01
Congress has demonstrated interest in toxic compensation legislation, but not enough agreement to make significant progress. Advocates of reform claim that the legal system is heavily weighed against victims who seek compensation through the courts. Proposed reforms include a compensation fund and a cause of action in federal court. Critics have questioned whether these changes in the law would represent an improvement. Existing income replacement, medical cost reimbursement, and survivor insurance programs largely cover the losses of individuals with chronic disease. Thus, the need for an additional compensation is not clear. Furthermore, experience with compensation funds such as the Black Lung Fund suggests that political rather than scientific criteria may be used to determine eligibility. Finally, under the proposed financing mechanisms the compensation funds that are being debated would not increase incentives for care in the handling of hazardous wastes or toxic substances. PMID:4085440
Lorentz-invariant actions for chiral p-forms
Pasti, P.; Sorokin, D.; Tonin, M.
1997-05-01
We demonstrate how a Lorentz-covariant formulation of the chiral p-form model in D=2(p+1) containing infinitely many auxiliary fields is related to a Lorentz-covariant formulation with only one auxiliary scalar field entering a chiral p-form action in a nonpolynomial way. The latter can be regarded as a consistent Lorentz-covariant truncation of the former. We make the Hamiltonian analysis of the model based on the nonpolynomial action and show that the Dirac constraints have a simple form and are all first class. In contrast with the Siegel model the constraints are not the square of second-class constraints. The canonical Hamiltonian is quadratic and determines the energy of a single chiral p-form. In the case of D=2 chiral scalars the constraint can be improved by use of a {open_quotes}twisting{close_quotes} procedure (without the loss of the property to be first class) in such a way that the central charge of the quantum constraint algebra is zero. This points to the possible absence of an anomaly in an appropriate quantum version of the model. {copyright} {ital 1997} {ital The American Physical Society}
Tweedale, G; Jeremy, D J
1999-01-01
In 1931 the British government introduced pioneering legislation to combat occupational disease in the asbestos industry. A key feature was an Asbestosis Scheme for compensating workers for industrial injury and death. This article examines the implementation of the Scheme at Turner & Newall, the leading UK asbestos producer. The evidence reveals an inequitable system of compensation, especially when compared to the company's generosity to its shareholders. Deficiencies in British compensation law, the weaknesses of regulatory forces, and the company's policy of minimising the extent of asbestos disease are held responsible.
Rationalizing vaccine injury compensation.
Mello, Michelle M
2008-01-01
Legislation recently adopted by the United States Congress provides producers of pandemic vaccines with near-total immunity from civil lawsuits without making individuals injured by those vaccines eligible for compensation through the Vaccine Injury Compensation Program. The unusual decision not to provide an alternative mechanism for compensation is indicative of a broader problem of inconsistency in the American approach to vaccine-injury compensation policy. Compensation policies have tended to reflect political pressures and economic considerations more than any cognizable set of principles. This article identifies a set of ethical principles bearing on the circumstances in which vaccine injuries should be compensated, both inside and outside public health emergencies. A series of possible bases for compensation rules, some grounded in utilitarianism and some nonconsequentialist, are discussed and evaluated. Principles of fairness and reasonableness are found to constitute the strongest bases. An ethically defensible compensation policy grounded in these principles would make a compensation fund available to all individuals with severe injuries and to individuals with less-severe injuries whenever the vaccination was required by law or professional duty.
38 CFR 3.708 - Federal Employees' Compensation.
Code of Federal Regulations, 2014 CFR
2014-07-01
...' Compensation Act (FECA) based upon disability or death due to service in the Armed Forces and is also entitled... Programs for disability or death incurred on or after January 1, 1957, based on military service. (2) Right... on death due to military service may elect to receive dependency and indemnity compensation at...
38 CFR 3.708 - Federal Employees' Compensation.
Code of Federal Regulations, 2013 CFR
2013-07-01
...' Compensation Act (FECA) based upon disability or death due to service in the Armed Forces and is also entitled... Programs for disability or death incurred on or after January 1, 1957, based on military service. (2) Right... on death due to military service may elect to receive dependency and indemnity compensation at...
38 CFR 3.708 - Federal Employees' Compensation.
Code of Federal Regulations, 2011 CFR
2011-07-01
...' Compensation Act (FECA) based upon disability or death due to service in the Armed Forces and is also entitled... Programs for disability or death incurred on or after January 1, 1957, based on military service. (2) Right... on death due to military service may elect to receive dependency and indemnity compensation at...
Doerry, Armin W.
2004-07-20
Movement of a GMTI radar during a coherent processing interval over which a set of radar pulses are processed may cause defocusing of a range-Doppler map in the video signal. This problem may be compensated by varying waveform or sampling parameters of each pulse to compensate for distortions caused by variations in viewing angles from the radar to the target.
NASA Technical Reports Server (NTRS)
Purvis, C. K.; Taylor, P. L.
1982-01-01
A method for computing the Lorentz tensor components in single crystals via rapidly convergent sums of Bessels functions is developed using the relationship between dipole-field sums and the tensor components. The Lorentz factors for simple, body-centered, and base-centered orthorhombic lattices are computed using this method, and the derivative Lorentz factors for simple orthorhombic lattices are also determined. Both the Lorentz factors and their derivatives are shown to be very sensitive to a lattice structure. The equivalent of the Clausius-Mossotti relation for general orthorhombic lattices is derived using the Lorentz-factor formalism, and the permanent molecular dipole moment is related to crystal polarization for the case of a ferroelectric of polarizable point dipoles. It is concluded that the polarization enhancement due to self-polarization familiar from classical theory may actually be a reduction in consequences of negative Lorentz factors in one or two lattice directions for noncubic crystals.
NASA Astrophysics Data System (ADS)
M, Haritha; P, Durganandini
2015-06-01
We study the scattering and confinement of Dirac particles in external electrostatic and Lorentz scalar potentials. We use a numerical finite difference time -domain method to solve the equation and obtain the particle dynamics. We find qualitatively different dynamical behavior for electrostatic and Lorentz scalar potentials. Electrostatic potentials lead to Klein tunneling and do not exhibit confinement, while Lorentz scalar potentials inhibit Klein tunneling and exhibit confinement.
Bounds on Lorentz and CPT violation from the Earth-ionosphere cavity
Mewes, Matthew
2008-11-01
Electromagnetic resonant cavities form the basis of many tests of Lorentz invariance involving photons. The effects of some forms of Lorentz violation scale with cavity size. We investigate possible signals of violations in the naturally occurring resonances formed in the Earth-ionosphere cavity. Comparison with observed resonances places the first terrestrial constraints on coefficients associated with dimension-three Lorentz-violating operators at the level of 10{sup -20} GeV.
El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.
1992-07-28
A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.
El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony
1992-01-01
A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.
Lorentz-invariant formulation of Cherenkov radiation by tachyons
NASA Technical Reports Server (NTRS)
Jones, F. C.
1972-01-01
Previous treatments of Cherenkov radiation, electromagnetic and gravitational, by tachyons were in error because the prescription employed to cut off the divergent integral over frequency is not a Lorentz invariant procedure. The resulting equation of motion for the tachyon is therefore not covariant. The proper procedure requires an extended, deformable distribution of charge or mass and yields a particularly simple form for the tachyon's world line, one that could be deduced from simple invariance considerations. It is shown that Cherenkov radiation by tachyons implys their ultimate annihilation with an antitachyon and demonstrates a disturbing property of tachyons, namely the impossibility of specifying arbitrary Cauchy data even in a purely classical theory.
Fluctuation formula for nonreversible dynamics in the thermostated Lorentz gas
NASA Astrophysics Data System (ADS)
Dolowschiák, M.; Kovács, Z.
2002-12-01
We investigate numerically the validity of the Gallavotti-Cohen fluctuation formula in the two- and three-dimensional periodic Lorentz gas subjected to constant electric and magnetic fields and thermostated by the Gaussian isokinetic thermostat. The magnetic field breaks the time reversal symmetry, and by choosing its orientation with respect to the lattice, one can have either a generalized reversing symmetry or no reversibility at all. Our results indicate that the scaling property described by the fluctuation formula may be approximately valid for large fluctuations even in the absence of reversibility.
Fluctuation formula for nonreversible dynamics in the thermostated Lorentz gas.
Dolowschiák, M; Kovács, Z
2002-12-01
We investigate numerically the validity of the Gallavotti-Cohen fluctuation formula in the two- and three-dimensional periodic Lorentz gas subjected to constant electric and magnetic fields and thermostated by the Gaussian isokinetic thermostat. The magnetic field breaks the time reversal symmetry, and by choosing its orientation with respect to the lattice, one can have either a generalized reversing symmetry or no reversibility at all. Our results indicate that the scaling property described by the fluctuation formula may be approximately valid for large fluctuations even in the absence of reversibility.
Chaos properties and localization in Lorentz lattice gases
NASA Astrophysics Data System (ADS)
Appert, C.; Ernst, M. H.
1997-11-01
The thermodynamic formalism of Ruelle, Sinai, and Bowen [David Ruelle, Thermodynamic Formalism (Addison-Wesley, Reading, MA, 1978)], in which chaotic properties of dynamical systems are expressed in terms of a free-energy-type function ψ(β), is applied to a Lorentz lattice gas, as typical for diffusive systems with static disorder. In the limit of large system sizes, the mechanism and effects of localization on large clusters of scatterers in the calculation of ψ(β) are elucidated and supported by strong numerical evidence. Moreover, we clarify and illustrate a previous theoretical analysis [C. Appert et al., J. Stat. Phys. 87, 1253 (1997)] of this localization phenomenon.
Direct measurement of correlation functions in a lattice Lorentz gas
NASA Technical Reports Server (NTRS)
Binder, P.-M.; Frenkel, D.
1990-01-01
Simulations of a two-dimensional ballistic Lorentz gas on a lattice are reported. A moment-propagation technique allows direct measurements of the velocity correlation function and its moments with low relative errors for all times. The predicted 1/t-sq algebraic tails in the velocity correlation function are observed at all studied scatterer densities, unlike what has been reported for continuous systems. In the square lattice a fast oscillation is observed, consistent with the existence of staggered density modes. For the second-rank tensor correlation function, an extremely slow approach to the expected 1/t exp 3 tail is found.
Cosmology of a universe with spontaneously broken Lorentz symmetry
Ferreira, P. G.; Gripaios, B. M.; Zlosnik, T. G.; Saffari, R.
2007-02-15
A self-consistent effective field theory of modified gravity has recently been proposed with spontaneous breaking of local Lorentz invariance. The symmetry is broken by a vector field with the wrong-sign mass term and it has been shown to have additional graviton modes and modified dispersion relations. In this paper we study the evolution of a homogeneous and isotropic universe in the presence of such a vector field with a minimum lying along the timelike direction. A plethora of different regimes is identified, such as accelerated expansion, loitering, collapse, and tracking.
The Lorentz gas in Kaluza's MHD: Transport equations
NASA Astrophysics Data System (ADS)
Sandoval-Villalbazo, Alfredo; Sagaceta-Mejia, Alma Rocio; Mondragon-Suarez, Jose Humberto
2016-11-01
Relativistic kinetic theory is applied to the study of the transport processes present in a Lorentz gas, using a geometric five-dimensional space-time. While the conventional transport equations are recovered in the Newtonian limit, it is shown that relativistic corrections to the conduction and diffusion fluxes arise within this formalism. A brief review of the conceptual advantages of the Kaluza-type approach to magnetohydrodynamics is also given. The authors acknowledge support from CONACyT through Grant CB2011/167563.
The Need for a First-order Quasi Lorentz Transformation
Censor, D.
2010-11-25
Solving electromagnetic scattering problems involving non-uniformly moving objects or media requires an approximate but consistent extension of Einstein's Special Relativity theory, originally valid for constant velocities only. For moderately varying velocities a quasi Lorentz transformation is presented. The conditions for form-invariance of the Maxwell equations, the so-called ''principle of relativity'', are shown to hold for a broad class of motional modes and time scales. A simple example of scattering by a harmonically oscillating mirror is analyzed in detail. Application to generally orbiting objects is mentioned.
Getting the Lorentz transformations without requiring an invariant speed
NASA Astrophysics Data System (ADS)
Pelissetto, Andrea; Testa, Massimo
2015-04-01
The structure of the Lorentz transformations follows purely from the absence of privileged inertial reference frames and the group structure (closure under composition) of the transformations—two assumptions that are simple and physically necessary. The existence of an invariant speed is not a necessary assumption and in fact is a consequence of the principle of relativity (though the finite value of this speed must, of course, be obtained from experiment). Von Ignatowsky derived this result in 1911, but it is still not widely known and is absent from most textbooks. Here, we present a completely elementary proof of the result, suitable for use in an introductory course in special relativity.
Lorentz invariant relative velocity and relativistic binary collisions
NASA Astrophysics Data System (ADS)
Cannoni, Mirco
2017-01-01
This paper reviews the concept of Lorentz invariant relative velocity that is often misunderstood or unknown in high energy physics literature. The properties of the relative velocity allow to formulate the invariant flux and cross-section without recurring to nonphysical velocities or any assumption about the reference frame. Applications such as the luminosity of a collider, the use as kinematic variable, and the statistical theory of collisions in a relativistic classical gas are reviewed. It is emphasized how the hyperbolic properties of the velocity space explain the peculiarities of relativistic scattering.
New limits on Planck scale Lorentz violation in QED.
Jacobson, T; Liberati, S; Mattingly, D; Stecker, F W
2004-07-09
Constraints on possible Lorentz symmetry violation (LV) of order E/M(Planck) for electrons and photons in the framework of effective field theory (EFT) are discussed. Using (i) the report of polarized MeV emission from GRB021206 and (ii) the absence of vacuum Cerenkov radiation from synchrotron electrons in the Crab Nebula, we improve previous bounds by 10(-10) and 10(-2), respectively. We also show that the LV parameters for positrons and electrons are different, discuss electron helicity decay, and investigate how prior constraints are modified by the relations between LV parameters implied by EFT.
Renormalization of high-energy Lorentz-violating QED
Anselmi, Damiano; Taiuti, Martina
2010-04-15
We study a QED extension that is unitary, CPT invariant, and super-renormalizable, but violates Lorentz symmetry at high energies, and contains higher-dimension operators (LVQED). Divergent diagrams are only one- and two-loop. We compute the one-loop renormalizations at high and low energies and analyze the relation between them. It emerges that the powerlike divergences of the low-energy theory are multiplied by arbitrary constants, inherited by the high-energy theory, and therefore can be set to zero at no cost, bypassing the hierarchy problem.
Beam transport and space charge compensation strategies (invited)
Meusel, O. Droba, M.; Noll, D.; Schulte, K.; Schneider, P. P.; Wiesner, C.
2016-02-15
The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.
Beam transport and space charge compensation strategies (invited).
Meusel, O; Droba, M; Noll, D; Schulte, K; Schneider, P P; Wiesner, C
2016-02-01
The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.
Comparison of various approaches to the calculation of optically induced forces
Torchigin, V.P. Torchigin, A.V.
