Energy Density Of Particles Research Articles

Heat capacity and quantum compressibility of dynamical spacetimes with thermal particle creation

This work continues the investigation in two recent papers on the quantum thermodynamics of spacetimes, (1) placing what was studied in [] for thermal quantum fields in the context of early universe cosmology, and (2) extending the considerations of vacuum compressibility of dynamical spaces treated in [] to dynamical spacetimes with thermal quantum fields. We begin with a warning that thermal equilibrium condition is not guaranteed to exist or maintained in a dynamical setting and thus finite temperature quantum field theory in cosmological spacetimes needs more careful considerations than what is often described in textbooks. A full description requires nonequilibrium quantum field theory in dynamical spacetimes using “in-in” techniques. A more manageable subclass of dynamics is where thermal equilibrium conditions are established at both the beginning and the end of evolution, where the in-thermal state and the out-thermal state are both well defined. Particle creation in the full history can then be calculated in this in-out asymptotically-stationary setup via the S-matrix transition amplitudes. Here we shall assume an in-vacuum state. It has been shown that if the intervening dynamics has an initial period of exponential expansion, such as in inflationary cosmology, particles created from the parametric amplification of the vacuum fluctuations in the initial vacuum will have a thermal spectrum measured at the out-state. Under these conditions finite temperature field theory can be applied to calculate the quantum thermodynamic quantities. Here we consider a massive conformal scalar field in a closed four-dimensional Friedmann-Lemaître-Robertson-Walker universe based on the simple analytically solvable Bernard-Duncan model. We calculate the energy density of particles created from an in-vacuum and derive the partition function. From the free energy we then derive the heat capacity and the quantum compressibility of these spacetimes with thermal particle creation. We end with some discussions and suggestions for further work in this program of studies. Published by the American Physical Society 2024

Characterizing the γ-Ray Emission from FR0 Radio Galaxies

FR0 galaxies constitute the most abundant jet population in the local Universe. With their compact jet structure, they are broadband photon emitters and have been proposed as multimessenger sources. Recently, these sources have been detected for the first time in γ rays. Using a revised FR0 catalog, we confirm that the FR0 population as a whole are γ-ray emitters, and we also identify two significant sources. For the first time, we find a correlation between the 5 GHz core radio luminosity and γ-ray luminosity in the 1–800 GeV band, having a 4.8σ statistical significance. This is clear evidence that the jet emission mechanism is similar in nature for FR0s and the well-studied canonical FR (FRI and FRII) radio galaxies. Furthermore, we perform broadband spectral energy distribution modeling for the significantly detected sources as well as the subthreshold source population using a one-zone synchrotron self-Compton model. Within the maximum jet power budget, our modeling shows that the detected γ rays from the jet can be explained as inverse Compton photons. To explain the multiwavelength observations for these galaxies, the modeling results stipulate a low bulk Lorentz factor and a jet composition far from equipartition, with the particle energy density dominating over the magnetic field energy density.

Constraints on real scalar inflation from preheating using LATTICEEASY* *Wei Cheng was Supported by the Natural Science Foundation of Chongqing, China (CSTB2022NSCQ-MSX0432), the Science and Technology Research Project of Chongqing Education Commission (KJQN202200621), and the Chongqing Human Resources and Social Security Administration Program (D63012022005). Ruiyu Zhou was Supported by the Chongqing Natural Science Foundation (CSTB2022NSCQ-MSX0534). This work was supported in

In this paper, we undertake a detailed study of real scalar inflation using LATTICEEASY simulations to investigate preheating phenomena. Generally, the scalar inflation potential with non-minimal coupling can be approximated using a quartic potential. We observe that the evolutionary behavior of this potential remains unaffected by the coupling coefficient. Furthermore, the theoretical predictions for the scalar spectral index ( ) and tensor-to-scalar power ratio (r) are independent of this coefficient. Consequently, the coefficients of this model are not constrained by Planck observations. Fortunately, the properties of preheating after inflation provide a viable approach to examining these coefficients. Through LATTICEEASY simulations, we trace the evolution of particle number density, scale factor, and energy density during the preheating process. Subsequently, we derive the parameters, such as the energy ratio (γ) and the e-folding number of preheating ( ), which facilitate further predictions of and r. We successfully validate real scalar inflation model using preheating in LATTICEEASY simulations based on the analytical relationship between preheating and inflation models.

