Relativistic Velocities Research Articles

Dynamics of U(1) gauged Q -balls in three spatial dimensions

We investigate the dynamics of U(1) gauged Q-balls using fully three-dimensional numerical simulations. We consider two different scenarios: first, the classical stability of gauged Q-balls with respect to generic three-dimensional perturbations, and second, the behavior of gauged Q-balls during head-on and off-axis collisions at relativistic velocities. With regard to stability, we find that there exist gauged Q-ball configurations which are classically stable in both logarithmic and polynomial scalar field models. With regard to relativistic collisions, we find that the dynamics can depend on many different parameters such as the collision velocity, relative phase, relative charge, and impact parameter of the colliding Q-balls. Published by the American Physical Society 2024

Gravastars formation with back-reaction effects from extended general relativity

Using an extended theory of General Relativity that incorporates normalized relativistic velocities, where the boundary terms in the varied Einstein–Hilbert action are considered. Within this context, I investigate the dynamic evolution of a collapsing spherical system characterized by a metric with spatial curvature and variable time-scale, aiming to describe the process of Gravastar formation. To illustrate the system’s dynamics, I analyze a power-law collapsing scenario and derive the equation of state for both cases, with and without geometrical perturbations. In particular, I derive the equation of state, incorporating back-reaction effects related with the boundary terms of the varied Einstein–Hilbert action.

Concept study of a storage ring-based gravitational wave observatory: Gravitational wave strain and synchrotron radiation noise

This work for the first time addresses the feasibility of measuring millihertz gravitational waves (mHz GWs) with a storage ring-based detector. While this overall challenge consists of several partial problems, here we focus solely on quantifying design limitations imposed by the kinetic energy and radiated power of circulating ions at relativistic velocities. We propose an experiment based on the measurement of the time-of-flight signal of an ion chain. One of the dominant noise sources inherent to the measurement principle for such a GW detector is the shot noise of the emitted synchrotron radiation. We compute the noise amplitude of arrival time signals obtained by analytical estimates and simulations of ions with different masses and velocities circulating in a storage ring with the circumference of the Large Hadron Collider. Thereby, we show that our experiment design could reduce the noise amplitude due to the synchrotron radiation in the frequency range 10−4–10−2 Hz to one or two orders of magnitude below the expected GW signals from of astrophysical sources, such as supermassive binary black holes or extreme mass-ratio inspirals. Other key requirements for building a working storage ring-based GW detector include the generation and acceleration of heavy ion chains with the required energy resolution, their injection and continued storage, as well as the detection method to be used for the determination of the particle arrival time. However, these are not the focus of the work presented here, in which we instead concentrate on the definition of a working principle in terms of ion type, kinetic energy, and ring design, which will later serve as a starting point when addressing a more complete experimental setup. Published by the American Physical Society 2024

The theory of thermodynamic relativity.

We introduce the theory of thermodynamic relativity, a unified theoretical framework for describing both entropies and velocities, and their respective physical disciplines of thermodynamics and kinematics, which share a surprisingly identical description with relativity. This is the first study to generalize relativity in a thermodynamic context, leading naturally to anisotropic and nonlinear adaptations of relativity; thermodynamic relativity constitutes a new path of generalization, as compared to the "traditional" passage from special to general theory based on curved spacetime. We show that entropy and velocity are characterized by three identical postulates, which provide the basis of a broader framework of relativity: (1) no privileged reference frame with zero value; (2) existence of an invariant and fixed value for all reference frames; and (3) existence of stationarity. The postulates lead to a unique way of addition for entropies and for velocities, called kappa-addition. We develop a systematic method of constructing a generalized framework of the theory of relativity, based on the kappa-addition formulation, which is fully consistent with both thermodynamics and kinematics. We call this novel and unified theoretical framework for simultaneously describing entropy and velocity "thermodynamic relativity". From the generality of the kappa-addition formulation, we focus on the cases corresponding to linear adaptations of special relativity. Then, we show how the developed thermodynamic relativity leads to the addition of entropies in nonextensive thermodynamics and the addition of velocities in Einstein's isotropic special relativity, as in two extreme cases, while intermediate cases correspond to a possible anisotropic adaptation of relativity. Using thermodynamic relativity for velocities, we start from the kappa-addition of velocities and construct the basic formulations of the linear anisotropic special relativity; e.g., the asymmetric Lorentz transformation, the nondiagonal metric, and the energy-momentum-velocity relationships. Then, we discuss the physical consequences of the possible anisotropy in known relativistic effects, such as, (i) matter-antimatter asymmetry, (ii) time dilation, and (iii) Doppler effect, and show how these might be used to detect and quantify a potential anisotropy.