2012-09-15
Various approaches used for the calculation of optically induced forces applied to a transparent optical medium imbedded in a close plane optical resonator are analyzed. The forces are calculated by means of analysis of a change in the eigen frequency and energy stored in the resonator at various positions of the medium. It is shown that results obtained are identical to those calculated by means of approaches based on the Maxwell stress tensor, based on an analysis of a change in the momentum of light. An exception is for results obtained on the base of last versions of the Lorentz density force. - Highlights: Black-Right-Pointing-Pointer There are no Lorentz forces in a homogeneous optical medium. Black-Right-Pointing-Pointer A net force produced by an inhomogeneous electrostriction pressure is equal to zero. Black-Right-Pointing-Pointer Any distributions of the Lorentz force in a homogeneous optical medium are misleading.
Federal Employees' Compensation Act.
Ladou, Joseph
2009-01-01
The Federal Employees' Compensation Act (FECA) program provides wage loss compensation and payments for medical treatment to federal civilian employees. Administered by the Department of Labor (DOL), FECA covers over 2.7 million federal employees in more than 70 different agencies. FECA costs rose from $1.4 billion in 1990 to $2.6 in 2006, while the federal workforce remained essentially unchanged. While federal civilian employees represent only 2.1% of all workers eligible for workers' compensation benefits, federal programs account for 6% of the benefits paid. Disability benefits under FECA are far greater than those in the state workers' compensation programs. The benefit payments often exceed the former salary of the injured employee. The last congressional hearings on the FECA program were held over thirty years ago. It is unlikely that Congressional review will occur any time soon, as the entrenched bureaucracy that benefits from the FECA program defines and protects its future.
NASA Technical Reports Server (NTRS)
Coney, Thom A.
1996-01-01
Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.
Compensation law in composites
NASA Astrophysics Data System (ADS)
Dufresne, A.; Lavergne, C.; Lacabanne, C.
1993-12-01
The experimental resolution of the α retardation / relaxation mode of model composites epoxy resin- glass beads has been performed using Thermo Stimulated Creep (TSCr) and Thermo Stimulated Currents (TSC) spectroscopies. The distributed retardation / relaxation times τ are found to obey a compensation law, which is characteristic of cooperative movements liberated at the vicinity of T g. The T c and τ c compensation parameters reveal that the microstructure is strongly linked to the nature of the interface.
Evaluating Military Compensation
2007-06-01
has also compared the out-of-pocket health costs of families who use its preferred-provider organization ( PPO ) or fee-for-service options with those...comparison controlled for demographic differ- ences between military and civilian families. EVALUATING MILITARY COMPENSATION 17using PPO plans. In 2005...governments would have to absorb the difference. A PP E N D IX A Total Compensation for the Median Enlisted MemberUsing a different approach from
A gyrokinetic collision operator for magnetized Lorentz plasmas
Liu Chang; Ma Chenhao; Yu Xiongjie; Qin, Hong
2011-03-15
A gyrocenter collision operator for magnetized Lorentz plasmas is derived using the Fokker-Plank method. The gyrocenter collision operator consists of drift and diffusion terms in the gyrocenter coordinates, including the diffusion of the gyrocenter, which does not exist for the collision operator in the particle phase space coordinates. The gyrocenter collision operator also depends on the transverse electric field explicitly, which is crucial for the correct treatment of collisional effects and transport in the gyrocenter coordinates. The gyrocenter collision operator derived is applied to calculate the particle and heat transport fluxes in a magnetized Lorentz plasma with an electric field. The particle and heat transport fluxes calculated from our gyrocenter collision operator agree exactly with the classical Braginskii's result [S. I. Braginskii, Reviews of Plasma Physics (Consultants Bureau, New York, 1965), Vol. 1, p. 205: P. Helander and D. J. Sigmar, Collisional Transport in Magnetized Plasmas (Cambridge University, Cambridge, 2002), p. 65], which validates the correctness of our collision operator. To calculate the transport fluxes correctly, it is necessary to apply the pullback transformation associated with gyrocenter coordinate transformation in the presence of collisions, which also serves as a practical algorithm for evaluating collisional particle and heat transport fluxes in the gyrocenter coordinates.
Cosmic censorship in Lorentz-violating theories of gravity
NASA Astrophysics Data System (ADS)
Meiers, Michael; Saravani, Mehdi; Afshordi, Niayesh
2016-05-01
Is cosmic censorship special to general relativity, or can it survive a violation of local Lorentz invariance? Recent studies have shown that singularities in Lorentz -violating Einstein-Aether (or Horava-Lifshitz) theories can lie behind a universal horizon in simple black hole spacetimes. Even infinitely fast signals cannot escape these universal horizons. We extend this result, for an incompressible aether, to 3 +1 d dynamical or spinning spacetimes which possess inner Killing horizons, and show that a universal horizon always forms in between the outer and (would-be) inner horizons. This finding suggests a notion of cosmic censorship, given that geometry in these theories never evolves beyond the universal horizon (avoiding potentially singular inner Killing horizons). A surprising result is that there are 3 distinct possible stationary universal horizons for a spinning black hole, only one of which matches the dynamical spherical solution. This motivates dynamical studies of collapse in Einstein-Aether theories beyond spherical symmetry, which may reveal instabilities around the spherical solution.
A test of local Lorentz invariance with Compton scattering asymmetry
Mohanmurthy, Prajwal; Narayan, Amrendra; Dutta, Dipangkar
2016-12-14
Here, we report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon-electron scattering. We also used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall~C at Jefferson Lab to test for deviations from unity of the vacuum refractive index ($n$). For photon energies in the range of 9 - 46 MeV, we obtain a new limit of $1-n < 1.4 \\times 10^{-8}$. In addition, the absence of sidereal variation over the six month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance using Compton asymmetry. Within the minimal standard model extension framework, our result yield limits on the photon and electron coefficients $\\tilde{\\kappa}_{0^+}^{YZ}, c_{TX}, \\tilde{\\kappa}_{0^+}^{ZX}$, and $c_{TY}$. Though, these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of Lorentz invariance. For future parity violating electron scattering experiments at Jefferson Lab we will use higher energy electrons enabling better constraints.
A test of local Lorentz invariance with Compton scattering asymmetry
Mohanmurthy, Prajwal; Narayan, Amrendra; Dutta, Dipangkar
2016-12-14
Here, we report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon-electron scattering. We also used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall~C at Jefferson Lab to test for deviations from unity of the vacuum refractive index (more » $n$). For photon energies in the range of 9 - 46 MeV, we obtain a new limit of $$1-n < 1.4 \\times 10^{-8}$$. In addition, the absence of sidereal variation over the six month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance using Compton asymmetry. Within the minimal standard model extension framework, our result yield limits on the photon and electron coefficients $$\\tilde{\\kappa}_{0^+}^{YZ}, c_{TX}, \\tilde{\\kappa}_{0^+}^{ZX}$$, and $$c_{TY}$$. Though, these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of Lorentz invariance. For future parity violating electron scattering experiments at Jefferson Lab we will use higher energy electrons enabling better constraints.« less
Eikonal equation of the Lorentz-violating Maxwell theory
NASA Astrophysics Data System (ADS)
Xiao, Zhi; Shao, Lijing; Ma, Bo-Qiang
2010-12-01
We derive the eikonal equation of light wavefront in the presence of Lorentz invariance violation (LIV) from the photon sector of the standard model extension (SME). The results obtained from the equations of the E and B fields, respectively, are the same. This guarantees the self-consistency of our derivation. We adopt a simple case with only one non-zero LIV parameter as an illustration, from which we find two points. One is that, in analogy with the Hamilton-Jacobi equation, from the eikonal equation, we can derive dispersion relations which are compatible with results obtained from other approaches. The other is that the wavefront velocity is the same as the group velocity, as well as the energy flow velocity. If further we define the signal velocity v s as the front velocity, there always exists a mode with v s >1; hence causality is violated classically. Thus, our method might be useful in the analysis of Lorentz violation in QED in terms of classical causality.
Non-dissipative electromagnetic media with two Lorentz null cones
Dahl, Matias F.
2013-03-15
We study Maxwell's equations on a 4-manifold where the electromagnetic medium is modeled by an antisymmetric (2/2 )-tensor with 21 real coefficients. In this setting the Fresnel surface is a fourth-order polynomial surface that describes the dynamical response of the medium in the geometric optics limit. For example, in an isotropic medium the Fresnel surface is a Lorentz null cone. The contribution of this paper is the pointwise description of all electromagnetic medium tensors {kappa} with real coefficients that satisfy the following three conditions: (i)medium {kappa} is invertible, (ii)medium {kappa} is skewon-free, or non-dissipative, (iii)the Fresnel surface of {kappa} is the union of two distinct Lorentz null cones. We show that there are only three classes of media with these properties and give explicit expressions in local coordinates for each class. - Highlights: Black-Right-Pointing-Pointer We find two new electromagnetic media classes for which the Fresnel surface decomposes into two light cones. Black-Right-Pointing-Pointer In a suitable setting we classify all electromagnetic media where this is the case. Black-Right-Pointing-Pointer We find an electromagnetic medium tensor with three different signal speeds in one direction. Black-Right-Pointing-Pointer The work is related to [5], which classifies all media with one light cone (in a suitable setting).
Lorentz-breaking massive gravity in curved space
Blas, D.; Nesti, F.; Pilo, L.
2009-08-15
A systematic study of the different phases of Lorentz-breaking massive gravity in a curved background is performed. For tensor and vector modes, the analysis is very close to that of Minkowski space. The most interesting results are in the scalar sector where, generically, there are two propagating degrees of freedom (DOF). While in maximally symmetric spaces ghostlike instabilities are inevitable, they can be avoided in a FRW background. The phases with less than two DOF in the scalar sector are also studied. Curvature allows an interesting interplay with the mass parameters; in particular, we have extended the Higuchi bound of de Sitter to Friedman-Robertson-Walker and Lorentz-breaking masses. As in dS, when the bound is saturated there is no propagating DOF in the scalar sector. In a number of phases the smallness of the kinetic terms gives rise to strongly coupled scalar modes at low energies. Finally, we have computed the gravitational potentials for pointlike sources. In the general case we recover the general relativity predictions at small distances, whereas the modifications appear at distances of the order of the characteristic mass scale. In contrast with Minkowski space, these corrections may not spoil the linear approximation at large distances.
Muehsam, D.J.; Pilla, A.A.
1996-05-01
The present study characterizes an ion-binding site, a molecular cleft in a signaling molecule such as calmodulin or troponin C, as a damped linear isotropic oscillator potential for small displacements about the origin. Quantitative assessments of the effects of thermal noise and exogenous static magnetic fields are made through a statistical mechanical treatment of the Lorentz-Langevin equation for an ion bound in a molecular cleft. Thermal noise causes a bound ion to e ejected from the site after a bound life-time dependent upon the thermal noise spectral density. It is shown that the Lorentz-Langevin model requires values of the viscous damping parameter many orders of magnitude below those for bulk water in order to characterize the binding site and to obtain realistic lifetimes for a bound ion. The model predicts that milliTesla-range magnetic fields are required for static field effects on dissociation kinetics. The Lorentz equation also yields a classic coherent solution describing precession of the bound-ion oscillator orientation at the Larmor frequency. The bound-ion dynamics described by this coherent solution are sensitive to microTesla-range static magnetic fields in the presence of thermal noise. Numerical integration of the contribution of thermal noise forces to these dynamics is in good agreement with the results of statistical mechanical analysis, also producing realistic bound lifetimes for only very low viscous damping values. The mechanisms by which modulation of precessional motion might enable a signaling molecule such as calmodulin to detect an exogenous magnetic field are presently unclear.
Relativistic Landau-Aharonov-Casher quantization based on the Lorentz symmetry violation background
NASA Astrophysics Data System (ADS)
Bakke, K.; Belich, H.; Silva, E. O.
2011-06-01
Based on the discussions about the Aharonov-Casher effect in the Lorentz symmetry violation background, we show that the analogue of the relativistic Landau quantization in the Aharonov-Casher setup can be achieved in the Lorentz-symmetry violation background.
Quasi-exact solvability of Dirac equation with Lorentz scalar potential
Ho, C.-L. . E-mail: hcl@mail.tku.edu.tw
2006-09-15
We consider exact/quasi-exact solvability of Dirac equation with a Lorentz scalar potential based on factorizability of the equation. Exactly solvable and sl (2)-based quasi-exactly solvable potentials are discussed separately in Cartesian coordinates for a pure Lorentz potential depending only on one spatial dimension, and in spherical coordinates in the presence of a Dirac monopole.
Relativistic Landau-Aharonov-Casher quantization based on the Lorentz symmetry violation background
Bakke, K.; Belich, H.; Silva, E. O.
2011-06-15
Based on the discussions about the Aharonov-Casher effect in the Lorentz symmetry violation background, we show that the analogue of the relativistic Landau quantization in the Aharonov-Casher setup can be achieved in the Lorentz-symmetry violation background.
Workers' Compensation and Teacher Stress.
ERIC Educational Resources Information Center
Nisbet, Michael K.
1999-01-01
Examines the Workers' Compensation system and teacher stress to determine if a burned-out teacher should be eligible for Workers' Compensation benefits. Concludes that although most states do not allow Workers' Compensation benefits to burned-out teachers, compensation should be granted because the injuries are real and work-related. (Contains 48…
Propagation of a radial phased-locked Lorentz beam array in turbulent atmosphere.
Zhou, Guoquan
2011-11-21
A radial phased-locked (PL) Lorentz beam array provides an appropriate theoretical model to describe a coherent diode laser array, which is an efficient radiation source for high-power beaming use. The propagation of a radial PL Lorentz beam array in turbulent atmosphere is investigated. Based on the extended Huygens-Fresnel integral and some mathematical techniques, analytical formulae for the average intensity and the effective beam size of a radial PL Lorentz beam array are derived in turbulent atmosphere. The average intensity distribution and the spreading properties of a radial PL Lorentz beam array in turbulent atmosphere are numerically calculated. The influences of the beam parameters and the structure constant of the atmospheric turbulence on the propagation of a radial PL Lorentz beam array in turbulent atmosphere are discussed in detail.
Lorentz invariance and quantum gravity: an additional fine-tuning problem?
Collins, John; Perez, Alejandro; Sudarsky, Daniel; Urrutia, Luis; Vucetich, Héctor
2004-11-05
Trying to combine standard quantum field theories with gravity leads to a breakdown of the usual structure of space time at around the Planck length, 1.6x10(-35) m, with possible violations of Lorentz invariance. Calculations of preferred-frame effects in quantum gravity have further motivated high precision searches for Lorentz violation. Here, we explain that combining known elementary particle interactions with a Planck-scale preferred frame gives rise to Lorentz violation at the percent level, some 20 orders of magnitude higher than earlier estimates, unless the bare parameters of the theory are unnaturally strongly fine tuned. Therefore an important task is not just the improvement of the precision of searches for violations of Lorentz invariance, but also the search for theoretical mechanisms for automatically preserving Lorentz invariance.
Strongly enhanced effects of Lorentz symmetry violation in entangled Yb+ ions
NASA Astrophysics Data System (ADS)
Dzuba, V. A.; Flambaum, V. V.; Safronova, M. S.; Porsev, S. G.; Pruttivarasin, T.; Hohensee, M. A.; Häffner, H.