Thermochemical heat storage performance and structural stability of SiO2-coated CaO particles under fluidization in CaO/Ca(OH)2 cycles

The decline in CaO/Ca(OH)2 heat storage performance of CaO-based material with the number of cycles due to its fast expansion and fragmentation is an problem in the fluidized bed reactor. In this paper, a novel SiO2-coated CaO particle was manufactured from limestone and silica sol via wet-mixing method. Exothermic performance (such as exothermic temperature, effective hydration conversion and volumetric energy density) and structural stability of SiO2-coated CaO particles in a fluidized bed reactor were studied. The effects of SiO2 addition and calcination temperature on the exothermic performance and structural stability were analyzed, respectively. The results show that the mass ratio of limestone to silica sol of 1:1 and calcination temperature of 850 °C are recommended for the preparation of SiO2-coated CaO. The SiO2 layer is observed on the surface of the CaO. SiO2-coated CaO particles exhibit superior structural stability than uncoated CaO particles. The SiO2 coating reduces the increase of average particle size during 10 cycles from 33 % to 11 %. After 10 heat storage cycles, SiO2-coated CaO particles achieve a reduction of 45.4 % in expansion rate and 48.5 % in attrition rate compared with uncoated CaO particles, respectively. The volumetric energy density of SiO2-coated CaO particles after 10 cycles is 33.2 % higher than that of uncoated CaO particles. The highest exothermic temperature of SiO2-coated CaO particles after 10 cycles reaches 455.4 °C (steam partial pressure @ 60 kPa). The SiO2-coated CaO seems a promising candidate for the CaO/Ca(OH)2 thermochemical heat storage in the fluidized bed rector.

How effective is N eff at discovering dark radiation in a cosmology with heavy particle decay?

Any light relic which was in thermal equilibrium with the Standard Model before it freezes out results in a shift in the effective number of neutrino species, N eff. This quantity is being measured with increasing precision, and planned experiments would seemingly rule out light particles beyond the Standard Model, even for rather high temperature light particle freeze out. Here we explore how these bounds are loosened if the energy density of the light particles is diluted with respect to that of Standard Model radiation. This can happen if a heavy particle that is decoupled from the Standard Model decays into the Standard Model bath after the light particle freezes out. After calculating how heavy state decays alter N eff for light particles beyond the Standard Model, we focus in particular on the case that the heavy decaying particle is a gravitino, and use current bounds on N eff to place constraints on the gravitino mass and the branching ratio into light particles for different values of the reheating temperature of the Universe.

Current Sheet as an Optimal Synchrotron Maser on a Radio Pulsar

Using a relativistic plasma with an isotropic monoenergetic distribution of electrons andpositrons as an example, we show that in the maser regime the maximum possible amplification ofsynchrotron radiation at a distance of one wavelength is achieved in a medium where the magnetic energydensity is of the order of the particle energy density. This ratio of the energy densities corresponds to a(Harris-type) current sheet. We have obtained an electron Lorentz factor of 350 and a magnetic fieldstrength of 10 kG in the maser radio emission region for the Crab pulsar. Our estimate suggests thatthe optical and coherent radio emissions of the object originate from one synchrotron source in the form ofa current sheet. The diameter of the source must exceed the light-cylinder radius approximately by a factorof 6 for the maser wave field to interact with particles in the linear regime, in particular, to keep its phasevelocity higher than the speed of light in a vacuum—a necessary condition for the synchrotron instability.

