Physics — Open Access Journal

We theoretically study the dynamical Casimir effect (DCE), i.e., parametric amplification of a quantum vacuum, in an optomechanical cavity interacting with a photonic crystal, which is considered to be an ideal system to study the microscopic dissipation effect on the DCE. Starting from a total Hamiltonian including the photonic band system as well as the optomechanical cavity, we have derived an effective Floquet–Liouvillian by applying the Floquet method and Brillouin–Wigner–Feshbach projection method. The microscopic dissipation effect is rigorously taken into account in terms of the energy-dependent self-energy. The obtained effective Floquet–Liouvillian exhibits the two competing instabilities, i.e., parametric and resonance instabilities, which determine the stationary mode as a result of the balance between them in the dissipative DCE. Solving the complex eigenvalue problem of the Floquet–Liouvillian, we have determined the stationary mode with vanishing values of the imaginary parts of the eigenvalues. We find a new non-local multimode DCE represented by a multimode Bogoliubov transformation of the cavity mode and the photon band. We show the practical advantage for the observation of DCE in that we can largely reduce the pump frequency when the cavity system is embedded in a narrow band photonic crystal with a bandgap. Full article

Herein we demonstrate the dramatic effect of non-locality on the plasmons which contribute to the Casimir forces, with a graphene sandwich as a case study. The simplicity of this system allowed us to trace each contribution independently, as we observed that interband processes, although dominating the forces at short separations, are poorly accounted for in the framework of the Dirac cone approximation alone, and should be supplemented with other descriptions for energies higher than 2.5 eV. Finally, we proved that distances smaller than 200 nm, despite being extremely relevant to state-of-the-art measurements and nanotechnology applications, are inaccessible with closed-form response function calculations at present. Full article

We present a new perspective on the link between quantum electrodynamics (QED) and Maxwell’s equations. We demonstrate that the interpretation of the electric displacement vector $\mathbf{D}={\epsilon }_0\mathbf{E}$ , where $\mathbf{E}$ is the electric field vector and ${\epsilon }_0$ is the permittivity of the vacuum, as vacuum polarization is consistent with QED. A free electromagnetic field polarizes the vacuum, but the polarization and magnetization currents cancel giving zero source current. The speed of light is a universal constant, while the fine structure constant, which couples the electromagnetic field to matter runs, as it should. Full article

We present the status of the art of the Archimedes experiment, devoted to measuring the debated interaction of quantum vacuum fluctuations and gravity. The method is essentially the weighing of the transition energy of a layered superconductor where the contribution of vacuum energy to the transition energy is expected to be relevant. The transition is obtained by modulating the temperature of the superconducting sample at a frequency of about 10 mHz and the expected change of weight is measured with a suitably designed high sensitivity cryogenic beam balance. In this paper, we present an overview of the experiment, discussing the expected signal to be measured, and presenting in particular the result of a prototype balance operated in our present laboratory. In the frequency range of the measurement, the sensitivity is affected mainly by seismic, thermal, sensor, and control noise. We discuss these points showing in particular the design of the cryogenic apparatus, the final balance, and the quiet seismic site that will host the final measurement. Full article