2016-05-01
A number of theories aiming at unifying gravity with other fundamental interactions, including field theory, suggest the violation of Lorentz symmetry. Whereas the energy scale of such strongly Lorentz-symmetry-violating physics is much higher than that attainable at present by particle accelerators, Lorentz violation may nevertheless be detectable via precision measurements at low energies. Here, we carry out a systematic theoretical investigation to identify which atom shows the greatest promise for detecting a Lorentz symmetry violation in the electron-photon sector. We found that the ytterbium ion (Yb+) is an ideal system with high sensitivity, as well as excellent experimental controllability. By applying quantum-information-inspired technology to Yb+, we expect tests of local Lorentz invariance (LLI) violating physics in the electron-photon sector to reach levels of 10-23--five orders of magnitude more sensitive than the current best bounds.
Decay of a Linear Pendulum in a Free-Molecular Gas and in a Special Lorentz Gas
NASA Astrophysics Data System (ADS)
Tsuji, Tetsuro; Aoki, Kazuo
2012-02-01
A circular disk without thickness is placed in a gas, and an external force, obeying Hooke's law, is acting perpendicularly on the disk. If the disk is displaced perpendicularly from its equilibrium position and released, then it starts an oscillatory or non-oscillatory unsteady motion, which decays as time goes on because of the drag exerted by the gas molecules. This unsteady motion, i.e., the decay of this linear pendulum, is investigated numerically, under the diffuse reflection condition on the surface of the disk, with special interest in the manner of its decay, for two kinds of gases: one is a collisionless gas (or Knudsen gas) and the other is a special Lorentz gas interacting with a background. It is shown that the decay of the displacement of the disk is slow and is in proportion to an inverse power of time for the collisionless gas. The result complements the existing mathematical study of a similar problem (Caprino et al. in Math. Models Methods Appl. Sci. 17:1369-1403, 2007) in the case of non-oscillatory decay. It is also shown that the manner of the decay changes significantly for the special Lorentz gas.
Compensation neurosis rides again.
Levy, A
1992-01-01
Compensation neurosis (CN), also known as accident neurosis, has generally not been considered to be a 'real' disorder. In 1961 it was seemingly laid to rest by Henry Miller, a distinguished neurologist, in a sharp article which appeared in the British Medical Journal. Miller's view of patients who presented psychological symptoms following accidents or traumas was suspicious. Compensated or not, his view seemed to be that they should have their legal process finished as quickly as possible and then they will miraculously convalescence. Miller's work, it appeared, was the coup de grâce for this ill-defined diagnosis. Today, however, compensation neurosis seems to ride again. After a prolonged silence in the psychiatric literature, new papers are emerging, strongly suggesting that this vanishing diagnosis be reconsidered. This new trend will be presented.
Constraints and stability in vector theories with spontaneous Lorentz violation
Bluhm, Robert; Gagne, Nolan L.; Potting, Robertus; Vrublevskis, Arturs
2008-06-15
Vector theories with spontaneous Lorentz violation, known as bumblebee models, are examined in flat spacetime using a Hamiltonian constraint analysis. In some of these models, Nambu-Goldstone modes appear with properties similar to photons in electromagnetism. However, depending on the form of the theory, additional modes and constraints can appear that have no counterparts in electromagnetism. An examination of these constraints and additional degrees of freedom, including their nonlinear effects, is made for a variety of models with different kinetic and potential terms, and the results are compared with electromagnetism. The Hamiltonian constraint analysis also permits an investigation of the stability of these models. For certain bumblebee theories with a timelike vector, suitable restrictions of the initial-value solutions are identified that yield ghost-free models with a positive Hamiltonian. In each case, the restricted phase space is found to match that of electromagnetism in a nonlinear gauge.
Lorentz violating p-form gauge theories in superspace
NASA Astrophysics Data System (ADS)
Upadhyay, Sudhaker; Shah, Mushtaq B.; Ganai, Prince A.
2017-03-01
Very special relativity (VSR) keeps the main features of special relativity but breaks rotational invariance due to an intrinsic preferred direction. We study the VSR-modified extended BRST and anti-BRST symmetry of the Batalin-Vilkovisky (BV) actions corresponding to the p=1,2,3-form gauge theories. Within the VSR framework, we discuss the extended BRST invariant and extended BRST and anti-BRST invariant superspace formulations for these BV actions. Here we observe that the VSR-modified extended BRST invariant BV actions corresponding to the p=1,2,3-form gauge theories can be written in a manifestly covariant manner in a superspace with one Grassmann coordinate. Moreover, two Grassmann coordinates are required to describe the VSR-modified extended BRST and extended anti-BRST invariant BV actions in a superspace. These results are consistent with the Lorentz-invariant (special relativity) formulation.
Test of Lorentz Invariance with Spin Precession of Ultracold Neutrons
Altarev, I.; Gutsmiedl, E.; Baker, C. A.; Iaydjiev, P.; Ivanov, S. N.; Ban, G.; Lefort, T.; Naviliat-Cuncic, O.; Quemener, G.; Bodek, K.; Kistryn, S.; Zejma, J.; Daum, M.; Henneck, R.; Kirch, K.; Knecht, A.; Lauss, B.; Mtchedlishvili, A.; Petzoldt, G.
2009-08-21
A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and {sup 199}Hg atoms, is reported. No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz invariance violating cosmic anisotropy field b{sub perpendicular}<2x10{sup -20} eV (95% C.L.). This is the first limit for the free neutron. This result is also interpreted as a direct limit on the gravitational dipole moment of the neutron |g{sub n}|<0.3 eV/c{sup 2} m from a spin-dependent interaction with the Sun. Analyzing the gravitational interaction with the Earth, based on previous data, yields a more stringent limit |g{sub n}|<3x10{sup -4} eV/c{sup 2} m.
Dual properties of spacetime under an alternative Lorentz transformation
NASA Technical Reports Server (NTRS)
Chang, T.; Torr, D. G.
1988-01-01
A coordinate time, t(A), with absolute synchronization is defined as an alternative fourth spatial coordinate for model universes with flat space-time, and the theoretical implications of t(A) are explored in detail. Particular attention is given to a t(A)-based reformulation of the Lorentz transformation, the generalized Galilean transformation, which is found to offer significant advantages in understanding special-relativistic phenomena such as length contraction, time dilation, and the interaction of objects with the physical vacuum. With respect to astrophysical observations of superluminal motion, it is shown that the problem of causality violation can be avoided; the theory also predicts that weak anisotropic effects may be detectable in the earth reference frame.
Spontaneous breaking of Lorentz symmetry in (2 +ɛ )-dimensional QED
NASA Astrophysics Data System (ADS)
Janssen, Lukas
2016-11-01
The phase diagram of massless quantum electrodynamics in three space-time dimensions as a function of fermion flavor number N exhibits two well-known phases: at large N >Ncconf the system is in a conformal gapless state, while for small N
New methods of testing Lorentz violation in electrodynamics
Tobar, Michael Edmund; Fowler, Alison; Hartnett, John Gideon; Wolf, Peter
2005-01-15
We investigate experiments that are sensitive to the scalar and parity-odd coefficients for Lorentz violation in the photon sector of the standard model extension (SME). We show that of the classic tests of special relativity, Ives-Stilwell (IS) experiments are sensitive to the scalar coefficient, but at only parts in 10{sup 5} for the state-of-the-art experiment. We then propose asymmetric Mach-Zehnder interferometers with different electromagnetic properties in the two arms, including recycling techniques based on travelling wave resonators to improve the sensitivity. With present technology we estimate that the scalar and parity-odd coefficients may be measured with a sensitivity better than parts in 10{sup 11} and 10{sup 15} respectively.
Lorentz effect imaging of ionic currents in solution
NASA Astrophysics Data System (ADS)
Truong, Trong-Kha; Avram, Alexandru; Song, Allen W.
2008-03-01
Current functional MRI techniques relying on hemodynamic modulations are inherently limited in their ability to accurately localize neural activity in space and time. To address these limitations, we previously proposed a novel technique based on the Lorentz effect and demonstrated its ability to directly image minute electrical activity with a millisecond temporal resolution in gel phantoms containing conductive wires as well as in the human median nerve in vivo. To better characterize its contrast mechanism and ultimately further improve its sensitivity for in vivo applications, we now apply this technique to image ionic currents in solution, which serve as a better model for neural conduction in biological systems than the electronic currents in conductive wires used in previous phantom studies. Our results demonstrate that ionic currents with durations and current densities on the same order of magnitude as those induced by neuroelectric activity in nerve fibers and in the brain can be detected.
Singular Lorentz-violating Lagrangians and associated Finsler structures
NASA Astrophysics Data System (ADS)
Colladay, Don; McDonald, Patrick
2015-10-01
Several Lagrangians associated with classical limits of Lorentz-violating fermions in the standard model extension (SME) have been shown to yield Finsler functions when the theory is expressed in Euclidean space. When spin couplings are present, the Lagrangian can develop singularities that obstruct the construction of a globally defined Legendre transformation, leading to singular Finsler spaces. A specific sector of the SME where such problems arise is studied. It is found that the singular behavior can be eliminated by an appropriate lifting of the problem to an associated algebraic variety. This provides a smooth classical model for the singular problem. In Euclidean space, the procedure involves combining two related singular Finsler functions into a single smooth function with a semi-positive-definite quadratic form defined on a desingularized variety.
Dosage Compensation in Mammals
Brockdorff, Neil; Turner, Bryan M.
2015-01-01
Many organisms show major chromosomal differences between sexes. In mammals, females have two copies of a large, gene-rich chromosome, the X, whereas males have one X and a small, gene-poor Y. The imbalance in expression of several hundred genes is lethal if not dealt with by dosage compensation. The male–female difference is addressed by silencing of genes on one female X early in development. However, both males and females now have only one active X chromosome. This is compensated by twofold up-regulation of genes on the active X. This complex system continues to provide important insights into mechanisms of epigenetic regulation. PMID:25731764
CONSTRAINTS ON THE BULK LORENTZ FACTORS OF GRB X-RAY FLARES
Yi, Shuang-Xi; Wang, Fa-Yin; Dai, Zi-Gao; Wu, Xue-Feng
2015-07-01
X-ray flares were discovered in the afterglow phase of gamma-ray bursts (GRBs) by the Swift satellite a decade ago and are known as a canonical component in GRB X-ray afterglows. In this paper, we constrain the Lorentz factors of GRB X-ray flares using two different methods. For the first method, we estimate the lower limit on the bulk Lorentz factor with the flare duration and jet break time. In the second method, the upper limit on the Lorentz factor is derived by assuming that the X-ray flare jet has undergone saturated acceleration. We also re-estimate the initial Lorentz factor with GRB afterglow onsets, and find the coefficient of the theoretical Lorentz factor is 1.67 rather than the commonly used 2 for the interstellar medium (ISM) and 1.44 for the wind case. We find that the correlation between the limited Lorentz factor and the isotropic radiation energy of X-ray flares in the ISM case is more consistent with that of prompt emission than the wind case in a statistical sense. For a comparison, the lower limit on the Lorentz factor is statistically larger than the extrapolation from prompt bursts in the wind case. Our results indicate that X-ray flares and prompt bursts are produced by the same physical mechanism.
Evolution of dosage compensation.
Steinemann, M; Steinemann, S; Turner, B M
1996-04-01
In polytene chromosome squashes from the fruit fly Drosophila melanogaster, the single, dosage-compensated X chromosome in males can be distinguished from the autosomes by the presence of an isoform of histone H4 acetylated at lysine 16, H4.Ac16. We have used H4.Ac16 as a marker to examine the evolving relationship between dosage compensation and sex chromosome composition in species of Drosophila with one (D. melanogaster), two (D. pseudoobscura) or three (D. miranda) identifiable X chromosome arms. In each case, we find that H4.Ac16 is distributed as discrete, closely spaced bands along the entire length of each X chromosome, the only exception being the X2 chromosome of D. miranda in which a terminal region constituting about 10% of the chromosome by length is not labelled with anti-H4.Ac16 antibodies. We conclude that, with this exception, dosage compensation extends along the X chromosomes of all three species. As D. pseudoobscura and D. miranda diverged only about 2 Mya, the spread of dosage-compensated loci along X2 has been rapid, suggesting that regional changes rather than piecemeal, gene-by-gene, changes may have been involved.
ERIC Educational Resources Information Center
Phillippe, Kent A.
2016-01-01
In 2015, the American Association of Community Colleges (AACC) conducted a survey of community college chief executive officers (CEOs) to collect their opinions on current issues, and gather information on their compensation. This report provides the results from this survey. The AACC CEO Survey was sent to 960 public community college presidents.…
Reactive Power Compensating System.
Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.
1985-01-04
The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.
Backlash compensator mechanism
Chrislock, Jerry L.
1979-01-01
Mechanism which compensates for backlash error in a lead screw position indicator by decoupling the indicator shaft from the lead screw when reversing rotation. The position indicator then displays correct information regardless of the direction of rotation of the lead screw.
ERIC Educational Resources Information Center
Richwine, Jason; Biggs, Andrew; Mishel, Lawrence; Roy, Joydeep
2012-01-01
Over the past few years, as cash-strapped states and school districts have faced tough budget decisions, spending on teacher compensation has come under the microscope. The underlying question is whether, when you take everything into account, today's teachers are fairly paid, underpaid, or overpaid. In this forum, two pairs of respected…
The Radiation Magnetic Force (FmR)
NASA Astrophysics Data System (ADS)
Yousif, Mahmoud
2017-01-01
The detection of Circular Magnetic Field (CMF), associated with electrons movement, not incorporated in theoretical works; is introduced as elements of attraction and repulsion for magnetic force between two conductors carrying electric currents; it also created magnetic force between charged particles and magnetic field, or Lorentz force; CMF contain energy of Electromagnetic Radiation (EM-R); a relationship has been established between the magnetic part of the EM-R, and radiation force, showing the magnetic force as a frequency controlled entity, in which a Radiation Magnetic Force formula is derived, the force embedded EM-Wave, similar to Electromagnetic Radiation Energy given by Planck's formula; the force is accountable for electron removal from atom in the Photoelectric Effects, stabilizing orbital atoms, excitation and ionization atoms, initiating production of secondary EM-R in Compton Effect mechanism; the paper aimed at reviving the wave nature of EM-R, which could reflects in a better understanding of the microscopic-world.
Traces of Lorentz symmetry breaking in a hydrogen atom at ground state
NASA Astrophysics Data System (ADS)
Borges, L. H. C.; Barone, F. A.
2016-02-01
Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schrödinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector.
Time delay and Doppler tests of the Lorentz symmetry of gravity
Bailey, Quentin G.
2009-08-15
Modifications to the classic time-delay effect and Doppler shift in general relativity (GR) are studied in the context of the Lorentz-violating standard-model extension (SME). We derive the leading Lorentz-violating corrections to the time-delay and Doppler shift signals, for a light ray passing near a massive body. It is demonstrated that anisotropic coefficients for Lorentz violation control a time-dependent behavior of these signals that is qualitatively different from the conventional case in GR. Estimates of sensitivities to gravity-sector coefficients in the SME are given for current and future experiments, including the recent Cassini solar conjunction experiment.
The Federal Employees' Compensation Act.
ERIC Educational Resources Information Center
Nordlund, Willis J.
