Pair production of open strings — relativistic versus dissipative dynamics

Pair production in a constant electric field is closely analogous to bubble nucleation in a false vacuum. The classical trajectories of the pairs are Lorentz invariant, but it appears that this invariance should be broken by the nucleation process. Here, we use a model detector, consisting of other particles interacting with the pairs, to investigate how pair production is seen by different Lorentzian observers. We focus on the idealized situation where a constant external electric field is present for an infinitely long time, and we consider the in-vacuum state for a charged scalar field that describes the nucleating pairs. The in-vacuum is defined in terms of modes which are positive frequency in the remote past. Even though the construction uses a particular reference frame and a gauge where the vector potential is time dependent, we show explicitly that the resulting quantum state is Lorentz invariant. We then introduce a ``detector'' particle which interacts with the nucleated pairs, and show that all Lorentzian observers will see the particles and antiparticles nucleating preferentially at rest in the detector's rest frame. Similar conclusions are expected to apply to bubble nucleation in a sufficiently long lived vacuum. We also comment on certain unphysical aspects of the Lorentz invariant in-vacuum, associated with the fact that it contains an infinite density of particles. This can be easily remedied by considering Lorentz breaking initial conditions.

We find dispersion laws for the photon propagating in the presence of mutually orthogonal constant external electric and magnetic fields in the context of the $\theta $-expanded noncommutative QED. We show that there is no birefringence to the first order in the noncommutativity parameter $% \theta .$ By analyzing the group velocities of the photon eigenmodes we show that there occurs superluminal propagation for any direction. This phenomenon depends on the mutual orientation of the external electromagnetic fields and the noncommutativity vector. We argue that the propagation of signals with superluminal group velocity violates causality in spite of the fact that the noncommutative theory is not Lorentz-invariant and speculate about possible workarounds.

The effect of homogeneous and constant external electric fields on the structural stability of chignolin, a typical β-hairpin peptide, has been studied for 10ns using molecular dynamics simulations. The peptide aligns quickly its total dipole moment with the external electric field and then a constant stress is applied on its charged residues. For weaker fields this has mixed effects on the creation, destruction or strength of hydrogen bonds, but ultimately for strong fields chignolin unfolds starting by the separation of the terminal residues. Since the function of proteins is critically linked to their three-dimensional structures, these findings indicate that exposure to external electric fields may induce changes in conformation that can potentially initiate severe cellular dysfunction.

The MHD equations are integrated numerically for a homogeneous plasma initially at rest near a null line in a hyperbolic magnetic field. The finite plasma conductivity is taken into account. A solution of the linearized equations far from the null line — a cylindrical potential-perturbation wave converging on the null line - is adopted as a boundary condition. This perturbation arises when a constant external electric field is applied parallel to the null line. As the null line is approached, the wave becomes nonlinear and leads to the appearance of a thin current sheet. There is no evidence of any kind for the system of slow-mode shockwaves corresponding to the Petschek model. Within the current sheet the plasma density increases, while the density just outside the sheet decreases. The plasma flows along the sheet at approximately the Alfven velocity. A return current flows at the edges of the sheet.

Vacuum bubbles nucleate at rest with a certain critical size and subsequently expand. But what selects the rest frame of nucleation? This question has been recently addressed in [1] in the context of Schwinger pair production in 1+1 dimensions, by using a model detector in order to probe the nucleated pairs. The analysis in [1] showed that, for a constant external electric field, the adiabatic ``in" vacuum of charged particles is Lorentz invariant, {and in this} case pairs tend to nucleate preferentially at rest with respect to the detector. Here, we sharpen this picture by showing that the typical relative velocity between the frame of nucleation and that of the detector is at most of order Δv ∼ SE−1/3 << 1. Here, SE >> 1 is the action of the instanton describing pair creation. The bound Δv coincides with the minimum uncertainty in the velocity of a non-relativistic charged particle embedded in a constant electric field. A velocity of order Δv is reached after a time interval of order Δt ∼ SE−1/3r0 << r0 past the turning point in the semiclassical trajectory, where r0 is the size of the instanton. If the interaction takes place in the vicinity of the turning point, the semiclassical description of collision does not apply. Nonetheless, we find that even in this case there is still a strong asymmetry in the momentum transferred from the nucleated particles to the detector, in the direction of expansion after the turning point. We conclude that the correlation between the rest frame of nucleation and that of the detector is exceedingly sharp.