Experimental apparatus for condensed excited hydrogen research

In this article, we report on a versatile experimental instrument for the study of hydrogen, condensed excited hydrogen, and hydrogen Rydberg matter, charged particles, and radiation from these systems. The system allows researchers to attach different detectors to the chamber to study condensed hydrogen, Rydberg matter, or excited hydrogen under different conditions. We show how the system is used to excite hydrogen to Rydberg atoms while monitoring Rydberg states using lasers and time-of-flight (TOF) on ions with radiation monitoring. We verify some of the work on using clustered hydrogen and laser to accelerate particles from rest to relativistic velocity. The experimental setup is an advanced replication of the reactor and detection system setup reported by researchers from Goteborg University. This experimental instrument can be used to replicate more of the work performed by the research group at Gothenburg University on Rydberg Matter, charged-particle acceleration, and experiments on ultra-dense hydrogen (UDH).

Assessment of Zitterbewegung Interpretation for Free Particle Solution Using the Concept of Relativistic Wave

The Assessment of the interpretation of Zitterbewegung for free particle solution using various models has been carried out in this work where we firstly considered by using the free particle solution for which Dirac equation and projection operator were carried out.. ln this case, it was invariably revealed that the solution have two doubly degenerate eigenvalues representing positive and negative state that was further support by the analysis which was carried out using Heisenberg’s equation and the representation in relativistic velocity and semi-classical equation of motion for acceleration., but in this second case, the results obtained were observed to have two terms, first terms standing in for rapidly oscillatory motion and the second term representing average motion of the particle in x-direction. The first term in the expression is the one deemed to signify zitterbewegung which is one considered to be sas a result of the fluctuation resulting from the interference between negative and positive energy state while the other term is the normal state terms signifying the average motion of the particle. This therefore confirms the explicit nature of using Dirac equation in handling problems involving the behavior of free particles in field as compared to the use of semiclassical equation of motion.

Pythagorean triples using the relativistic velocity addition formula

In the special theory of relativity, there is an unusual formula for addition of velocities. We will use this formula to generate Pythagorean triples. We define a Pythagorean triple in the usual manner as a triple of positive integers (a, b, c) such that a2 + b2 = c2. The numbers a and b are called legs, and c is called the hypotenuse. Later, we will allow b to take on the value of any integer. A primitive Pythagorean triple is a Pythagorean triple for which a, b and c are relatively prime.

The impact of cross-Kerr nonlinearity on rotary photon drag and temporal cloaking in Sagnac interferometry

We theoretically explore the impact of cross-Kerr nonlinearity (CKN) on rotary photon drag (RPD) and temporal cloaking in a Sagnac interferometer. With the activation of CKN, significant improvements in RPD and temporal cloaking are observed. Drag angles of ±1×10−3 and ±5×10−3 radians are attained, similarly, temporal gaps of 10μ s, 12μ s and 13μ s are observed. In addition to the observed electromagnetically induced transparency window, the group refractive index is drastically enhanced, time delay/advance are tuned from pico-radians to micro-radians, and reduced relativistic group velocities are achieved by activating CKN within the system. Additionally, the transmission pulses intensities are observed to be reduced with the dragging phenomenon. The findings may have potential applications in controlled image coding, rotation sensing and secure communication technologies.

Geometric construction of relativistic and non-relativistic distortion

To an observer moving through a scene with a relativistic velocity, the scene appears distorted. Here we present a simple geometric interpretation of this relativistic distortion. This interpretation is exact for pinhole cameras whose shutter coincides with the pinhole, and it can easily be modified to take into account time-of-flight effects only that lead to a “non-relativistic distortion,” allowing a separation of the relativistic distortion into time-of-flight effects and “truly relativistic” effects. We make use of our construction in Einstagram, a web app designed for running on mobile devices that displays the video streams from the device cameras, relativistically or non-relativistically distorted for an arbitrary, user-defined, observer velocity. Our work facilitates an intuitive understanding of relativistic distortion.