In this paper, we dwell on three issues: (1) revisit the relation between vacuum fluctuations and radiation reaction in atom-field interactions, an old issue that began in the 1970s and settled in the 1990s with its resolution recorded in monographs; (2) the fluctuation–dissipation relation (FDR) of the system, pointing out the differences between the conventional form in linear response theory (LRT) assuming ultra-weak coupling between the system and the bath, and the FDR in an equilibrated final state, relaxed from the nonequilibrium evolution of an open quantum system; (3) quantum radiation from an atom interacting with a quantum field: We begin with vacuum fluctuations in the field acting on the internal degrees of freedom (idf) of an atom, adding to its dynamics a stochastic component which engenders quantum radiation whose backreaction causes quantum dissipation in the idf of the atom. We show explicitly how different terms representing these processes appear in the equations of motion. Then, using the example of a stationary atom, we show how the absence of radiation in this simple cases is a result of complex cancellations, at a far away observation point, of the interference between emitted radiation from the atom and the local fluctuations in the free field. In so doing we point out in Issue 1 that the entity which enters into the duality relation with vacuum fluctuations is not radiation reaction, which can exist as a classical entity, but quantum dissipation. Finally, regarding issue 2, we point out for systems with many atoms, the co-existence of a set of correlation-propagation relations (CPRs) describing how the correlations between the atoms are related to the propagation of their (retarded non-Markovian) mutual influence manifesting in the quantum field. The CPR is absolutely crucial in keeping the balance of energy flows between the constituents of the system, and between the system and its environment. Without the consideration of this additional relation in tether with the FDR, dynamical self-consistency cannot be sustained. A combination of these two sets of relations forms a generalized matrix FDR relation that captures the physical essence of the interaction between an atom and a quantum field at arbitrary coupling strength. Full article

Here we introduce the latest version of the GAMESH model, capable to consistently account for the formation and evolution of compact binary systems along the cosmic assembly of a Milky Way (MW)-like galaxy, centered on a local group volume resolving a large population of dwarf satellites. After describing the galaxy assembly process and how the formation of binary systems is accounted for, we summarize some recent findings on the properties and evolution of low-metallicity dwarf galaxies hosting the birth/coalescence of stellar/compact binaries generating GW150914-like signals. Finally, we focus on the mass and orbital properties of the above compact binary candidates assessing their impact on the resulting coalescence times and on selecting suitable galaxy hosts. Full article

When a quantum field is in contact with a thermal bath, the vacuum state of the field may be generalized to a thermal vacuum state, which takes into account the thermal noise. In thermo field dynamics, this is realized by doubling the dimensionality of the Fock space of the system. Interestingly, the representation of thermal noise by means of an augmented space is also found in a distinctly different approach based on the Wigner transform of both the field operators and density matrix, which we pursue here. Specifically, the thermal noise is introduced by augmenting the classical-like Wigner phase space by means of Nosé–Hoover chain thermostats, which can be readily simulated on a computer. In this paper, we illustrate how this may be achieved and discuss how non-equilibrium quantum thermal distributions of the field modes can be numerically simulated. Full article

Radio-frequency (RF) charged particle traps, such as the Paul trap or higher order RF multipole traps, may be used to trap quasi-neutral plasma. The presence of positive and negative plasma species mitigates the ejection of particles that occurs due to space charge repulsion. For symmetric species, such as a pair plasma, the trapped particle distribution is essentially equal for both species. For plasma with species of disparate charge-to-mass ratio, the RF parameters are chosen to directly trap the lighter species, leading to loss of the heavier species until sufficient net space charge develops to prevent further loss. Two-dimensional (2D) electrostatic particle-in-cell simulations are performed of cases with mass ratio m₊/m₋ = 10, and also with ion–electron plasma. Multipole cases including order N = 2 (quadrupole) and higher order N = 8 (hexadecapole) are considered. The light ion-heavy ion N = 8 case exhibits particles losses less than 5% over 2500 RF periods, but the N = 8 ion–electron case exhibits a higher loss rate, likely due to non-adiabaticity of electron trajectories at the boundary, but still with low total electron loss current on the order of 10 μA. The N = 2 ion-electron case is adiabatic and stable, but is subject to a smaller trapping volume and greater initial perturbation of the bulk plasma by the trapping field. Full article