1991-01-01
The 1916 Federal Employees' Compensation Act is still the focal point around which the federal workers compensation program works today. The program has gone through many changes on its way to becoming a modern means of compensating workers for job-related injury, disease, and death. (Author)
Deferred Compensation Becomes More Common
ERIC Educational Resources Information Center
June, Audrey Williams
2006-01-01
A key part of the compensation package for some college and university presidents is money that they do not receive in their paychecks. Formally known as deferred compensation, such payments can take many forms, including supplemental retirement pay, severance pay, or even bonuses. With large institutions leading the way, deferred compensation has…
Wilson polynomials and the Lorentz transformation properties of the parity operator
Bender, Carl M.; Meisinger, Peter N.; Wang Qinghai
2005-05-01
The parity operator for a parity-symmetric quantum field theory transforms as an infinite sum of irreducible representations of the homogeneous Lorentz group. These representations are connected with Wilson polynomials.
Testing Lorentz invariance using an odd-parity asymmetric optical resonator
Baynes, Fred N.; Luiten, Andre N.; Tobar, Michael E.
2011-10-15
We present the first experimental test of Lorentz invariance using the frequency difference between counter-propagating modes in an asymmetric odd-parity optical resonator. This type of test is {approx}10{sup 4} more sensitive to odd-parity and isotropic (scalar) violations of Lorentz invariance than equivalent conventional even-parity experiments due to the asymmetry of the optical resonator. The disadvantages of odd-parity resonators have been negated by the use of counter-propagating modes, delivering a high level of immunity to environmental fluctuations. With a nonrotating experiment our result limits the isotropic Lorentz violating parameter {kappa}-tilde{sub tr} to 3.4{+-}6.2x10{sup -9}, the best reported constraint from direct measurements. Using this technique the bounds on odd-parity and scalar violations of Lorentz invariance can be improved by many orders of magnitude.
Two-pion exchange NN potential from Lorentz-invariant $\\chi$EFT
Higa, Renato; Robilotta, Manoel; da Rocha, Carlos A
2006-10-12
We outline the progress made in the past five years by the Sao Paulo group in the development of a two-pion exchange nucleon-nucleon potential within a Lorentz-invariant framework of (baryon) chiral perturbation theory.
Testing Lorentz Invariance with Laser-Cooled Cesium Atomic Frequency Standards
NASA Technical Reports Server (NTRS)
Klipstein, William M.
2004-01-01
This slide presentation reviews the Lorentz invariance testing during the proposed PARCS experiment. It includes information on the primary atomic reference clock in space (PARCS), cesium, laser cooling, and the vision for the future.
NASA Technical Reports Server (NTRS)
Mcfarland, Richard E.
1986-01-01
Computer-generated graphics in real-time helicopter simulation produces objectionable scene-presentation time delays. In the flight simulation laboratory at Ames Research Center, it has been determined that these delays have an adverse influence on pilot performance during aggressive tasks such as nap-of-the-earth (NOE) maneuvers. Using contemporary equipment, computer-generated image (CGI) time delays are an unavoidable consequence of the operations required for scene generation. However, providing that magnitide distortions at higher frequencies are tolerable, delay compensation is possible over a restricted frequency range. This range, assumed to have an upper limit of perhaps 10 or 15 rad/sec, conforms approximately to the bandwidth associated with helicopter handling qualities research. A compensation algorithm is introduced here and evaluated in terms of tradeoffs in frequency responses. The algorithm has a discrete basis and accommodates both a large, constant transport delay interval and a periodic delay interval, as associated with asynchronous operations.
Ground difference compensating system
Johnson, Kris W.; Akasam, Sivaprasad
2005-10-25
A method of ground level compensation includes measuring a voltage of at least one signal with respect to a primary ground potential and measuring, with respect to the primary ground potential, a voltage level associated with a secondary ground potential. A difference between the voltage level associated with the secondary ground potential and an expected value is calculated. The measured voltage of the at least one signal is adjusted by an amount corresponding to the calculated difference.
The Sidereal Time Variations of the Lorentz Force and Maximum Attainable Speed of Electrons
NASA Astrophysics Data System (ADS)
Nowak, Gabriel; Wojtsekhowski, Bogdan; Roblin, Yves; Schmookler, Barak
2016-09-01
The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab produces electrons that orbit through a known magnetic system. The electron beam's momentum can be determined through the radius of the beam's orbit. This project compares the beam orbit's radius while travelling in a transverse magnetic field with theoretical predictions from special relativity, which predict a constant beam orbit radius. Variations in the beam orbit's radius are found by comparing the beam's momentum entering and exiting a magnetic arc. Beam position monitors (BPMs) provide the information needed to calculate the beam momentum. Multiple BPM's are included in the analysis and fitted using the method of least squares to decrease statistical uncertainty. Preliminary results from data collected over a 24 hour period show that the relative momentum change was less than 10-4. Further study will be conducted including larger time spans and stricter cuts applied to the BPM data. The data from this analysis will be used in a larger experiment attempting to verify special relativity. While the project is not traditionally nuclear physics, it involves the same technology (the CEBAF accelerator) and the same methods (ROOT) as a nuclear physics experiment. DOE SULI Program.
Observation of flux-creep in direction opposite to the Lorentz force
NASA Astrophysics Data System (ADS)
Sawh, R.-P.; Weinstein, R.; Carpenter, K.; Parks, D.; Davey, K.
2017-04-01
The conclusion that free fluxoids move in the direction of \\mathop{{\\boldsymbol{F}}}\\limits \\rightharpoonup ={\\mathop{J}\\limits \\rightharpoonup }{{c}}× \\mathop{{\\boldsymbol{B}}}\\limits \\rightharpoonup is broadly accepted. For certain spatial distributions of flux in HTS bulks, this requires free fluxoids to collect at the center of the bulk. Here, we report experiments in which such spatial distributions are created by means of zero-field-cool partial magnetization of the bulk, and the temporal changes in flux are measured. We report that the direction of the flux creep is observed to be opposite to \\mathop{{\\boldsymbol{F}}}\\limits \\rightharpoonup ={\\mathop{J}\\limits \\rightharpoonup }{{c}}× \\mathop{{\\boldsymbol{B}}.}\\limits \\rightharpoonup
Joulean Heating and Lorentz Force Effects on Gaseous Detonation Flow Fields
1966-09-01
Massachusetts Institute of Technology (1964) Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Science at the...Massachusetts Institute of Technology September, 1966 Signature of Author . . . . Department of Mechanical Engineering September 12, 1966 Certified by Thesis...AND ADDRESS(ES) Massachusetts Institute of Technology ,77 Massachusetts Avenue,Cambridge,MA,02139 8. PERFORMING ORGANIZATION REPORT NUMBER 9
Lyapunov Exponents and Kolmogorov-Sinai Entropy for the Lorentz Gas at Low Densities
NASA Astrophysics Data System (ADS)
van Beijeren, Henk; Dorfman, J. R.
1995-05-01
The Lyapunov exponents and the Kolmogorov-Sinai (KS) entropy for a two-dimensional Lorentz gas at low densities are defined for general nonequilibrium states and calculated with the use of a Lorentz-Boltzmann type equation. In equilibrium the density dependence of these quantities, predicted by Krylov, is recovered and explicit expressions are obtained. The relationship between KS entropy, Lyapunov exponents, and diffusion coefficients, developed by Gaspard and Nicolis, is generalized to a wide class of nonequilibrium states.
New parametrization of lorentz transformations and tachyonic motion in special theory of relativity
Kapuscik, E.
2011-06-15
Assuming the existence of an invariant velocity a slightly generalized form of Lorentz transformations is derived. The group of these transformations has a simpler composition law than the group of standard Lorentz transformations has. It is shown that this new form allows the description of both subluminal and superluminal motions. It also allows to find all velocity-dependent tensors. In particular, the tachyonic momentum as a function of superluminal velocity is derived.
Radiatively induced Lorentz-violating operator of mass dimension five in QED
Mariz, T.
2011-02-15
The first higher derivative term of the photon sector of Lorentz-violating QED, with an operator of mass dimension d=5, is radiatively induced from the fermion sector, which contains a derivative term with the dimensionless coefficient g{sup {lambda}{mu}{nu}}. The calculation is performed perturbatively in the coefficient for Lorentz violation, and, due to the fact that the contributions are quadratically divergent, we adopt dimensional regularization.
Computer simulation of some dynamical properties of the Lorentz gas
NASA Astrophysics Data System (ADS)
Joslin, C. G.; Egelstaff, P. A.
1989-07-01
We carried out molecular dynamics simulations of a Lorentz gas, consisting of a lone hydrogen molecule moving in a sea of stationary argon atoms. A Lennard-Jones form was assumed for the H2-Ar potential. The calculations were performed at a reduced temperature K * = kT/ɛH 2-Ar = 4.64 and at reduced densities ρ *= ρ Arσ{Ar/3} in the range 0.074-0.414. The placement of Ar atoms was assumed to be random rather than dictated by equilibrium considerations. We followed the trajectories of many H2 molecules, each of which is assigned in turn a velocity given by the Maxwell-Boltzmann distribution at the temperature of the simulation. Solving the equations of motion classically, we obtained the translational part of the incoherent dynamic structure factor for the H2 molecule, S tr( q, ω). This was convoluted with the rotational structure factor S rot( q, ω) calculated assuming unhindered rotation to obtain the total structure factor S( q, ω). Our results agree well with experimental data on this function obtained by Egelstaff et al. At the highest density ( ρ *=0.414) we studied the dependence of S( q, ω) on system size (number of Ar atoms), number of H2 molecules for which trajectories are generated, and the length of time over which these trajectories are followed.
Dynamic-structure-factor measurements on a model Lorentz gas
NASA Astrophysics Data System (ADS)
Egelstaff, P. A.; Eder, O. J.; Glaser, W.; Polo, J.; Renker, B.; Soper, A. K.
1990-02-01
A model system for the Lorentz gas can be made [Eder, Chen, and Egelstaff, Proc. Phys. Soc. London 89, 833 (1966); McPherson and Egelstaff, Can. J. Phys. 58, 289 (1980)] by mixing small quantities of hydrogen with an argon host. For neutron-scattering experiments the large H-to-Ar cross section ratio (~200) makes the argon relatively invisible. Dynamic-structure-factor [S(Q,ω) for H2] measurements at room temperature have been made on this system using the IN4 spectrometer at the Institute Laue Langevin, Grenoble, France. Argon densities between 1.9 and 10.5 atoms/nm3 were used for 0.4
Effective photon mass by Super and Lorentz symmetry breaking
NASA Astrophysics Data System (ADS)
Bonetti, Luca; dos Santos Filho, Luís R.; Helayël-Neto, José A.; Spallicci, Alessandro D. A. M.
2017-01-01
In the context of Standard Model Extensions (SMEs), we analyse four general classes of Super Symmetry (SuSy) and Lorentz Symmetry (LoSy) breaking, leading to observable imprints at our energy scales. The photon dispersion relations show a non-Maxwellian behaviour for the CPT (Charge-Parity-Time reversal symmetry) odd and even sectors. The group velocities exhibit also a directional dependence with respect to the breaking background vector (odd CPT) or tensor (even CPT). In the former sector, the group velocity may decay following an inverse squared frequency behaviour. Thus, we extract a massive Carroll-Field-Jackiw photon term in the Lagrangian and show that the effective mass is proportional to the breaking vector and moderately dependent on the direction of observation. The breaking vector absolute value is estimated by ground measurements and leads to a photon mass upper limit of 10-19 eV or 2 ×10-55 kg, and thereby to a potentially measurable delay at low radio frequencies.
Completing Lorentz violating massive gravity at high energies
Blas, D.; Sibiryakov, S.
2015-03-15
Theories with massive gravitons are interesting for a variety of physical applications, ranging from cosmological phenomena to holographic modeling of condensed matter systems. To date, they have been formulated as effective field theories with a cutoff proportional to a positive power of the graviton mass m{sub g} and much smaller than that of the massless theory (M{sub P} ≈ 10{sup 19} GeV in the case of general relativity). In this paper, we present an ultraviolet completion for massive gravity valid up to a high energy scale independent of the graviton mass. The construction is based on the existence of a preferred time foliation combined with spontaneous condensation of vector fields. The perturbations of these fields are massive and below their mass, the theory reduces to a model of Lorentz violating massive gravity. The latter theory possesses instantaneous modes whose consistent quantization we discuss in detail. We briefly study some modifications to gravitational phenomenology at low-energies. The homogeneous cosmological solutions are the same as in the standard cosmology. The gravitational potential of point sources agrees with the Newtonian one at distances small with respect to m{sub g}{sup −1}. Interestingly, it becomes repulsive at larger distances.
A test of local Lorentz invariance with Compton scattering asymmetry
NASA Astrophysics Data System (ADS)
Mohanmurthy, Prajwal; Narayan, Amrendra; Dutta, Dipangkar
2016-11-01
We report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon-electron scattering. We used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall C at Jefferson Lab (JLab) to test for deviations from unity of the vacuum refractive index (n). For photon energies in the range of 9-46 MeV, we obtain a new limit of 1 - n < 1.4 × 10-8. In addition, the absence of sidereal variation over the six-month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance (LI) using Compton asymmetry. Within the minimal Standard Model extension (MSME) framework, our result yield limits on the photon and electron coefficients κ˜0+Y Z, cTX, κ˜0+ZX and cTY. Although these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of LI. Future parity-violating electron-scattering experiments at JLab will use higher energy electrons enabling better constraints.
Direct terrestrial test of Lorentz symmetry in electrodynamics to 10−18
Nagel, Moritz; Parker, Stephen R.; Kovalchuk, Evgeny V.; Stanwix, Paul L.; Hartnett, John G.; Ivanov, Eugene N.; Peters, Achim; Tobar, Michael E.
2015-01-01
Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson–Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δν/ν to 9.2±10.7 × 10−19 (95% confidence interval). This order of magnitude improvement over previous Michelson–Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry. PMID:26323989
Direct terrestrial test of Lorentz symmetry in electrodynamics to 10(-18).
Nagel, Moritz; Parker, Stephen R; Kovalchuk, Evgeny V; Stanwix, Paul L; Hartnett, John G; Ivanov, Eugene N; Peters, Achim; Tobar, Michael E
2015-09-01
Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson-Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δν/ν to 9.2±10.7 × 10(-19) (95% confidence interval). This order of magnitude improvement over previous Michelson-Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry.
Direct terrestrial test of Lorentz symmetry in electrodynamics to 10-18
NASA Astrophysics Data System (ADS)
Nagel, Moritz; Parker, Stephen R.; Kovalchuk, Evgeny V.; Stanwix, Paul L.; Hartnett, John G.; Ivanov, Eugene N.; Peters, Achim; Tobar, Michael E.
2015-09-01
Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson-Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δν/ν to 9.2+/-10.7 × 10-19 (95% confidence interval). This order of magnitude improvement over previous Michelson-Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...
Code of Federal Regulations, 2011 CFR
2011-07-01
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Code of Federal Regulations, 2014 CFR
2014-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...
Code of Federal Regulations, 2013 CFR
2013-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...
Code of Federal Regulations, 2010 CFR
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Compensation. 3.4 Section..., Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term...) Disability compensation. (1) Basic entitlement for a veteran exists if the veteran is disabled as the...
Conditions for Lorentz-invariant superluminal information transfer without signaling
NASA Astrophysics Data System (ADS)
Grössing, G.; Fussy, S.; Mesa Pascasio, J.; Schwabl, H.