The Central Role of the Relativistic Velocity Transformation in Modern Physics Theory

The Relativistic Velocity Transformation (RVT) is a very valuable tool for understanding the results of experiments. It was first used in 1907 by von Laue to explain the Fresnel-Fizeau light-damping phenomenon associated with the passage of light through a tube filled with a non-dispersive liquid. It is also essential for the prediction of characteristics of modern-day high-energy collision and decay processes. The purpose of the present work is to show that the RVT successes are in no way attributable to the Lorentz Transformation (LT), which is the cornerstone of Einstein’s Special Theory of Relativity (SR) published in 1905. It is shown instead that the space-time transformation (VT) introduced in 1887 by Voigt can be used directly to derive the RVT. This is an important observation since it easily proven the LT is not internally consistent and therefore is not a viable component of relativity theory. There are nonetheless experiments which cannot be understood on the basis of the RVT, but rather require the use of the classical (Galilean) velocity transformation (GVT). It is pointed out the ranges of applicability for the GVT and RVT are mutually exclusive, and that it is a straightforward manner to distinguish between them on the basis of the specific characteristics of the experiments being carried out. The “distance rephrasing procedure” is introduced to prove that the GVT can be used successfully in examples involving light pulses, contrary to what is claimed in SR. Finally, the Law of Causality is shown to lead to a strict proportionality between the timing results of two observers in relative motion to one another. This relationship is referred to as “Newtonian Simultaneity” since it requires that events which are simultaneous for one observer will also be simultaneous for the other, unlike the prediction of remote non-simultaneity (RNS) which follows from the LT. The Newton-Voigt space-time transformation (NVT) employs the Newtonian Simultaneity proportional relationship explicitly and is also consistent with Galileo’s Relativity Principle (RP). It therefore serves as a viable replacement for the LT. Newtonian Simultaneity is also a key element of the Uniform Scaling Method discussed in previous work.

Non-thermal emission from mildly relativistic dynamical ejecta of neutron star mergers: spectrum and sky image

Abstract Binary neutron star mergers are expected to produce fast dynamical ejecta, with mildly relativistic velocities extending to β = v/c > 0.6. In a preceding paper, we derived an analytic description of the time-dependent radio to X-ray synchrotron flux produced by collisionless shocks driven by such fast ejecta into the interstellar medium, for spherical ejecta with broken power-law mass (or energy) distributions, M( > γβ)∝(γβ)−s with s = sKN at γβ < γ0β0 and s = sft at γβ > γ0β0 (where γ is the Lorentz factor). Here, we extend our analysis and provide analytic expressions for the self-absorption frequency, the cooling frequency, and the observed angular size of the emitting region (which appears as a ring in the sky). For parameter values characteristic of merger calculation results - a ”shallow” mass distribution, 1 < sKN < 3, for the bulk of the ejecta (at γβ ≈ 0.2), and a steep, sft > 5, ”fast tail” mass distribution – the analytic results reproduce well (to tens of percent accuracy) the results of detailed numeric calculations, a significant improvement over earlier order-of-magnitude estimates (based on extrapolations of results valid for γβ ≪ 1).

Dynamically stable radiation pressure propulsion of flexible lightsails for interstellar exploration

Meter-scale, submicron-thick lightsail spacecraft, propelled to relativistic velocities via photon pressure using high-power density laser radiation, offer a potentially new route to space exploration within and beyond the solar system, posing substantial challenges for materials science and engineering. We analyze the structural and photonic design of flexible lightsails by developing a mesh-based multiphysics simulator based on linear elastic theory. We observe spin-stabilized flexible lightsail shapes and designs that are immune to shape collapse during acceleration and exhibit beam-riding stability despite deformations caused by photon pressure and thermal expansion. Excitingly, nanophotonic lightsails based on planar silicon nitride membranes patterned with suitable optical metagratings exhibit both mechanically and dynamically stable propulsion along the pump laser axis. These advances suggest that laser-driven acceleration of membrane-like lightsails to the relativistic speeds needed to access interstellar distances is conceptually feasible, and that their fabrication could be achieved by scaling up modern microfabrication technology.

