arXiv subjects

Iver Brevik

Publications and source records attributed to Iver Brevik.

At least 19 recordsLinked to original sources

arXiv2025

Stefan-Boltzmann Law and Thermal Casimir Effect in Neutron Star Spacetime via Thermo Field Dynamics

We investigate the thermal Casimir effect for a massless scalar field in the curved spacetime of a neutron star within the Thermo Field Dynamics (TFD) formalism. Starting from the renormalized energy-momentum tensor, we generalize the Stefan-Boltzmann law to include gravitational redshift and curvature corrections governed by the Tolman-Oppenheimer-Volkoff (TOV) metric. Finite temperature and spatial compactification are introduced simultaneously, allowing a unified and consistent treatment of both vacuum and thermal contributions inside and outside the star. Analytical expressions are derived for the high- and low-temperature limits, showing explicitly how curvature and redshift modify the characteristic $T^4$ dependence of thermal radiation. The results reveal that strong gravity significantly alters the local energy density and pressure, demonstrating the nontrivial interplay between quantum vacuum fluctuations and compact astrophysical geometries. A polytropic model is considered to perform numerical analyses, highlighting the influence of the spacetime background on vacuum fluctuations.

gr-qc↗

arXiv2025

The 2D Lorentz-violating fermionic Casimir effect under thermal conditions

In the present work, we study a fermionic Lorentz invariance violation (LIV) theory with a CPT-even extension and analyze its impact on the Casimir effect under the MIT bag boundary condition model in a low-dimensional setting, where results are obtained without any approximations for a null-temperature system. Moreover, the Matsubara formalism is applied to derive closed expressions for the influence of temperature on the physical observables: Casimir energy, Casimir force, and entropy associated with the system in a LIV context. For each thermal observable, the influence of the LIV correction term is considered in the analysis of both low- and high-temperature regimes. Additionally, we construct a condensed matter analogue using the SSH model, where nonlinear fermionic dispersion and boundary-induced vacuum energy emerge, reproducing the analytical structure of the LIV Casimir effect.

hep-th↗

arXiv2025

A mechanism for ice growth on the surface of a spherical water droplet

The formation and growth of ice particles, particularly on the surfaces of spherical water droplets, bear profound implications for localized weather systems and global climate. Herein, we develop a theoretical framework for ice nucleation on minuscule water droplets, establishing that $10\sim5000\rm\ nm$ droplets can considerably increase in volume, making a substantial contribution to ice formation within mist, fog, or even cloud systems. We reveal that the Casimir-Lifshitz (van der Waals) interaction within these systems is robust enough to stimulate both water and ice growth on the surfaces of ice-cold spherical water droplets. The significant impacts and possible detectable phenomena from the curvature are demonstrated.

cond-mat.mtrl-sci↗

arXiv2024

Dispersion Interaction Between Thin Conducting Cylinders

The ground state and excited state resonance dipole-dipole interaction energy between two elongated conducting molecules are explored. We review the current status for ground state interactions. This interaction is found to be of a much longer range than in the case when the molecules are pointlike and nonconducting. These are well known results found earlier by Davies, Ninham, and Richmond, and later, using a different formalism, by Rubio and co-workers. We show how the theory can be extended to excited state interactions. A characteristic property following from our calculation is that the interaction energy dependence with separation ($R$) goes like $f(R)/R^2$ both for resonance and for the van der Waals case in the long range limit. In some limits $f(R)$ has a logarithmic dependency and in others it takes constant values. We predict an unusual slow decay rate for the energy transfer between conducting molecules.

physics.chem-ph↗

arXiv2023

Aether-Electromagnetic theory and the Casimir effect

In this study, we explore the impact of an additional dimension, as proposed in Kaluza-Klein's theory, on the Casimir effect within the context of Lorentz invariance violation (LIV), which is represented by the ``aether field''. We demonstrate that the Casimir energy is directly influenced by the presence of the fifth dimension, as well as by the aether parameter. Consequently, the force between the plates is also subject to variations of these parameters. Furthermore, we examine constraints on both the size of the extra dimension and the aether field parameter based on experimental data. The LIV parameter can provide insights into addressing the size-related challenges in Kaluza-Klein's theory and offers a mean to establish an upper limit on the size of the extra dimension. This helps to rationalize the difficulties associated with its detection in current experiments.