2016-03-01
We understand emergent quantum mechanics in the sense that quantum mechanics describes processes of physical emergence relating an assumed sub-quantum physics to macroscopic boundary conditions. The latter can be shown to entail top-down causation, in addition to usual bottom-up scenarios. With this example it is demonstrated that definitions of “realism” in the literature are simply too restrictive. A prevailing manner to define realism in quantum mechanics is in terms of pre-determination independent of the measurement. With our counter-example, which actually is ubiquitous in emergent, or self-organizing, systems, we argue for realism without pre-determination. We refer to earlier results of our group showing how the guiding equation of the de Broglie-Bohm interpretation can be derived from a theory with classical ingredients only. Essentially, this corresponds to a “quantum mechanics without wave functions” in ordinary 3-space, albeit with nonlocal correlations. This, then, leads to the central question of how to deal with the nonlocality problem in a relativistic setting. We here show that a basic argument discussing the allegedly paradox time ordering of events in EPR-type two-particle experiments falls short of taking into account the contextuality of the experimental setup. Consequently, we then discuss under which circumstances (i.e. physical premises) superluminal information transfer (but not signaling) may be compatible with a Lorentz-invariant theory. Finally, we argue that the impossibility of superluminal signaling - despite the presence of superluminal information transfer - is not the result of some sort of conspiracy (á la “Nature likes to hide”), but the consequence of the impossibility to exactly reproduce in repeated experimental runs a state's preparation, or of the no-cloning theorem, respectively.
Direct measurement of Lorentz transformation with Doppler effects
NASA Astrophysics Data System (ADS)
Chen, Shao-Guang
, r is the unit vector from lamphouse point to counters. Or: L (0) L (pi) =L0 (1+(v/c)) L0 (1 - (v/c)) =L0 2 y2 =L2 Or: L ≡ [L(0)L(pi)]1/2 =L0 y , which y ≡ (1 - (v/c)2 )1/2 is just Fitzgerald-Lorentzian contraction-factor. Also, when a light-wave period p is defined as time unit, from Doppler's frequency-shift the count N with p of one period T of moving-clock is: T(q) = N(q) p = T0 /(1+(v/c) cos q) Or: T ≡ (T(0) T(pi))1/2 = T 0 /y , where T0 is the proper period when v = 0, which is just the moving-clock-slower effect. Let r from clock point to lamp-house ((v/c) symbol reverse), Doppler formula in the usual form is: f (q) = 1/T(q) = f0 (1 - (v/c) cos q). Therefore, Lorentz transformation is the square root average of positive and negative directions twice metrical results of Doppler's frequency-shift, which Doppler's once items ( positive and negative v/c ) are counteract only residual twice item (v/c)2 (relativity-factor). Then Lorentz transformation can be directly measured by Doppler's frequency-shift method. The half-life of moving mu-meson is statistical average of many particles, the usual explanation using relativity-factor y is correct. An airship moving simultaneously along contrary directions is impossible, which makes that the relativity-factor y and the twin-paradox are inexistent in the macroscopical movement. Thereby, in the navigations of airship or satellite only use the measurement of Doppler's frequency-shift but have no use for Lorentz transformation.
Transverse optical forces for manipulating nanoparticles
NASA Astrophysics Data System (ADS)
Zharov, Alexander A.; Zharov, Alexander A.; Shadrivov, Ilya V.; Zharova, Nina A.
2016-12-01
We study optical forces acting on a subwavelength particle with anisotropic polarizability and discover an optomechanical effect that resembles the Hall effect for electrons. While in the classical Hall effect the transverse Lorentz force and the transverse voltage appear due to the static magnetic field which induces the nondiagonal components of the electric conductivity tensor; in our case the imaginary parts of the nondiagonal elements of the polarizability tensor are responsible for the transverse scattering force. We calculate this force for the examples of the ellipsoidal plasmonic nanoparticles and the spherical particle with gyromagnetic properties, and show that the transverse force depends on the physical origin of the anisotropy of the polarizability, and on the electromagnetic wave structure around the particle. Moreover, this force primarily occurs in the inhomogeneous field only.
Current-induced forces: a simple derivation
NASA Astrophysics Data System (ADS)
Todorov, Tchavdar N.; Dundas, Daniel; Lü, Jing-Tao; Brandbyge, Mads; Hedegård, Per
2014-11-01
We revisit the problem of forces on atoms under current in nanoscale conductors. We derive and discuss the five principal kinds of force under steady-state conditions from a simple standpoint that—with the help of background literature—should be accessible to physics undergraduates. The discussion aims at combining methodology with an emphasis on the underlying physics through examples. We discuss and compare two forces present only under current—the non-conservative electron wind force and a Lorentz-like velocity-dependent force. It is shown that in metallic nanowires both display significant features at the wire surface, making it a candidate for the nucleation of current-driven structural transformations and failure. Finally we discuss the problem of force noise and the limitations of Ehrenfest dynamics.
Performance constraints and compensation for teleoperation with delay
NASA Technical Reports Server (NTRS)
Mclaughlin, J. S.; Staunton, B. D.
1989-01-01
A classical control perspective is used to characterize performance constraints and evaluate compensation techniques for teleoperation with delay. Use of control concepts such as open and closed loop performance, stability, and bandwidth yield insight to the delay problem. Teleoperator performance constraints are viewed as an open loop time delay lag and as a delay-induced closed loop bandwidth constraint. These constraints are illustrated with a simple analytical tracking example which is corroborated by a real time, 'man-in-the-loop' tracking experiment. The experiment also provides insight to those controller characteristics which are unique to a human operator. Predictive displays and feedforward commands are shown to provide open loop compensation for delay lag. Low pass filtering of telemetry or feedback signals is interpreted as closed loop compensation used to maintain a sufficiently low bandwidth for stability. A new closed loop compensation approach is proposed that uses a reactive (or force feedback) hand controller to restrict system bandwidth by impeding operator inputs.
NASA Astrophysics Data System (ADS)
Qi, Chenkun; Zhao, Xianchao; Gao, Feng; Ren, Anye; Hu, Yan
2016-11-01
The hardware-in-the-loop (HIL) contact simulation for flying objects in space is challenging due to the divergence caused by the time delay. In this study, a divergence compensation approach is proposed for the stiffness-varying discrete contact. The dynamic response delay of the motion simulator and the force measurement delay are considered. For the force measurement delay, a phase lead based force compensation approach is used. For the dynamic response delay of the motion simulator, a response error based force compensation approach is used, where the compensation force is obtained from the real-time identified contact stiffness and real-time measured position response error. The dynamic response model of the motion simulator is not required. The simulations and experiments show that the simulation divergence can be compensated effectively and satisfactorily by using the proposed approach.
State Initiatives To Increase Compensation for Child Care Workers.
ERIC Educational Resources Information Center
Twombly, Eric C.; Montilla, Maria D.; De Vita, Carol J.
Noting that wages for child care workers are among the lowest in the U.S. labor force and that generally caregivers are offered few employee benefits, this paper summarizes proposals and programs in the 50 states and the District of Columbia to raise child care worker compensation. The paper classifies state-level initiatives into two categories:…
Reviewing the Language Compensation Policy in the National Senior Certificate
ERIC Educational Resources Information Center
Taylor, Stephen
2014-01-01
The National Senior Certificate or "matric" examination is a key point of access to further education and the labour market in South Africa. Since 1999, matric candidates whose first language is not Afrikaans or English and are, therefore, forced to write in a second or third language have received a compensation of five per cent of…
Lorentz-Lorenz coefficient, critical point constants, and coexistence curve of 1,1-difluoroethylene.
Fameli, Nicola; Balzarini, David A
2005-11-01
We report measurements of the Lorentz-Lorenz coefficient density dependence L(rho), the critical temperature Tc, and the critical density rho c of the fluid 1,1-difluoroethylene H2C2F2. Lorentz-Lorenz coefficient data were obtained by measuring refractive index n, and density rho of the same fluid sample independently of one another. Accurate determination of the Lorentz-Lorenz coefficient is necessary for the transformation of refractive index data into density data from optics-based experiments on critical phenomena of fluid systems done with different apparatuses, with which independent measurement of n and rho is not possible. Measurements were made along the coexistence curve of the fluid and span the density range 0.01 to 0.80 g cm(-3). The Lorentz-Lorenz coefficient results show a stronger density dependence along the coexistence curve than previously observed in other fluids, with a monotonic decrease from a density of about onward, and an overall variation of about 2.5% in the density range studied. No anomaly in the Lorentz-Lorenz function was observed near the critical density. The critical temperature is measured at Tc=(302.964+/-0.002) K (29.814 degrees C) and the measured critical density is rho c=(0.4195+/-0.0018) g cm(-3).
Beam propagation factors and kurtosis parameters of a Lorentz-Gauss vortex beam.
Zhou, Guoquan
2014-06-01
Based on the second-order and the higher-order moments, analytical expressions for the beam propagation factors of a Lorentz-Gauss vortex beam with l=1 have been derived, and analytical propagation expressions for the kurtosis parameters of a Lorentz-Gauss vortex beam with l=1 through a paraxial and real ABCD optical system have also been presented. The M² factor is determined by the parameters a and b and decreases with increasing the parameter a or b. The M² factor is validated to be larger than 2. The kurtosis parameters depend on the diffraction-free ranges of the Lorentz part, the parameters a and b, and the ratio A/B. The kurtosis parameters of a Lorentz-Gauss vortex beam propagating in free space are demonstrated in different reference planes. In the far field, the kurtosis parameter K decreases with increasing one of the parameters a and b. Upon propagation, the kurtosis parameter K first decreases, then increases, and finally tends to a saturated value. In any case, the kurtosis parameter K is larger than 2. This research is beneficial to optical trapping, guiding, and manipulation of microscopic particles and atoms using Lorentz-Gauss vortex beams.
Nonparaxial propagation of Lorentz-Gauss beams in uniaxial crystal orthogonal to the optical axis.
Wang, Xun; Liu, Zhirong; Zhao, Daomu
2014-04-01
Analytical expressions for the three components of nonparaxial propagation of a polarized Lorentz-Gauss beam in uniaxial crystal orthogonal to the optical axis are derived and used to investigate its propagation properties in uniaxial crystal. The influences of the initial beam parameters and the parameters of the uniaxial crystal on the evolution of the beam-intensity distribution in the uniaxial crystal are examined in detail. Results show that the statistical properties of a nonparaxial Lorentz-Gauss beam in a uniaxial crystal orthogonal to the optical axis are closely determined by the initial beam's parameters and the parameters of the crystal: the beam waist sizes-w(0), w(0x), and w(0y)-not only affect the size and shape of the beam profile in uniaxial crystal but also determine the nonparaxial effect of a Lorentz-Gauss beam; the beam profile of a Lorentz-Gauss beam in uniaxial crystal is elongated in the x or y direction, which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index; with increasing deviation of the ratio from unity, the extension of the beam profile augments. The results indicate that uniaxial crystal provides an effective and convenient method for modulating the Lorentz-Gauss beams. Our results may be valuable in some fields, such as optical trapping and nonlinear optics, where a light beam with a special profile and polarization is required.
White matter shifts in MRI: Rehabilitating the Lorentz sphere in magnetic resonance
NASA Astrophysics Data System (ADS)
Barbara, Thomas M.
2016-09-01
A thorough exposition and analysis of the role of the Lorentz sphere in magnetic resonance is presented from the fundamental standpoint of macroscopic magnetostatics. The analysis will be useful to those interested in understanding susceptibility and chemical shift contributions to frequency shifts in magnetic resonance. Though the topic is mature, recent research on white matter shifts in the brain promotes the notion of replacing the Lorentz sphere with a generalized Lorentzian cylinder, and has put into question the long standing spherical approach when elongated structures are present. The cavity shape issue can be resolved by applying Helmholtz's theorem, which can be expressed in a differential and an integral formulation. The general validity of the Lorentz sphere for any situation is confirmed. Furthermore, a clear exposition of the "generalized approach" is offered, using the language of Lorentz's theory. With the rehabilitation of the Lorentz sphere settled, one must consider alternative contributions to white matter shifts and a likely candidate is the effect of molecular environment on chemical shifts.
Cosmological constraints on deviations from Lorentz invariance in gravity and dark matter
Audren, B.; Lesgourgues, J.; Sibiryakov, S.; Ivanov, M.M. E-mail: diego.blas@cern.ch E-mail: Julien.Lesgourgues@cern.ch
2015-03-01
We consider a scenario where local Lorentz invariance is violated by the existence of a preferred time direction at every space-time point. This scenario can arise in the context of quantum gravity and its description at low energies contains a unit time-like vector field which parameterizes the preferred direction. The particle physics tests of Lorentz invariance preclude a direct coupling of this vector to the fields of the Standard Model, but do not bear implications for dark matter. We discuss how the presence of this vector and its possible coupling to dark matter affect the evolution of the Universe. At the level of homogeneous cosmology the only effect of Lorentz invariance violation is a rescaling of the expansion rate. The physics is richer at the level of perturbations. We identify three effects crucial for observations: the rescaling of the matter contribution to the Poisson equation, the appearance of an extra contribution to the anisotropic stress and the scale-dependent enhancement of dark matter clustering. These effects result in distinctive features in the power spectra of the CMB and density fluctuations. Making use of the data from Planck and WiggleZ we obtain the most stringent cosmological constraints to date on departures from Lorentz symmetry. Our analysis provides the first direct bounds on deviations from Lorentz invariance in the dark matter sector.
NASA Astrophysics Data System (ADS)
Schreck, M.
2015-12-01
In the current article, the classical analog of the minimal photon sector in the Lorentz-violating Standard-Model extension (SME) is investigated. The analysis is based on describing a photon classically by a geometric ray that satisfies the eikonal equation. The action principle, which leads to the eikonal equation in conventional optics, is demonstrated to work in most (but not all) Lorentz-violating cases as well. Furthermore it is found that the integrands of the action functional correspond to Finsler structures. Based on these results, Lorentz-violating light rays in a weak gravitational background are treated through the use of the minimal-coupling principle. This allows for obtaining sensitivities on Lorentz violation in the photon sector by measurements of light bending at massive bodies such as the Sun. The computations are carried out for the currently running ESA mission GAIA and the planned NASA/ESA mission LATOR. Finally, a range of aspects of explicit Lorentz violation for photons is discussed in the Finsler setting.
Analytic electrical-conductivity tensor of a nondegenerate Lorentz plasma
NASA Astrophysics Data System (ADS)
Stygar, W. A.; Gerdin, G. A.; Fehl, D. L.