GRB Afterglows with Energy Injections in AGN Accretion Disks

Active galactic nucleus (AGN) disks are widely considered potential hosts for various high-energy transients, including gamma-ray bursts (GRBs). The reactivation of GRB central engines can provide additional energy to shocks formed during the interaction of the initially ejected GRB jets with the circumburst material, commonly referred to as energy injections. In this paper, we study GRBs occurring in AGN disks within the context of energy injections. We adopt the standard external forward shock (EFS) model and consider both short- and long-duration GRB scenarios. Light curves for two types of radiation, namely, the radiation from the heated disk material (RHDM) and GRB afterglows, are computed. We find that the energy injection facilitates the EFS to break out from the photosphere of the low-density AGN disk at relativistic velocity. Moreover, the energy injection almost does not affect the RHDM but significantly enhances the peak flux of the GRB afterglows.

Supermassive Black Hole Winds in X-rays -- SUBWAYS. III. A population study on ultra-fast outflows

The detection of blueshifted absorption lines likely associated with ionized iron K-shell transitions in the X-ray spectra of many active galactic nuclei (AGNs) suggests the presence of a highly ionized gas outflowing with mildly relativistic velocities (0.03c - 0.6c) named ultra-fast outflow (UFO). Within the SUBWAYS project, we characterized these winds starting from a sample of 22 radio-quiet quasars at an intermediate redshift (0.1 leq z leq 0.4) and compared the results with similar studies in the literature on samples of local Seyfert galaxies (i.e., 42 radio-quiet AGNs observed with XMM-Newton at z leq 0.1) and high redshift radio-quiet quasars (i.e., 14 AGNs observed with XMM-Newton and Chandra at z geq 1.4). The scope of our work is a statistical study of UFO parameters and incidence considering the key physical properties of the sources, such as supermassive black hole (SMBH) mass, bolometric luminosity, accretion rates, and spectral energy distribution (SED) with the aim of gaining new insights into the UFO launching mechanisms. We find indications that highly luminous AGNs with a steeper X-ray/UV ratio, $ ox $, are more likely to host UFOs. The presence of UFOs is not significantly related to any other AGN property in our sample. These findings suggest that the UFO phenomenon may be transient. Focusing on AGNs with UFOs, other important findings from this work include: (1) faster UFOs have larger ionization parameters and column densities; (2) X-ray radiation plays a more crucial role in driving highly ionized winds compared to UV; (3) the correlation between outflow velocity and luminosity is significantly flatter than what is expected for radiatively driven winds; (4) more massive black holes experience higher wind mass losses, suppressing the accretion of matter onto the black hole; (5) the UFO launching radius is positively correlated with the Eddington ratio. Furthermore, our analysis suggests the involvement of multiple launching mechanisms, including radiation pressure and magneto-hydrodynamic processes, rather than pointing to a single, universally applicable mechanism.

Cosmic-ray boosted dark matter confronted by constraints on new light mediators

The detectability of light dark matter in direct detection experiments is limited by the small kinetic energy of the recoiling targets. Thus, scenarios where dark matter is boosted to relativistic velocities provide a useful tactic to constrain sub-GeV dark matter particles. Of the possible dark matter boosting mechanisms, cosmic-ray upscattering is an appealing paradigm as it does not require any additional assumptions beyond dark matter coupling to nucleons or electrons. However, detectable signals are obtained only with relatively large cross sections which, in turn, can only be realized with large couplings, light mediators or composite dark matter. In this work we consider a general set of light mediators that couple dark matter to hadrons. Using data from Borexino, XENON1T, LZ and Super-K, we show that existing constraints on such mediators preclude appreciable cosmic-ray dark matter upscattering. This finding highlights the limited applicability of cosmic-ray upscattering constraints and suggests they only be used in model-dependent studies. Published by the American Physical Society 2024