hep-th↗

arXiv2023

On the Axion Electrodynamics in a two-dimensional slab and the Casimir effect

We analyze the Axion Electrodynamics in a two-dimensional slab of finite width $L$ containing a homogeneous and isotropic dielectric medium with constant permittivity and permeability. We start from the known decomposition of modes in the nonaxion case and then solve perturbatively the governing equations for the electromagnetic fields to which the axions are also coupled. This is a natural approach, since the finiteness of $L$ destroys the spatial invariance of the theory in the $z$ direction normal to the plates. In this way we derive the value of the axion-generated rotation angle of the electric and magnetic fields after their passage through the slab, and use the obtained results to calculate the Casimir force between the two conducting plates. Our calculations make use of the same method as previously outlined in \cite{hoye20} for the case of Casimir calculations in chiral media and extend former results on the Casimir force in the Axion Electrodynamics.

hep-th↗

arXiv2023

Thermal Casimir interactions in multi-particle systems: scattering channel approach

Multi-particle thermal Casimir interactions are investigated, mostly in terms of the Casimir entropy, from the point of view based on multiple-scattering processes. The geometry of the scattering path is depicted in detail, and the contributions from different types of channels, namely the transverse, longitudinal and mixing channels, are demonstrated. The geometry of the path can strongly influence the weight of each channel in the path. Negativity and nonmonotonicity are commonly seen in the multi-particle Casimir entropy, the sources of which are diverse, including the geometry of the path, the types of polarization mixing, the polarizability of each particle, etc. Thermal contributions from multi-particle scatterings can be significant in the system, while the zero-temperature multi-particle scattering effects are insignificant. Limiting behaviors from a multi-particle configuration to a continuum are briefly explored.

hep-th↗

arXiv2023

Possible expansion of blood vessels by means of the electrostrictive effect

In cases when it is desirable to transport medication through blood vessels, especially when dealing with brain cancer being confronted with the narrow arteries in the brain, the blood-brain barrier makes the medical treatment difficult. There is a need of expanding the diameters of the arteries in order to facilitate the transport of medicaments. Recent research has pointed to various ways to improve this situation; in particular, the use ultrasound acting on microbubbles in the blood stream has turned out to be a promising option. Here, a different possibility of enlarging the diameters of arteries is discussed, namely to exploit the electrostrictive pressure produced by internal strong, ultrashort and repetitive laser pulses. Each pulse will at first give rise to inward directed optical forces, and once the pulse terminates there will be a hydrodynamical bouncing flow in the outward radial direction giving an outward impulse to the vessel wall. In the absence of friction a symmetric oscillation picture emerges. Clearly, a supply of repetitive pulses will be needed (at parametric resonance) to make the effect appreciable. The effect has to our knowledge not been discussed before. We give an approximate optical and hydrodynamical theory of it. The calculations indicate promising results for the wall pressure, although experimental work is desirable to show whether the idea can be useful in practice. Our calculation is made from a general physical perspective, not necessarily linked to medical applications.

physics.flu-dyn↗

arXiv2023

Axion electrodynamics: Green's functions, zero-point energy and optical activity

Starting from the theory of Axion Electrodynamics, we work out the axionic modifications to the electromagnetic Casimir energy using the Green's function, both when the axion field is initially assumed purely time-dependent and when the axion field configuration is a static domain wall. For the first case it means that the oscillating axion background is taken to resemble an axion fluid at rest in a conventional Casimir setup with two infinite parallel conducting plates, while in the second case we evaluate the radiation pressure acting on an axion domain wall. We extend previous theories in order to include finite temperatures. Various applications are discussed. 1. We review the theory of Axion Electrodynamics and particularly the energy-momentum conservation in a linear dielectric and magnetic material. We treat this last aspect by extending former results by Brevik and Chaichian (2022) and Patkos (2022). 2. Adopting the model of the oscillating axion background we discuss the axion-induced modifications to the Casimir force between two parallel plates by using a Green's function approach. 3. We calculate the radiation pressure acting on an axion domain wall at finite temperature T. Our results for an oscillating axion field and a domain wall are also useful for condensed matter physics, where "axionic topological insulators" interact with the electromagnetic field with a Chern-Simons interaction, like the one in Axion Electrodynamics, and there are experimental systems analogous to time-dependent axion fields and domain walls as the ones showed by Jiang, Q. D., \& Wilczek, F. (2019) and Fukushima et al. (2019). 4. We compare our results, where we assume time-dependent or space-dependent axion configurations, with the discussion of the optical activity of Axion Electrodynamics by Sikivie (2021) and Carrol et al. (1990).