2002-10-01
We have developed explicit quantum-mechanical expressions for the conductivity and resistivity tensors of a Lorentz plasma in a magnetic field. The expressions are based on a solution to the Boltzmann equation that is exact when the electric field is weak, the electron-Fermi-degeneracy parameter Θ>>1, and the electron-ion Coulomb-coupling parameter Γ/Z<<1. (Γ is the ion-ion coupling parameter and Z is the ion charge state.) Assuming a screened 1/r electron-ion scattering potential, we calculate the Coulomb logarithm in the second Born approximation. The ratio of the term obtained in the second approximation to that obtained in the first is used to define the parameter regime over which the calculation is valid. We find that the accuracy of the approximation is determined by Γ/Z and not simply the temperature, and that a quantum-mechanical description can be required at temperatures orders of magnitude less than assumed by Spitzer [Physics of Fully Ionized Gases (Wiley, New York, 1962)]. When the magnetic field B=0, the conductivity is identical to the Spitzer result except the Coulomb logarithm ln Λ1=(ln χ1- 1/2)+[(2Ze2/λmev2e1)(ln χ1-ln 24/3)], where χ1≡2meve1λ/ħ, me is the electron mass, ve1≡(7kBT/me)1/2, kB is the Boltzmann constant, T is the temperature, λ is the screening length, ħ is Planck's constant divided by 2π, and e is the absolute value of the electron charge. When the plasma Debye length λD is greater than the ion-sphere radius a, we assume λ=λD otherwise we set λ=a. The B=0 conductivity is consistent with measurements when Z>~1, Θ>~2, and Γ/Z<~1, and in this parameter regime appears to be more accurate than previous analytic models. The minimum value of ln Λ1 when Z>=1, Θ>=2, and Γ/Z<=1 is 1.9. The expression obtained for the resistivity tensor (B≠0) predicts that η⊥/η∥ (where η⊥ and η∥ are the resistivities perpendicular and parallel to the magnetic field) can be as much as 40% less than previous analytic
Temperature compensated photovoltaic array
Mosher, Dan Michael
1997-11-18
A temperature compensated photovoltaic module (20) comprised of a series of solar cells (22) having a thermally activated switch (24) connected in parallel with several of the cells (22). The photovoltaic module (20) is adapted to charge conventional batteries having a temperature coefficient (TC) differing from the temperature coefficient (TC) of the module (20). The calibration temperatures of the switches (24) are chosen whereby the colder the ambient temperature for the module (20), the more switches that are on and form a closed circuit to short the associated solar cells (22). By shorting some of the solar cells (22) as the ambient temperature decreases, the battery being charged by the module (20) is not excessively overcharged at lower temperatures. PV module (20) is an integrated solution that is reliable and inexpensive.
Temperature compensated photovoltaic array
Mosher, D.M.
1997-11-18
A temperature compensated photovoltaic module comprises a series of solar cells having a thermally activated switch connected in parallel with several of the cells. The photovoltaic module is adapted to charge conventional batteries having a temperature coefficient differing from the temperature coefficient of the module. The calibration temperatures of the switches are chosen whereby the colder the ambient temperature for the module, the more switches that are on and form a closed circuit to short the associated solar cells. By shorting some of the solar cells as the ambient temperature decreases, the battery being charged by the module is not excessively overcharged at lower temperatures. PV module is an integrated solution that is reliable and inexpensive. 2 figs.
Pneumatic load compensating or controlling system
NASA Technical Reports Server (NTRS)
Rogers, J. R. (Inventor)
1975-01-01
A pneumatic load compensating or controlling system for restraining a load with a predetermined force or applying a predetermined force to the load is described; it includes a source of pressurized air, a one-way pneumatic actuator operatively connected to a load, and a fluid conduit fluidically connecting the actuator with the source of pressurized air. The actuator is of the piston and cylinder type, and the end of the fluid conduit is connected to the upper or lower portion of the cylinder whereby the actuator alternatively and selectively restrains the load with a predetermined force or apply a predetermined force to the load. Pressure regulators are included within the system for variably selectively adjusting the pressurized fluid to predetermined values as desired or required; a pressure amplifier is included within the system for multiplying the pressurized values so as to achieve greater load forces. An accumulator is incorporated within the system as a failsafe operating mechanism, and visual and aural alarm devices, operatively associated with pressure detecting apparatus, readily indicate the proper or improper functioning of the system.
NASA Astrophysics Data System (ADS)
Moggia, Elsa; Chiabrera, Alessandro; Bianco, Bruno
1997-11-01
The statistical properties of the solution of the Langevin-Lorentz equation are analyzed by means of the Fokker-Planck approach. The equation describes the dynamics of an ion that is attracted by a central field and is interacting with a time-varying magnetic field and with the thermal bath. If the endogenous force is assumed to be elastic, then a closed-form expression for the probability density of the process can be obtained, in the case of constant magnetic exposure and, for the time-varying case, at least asymptotically. In the general case, a numerical integration of the resulting set of differential equations with periodically time-varying coefficients has been implemented. A framework for studying the possible effects of low-frequency, low-intensity electromagnetic fields on biological systems has been developed on the basis of the equation. The model assumes that an exogenous electromagnetic field may affect the binding of a messenger attracted by the endogenous force field of its receptor protein. The results are applicable to the analysis of experiments, e.g., exposing a Petri dish, containing a biological sample, to a periodically time-varying magnetic field generated by a pair of Helmholtz coils, most widely used in the scientific literature. The proposed model provides a theoretical mean for evaluating the biological effectiveness of low-frequency, low-intensity electromagnetic exposure.
Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube
IceCube; etal, Abbasi, R,
2010-11-11
A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillationmodels, derivable from extensions to the Standard Model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. Adiscrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Due to the unique high energy reach of IceCube, it was possible to improveconstraints on certain Lorentz-violating oscillations by three orders of magnitude with respect to limits set by other experiments.
Low-energy phenomenology of scalarless standard-model extensions with high-energy Lorentz violation
Anselmi, Damiano; Ciuffoli, Emilio
2011-03-01
We consider renormalizable standard model extensions that violate Lorentz symmetry at high energies, but preserve CPT, and do not contain elementary scalar fields. A Nambu-Jona-Lasinio mechanism gives masses to fermions and gauge bosons and generates composite Higgs fields at low energies. We study the effective potential at the leading order of the large-N{sub c} expansion, prove that there exists a broken phase, and study the phase space. In general, the minimum may break invariance under boosts, rotations, and CPT, but we give evidence that there exists a Lorentz invariant phase. We study the spectrum of composite bosons and the low-energy theory in the Lorentz phase. Our approach predicts relations among the parameters of the low-energy theory. We find that such relations are compatible with the experimental data within theoretical errors. We also study the mixing among generations, the emergence of the CKM matrix, and neutrino oscillations.
Vacuum Cherenkov radiation in quantum electrodynamics with high-energy Lorentz violation
Anselmi, Damiano; Taiuti, Martina
2011-03-01
We study phenomena predicted by a renormalizable, CPT invariant extension of the standard model that contains higher-dimensional operators and violates Lorentz symmetry explicitly at energies greater than some scale {Lambda}{sub L}. In particular, we consider the Cherenkov radiation in vacuo. In a rather general class of dispersion relations, there exists an energy threshold above which radiation is emitted. The threshold is enhanced in composite particles by a sort of kinematic screening mechanism. We study the energy loss and compare the predictions of our model with known experimental bounds on Lorentz violating parameters and observations of ultrahigh-energy cosmic rays. We argue that the scale of Lorentz violation {Lambda}{sub L} (with preserved CPT invariance) can be smaller than the Planck scale, actually as small as 10{sup 14}-10{sup 15} GeV. Our model also predicts the Cherenkov radiation of neutral particles.
An extension of the concept of inertial frame and of Lorentz transformation.
Kerner, E H
1976-05-01
It is shown how particular kinds of fractional-linear (or projective) transformations generalize the notion of inertial frame in that they ensure that free-particle motion goes over into free-particle motion. A ten-parameter group of such transformations is produced which generalize Lorentz transformations, and which involve besides c (velocity of light) a new fundamental length b; they encompass the ordinary Lorentz group in the limit that b becomes infinite. These extended Lorentz transformations are most simply understood as a type of rotation in the space of homogeneous coordinates, a rotation that unifies 3-space rotations, frame-shifts to moving frames, and space- as well as time-translations. The structure of the invariant differential line element and of the wave operator that generalize those of special relativity are discussed, and implications for the possible revision of usual physical statements are pointed out.
Lifshitz scaling to Lorentz-violating high derivative operator and gamma-ray bursts
NASA Astrophysics Data System (ADS)
Passos, E.; Abreu, E. M. C.; Anacleto, M. A.; Brito, F. A.; Wotzasek, C.; Zarro, C. A. D.
2016-04-01
In this work, we use a Hořava-Lifshitz scaling to rewrite a Lorentz-violating higher-order derivative electrodynamics controlled by a background 4-vector nμ . The photon propagator is obtained, and we analyze the dispersion relation, and the observational results of gamma-ray burst (GRB) experiments are used. The limits of the critical exponent are discussed in light of the GRB data, and the physical implications are compared with the current GRB-Lorentz-invariance-violation literature. We show that the bound for the Lorentz-violating coupling for dimension-6 operators, obtained from a Hořava-Lifshitz scaling, is 8 orders of magnitude better than the result found without considering a Hořava-Lifshitz scaling and also that this bound is near to 1, which is expected to be relevant phenomenologically.
Battat, James B. R.; Chandler, John F.; Stubbs, Christopher W.
2007-12-14
We present constraints on violations of Lorentz invariance based on archival lunar laser-ranging (LLR) data. LLR measures the Earth-Moon separation by timing the round-trip travel of light between the two bodies and is currently accurate to the equivalent of a few centimeters (parts in 10{sup 11} of the total distance). By analyzing this LLR data under the standard-model extension (SME) framework, we derived six observational constraints on dimensionless SME parameters that describe potential Lorentz violation. We found no evidence for Lorentz violation at the 10{sup -6} to 10{sup -11} level in these parameters. This work constitutes the first LLR constraints on SME parameters.
Battat, James B R; Chandler, John F; Stubbs, Christopher W
2007-12-14
We present constraints on violations of Lorentz invariance based on archival lunar laser-ranging (LLR) data. LLR measures the Earth-Moon separation by timing the round-trip travel of light between the two bodies and is currently accurate to the equivalent of a few centimeters (parts in 10(11) of the total distance). By analyzing this LLR data under the standard-model extension (SME) framework, we derived six observational constraints on dimensionless SME parameters that describe potential Lorentz violation. We found no evidence for Lorentz violation at the 10(-6) to 10(-11) level in these parameters. This work constitutes the first LLR constraints on SME parameters.
The origins of length contraction: I. The FitzGerald-Lorentz deformation hypothesis
NASA Astrophysics Data System (ADS)
Brown, Harvey R.
2001-10-01
"Can there be some point in the theory of Mr. Michelson's experiment which has yet been overlooked?" H. A. Lorentz, letter to Lord Rayleigh, August 1892. One of the widespread confusions concerning the history of the 1887 Michelson-Morley experiment has to do with the initial explanation of this celebrated null result due independently to FitzGerald and Lorentz. In neither case was a strict, longitudinal length contraction hypothesis invoked, as is commonly supposed. Lorentz postulated, particularly in 1895, any one of a certain family of possible deformation effects for rigid bodies in motion, including purely transverse alteration, and expansion as well as contraction; FitzGerald may well have had the same family in mind. A careful analysis of the Michelson-Morley experiment (which reveals a number of serious inadequacies in many textbook treatments) indeed shows that strict contraction is not required.
High Energy Astrophysics Tests of Lorentz Invariance and Quantum Gravity Models
NASA Technical Reports Server (NTRS)
Stecker, Floyd W.
2011-01-01
High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10-35 m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations ofthe spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV at a proton Lorentz factor of -2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future.
Gamma-Ray, Cosmic Ray and Neutrino Tests of Lorentz Invariance and Quantum Gravity Models
NASA Technical Reports Server (NTRS)
Stecker, Floyd
2011-01-01
High-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10(exp -35) m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations of the spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV of at a proton Lorentz factor of approximately 2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future.
The CTA sensitivity to Lorentz-violating effects on the gamma-ray horizon
Fairbairn, M.; Ellis, J.; Nilsson, A.; Hinton, J.; White, R. E-mail: atf10ani@student.lu.se E-mail: jah85@leicester.ac.uk
2014-06-01
The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process γ+γ→e{sup +}+e{sup −} is altered and the cross section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the gamma-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints.
The CTA sensitivity to Lorentz-violating effects on the gamma-ray horizon
NASA Astrophysics Data System (ADS)
Fairbairn, M.; Nilsson, A.; Ellis, J.; Hinton, J.; White, R.
2014-06-01
The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process γ+γ→e++e- is altered and the cross section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the gamma-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints.
Influence of Lorentz-violating terms on a two-level system
Ferreira, Manoel M. Jr.; Gomes, Adalto R.; Lopes, Rafael C. C.
2007-11-15
The influence of Lorentz- and CPT-violating terms of the extended standard model on a semiclassical two-level system is analyzed. It is shown that the Lorentz-violating background (when coupled with the fermion sector in a vector way) is able to induce modifications on the Rabi oscillation pattern, promoting sensitive modulations on the usual oscillations. As for the term involving the coefficient coupled in an axial vector way, it brings about oscillations both on energy states and on the spin states (implied by the background). It is also seen that such backgrounds are able to yield state oscillations even in the absence of the electromagnetic field. The foreseen effects are used to establish upper bounds on the Lorentz-violating coefficients.
A Search for Lorentz-Violation in Double Beta Decay with EXO-200
NASA Astrophysics Data System (ADS)
Johnson, Tessa; EXO-200 Collaboration
2015-10-01
The Standard-Model Extension (SME) framework assumes Lorentz-violation at the Planck scale, a result of certain theories uniting quantum mechanics to General Relativity. Lorentz-violating operators are added to the current Standard Model, potentially producing effects that could be observed on a macroscopic scale, for instance altering the standard spectrum of double beta decay. The EXO-200 experiment uses 175 kg of enriched liquid xenon to search for neutrinoless double beta decay in 136Xe, and the low background and high precision of the experiment create a good platform to search for other phenomena in double beta decay. The results of a search for deviations to the two-neutrino double beta decay spectrum of 136Xe that would indicate neutrino coupling to a Lorentz-violating operator in the SME are presented.
An extension of the concept of inertial frame and of Lorentz transformation*
Kerner, Edward H.
1976-01-01
It is shown how particular kinds of fractional-linear (or projective) transformations generalize the notion of inertial frame in that they ensure that free-particle motion goes over into free-particle motion. A ten-parameter group of such transformations is produced which generalize Lorentz transformations, and which involve besides c (velocity of light) a new fundamental length b; they encompass the ordinary Lorentz group in the limit that b becomes infinite. These extended Lorentz transformations are most simply understood as a type of rotation in the space of homogeneous coordinates, a rotation that unifies 3-space rotations, frame-shifts to moving frames, and space- as well as time-translations. The structure of the invariant differential line element and of the wave operator that generalize those of special relativity are discussed, and implications for the possible revision of usual physical statements are pointed out. PMID:16592318
Alternative Teacher Compensation: A Primer
ERIC Educational Resources Information Center
Koppich, Julia E.; Rigby, Jessica
2009-01-01
This policy primer is designed to provide base-line information about new forms of teacher pay that are emerging around the country, to support the local conversations and negotiations that will lead to the development of innovative compensation systems. It identifies reasons why teacher compensation is high on local, state, and federal policy…
Compensation: The Impact of Policy.
ERIC Educational Resources Information Center
Morrell, Louis R.
1994-01-01
Complexity of employee compensation policy is examined as it applies to colleges and universities. It is argued that sound compensation policy helps the institution attract and retain qualified, skilled employees. New approaches that shift the focus from job to employee are outlined, and their implications for institutions of higher education are…
Workers' compensation law: an overview.
Yorker, B
1994-09-01
1. The workers' compensation system provides benefits to workers who are injured or made ill in the course of employment or their dependents regardless of fault. 2. The current workers' compensation laws benefit both the employer and the employee; however, workers' compensation is an exclusive remedy which bars recovery through a negligence lawsuit. 3. Workers' compensation regulations interact with other federal statutes such as the Americans With Disabilities Act and the Family Medical Leave Act. 4. Workers' compensation covers occupational injuries and occupational diseases, which may include cumulative trauma and mental stress claims. Nurses may be instrumental in evaluating and planning for an injured employee's return to work and occasionally in detecting fraudulent claims.