Magnetic and thermal acceleration in extragalactic jets

Aims. Relativistic jets launched from active galactic nuclei accelerate up to highly relativistic velocities within a length scale of between a few parsecs and tens of parsecs. The precise way in which this process takes place is still unclear. While magnetic acceleration is known to be able to accelerate relativistic outflows, little attention has been paid to the role of thermal acceleration. The latter has been assumed to act only on compact regions very close to the central engine, and to become negligible on parsec scales. However, this holds under the assumption of small internal energies relative to the magnetic ones, and whether or not this assumption is valid and what happens when we drop this assumption are open questions. Methods. We used a 2D relativistic magnetohydrodynamical code to explore jet acceleration from subparsec to parsec scales. As initial conditions for our models, we used observational constraints on jet properties derived by means of very long-baseline interferometry observations for a Fanaroff Riley I radio galaxy, NGC 315. We investigated the parameter space established for this source and performed a number of simulations of magnetically, thermally, or kinetically dominated jets at injection, and compared our results with the observations. Furthermore, we employed different models to characterize our jets, involving different magnetic field configurations (i.e., force-free vs. nonforce-free) and varying shear layer thicknesses. Results. Our simulated jets show that when thermal energy is comparable to or exceeds magnetic energy, thermal acceleration becomes significant at parsec scales. This result has important consequences, potentially extending the acceleration region far beyond the collimation scales, as thermal acceleration can effectively operate within a conically expanding jet. In all the models, we find acceleration to be driven by expansion, as expected. A number of our models allow us to reproduce the acceleration and opening angles observed in NGC 315. Finally, our results indicate that disk-launched winds might play an important role in jet propagation. Namely, when the jet has an initial force-free magnetic field configuration, thicker shear layers are needed to shield the internal spine from the action of the external medium and thus delay the growth of instabilities.

X-Ray Polarization of the Black Hole X-Ray Binary 4U 1630–47 Challenges the Standard Thin Accretion Disk Scenario

A large energy-dependent X-ray polarization degree is detected by the Imaging X-ray Polarimetry Explorer (IXPE) in the high-soft emission state of the black hole X-ray binary 4U 1630–47. The highly significant detection (at ≈50σ confidence level) of an unexpectedly high polarization, rising from ∼6% at 2 keV to ∼10% at 8 keV, cannot be easily reconciled with standard models of thin accretion disks. In this work, we compare the predictions of different theoretical models with the IXPE data and conclude that the observed polarization properties are compatible with a scenario in which matter accretes onto the black hole through a thin disk covered by a partially ionized atmosphere flowing away at mildly relativistic velocities.

Sagnac interferometry and the impact of conductivity-dependent Raman gain on rotary photon drag

We theoretically demonstrate the impact of conductivity-dependent Raman gain (RG) on rotary photon drag (RPD) in a Sagnac interferometer (SI). The presence of conductivity-dependent Raman gain results in enhanced RPD angles, ranging from θ d = ± 0.56 radians to θ d = ± 0.7 radians. The susceptibility, group index, relativistic group velocities, and RPD exhibit significant fluctuations with changes in the conductivity phase. Specifically, we observe gain-singlets when the control field is deactivated, while gain doublets are achieved when the control field is activated. Moreover, within the gain regions, we observe normal dispersion, whereas anomalous dispersion is observed around the gain regions. These findings have potential applications in controlled image coding/design, four-wave mixing, photo detectors, light modulation, and phase-matching in Brillouin scattering.

Complexity growth in a holographic QCD model* *Supported in part by the National Key Research and Development Program of China (2022YFA1604900). This work is also partly supported by the National Natural Science Foundation of China (NSFC) (12275104, 11890711, 11890710, 11735007)

In this study, we utilize the complexity-action duality to study the evolution of complexity in a holographic QCD model at finite temperature and chemical potential. By inserting a fundamental string as a probe, we investigated the properties of complexity growth in this Einstein-Maxwell-scalar gravity system, which is affected by the string velocity, chemical potential, and temperature. Our results show that the complexity growth is maximized when the probe string is stationary, and it decreases as the velocity of the string increases. When the string approaches relativistic velocities, the complexity growth always increases monotonically with respect to the chemical potential. Furthermore, we find that the complexity growth can be used to identify phase transitions and crossovers in the model.

Time-space formulation of a conservative string subject to finite transformations

This paper investigates power-balanced descriptions of the conservative vibrating string. First, the hypotheses of continuum mechanics are recalled for the case of infinitesimal transformations. The string is described by classical partial differential equations (PDEs) and reformulated as a port Hamiltonian system (PHS). Second, the case of finite (possibly large) transformations is considered, for which the time variation of the elastic energy appears to be no longer the elastic power. To naturally solve this difficulty and ensure the invariance of the elastic power with respect to the superposition of rigid body motion, the problem is here addressed in the framework of a time-space formulation. Eulerian and Lagrangian conservative formulations are proposed in the context of non relativistic velocities. This work also yields perspectives for a time-space representation of a port-Hamiltonian vibrating string invariant to the change of observer in a relativistic context.