We present an open-source kinematic fitting routine designed for low-energy nuclear physics applications. Although kinematic fitting is commonly used in high-energy particle physics, it is rarely used in low-energy nuclear physics, despite its effectiveness. A FORTRAN and ROOT C++ version of the FUNKI_FIT kinematic fitting code have been developed and published open access. The FUNKI_FIT code is universal in the sense that the constraint equations can be easily modified to suit different experimental set-ups and reactions. Two case studies for the use of this code, utilising experimental and Monte–Carlo data, are presented: (1) charged-particle spectroscopy using silicon-strip detectors; (2) charged-particle spectroscopy using active target detectors. The kinematic fitting routine provides an improvement in resolution in both cases, demonstrating, for the first time, the applicability of kinematic fitting across a range of nuclear physics applications. The ROOT macro has been developed in order to easily apply this technique in standard data analysis routines used by the nuclear physics community. Full article

We propose a method for the estimation of the spectral response of a photodetector, using only the variation of the temperature of a black body source without the need of an expensive monochromator or a circular filter. The proposed method is suitable especially for infrared detectors in which the cut-off wavelength and the responsivity vs. wavelength is not exactly known. The method provides a rough estimation of the spectral response solving a Fredholm integral equation of the first kind. The precision of this technique depends on the temperatures at which the detector output is measured. Some examples are given for illustration. Full article

The canonical formulation of general relativity (GR) is based on decomposition space–time manifold M into $R\times \Sigma$ , where $R$ represents the time, and $\Sigma$ is the three-dimensional space-like surface. This decomposition has to preserve the invariance of GR, invariance under general coordinates, and local Lorentz transformations. These symmetries are associated with conserved currents that are coupled to gravity. These symmetries are studied on a three dimensional space-like hypersurface $\Sigma$ embedded in a four-dimensional space–time manifold. This implies continuous symmetries and conserved currents by Noether’s theorem on that surface. We construct a three-form $E_i\wedge D{A}^i$ (D represents covariant exterior derivative) in the phase space $(E_i^a,A_a^i)$ on the surface $\Sigma$ , and derive an equation of continuity on that surface, and search for canonical relations and a Lagrangian that correspond to the same equation of continuity according to the canonical field theory. We find that ${\Sigma }_i^{0a}$ is a conjugate momentum of $A_a^i$ and ${\Sigma }_i^{ab}{F}_{ab}^i$ is its energy density. We show that there is conserved spin current that couples to $A^i$ , and show that we have to include the term $F_{\mu \nu i}{F}^{\mu \nu i}$ in GR. Lagrangian, where $F^i=D{A}^i$ , and $A^i$ is complex $SO\left(3\right)$ connection. The term $F_{\mu \nu i}{F}^{\mu \nu i}$ includes one variable, $A^i$ , similar to Yang–Mills gauge theory. Finally we couple the connection $A^i$ to a left-handed spinor field $\psi$ , and find the corresponding beta function. Full article

We consider a finite-size spherical bubble with a nonequilibrium value of the q-field, where the bubble is immersed in an infinite vacuum with the constant equilibrium value $q_0$ for the q-field (this $q_0$ has already cancelled an initial cosmological constant). Numerical results are presented for the time evolution of such a q-bubble with gravity turned off and with gravity turned on. For small enough bubbles and a q-field energy scale sufficiently below the gravitational energy scale $E_{\mathrm{Planck}}$ , the vacuum energy of the q-bubble is found to disperse completely. For large enough bubbles and a finite value of $E_{\mathrm{Planck}}$ , the vacuum energy of the q-bubble disperses only partially and there occurs gravitational collapse near the bubble center. Full article