view Abstract Citations (753) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Does the missing mass problem signal the breakdown of Newtonian gravity? Bekenstein, J. ; Milgrom, M. Abstract A nonrelativistic potential theory for gravity is considered which differs from the Newtonian theory. The theory is built on the basic assumptions of the modified dynamics, which were shown earlier to reproduce dynamical properties of galaxies and galaxy aggregates without having to assume the existence of hidden mass. The theory involves a modification of the Poisson equation and can be derived from a Lagrangian. The total momentum, angular momentum, and (properly defined) energy of an isolated system are conserved. The center-of-mass acceleration of an arbitrary bound system in a constant external gravitational field is independent of any property of the system. In other words, all isolated objects fall in exactly the same way in a constant external gravitational field (the weak equivalence principle is satisfied). However, the internal dynamics of a system in a constant external field is different from that of the same system in the absence of the external field, in violation of the strong principle of equivalence. These two results are consistent with the phenomenological requirements of the modified dynamics. A toy relativistic theory is sketched which has a nonrelativistic limit satisfying the requirements of the modified dynamics. Publication: The Astrophysical Journal Pub Date: November 1984 DOI: 10.1086/162570 Bibcode: 1984ApJ...286....7B Keywords: Galactic Rotation; Gravitation Theory; Mass Distribution; Missing Mass (Astrophysics); Newton Theory; Nonrelativistic Mechanics; Potential Theory; Computational Astrophysics; Cosmology; Equivalence; Poisson Equation; Astrophysics full text sources ADS |

The electric dipole transitions between states of the intervalley donor multiplet in Ge‐type semiconductors placed in an external constant electric field are considered. The assumption that a short range component of the impurity potential plays a dominant role is used in the calculations. For transitions of different types expressions for the oscillator strengths, describing their field and angle dependences, are derived.

The phenomenology of the instability of charged and uncharged drops and liquid menisci at the end of a capillary through which liquid is fed in constant and variable external electric fields, both uniform and nonuniform, is considered. Methods of investigating such instability are described. The steady-state deformation of drops in electric fields, the critical conditions under which their charged surface loses stability, and the laws of electrical dispersion of liquids in the final stage of instability are discussed.

Massive scalar and spin 1/2 fields are considered on a two-dimensional space-time with constant background curvature and in the presence of an external constant field. For each case, the Euler–Heisenberg effective action and the pair creation rate and their dependence on both the curvature and external field is determined exactly.

Having established in previous articles that the principle of the constancy of speed of light of Special Relativity Theory is false in general, we examine some consequences of the non-constancy of speed of light in vacuum for different Galilean reference systems. We consider the modified Lorentz transformation incorporating different speeds of light for different inertial frames and which is a result of the non-constancy of speed of light in vacuum for different Galilean reference systems, i.e., reference systems in uniform rectilinear motion with respect to each other. Some consequences of this transform including the limit speed concept, transformation of lengths, summation and transformation of velocities are considered. Results of the transformation of the electromagnetic field are given. Also discussed are some consequences of the relativity of the electromagnetic field, all under the modified Lorentz transformation. These include variance of the electric charge, transformation of the potentials, transformation of the force. Some of the highlights of these consequences are as follows. The transformation of lengths abide by the same rule as in Special Relativity Theory, at least in form. Transformation of time intervals and velocities now involve the speeds of light in vacuum for both inertial frames in distinction from Special Relativity Theory. The invariance of charge no longer applies and charge measured depends on the reference frame the measurement is made from. Force acting on a charge q in an external electromagnetic field has the same form as in Special Relativity Theory, but now because charge is no longer invariant, the force transformation also has to be modified accordingly.

The local densities of states (LDOSs) in electrified simple cubic crystals have been studied within the semi-empirical tight-binding (TB) model. One-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) cases are investigated, taking into account first neighbours and one band, when an external constant electric field with arbitrary direction is applied. The increasing strength of the field in a given direction turns smoothly the LDOSs of an n-dimensional crystal (n = 1, 2, 3) into the LDOSs of an (n — 1)-dimensional crystal. The Wannier-Stark ladder phenomenon for crystals of different dimensionalities is discussed and the role of the electric field strength for the effective crystal dimension is assessed. The LDOSs are calculated by means of a new convolution technique which allows to compute the results faster than any conventional method.