Test of Lorentz Invariance with a RB-21NE Comagnetometer at the South Pole
NASA Astrophysics Data System (ADS)
Smiciklas, M. A.; Romalis, M. V.
2014-01-01
Atomic spin comagnetometers are among the most sensitive devices for testing Lorentz symmetry of fermions. In Princeton, we have used our rotating comagnetometer to set the most stringent limits on CPT-odd and CPT-even Lorentz violating effects in neutrons. However, gyroscopic pickup of the Earth's rotation represents a significant systematic effect limiting sensitivity. To suppress this systematic, we have installed a Rb-21Ne comagnetometer at the Amundsen-Scott South Pole Station with data collection being performed over the course of the austral winter.
Transport coefficients in Lorentz plasmas with the power-law kappa-distribution
Jiulin, Du
2013-09-15
Transport coefficients in Lorentz plasma with the power-law κ-distribution are studied by means of using the transport equation and macroscopic laws of Lorentz plasma without magnetic field. Expressions of electric conductivity, thermoelectric coefficient, and thermal conductivity for the power-law κ-distribution are accurately derived. It is shown that these transport coefficients are significantly modified by the κ-parameter, and in the limit of the parameter κ→∞ they are reduced to the standard forms for a Maxwellian distribution.
Ultra-large distance modification of gravity from Lorentz symmetry breaking at the Planck scale
NASA Astrophysics Data System (ADS)
Gorbunov, Dmitry S.; Sibiryakov, Sergei M.
2005-09-01
We present an extension of the Randall-Sundrum model in which, due to spontaneous Lorentz symmetry breaking, graviton mixes with bulk vector fields and becomes quasilocalized. The masses of KK modes comprising the four-dimensional graviton are naturally exponentially small. This allows to push the Lorentz breaking scale to as high as a few tenth of the Planck mass. The model does not contain ghosts or tachyons and does not exhibit the van Dam-Veltman-Zakharov discontinuity. The gravitational attraction between static point masses becomes gradually weaker with increasing of separation and gets replaced by repulsion (antigravity) at exponentially large distances.
NASA Astrophysics Data System (ADS)
Sakharov, Alexander; Ellis, John; Harries, Nicholas; Meregaglia, Anselmo; Rubbia, André
2009-06-01
It has been suggested that the interactions of energetic particles with the foamy structure of space-time thought to be generated by quantum-gravitational (QG) effects might violate Lorentz invariance, so that they do not propagate at a universal speed of light. We consider the limits that may be set on a linear or quadratic violation of Lorentz invariance in the propagation of energetic neutrinos, v/c = [1 ± (E/MvQG1)] or [1 ± (E/MvQG2)2], using data from supernova explosions and the OPERA long-baseline neutrino experiment.
Laboratory-based limits on the Carroll-Field-Jackiw Lorentz-violating electrodynamics
NASA Astrophysics Data System (ADS)
Gomes, Y. M. P.; Malta, P. C.
2016-07-01
The C P T -odd and Lorentz-violating Carroll-Field-Jackiw (CFJ) modification of electrodynamics is discussed, and we study its effects on the energy spectrum of hydrogen, as well as in the generation of a momentum-dependent electric dipole moment for charged leptons. We also briefly comment on the possibility of the detection of Lorentz violation in measurements of vacuum birefringence in resonant cavities. The bounds found are based on local laboratory experimental limits and are not competitive with the ones coming from astrophysical considerations.
A Search for Lorentz Invariance and CPT Violation with the MINOS Far Detector
Adamson, P.; Auty, D.J.; Ayres, D.S.; Backhouse, C.; Barr, G.; Barrett, W.L.; Bishai, M.; Blake, A.; Bock, G.J.; Boehnlein, D.J.; Bogert, D.; /Fermilab /Indiana U.
2010-07-01
We searched for a sidereal modulation in the MINOS far detector neutrino rate. Such a signal would be a consequence of Lorentz and CPT violation as described by the Standard-Model Extension framework. It also would be the first detection of a perturbative effect to conventional neutrino mass oscillations. We found no evidence for this sidereal signature and the upper limits placed on the magnitudes of the Lorentz and CPT violating coefficients describing the theory are an improvement by factors of 20-510 over the current best limits found using the MINOS near detector.
Axial force imparted by a current-free magnetically expanding plasma
Takahashi, Kazunori; Lafleur, Trevor; Charles, Christine; Alexander, Peter; Boswell, Rod W.
2012-08-15
The axial force imparted from a magnetically expanding, current-free, radiofrequency plasma is directly measured. For an argon gas flow rate of 25 sccm and an effective rf input power of {approx}800W, a maximum force of {approx}6mN is obtained; {approx}3mN of which is transmitted via the expanding magnetic field. The measured forces are reasonably compared with a simple fluid model associated with the measured electron pressure. The model suggests that the total force is the sum of an electron pressure inside the source and a Lorentz force due to the electron diamagnetic drift current and the applied radial magnetic field. It is shown that the Lorentz force is greatest near the magnetic nozzle surface where the radial pressure gradient is largest.
A century of miners' compensation in South Africa.
Ehrlich, Rodney
2012-06-01
The year 2011 marked the centenary of compensation legislation for miners' lung disease in South Africa. This commentary aims to demonstrate that the current compensation system does not serve its intended beneficiaries, particularly the large population of former gold miners affected by high rates of silicosis and tuberculosis. The system has a complex legislative history, reflecting contending political, and economic forces, and characterized by racial discrimination. The financial basis of the system is currently in crisis owing to historical underfunding and failure to take into account the mounting burden of disease among black former miners. The real value of compensation awards fell sharply between 1973 and 1993, only partly recovering in recent years. Barriers to claiming benefits, particularly by black former miners who know little about the process, have been extensively documented. Integration of miners' compensation into general workers' compensation has been mooted since the 1980s but has stalled, owing to the high cost of closing the gap between the mostly inferior financial benefits under the mining legislation and those available under workers' compensation legislation. A recent constitutional court decision has opened the way for unprecedented civil litigation against the gold mining industry for silicosis, adding to the pressure for reform. A number of changes are called for: harmonization of financial benefits with retention of certain of the special arrangements for miner claims, a regional cross-border system of medical examination points for former miners, education of miners about the system, and some degree of privatization of claims processing.
[Vestibular compensation studies]. [Vestibular Compensation and Morphological Studies
NASA Technical Reports Server (NTRS)
Perachio, Adrian A. (Principal Investigator)
1996-01-01
The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging.
NASA Astrophysics Data System (ADS)
Ebner, Dieter W.
1991-11-01
A Lorentz-invariant model of vacuum is given in the form of a 7-dimensional manifold endowed with a statistical metrical tensor. Certain scalar fields on this manifold behave then as spinor fields when viewed from their space-time projection. This paper generalizes previous work fromSO(3)-covariance to Lorentz-covariance.
Reserve Compensation System Study
1978-06-30
Project Readiness coinci- dental with the development of the RCSS data reports. The Army Guard, the Army Reserve, and the Marine Corps Reserve provided...Management Analysis, and Dental . iary. Both authorized and actual strengths of the tir National Guard have risen since FY 70. Actual ANG accession...Information, and Dental . AIR FORCE RESERVE EKLIS7ED STRENGTH SNORTAGES* SELECTED CAREER MNAGEflENT FIELDS CAREER NANAGEflENT FIELD REO INV SHORTAGES
Temperature Compensated Piezoelectric Materials
1975-07-15
Barsch, et al Pennsylvania State University Prepared fo •: Air Force Cambridge Research Laboratories 15 July 1975 DISTRIBUTED BY: KUri National...time and for the resonance frequency, respectively, are shown as a function of rotation angle. The plots in Fig. 4 are qualitatively very similar to...the corresponding plots for a-quartz (19). The resonance frequency passes through a maximum at -60°, and a minimum at 29°. The rotation angles
Weldon, William F.; Driga, Mircea D.; Woodson, Herbert H.
1980-01-01
This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.
NASA Astrophysics Data System (ADS)
Setare, M. R.; Adami, H.
2016-01-01
In the first order formalism of gravity theories, there are some theories which are not Lorentz-diffeomorphism covariant. In the framework of such theories we cannot apply the method of conserved charge calculation used in Lorentz-diffeomorphism covariant theories. In this paper we firstly introduce the total variation of a quantity due to an infinitesimal Lorentz-diffeomorphism transformation. Secondly, in order to obtain the conserved charges of Lorentz-diffeomorphism non-covariant theories, we extend the Tachikawa method [1]. This extension includes not only Lorentz gauge transformation but also the diffeomorphism. We apply this method to the Chern-Simons-like theories of gravity (CSLTG) and obtain a general formula for the entropy of black holes in those theories. Finally, some examples on CSLTG are provided and the entropy of the BTZ black hole is calculated in the context of the examples.
Force Limited Vibration Testing
NASA Technical Reports Server (NTRS)
Scharton, Terry; Chang, Kurng Y.
2005-01-01
This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test
An operational approach to spacetime symmetries: Lorentz transformations from quantum communication
NASA Astrophysics Data System (ADS)
Höhn, Philipp A.; Müller, Markus P.
2016-06-01
In most approaches to fundamental physics, spacetime symmetries are postulated a priori and then explicitly implemented in the theory. This includes Lorentz covariance in quantum field theory and diffeomorphism invariance in quantum gravity, which are seen as fundamental principles to which the final theory has to be adjusted. In this paper, we suggest, within a much simpler setting, that this kind of reasoning can actually be reversed, by taking an operational approach inspired by quantum information theory. We consider observers in distinct laboratories, with local physics described by the laws of abstract quantum theory, and without presupposing a particular spacetime structure. We ask what information-theoretic effort the observers have to spend to synchronize their descriptions of local physics. If there are ‘enough’ observables that can be measured universally on several different quantum systems, we show that the observers’ descriptions are related by an element of the orthochronous Lorentz group {{{O}}}+(3,1), together with a global scaling factor. Not only does this operational approach predict the Lorentz transformations, but it also accurately describes the behavior of relativistic Stern-Gerlach devices in the WKB approximation, and it correctly predicts that quantum systems carry Lorentz group representations of different spin. This result thus hints at a novel information-theoretic perspective on spacetime.
The Pólya-Szegö Principle and the Anisotropic Convex Lorentz-Sobolev Inequality
Liu, Shuai; He, Binwu
2014-01-01
An anisotropic convex Lorentz-Sobolev inequality is established, which extends Ludwig, Xiao, and Zhang's result to any norm from Euclidean norm, and the geometric analogue of this inequality is given. In addition, it implies that the (anisotropic) Pólya-Szegö principle is shown. PMID:25136698
Spectra of Lorentz-violating Dirac bound states in a cylindrical well
NASA Astrophysics Data System (ADS)
Xiao, Zhi
2016-12-01
In the presence of the Lorentz-violating bμ coefficient, the spectra of bound states for a Dirac particle in a cylindric well are changed. Compared to the Lorentz invariant (LI) spectrum, the Lorentz violation deviation becomes significant when eigenenergy E is sufficiently close to the critical values ±m , where m is the particle's mass. The detailed profile of the deviation depends on the observer Lorentz nature of bμ. We discussed three types of bμ configuration. When bμ=(0 ,0 ,0 ,bZ) is parallel to the well axis, the would be degenerate LI spectra split into two subspectra, reminiscent of the Zeeman splitting in the presence of a weak magnetic field. Depending on the relative sign of bZ accompanying mass m in the dispersion relation, the spectrum extends or shrinks in the allowed eigenenergy region. When bμ is a radial [bμ=(0 ,b cos ϕ ,b sin ϕ ,0 ) ] or purely timelike vector [bμ=(bT,0 →)], the spin-up and down components are coupled together, and there is no splitting. However, the monotonic increasing behavior of well depth V0 with the decrease of eigenenergy E is slightly changed when E is sufficiently close to -m .
Perturbative generation of the higher-derivative Lorentz-breaking terms
NASA Astrophysics Data System (ADS)
Mariz, T.; Nascimento, J. R.; Petrov, A. Yu.
2012-06-01
In this paper, we describe the perturbative generation of the higher-derivative Lorentz-breaking terms for the gauge field, that is, the Myers-Pospelov term and the higher-derivative Carroll-Field-Jackiw term. These terms are explicitly calculated in the one-loop approximation and shown to be finite and ambiguous.
Lorentz Contraction, Bell's Spaceships and Rigid Body Motion in Special Relativity
ERIC Educational Resources Information Center
Franklin, Jerrold
2010-01-01
The meaning of Lorentz contraction in special relativity and its connection with Bell's spaceships parable is discussed. The motion of Bell's spaceships is then compared with the accelerated motion of a rigid body. We have tried to write this in a simple form that could be used to correct students' misconceptions due to conflicting earlier…
Entropic information for travelling solitons in Lorentz and CPT breaking systems
Correa, R.A.C.; Rocha, Roldão da; Souza Dutra, A. de
2015-08-15
In this work we group four research topics apparently disconnected, namely solitons, Lorentz symmetry breaking, supersymmetry, and entropy. Following a recent work (Gleiser and Stamatopoulos, 2012), we show that it is possible to construct in the context of travelling wave solutions a configurational entropy measure in functional space, from the field configurations. Thus, we investigate the existence and properties of travelling solitons in Lorentz and CPT breaking scenarios for a class of models with two interacting scalar fields. Here, we obtain a complete set of exact solutions for the model studied which display both double and single-kink configurations. In fact, such models are very important in applications that include Bloch branes, Skyrmions, Yang–Mills, Q-balls, oscillons and various superstring-motivated theories. We find that the so-called Configurational Entropy (CE) for travelling solitons shows that the best value of parameter responsible to break the Lorentz symmetry is one where the energy density is distributed equally around the origin. In this way, the information-theoretical measure of travelling solitons in Lorentz symmetry violation scenarios opens a new window to probe situations where the parameters responsible for breaking the symmetries are arbitrary. In this case, the CE selects the best value of the parameter in the model.
Bound on Lorentz and CPT Violating Boost Effects for the Neutron
NASA Technical Reports Server (NTRS)
Walsworth, Ronald
2003-01-01
A search for a sidereal annual variation in the frequency difference between co-located Xe-129 and He-3 Zeeman masers sets a limit of approximately 10(exp -27) GeV on the coupling of the neutron to the time component of a possible background Lorentz and CPT violating tensor field.
An Implicit δf Sub-cycled and Orbit Averaged Lorentz Ion Model
NASA Astrophysics Data System (ADS)
Sturdevant, Benjamin; Parker, Scott; Chen, Yang; Hause, Benjamin
2015-11-01
A second order implicit δf Lorentz ion hybrid model with sub-cycling and orbit averaging has been developed to study low-frequency, quasi-neutral plasmas. This model may be useful for verifying gyrokinetic simulation models in applications where higher order terms may be important, for example, in the tokamak edge pedestal region, where the equilibrium gradient scale lengths are quite short. A significant challenge for simulations using Lorentz ions in the presence of a strong guide field is the small time step size requirements for fully resolving the ion gyromotion. In this work, we present a GPU accelerated sub-cycling and orbit averaging method which has been developed to make the Lorentz ion model more viable and has been successfully applied to a test bed model for ion Landau damped ion acoustic waves in a uniform magnetic field. Simulation results will be presented to demonstrate the accurate reproduction of finite-Larmor-radius effects using large macro time steps to advance the fields. Future plans to implement the method in the GEM gyrokinetic simulation code to study the toroidal ITG instability with Lorentz ions will also be presented.