Synergy between cosmological and laboratory searches in neutrino physics

The intersection of the cosmic and neutrino frontiers is a rich field where much discovery space still remains. Neutrinos play a pivotal role in the hot big bang cosmology, influencing the dynamics of the universe over numerous decades in cosmological history. Recent studies have made tremendous progress in understanding some properties of cosmological neutrinos, primarily their energy density. Upcoming cosmological probes will measure the energy density of relativistic particles with higher precision, but could also start probing other properties of the neutrino spectra. When convolved with results from terrestrial experiments, cosmology can become even more acute at probing new physics related to neutrinos or even Beyond the Standard Model (BSM). Any discordance between laboratory and cosmological data sets may reveal new BSM physics and/or suggest alternative models of cosmology. We give examples of the intersection between terrestrial and cosmological probes in the neutrino sector, and briefly discuss the possibilities of what different laboratory experiments may see in conjunction with cosmological observatories.

Analytic formula to calculate the reheating temperature via gravitational particle production in smooth nonoscillating backgrounds

We present for smooth nonoscillating backgrounds an analytic formula which calculates the energy density of massive and massless particles created via gravitational particle production, thus giving the corresponding reheating temperature. It can be applied to models of quintessential inflation such as $\ensuremath{\alpha}$-attractors, and shows that for masses larger than the Hubble rate at the end of inflation, namely ${H}_{\mathrm{END}}$, the reheating temperature is exponentially suppressed. On the contrary, for masses of the order of ${H}_{\mathrm{END}}$ one obtains a maximum reheating temperature of the order of ${10}^{7}\text{ }\text{ }\mathrm{GeV}$. Finally, to overcome the constraints coming from the overproduction of gravitational waves in quintessential inflation, we have shown that the viable masses which ensure the big bang nucleosynthesis success are in the range between $2\ifmmode\times\else\texttimes\fi{}{10}^{10}\text{ }\text{ }\mathrm{GeV}$ and $4\ifmmode\times\else\texttimes\fi{}{10}^{13}\text{ }\text{ }\mathrm{GeV}$, leading to a maximum reheating temperature of the order ${10}^{5}--{10}^{7}\text{ }\text{ }\mathrm{GeV}$.

Phenomenological modelling of the Crab Nebula’s broadband energy spectrum and its apparent extension

Context. The Crab Nebula emits exceptionally bright non-thermal radiation across the entire wavelength range from the radio to the most energetic photons. So far, the underlying physical model of a relativistic wind from the pulsar terminating in a hydrodynamic standing shock has remained fairly unchanged since the early 1970s when it was first introduced. One of the predictions of this model is an increase in the toroidal magnetic field downstream from the shock where the flow velocity drops quickly with increasing distance until it reaches its asymptotic value, matching the expansion velocity of the nebula. Aims. The magnetic field strength in the nebula is poorly known. Using the recent measurements of the spatial extension and improved spectroscopy of the gamma-ray nebula, it has become –for the first time – feasible to determine in a robust way both the strength as well as the radial dependence of the magnetic field in the downstream flow. Methods. In this work, we introduce a detailed radiative model which was used to calculate the emission from non-thermal electrons (synchrotron and inverse Compton) as well as from thermal dust present in the Crab Nebula in a self-consistent way to compare it quantitatively with observational data. Special care was given to the radial dependence of the electron and seed field density. Results. The radiative model was used to estimate the parameters related to the electron populations responsible for radio and optical/X-ray synchrotron emission. In this context, the mass of cold and warm dust was determined. A combined fit based upon a χ2 minimisation successfully reproduced the complete data set used. For the best-fitting model, the energy density of the magnetic field dominates over the particle energy density up to a distance of ≈1.3 rs (rs: distance of the termination shock from the pulsar). The very high energy (VHE: E > 100 GeV) and ultra-high energy (UHE: E > 100 TeV) gamma-ray spectra set the strongest constraints on the radial dependence of the magnetic field, favouring a model where B(r) = (264 ± 9) μG(r/rs)−0.51 ± 0.03. For a collection of VHE measurements during epochs of higher hard X-ray emission, a significantly different solution B(r) = (167 ± 5) μG(r/rs)−0.29(+0.03, −0.06) is found. Conclusions. The high energy (HE: E > 100 MeV) and VHE gamma-ray observations of the Crab Nebula lift the degeneracy of the synchrotron emission between particle and magnetic field energy density. The reconstructed magnetic field and its radial dependence indicates a ratio of Poynting to kinetic energy flux σ ≈ 0.1 at the termination shock, which is ≈30 times larger than estimated up to now. Consequently, the confinement of the nebula would require additional mechanisms to slow the flow down through, for example, excitation of small-scale turbulence with possible dissipation of the magnetic field.