hep-th↗

arXiv2023

Singular behavior of the dark universe under the effect of thermal radiation in curved spacetime

We consider the late-time accelerated universe in the Friedmann-Robertson-Walker (FRW) spacetime with a nonzero curvature, and investigate cosmological models when the cosmic fluid is taken to be inhomogeneous and viscous (bulk viscous), coupled to dark matter. We consider the influence from thermal effects caused by Hawking radiation on the formation of singularities of various classified types, within a finite time. It is shown that under the influence of Hawking radiation the time of formulation of a singularity, and the nature of the singularity itself, can change. It is also shown that by jointly taking into account radiation, viscosity, and space curvature, one can obtain a singularity-free universe. The symmetry properties of this kind of theory lie in the assumption about spatial isotropy. The spatial isotropy is also reflected in our use of a bulk, instead of a shear, viscosity.

gr-qc↗

arXiv2022

Axionic and nonaxionic electrodynamics in plane and circular geometry

Various aspects of axion electrodynamics in the presence of a homogeneous and isotropic dielectric medium are discussed. 1. We consider first the "antenna-like" property of a planar dielectric surface in axion electrodynamics, elaborating on the treatment given earlier on this topic by Millar {\it et al.} (2017). We calculate the electromagnetic energy transmission coefficient for a dielectric plate, and compare with the conventional expression in ordinary electrodynamics. 2. We consider the situation where the medium exterior to the plate, assumed elastic, is "bent back" and glued together, so that we obtain a circular dielectric string in which the waves can propagate clockwise or counterclockwise. As will be shown, a stationary wave pattern is permitted by the formalism, and we show how the amplitudes for the two counterpropagating waves can be found. 3. As a special case, by omitting axions for a moment, we analyze the Casimir effect for the string, showing its similarity as well as its difference with the Casimir effect of a scalar field for a piecewise uniform string (Brevik and Nielsen 1990). 4. Finally, including axions again we analyze the enhancement of the surface-generated electromagnetic radiation near the center of a cylindrical haloscope, where the interior region is a vacuum and the exterior region a metal. This enhancement is caused by the curvature of the boundary, and is mathematically a consequence of the behavior of the Hankel function of the second kind for small arguments. A simple estimate shows that enhancement may be quite significant, and can therefore be of experimental interest. This proposal is suggested as an alternative to the reflector arrangement in a similar arrangement recently discussed by Liu {\it et al.} (2022).

hep-th↗

arXiv2022

Fluctuational electrodynamics in and out of equilibrium

Dispersion forces between neutral material bodies are due to fluctuations of the polarization of the bodies. For bodies in equilibrium these forces are often referred to as Casimir-Lifshitz forces. For bodies in relative motion, in addition to the Casimir-Lifshitz force, a lateral frictional force ("quantum friction", in the zero temperature limit) comes into play. The widely accepted theory of the fluctuation induced forces is based on the "fluctuational electrodynamics" , when the Maxwell equations are supplemented by random current sources responsible for the fluctuations of the medium polarization. The first part of our paper touches on some conceptual issues of the theory, such as the dissipation-less limit and the link between Rytov's approach and quantum electrodynamics. We point out the problems with the dissipation-less plasma model (with its unphysical double pole at zero frequency) which still appears in the literature. The second part of the paper is devoted to "quantum friction", in a broad sense, and it contains some novel material. In particular, it is pointed out that in weakly dissipative systems the friction force may not be a stationary process. It is shown, using an "exact" (nonpertubative) quantum treatment that under appropriate conditions, an instability can occur when the kinetic energy (due to the relative motion between the bodies) is transformed into coherent radiation, exponentially growing in intensity (the instability gets eventually limited by non-linear effects). We also discuss a setup when the two bodies are at rest but a constant electric current is flowing in one of the bodies. One may say that only the electron component of one body is dragged with respect to the other body, unlike the usual setup when the two bodies are in relative motion. Clearly there are differences in the frictional forces between the two setups.