This paper presents results for the anapole magnetic field moment due to the mixing of states with opposite parity in the n = 2 hydrogen atom in an external constant electric field. The evaluation of the current densities of the four n = 2 states is carried out to first order in the field strength. These current densities and their associated magnetic fields are expanded in multipoles, including both the ordinary poloidal and the toroidal fields. The dominant contribution to the toroidal dipole (anapole) magnetic field comes from the strong mixing of the degenerate 2S, 2P states within the n = 2 shell. A brief discussion is also presented of the electronic scattering from the anapole field of a Rydberg atom. The experimental conditions under which the atomic anapole field could be detected are critically considered, in particular, in terms of the quasi-resonant dependence of the anapole field on the applied electric field.

The effect of a pulsed (with a duration on the order of 1 ms) and of a constant external electric field on plasma-chemical processes in the lower ionosphere at altitudes of 70–100 km above the Earth’s surface is considered. Interest in these externally stimulated physical settings is associated with traditional radiophysical research and problems of radio-chemical atmospheric physics, which has been actively in recent years due to its various scientific and technical applications. A new page in this field of science (unlike the use of spurious radio signals) opens up the possibility of the purposeful field impact on a GPS receiver on the improvement of work and the further development of satellite navigation systems, which, undoubtedly, has not been discussed previously in the literature. In this work, on the basis of the numerical simulation, the concentrations of the main charged particles and the electron temperature in the presence of a strong external electric field have been calculated at an altitude of 100 km.

Theory of nonlinear stationary longitudinal waves in relativistic plasmas is treated by solving a relativistic Boltzmann equation without the conventional approximation of linearization. It is proved here that in plasmas of physically reasonable electron velocity distributions, stationary waves of arbitrary amplitude can be propagated and obey a dispersion equation. If the velocity of propagation V is less than the velocity of light c, the amplitude of these waves will generally be limited; if the velocity of wave propagation is greater than c, however, there is no amplitude limitation. The nonlinearity in the Boltzmann equation causes a decrease of frequency of oscillation for a given wave velocity in addition to the distortion in waveform from pure sinusoidal waves. Detailed solutions for plasmas with Maxwellian electron velocity distribution and relativistic electron beams are given. In the former case, a dispersion equation including nonlinear effect is derived through a series expansion to an order higher than that used in the linearized theory. In the latter, a complete analytic solution in terms of elliptical integrals is given. In both cases dispersion characteristics for several parameters are computed and plotted. The agreement between these nonlinear dispersion equations in the limit of vanishing amplitudes and those of the linearized theory published in literature is indicated.

The aim of the study is to investigate the influence of the physicochemical characteristics of the molecular and supramolecular structure of polymers on electroadhesive interactions and their change under the action of a constant electric field. Currently, this effect is modeled in electroadhesion studies, but the range of variable parameters is limited and includes permittivity, moisture content, and surface roughness. It is important to consider other physicochemical parameters, such as material crystallinity and surface characteristics, changes in which can affect the magnitude of electroadhesive forces. In this study, the electric field strength was varied by altering the constant voltage in the range of 3–8 kV. Polyethylene, ethylene-vinyl acetate copolymers, and polyvinyl acetate were used as substrates for adhesive systems. The influence of the concentration of vinyl acetate groups, which determine the energy characteristics of the surface, and the degree of crystallinity on electroadhesive interactions under conditions of an external constant electric field and without it was traced. The degree of crystallinity was varied both by the cooling rate and the orientation during drawing. It was shown that by changing the polar component of the surface energy and the proportion of the crystalline phase in the substrate, electroadhesive interactions can be increased by 4 times to 120 Pa compared to polyethylene. The obtained laws are explained by the local dipoles induced by polar functional groups, which enhance the polymer’s surface interactions with other materials and external fields. At the same time, the fixation of macromolecules in crystalline regions complicates polarization under the influence of an electric field.