Cosmological implications of photon-flux upper limits at ultrahigh energies in scenarios of Planckian-interacting massive particles for dark matter

Using the data of the Pierre Auger Observatory, we report on a search for signatures that would be suggestive of super-heavy particles decaying in the Galactic halo. From the lack of signal, we present upper limits for different energy thresholds above ≳108 GeV on the secondary by-product fluxes expected from the decay of the particles. Assuming that the energy density of these super-heavy particles matches that of dark matter observed today, we translate the upper bounds on the particle fluxes into tight constraints on the couplings governing the decay process as a function of the particle mass. Instantons, which are nonperturbative solutions to Yang-Mills equations, can give rise to decay channels otherwise forbidden and transform stable particles into metastable ones. Assuming such instanton-induced decay processes, we derive a bound on the reduced coupling constant of gauge interactions in the dark sector: αX≲0.09, for 109≲MX/GeV<1019. Conversely, we obtain that, for instance, a reduced coupling constant αX=0.09 excludes masses MX≳3×1013 GeV. In the context of dark matter production from gravitational interactions alone during the reheating epoch, we derive constraints on the parameter space that involves, in addition to MX and αX, the Hubble rate at the end of inflation, the reheating efficiency, and the nonminimal coupling of the Higgs with curvature.1 MoreReceived 9 August 2022Accepted 14 December 2022DOI:https://doi.org/10.1103/PhysRevD.107.042002© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCosmic rays & astroparticlesCosmologyDark matterParticle dark matterGravitation, Cosmology & Astrophysics

A multi-band study and exploration of the radio wave–γ-ray connection in 3C 84

Total intensity variability light curves offer a unique insight into the ongoing debate about the launching mechanism of jets. For this work, we utilised the availability of radio and γ-ray light curves over a few decades of the radio source 3C 84 (NGC 1275). We calculated the multi-band time-lags between the flares identified in the light curves via discrete cross-correlation and Gaussian process regression. We find that the jet particle and magnetic field energy densities are in equipartition (kr = 1.08 ± 0.18). The jet apex is located z91.5 GHz = 22−645 Rs (2 − 20 × 10−3 pc) upstream of the 3 mm radio core; at that position, the magnetic field amplitude is Bcore91.5 GHz = 3−10 G. Our results are in good agreement with earlier studies that utilised very-long-baseline interferometry. Furthermore, we investigated the temporal relation between the ejection of radio and γ-ray flares. Our results are in favour of the γ-ray emission being associated with the radio emission. We are able to tentatively connect the ejection of features identified at 43 and 86 GHz to prominent γ-ray flares. Finally, we computed the multiplicity parameter λ and the Michel magnetisation σM, and find that they are consistent with a jet launched by the Blandford &amp; Znajek (1977, MNRAS, 179, 433) mechanism.

The full viscous quantum hydrodynamic system in one dimensional space

A viscous quantum hydrodynamic system for particle density, current density, energy density, and electrostatic potential, coupled with a Poisson equation, is studied in spatial one dimensional real line. The system is self-consistent in the sense that the electric field, which forms a forcing term in the momentum and energy equations, is determined by the coupled Poisson equation. First, the existence and uniqueness of the stationary solution is proved in an appropriate Sobolev space. Then, exponential stability of the stationary solution is established by constructing an a priori estimate. Since the techniques for classical hydrodynamic equations are not applicable here due to the quantum term, the existence of a local-in-time solution is obtained by showing the existence of local-in-time solutions of a reformulated system via the iteration method.