We study Gaussian wave beam and wave packet types of solutions to the linearized cold plasma system in a toroidal domain (tokamak). Such solutions are constructed with help of Maslov’s complex germ theory (short-wave or semi-classical asymptotics with complex phases). The term “semi-classical” asymptotics is understood in a broad sense: asymptotic solutions of evolutionary and stationary partial differential equations from wave or quantum mechanics are expressed through solutions of the corresponding equations of classical mechanics. This, in particular, allows one to use useful geometric considerations. The small parameter of the expansion is $h=\lambda /2\pi L$ where $\lambda$ is the wavelength and L the dimension of the system. In order to apply the asymptotic algorithm, we need this parameter to be small, so we deal only with high-frequency waves, which are in the range of lower hybrid waves used to heat the plasma. The asymptotic solution appears to be a Gaussian wave packet divided by the square root of the determinant of an appropriate Jacobi matrix (“complex divergence”). When this determinant is zero, focal points appear. Our approach allows one to write out asymptotics near focal points. We also claim that this approach is very practical and leads to formulas that can be used for numerical simulations in software like Wolfram Mathematica, Maple, etc. For the particular case of high-frequency beams, we present a recipe for constructing beams and packets and show the results of their numerical implementation. We also propose ideas to treat the more difficult general case of arbitrary frequency. We also explain the main ideas of asymptotic theory used to obtain such formulas. Full article

Rutile TiO₂, VO₂, CrO₂, MnO₂, NbO₂, RuO₂, RhO₂, TaO₂, OsO₂, IrO₂, SnO₂, PbO₂, SiO₂, and GeO₂ (space group P4₂/mnm) were explored for thermal shock resistance applications using density functional theory in conjunction with acoustic phonon models. Four relevant thermomechanical properties were calculated, namely thermal conductivity, Poisson’s ratio, the linear coefficient of thermal expansion, and elastic modulus. The thermal conductivity exhibited a parabolic relationship with the linear coefficient of thermal expansion and the extremes were delineated by SiO₂ (the smallest linear coefficient of thermal expansion and the largest thermal conductivity) and PbO₂ (vice versa). It is suggested that stronger bonding in SiO₂ than PbO₂ is responsible for such behavior. This also gave rise to the largest elastic modulus of SiO₂ in this group of rutile oxides. Finally, the intrinsic thermal shock resistance was the largest for SiO₂, exceeding some of the competitive phases such as Al₂O₃ and nanolaminated Ti₃SiC₂. Full article

We discuss the possibility of the transition magnetic moments (TMM) between the neutron n and its hypothetical sterile twin “mirror neutron” $n^{\prime }$ from a parallel particle “mirror” sector. The neutron can be spontaneously converted into mirror neutron via the TMM (in addition to the more conventional transformation channel due to $n-n^{\prime }$ mass mixing) interacting with the magnetic field $\mathbf{B}$ as well as with mirror magnetic field ${\mathbf{B}}^{\prime }$. We derive analytic formulae for the average probability of $n-n^{\prime }$ conversion and consider possible experimental manifestations of neutron TMM effects. In particular, we discuss the potential role of these effects in the neutron lifetime measurement experiments leading to new, testable predictions. Full article

The proof of the Abramovsky—Gribov—Kancheli (AGK) theorem for black hole physics is given. Based on the AGK relations, a formula for the luminosity of a black hole as a function of the mass of the black hole is derived. The correspondence to experimental data is considered. It is shown that the black holes of the galaxies NGC3842 and NGC4889 do not differ from those of the other galaxies. Full article

The question of constructing models for the evolution of clusters that differ in shape based on the Boltzmann’s H-theorem is investigated. The first, simplest kinetic equations are proposed and their properties are studied: the conditions for fulfilling the H-theorem (the conditions for detailed and semidetailed balance). These equations are to generalize the classical coagulation–fragmentation type equations for cases when not only mass but also particle shape is taken into account. To construct correct (physically grounded) kinetic models, the fulfillment of the condition of detailed balance is shown to be necessary to monitor, since it is proved that for accepted frequency functions, the condition of detailed balance is fulfilled and the H-theorem is valid. It is shown that for particular and very important cases, the H-theorem holds: the fulfillment of the Arrhenius law and the additivity of the activation energy for interacting particles are found to be essential. In addition, based on the connection of the principle of detailed balance with the Boltzmann equation for the probability of state, the expressions for the reaction rate coefficients are obtained. Full article