Temperature-compensating dc restorer
NASA Technical Reports Server (NTRS)
Thomas, H. M.
1980-01-01
Circuit provides stable references restoration in addition to temperature compensation. Possible TV monitor applications include traffic and security surveillance systems, where cameras are subject to environmental extremes, as in unheated warehouses or outdoors.
NASA Astrophysics Data System (ADS)
Rajapaksa, Indrajith
In this thesis we describe an enhancement to the Atomic force microscope (AFM) to simultaneously gather topographic features and spectroscopic information .Compared to the current state of the art of near-field excitation and far-field detection AFM imaging techniques our system uses a radical new approach near-field excitation and near-field detection. By placing the detector in the near-field we achieve high signal to noise and single molecular resolution. The origin of our near-field detector signal is the image force gradient due to the interaction of the stimulated molecular dipole with its image on the metal probe. We designed and built an optical and electronic system to capture this signal and simultaneously image nano-scale surface topography and optical image force gradient. By varying the wavelength of the excitation beam we measure the induced optical image force gradient spectra of molecules on surface. These spectra show good agreement with the absorption spectra of the bulk molecules measured by conventional absorption spectroscopy. We show that image force gradient is directly proportional to the optical absorption dipole strength. Using Finite Element 3D electromagnetic simulations and using Lorentz model for the excited molecular dipole we showed that the image force gradient has a decay length of 1nm, making the theoretical resolution of this microscopy technique approximately 1 nm. This rapid decay was measured experimentally .This resolution was seen by the high contrasting spectroscopic images of molecules on the surface. In follow on experiments this technique was extended to provide surface Raman spectroscopy and microscopy at molecular resolution. We create an image force gradient interaction through optical parametric down conversion between stimulated Raman excited molecules on a surface and a cantilevered nanometer scale probe brought very close to it. Spectroscopy and microscopy on clusters of molecules have been performed. Single
Levitation forces in bearingless permanent magnet motors
Amrhein, W.; Silber, S.; Nenninger, K.
1999-09-01
Bearingless motors combine brushless AC-motors with active magnetic bearings by the integration of two separate winding systems (torque and radial levitation force windings with different pole pairs) in one housing. This paper gives an insight into the influences of the motor design on the levitation force and torque generation. It is shown that especially for machines with small air gaps it can be very important to choose the right design parameters. Increasing the permanent magnet height in order to increase the motor torque can result in a remarkable reduction of radial forces. The interrelationships are discussed on the basis of Maxwell and Lorentz forces acting upon the stator surface. The investigations are presented for a bearingless low cost motor, suited for pump, fan or blower applications. The presented motor needs only four coils for operation.
Flow compensating pressure regulator
NASA Technical Reports Server (NTRS)
Baehr, E. F. (Inventor)
1978-01-01
An apparatus for regulating pressure of treatment fluid during ophthalmic procedures is described. Flow sensing and pressure regulating diaphragms are used to modulate a flow control valve. The pressure regulating diaphragm is connected to the flow control valve to urge the valve to an open position due to pressure being applied to the diaphragm by bias means such as a spring. The flow sensing diaphragm is mechanically connected to the flow control valve and urges it to an opened position because of the differential pressure on the diaphragm generated by a flow of incoming treatment fluid through an orifice in the diaphragm. A bypass connection with a variable restriction is connected in parallel relationship to the orifice to provide for adjusting the sensitivity of the flow sensing diaphragm. A multiple lever linkage system is utilized between the center of the second diaphragm and the flow control valve to multiply the force applied to the valve by the other diaphragm and reverse the direction of the force.
Comparison of the electron-spin force and radiation reaction force
NASA Astrophysics Data System (ADS)
Mahajan, Swadesh M.; Asenjo, Felipe A.; Hazeltine, Richard D.
2015-02-01
It is shown that the forces that originate from the electron-spin interacting with the electromagnetic field can play, along with the Lorentz force, a fundamentally important role in determining the electron motion in a high energy density plasma embedded in strong high-frequency radiation, a situation that pertains to both laser-produced and astrophysical systems. These forces, for instance, dominate the standard radiation reaction force as long as there is a `sufficiently' strong ambient magnetic field for affecting spin alignment. The inclusion of spin forces in any advanced modelling of electron dynamics pertaining to high energy density systems (for instance in particle-in-cell codes), therefore, is a must.
Gravitomagnetic Field of the Universe and Coriolis Force on the Rotating Earth
ERIC Educational Resources Information Center
Veto, B.
2011-01-01
The Machian effect of distant masses of the universe in the frame of reference of the rotating Earth is demonstrated using the gravitomagnetic approach of general relativity. This effect appears in the form of a gravitomagnetic Lorentz force acting on moving bodies on the Earth. The gravitomagnetic field of the universe--deduced from a simple…
Oliveira, Diego F M; Leonel, Edson D
2012-06-01
Some dynamical properties for a time dependent Lorentz gas considering both the dissipative and non dissipative dynamics are studied. The model is described by using a four-dimensional nonlinear mapping. For the conservative dynamics, scaling laws are obtained for the behavior of the average velocity for an ensemble of non interacting particles and the unlimited energy growth is confirmed. For the dissipative case, four different kinds of damping forces are considered namely: (i) restitution coefficient which makes the particle experiences a loss of energy upon collisions; and in-flight dissipation given by (ii) F=-ηV(2); (iii) F=-ηV(μ) with μ≠1 and μ≠2 and; (iv) F=-ηV, where η is the dissipation parameter. Extensive numerical simulations were made and our results confirm that the unlimited energy growth, observed for the conservative dynamics, is suppressed for the dissipative case. The behaviour of the average velocity is described using scaling arguments and classes of universalities are defined.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Compensation. 96.34 Section 96.34 Foreign... Financial and Risk Management § 96.34 Compensation. (a) The agency or person does not compensate any... for compensation within the intercountry adoption community in that country, to the extent that...
14 CFR 158.53 - Collection compensation.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Collection compensation. 158.53 Section 158... Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue, the... a new compensation level based on an analysis of the data provided under paragraph (c)(1) of...
14 CFR 158.53 - Collection compensation.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Collection compensation. 158.53 Section 158... Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue, the... a new compensation level based on an analysis of the data provided under paragraph (c)(1) of...
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Compensation. 90.103 Section 90.103 Mineral..., Rights of Part 90 Miners § 90.103 Compensation. (a) The operator shall compensate each Part 90 miner at... part. (d) In addition to the compensation required to be paid under paragraphs (a), (b) and (c) of...
Code of Federal Regulations, 2010 CFR
2010-04-01
... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Compensation. 96.34 Section 96.34 Foreign... Financial and Risk Management § 96.34 Compensation. (a) The agency or person does not compensate any... for compensation within the intercountry adoption community in that country, to the extent that...
48 CFR 752.7007 - Personnel compensation.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...
12 CFR 7.2011 - Compensation plans.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks... Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30, a national bank may adopt compensation plans, including,...
12 CFR 9.15 - Fiduciary compensation.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Fiduciary compensation. 9.15 Section 9.15 Banks... BANKS Regulations § 9.15 Fiduciary compensation. (a) Compensation of bank. If the amount of a national bank's compensation for acting in a fiduciary capacity is not set or governed by applicable law,...
23 CFR 751.15 - Just compensation.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 23 Highways 1 2013-04-01 2013-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... removed, relocated, or disposed of pursuant to 23 U.S.C. 136. (b) No rights to compensation accrue until...
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Compensation. 90.103 Section 90.103 Mineral..., Rights of Part 90 Miners § 90.103 Compensation. (a) The operator shall compensate each Part 90 miner at... part. (d) In addition to the compensation required to be paid under paragraphs (a), (b) and (c) of...
12 CFR 7.2011 - Compensation plans.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 1 2012-01-01 2012-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks... Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30, a national bank may adopt compensation plans, including,...
7 CFR 930.133 - Compensation rate.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 7 Agriculture 8 2013-01-01 2013-01-01 false Compensation rate. 930.133 Section 930.133 Agriculture... Regulations § 930.133 Compensation rate. A compensation rate of $250 per meeting shall be paid to the public member and to the alternate public member when attending Board meetings. Such compensation is a...
12 CFR 9.15 - Fiduciary compensation.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 1 2011-01-01 2011-01-01 false Fiduciary compensation. 9.15 Section 9.15 Banks... BANKS Regulations § 9.15 Fiduciary compensation. (a) Compensation of bank. If the amount of a national bank's compensation for acting in a fiduciary capacity is not set or governed by applicable law,...
7 CFR 930.133 - Compensation rate.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 8 2011-01-01 2011-01-01 false Compensation rate. 930.133 Section 930.133 Agriculture... Regulations § 930.133 Compensation rate. A compensation rate of $250 per meeting shall be paid to the public member and to the alternate public member when attending Board meetings. Such compensation is a...
48 CFR 752.7007 - Personnel compensation.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...
12 CFR 7.2011 - Compensation plans.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 1 2013-01-01 2013-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks... Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30, a national bank may adopt compensation plans, including,...
7 CFR 930.133 - Compensation rate.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 7 Agriculture 8 2012-01-01 2012-01-01 false Compensation rate. 930.133 Section 930.133 Agriculture... Regulations § 930.133 Compensation rate. A compensation rate of $250 per meeting shall be paid to the public member and to the alternate public member when attending Board meetings. Such compensation is a...
23 CFR 751.15 - Just compensation.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 23 Highways 1 2014-04-01 2014-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... removed, relocated, or disposed of pursuant to 23 U.S.C. 136. (b) No rights to compensation accrue until...
48 CFR 752.7007 - Personnel compensation.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...
12 CFR 9.15 - Fiduciary compensation.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 1 2012-01-01 2012-01-01 false Fiduciary compensation. 9.15 Section 9.15 Banks... BANKS Regulations § 9.15 Fiduciary compensation. (a) Compensation of bank. If the amount of a national bank's compensation for acting in a fiduciary capacity is not set or governed by applicable law,...
14 CFR 158.53 - Collection compensation.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Collection compensation. 158.53 Section 158... Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue, the... a new compensation level based on an analysis of the data provided under paragraph (c)(1) of...
12 CFR 7.2011 - Compensation plans.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 1 2011-01-01 2011-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks... Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30, a national bank may adopt compensation plans, including,...
7 CFR 930.133 - Compensation rate.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 7 Agriculture 8 2014-01-01 2014-01-01 false Compensation rate. 930.133 Section 930.133 Agriculture... Regulations § 930.133 Compensation rate. A compensation rate of $250 per meeting shall be paid to the public member and to the alternate public member when attending Board meetings. Such compensation is a...
12 CFR 9.15 - Fiduciary compensation.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 1 2013-01-01 2013-01-01 false Fiduciary compensation. 9.15 Section 9.15 Banks... BANKS Regulations § 9.15 Fiduciary compensation. (a) Compensation of bank. If the amount of a national bank's compensation for acting in a fiduciary capacity is not set or governed by applicable law,...
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Compensation. 90.103 Section 90.103 Mineral..., Rights of Part 90 Miners § 90.103 Compensation. (a) The operator shall compensate each Part 90 miner at... part. (d) In addition to the compensation required to be paid under paragraphs (a), (b) and (c) of...
23 CFR 751.15 - Just compensation.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 23 Highways 1 2010-04-01 2010-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... removed, relocated, or disposed of pursuant to 23 U.S.C. 136. (b) No rights to compensation accrue until...
Code of Federal Regulations, 2014 CFR
2014-04-01
... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Compensation. 96.34 Section 96.34 Foreign... Financial and Risk Management § 96.34 Compensation. (a) The agency or person does not compensate any... for compensation within the intercountry adoption community in that country, to the extent that...
23 CFR 751.15 - Just compensation.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 23 Highways 1 2012-04-01 2012-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... removed, relocated, or disposed of pursuant to 23 U.S.C. 136. (b) No rights to compensation accrue until...
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Compensation. 90.103 Section 90.103 Mineral..., Rights of Part 90 Miners § 90.103 Compensation. (a) The operator shall compensate each Part 90 miner at... part. (d) In addition to the compensation required to be paid under paragraphs (a), (b) and (c) of...
23 CFR 751.15 - Just compensation.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 23 Highways 1 2011-04-01 2011-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... removed, relocated, or disposed of pursuant to 23 U.S.C. 136. (b) No rights to compensation accrue until...
12 CFR 620.31 - Compensation committees.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 6 2011-01-01 2011-01-01 false Compensation committees. 620.31 Section 620.31... Association Audit and Compensation Committees § 620.31 Compensation committees. Each Farm Credit bank and association must establish and maintain a compensation committee by adopting a written charter describing...
48 CFR 752.7007 - Personnel compensation.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...
Code of Federal Regulations, 2013 CFR
2013-04-01
... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Compensation. 96.34 Section 96.34 Foreign... Financial and Risk Management § 96.34 Compensation. (a) The agency or person does not compensate any... for compensation within the intercountry adoption community in that country, to the extent that...
Code of Federal Regulations, 2012 CFR
2012-04-01
... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Compensation. 96.34 Section 96.34 Foreign... Financial and Risk Management § 96.34 Compensation. (a) The agency or person does not compensate any... for compensation within the intercountry adoption community in that country, to the extent that...
12 CFR 9.15 - Fiduciary compensation.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 1 2014-01-01 2014-01-01 false Fiduciary compensation. 9.15 Section 9.15 Banks... BANKS Regulations § 9.15 Fiduciary compensation. (a) Compensation of bank. If the amount of a national bank's compensation for acting in a fiduciary capacity is not set or governed by applicable law,...
48 CFR 752.7007 - Personnel compensation.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...
12 CFR 7.2011 - Compensation plans.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 1 2014-01-01 2014-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks... Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30, a national bank may adopt compensation plans, including,...
14 CFR 158.53 - Collection compensation.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Collection compensation. 158.53 Section 158... Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue, the... a new compensation level based on an analysis of the data provided under paragraph (c)(1) of...
12 CFR 620.31 - Compensation committees.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 7 2012-01-01 2012-01-01 false Compensation committees. 620.31 Section 620.31... Association Audit and Compensation Committees § 620.31 Compensation committees. Each Farm Credit bank and association must establish and maintain a compensation committee by adopting a written charter describing...
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Compensation. 90.103 Section 90.103 Mineral..., Rights of Part 90 Miners § 90.103 Compensation. (a) The operator shall compensate each Part 90 miner at... part. (d) In addition to the compensation required to be paid under paragraphs (a), (b) and (c) of...
48 CFR 970.2270 - Unemployment compensation.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...
48 CFR 970.2270 - Unemployment compensation.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...
48 CFR 970.2270 - Unemployment compensation.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...
48 CFR 970.2270 - Unemployment compensation.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...
48 CFR 970.2270 - Unemployment compensation.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...
29 CFR 525.6 - Compensable time.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 29 Labor 3 2011-07-01 2011-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...
29 CFR 525.6 - Compensable time.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 29 Labor 3 2013-07-01 2013-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...