К выводу в рамках статистики Тсаллиса релятивистского кинетического уравнения для разреженной идеальной газовой системы высокоэнергетических частиц

In this work we discuss the nonextensive kinetic theory for anomalous gas q-systems in a general relativistic framework. By including nonextensive effects in the collision term of the relativistic equation (violating Boltzmann molecular chaos hypothesis) and in a modified 4-vector expression for the q-entropy flux it is shown that the entropic Tsallis formalism preserves a local form of the relativistic H-theorem according to which the entropy growth in any point of space-time is never negative. It is shown that the local collision equilibrium (the zero-point entropy source term) is described by a generalized version of the Yuttner relativistic distribution. Using this distribution, the particle number, energy and entropy densities and the thermal equation of state for a relativistic q-gas of identical particles in the equilibrium state are determined explicitly. The results are reduced to the standard ones in the extensive limit, thus showing that the nonex-tensive entropic scheme can be consistent with the space-time ideas contained in the general rela-tivistic theory. The constructed kinetic equation is designed to describe a wide range of phenomena in as-trophysics, cosmology and high-energy physics, in particular, multiparticle production processes in relativistic collisions.

Geometric phase for spherical magnetic particles

In this study, we study on the characterization of the behavior of a dynamically charged magnetic particle in spherical space and on the geometrical expressions of electromagnetic parameters resulting from this behavior in spherical space. First, we characterize the spherical-magnetic particles and spherical-magnetic fields, which we named associated with the spherical frame. Then, with the help of the Lorentzian force and the Newtonian force relationship, we obtain the electric field of these magnetic particles in terms of the particle’s charge and mass. Next, with the help of electric field and magnetic field, we obtain important electromagnetic parameters such as energy density, power flow, light intensity and power of these spherical magnetic particles. Finally, we obtain the geometric (Berry) phases formed by Heisenberg antiferromagnetic models of the power flows.

Thermochemical heat storage performance of CaO particles under fluidization in coupled CaO/Ca(OH)2 cycles and CaO/CaCO3 cycles

The sintering of CaO in CaO/CaCO3 heat storage cycles and the agglomeration of CaO in CaO/Ca(OH)2 heat storage cycles are the main reasons for the decay in heat storage performance of CaO-based materials, respectively. In this work, a novel CaO/Ca(OH)2/CaCO3 coupling process using limestone under fluidization was proposed to realize the sequential CaO/Ca(OH)2 heat storage and CaO/CaCO3 heat storage. The exothermic performance of CaO particles under fluidization in the CaO/Ca(OH)2/CaCO3 coupling heat storage process were investigated. Two coupling modes were compared according to the different feeding methods of fresh CaO particles. The maximum exothermic temperature of CaO particles in the optimal coupling mode reaches 456.9 °C in the first CaO/Ca(OH)2 cycle and 783.8 °C in the first CaO/CaCO3 cycle, respectively. The interaction mechanism between CaO/CaCO3 heat storage cycles and CaO/Ca(OH)2 heat storage cycles was determined. The volume shrinkage caused by the sintering of CaO in CaO/CaCO3 cycles improves the volumetric energy density of CaO particles in CaO/Ca(OH)2 cycles. After introducing 10 CaO/CaCO3 cycles in the first coupling step, the energy density of CaO particles in CaO/Ca(OH)2 cycles is improved by 190 %. The CaO/Ca(OH)2 cycles reactivate carbonation activity of CaO particles in CaO/CaCO3 cycles by increasing porosity of CaO. Therefore, after introducing 10 CaO/Ca(OH)2 cycles in the first coupling step, the carbonation conversion of CaO particles increases by 64.7 %. This work provides a novel and promising heat storage process by integrating efficient CaO/Ca(OH)2 and CaO/CaCO3 cycles under the fluidization.

Energy Partition and Balance at Dipolarization Fronts

AbstractDipolarization fronts (DFs) have been documented as important structures contributing to energy conversion and flux transport in Earth's magnetotail. However, energy partition and balance at DFs still remain elusive. Using high‐cadence data from NASA's Magnetospheric Multiscale mission, we preform a comprehensive investigation of energy budgets at the DFs. We find that material derivatives of particle energy densities in the DF frame are basically close to zero, indicating that particles experience negligible heating and/or acceleration and that the energy released at the DFs is predominantly manifested in the form of energy flux. The energy flux is found to be dominated by ion and electron enthalpy flux, ion heat flux, and Poynting flux, with electron enthalpy flux being locally elevated. In addition, the energy flux tends to increase during the DFs' earthward propagation, without exhibiting clear asymmetry in the dawn‐dusk direction. These results help further understand energy budgets at the DFs.

Pseudorapidity distribution of energy density and distribution of charged particles in different categories of the final state in pp collisions at s = 13 TeV

In this paper, we present here a detailed study of several observables as a function of pseudorapidity from several hadron production models commonly used for extended air shower simulations and compare these predictions with [Formula: see text] collisions measured by the CMS experiment at [Formula: see text] TeV. To facilitate the model/data comparisons, the pseudorapidity binning used in the energy density spectra data was also applied to the Monte Carlo analysis ([Formula: see text] and [Formula: see text]). Given that no model currently describes the full breadth of available hadronic collision data, four independent models were used in the comparison study, each with differences in the handling of soft quantum chromodynamics processes, in particular. The analysis results show that predictions from EPOS-LHC provide good agreement with the data, in contrast with the other models used in the study (QGSJETII-04, DPMJET-3.19, Sibyll2.3d). Significant modifications may be required in the rest of the model-based generators for them to provide a better description of the experimental observations.

Data-driven intrinsic localized mode detection and classification in one-dimensional crystal lattice model

In this work we propose Support Vector Machine classification algorithms to classify one-dimensional crystal lattice waves from locally sampled data. Different learning datasets of particle displacements, momenta and energy density values are considered. Efficiency of the classification algorithms is further improved by two dimensionality reduction techniques: Principal Component Analysis and Locally Linear Embedding. Robustness of classifiers is investigated and demonstrated. Developed algorithms are successfully applied to detect localized intrinsic modes in three numerical simulations considering a case of two localized stationary breather solutions, a single stationary breather solution in noisy background and two mobile breather collision.

Comparative Analysis of the 2020 November 29 Solar Energetic Particle Event Observed by Parker Solar Probe

Abstract We analyze two specific features of the intense solar energetic particle (SEP) event observed by Parker Solar Probe (PSP) between 2020 November 29 and 2020 December 2. The interplanetary counterpart of the coronal mass ejection (CME) on 2020 November 29 that generated the SEP event (hereafter ICME-2) arrived at PSP (located at 0.8 au from the Sun) on 2020 December 1. ICME-2 was preceded by the passage of an interplanetary shock at 18:35 UT on 2020 November 30 (hereafter S2), that in turn was preceded by another ICME (i.e., ICME-1) observed in situ on 2020 November 30. The two interesting features of this SEP event at PSP are the following: First, the presence of the intervening ICME-1 affected the evolution of the ≲8 MeV proton intensity-time profiles resulting in the observation of inverted energy spectra throughout the passage of ICME-1. Second, the sheath region preceding ICME-2 was characterized by weak magnetic fields compared to those measured immediately after the passage of the shock S2 and during the passage of ICME-2. Comparison with prior SEP events measured at 1 au but with similar characteristics indicates that (1) low-energy particles accelerated by S2 were excluded from propagating throughout ICME-1, and (2) the low magnetic fields measured in the sheath of ICME-2 resulted from the properties of the upstream solar wind encountered by ICME-2 that was propagated into the sheath, whereas the energy density of the high-energy particles in the sheath did not play a dominant role in the formation of these low magnetic fields.

Massless charged particles tunneling radiation from a RN-dS horizon and the linear and quadratic GUP

In this paper, we investigate the massless Reissner–Nordstrom de Sitter metric in the context of minimal length scenarios. We prove not only the confinement of the energy density of massless charged particles, both fermions and bosons, but also their ability to tunnel through the cosmological horizon. These massless particles might be interacting with Dirac sea and in this case they will appear outside the cosmological horizon in the context of dS/CFT holography. This result may formulate a fundamental reason for the expansion of the Dirac sea. Therefore, a spacetime Big Crunch may occur.