quant-ph↗

arXiv2022

Connection between time-splitting parameter and surface tension in Casimir problems. Related phenomena in relativistic collapse of a singular shell

We discuss four different, though related, fundamental topics related to the Casimir effect: 1) We suggest that the application of Casimir theory to real dielectric materials, thus implying the atomic spacing as a course-grained length parameter, makes it natural to assume that this parameter is of the same order of magnitude as the QFT time-splitting parameter multiplied with the velocity of light. 2) We show that application of Casimir theory to a thick fluid shell (apparently a closed mechanical system), leads actually to an unstable situation if not extra mechanical forces, typically surface tension forces, are brought into consideration. 3) We analyze how the presence of a radial Casimir repulsive pressure modifies the filling process of a spherical vacuum hole in an infinite fluid (the Reynolds problem), with the result that a bounce occurs at a finite though very small radius. 4) As a comment on an apparently similar situation in general relativity, we consider the gravitational collapse of a singular shell. It might seem natural to allow for the presence of a repulsive Casimir pressure in this case also, thereby obtaining a bounce-like situation again. However, we have to conclude that such a procedure implies an omission of the Casimir field's gravitational energy, and is therefore hardly tenable, although it is in our opinion worth mentioning.

quant-ph↗

arXiv2022

Proposal to repeat the Abraham force experiment using giant permittivity materials

In the more than 100 years-old Abraham-Minkowski problem in macroscopic electrodynamics, the issue of how to observe the so-called Abraham term ${\bf f}^{\rm Aterm} = [(\varepsilon\mu-1)/c^2] \partial/\partial t ({\bf E}\times {\bf H})$ has been a main point. Recent years have seen a number of beautiful experiments in radiation optics, but these experiments usually give no information about the Abraham term as this term simply fluctuates out. So one is left with somewhat indirect verifications of this force, as in the radiation pressure of Jones {et al.} in the 1950's, testing the radiation pressure on a mirror immersed in a dielectric liquid. Now, there is a different way to test the existence of ${\bf f}^{ \rm Aterm}$, namely to work with low (quasi-stationary) frequencies enabling one to observe the sinusoidal variation of the force directly. These kind of experiments were actually done by Walker {\it et al.} in 1he 1970's, using BaTiO$_3$ as a high-frequency dielectric (permittivity $\varepsilon \sim 3600$). Now, in recent years there have appeared dielectric materials with giant permittivities, of order $10^5$ or even higher. It is therefore natural to consider the idea of Walker {\it et al.} anew, in order to test if this demanding experiment can be facilitated and give better accuracy. That is the main topic of the present paper. The positive outcome of these kinds of experiments clearly supports the Abraham energy-momentum tensor at low frequencies. The Minkowski tensor is unable to predict a torque at all. The low-frequency and the high-frequency regimes are in this way highly contrasted, as it is obvious that in optical experiments the Minkowski tensor is by far the simplest and most convenient one to use. We end this note by commenting upon the use of the Einstein-Laub tensor (1908) in explaining this experiment, and discuss also the influence from air friction.

physics.class-ph↗

arXiv2022

Axion Electrodynamics and the Axionic Casimir Effect

A general scheme for axion electrodynamics is given, in which a surrounding medium of constant permittivity and permeability is assumed. Then, as an application we give simple numerical estimates for the electromagnetic current density produced by the electrically neutral time-dependent axions $a=a(t)$ in a strong magnetic field. As is known, the assumption $a=a(t)$ is common under astrophysical conditions. In the third part of the paper, we consider the implications by assuming instead an axion amplitude $a(z)$ depending on one coordinate $z$ only. If such an axion field is contained within two large metal plates one obtains an axion-generated splitting of the eigenmodes for the dispersion relation. These modes yield equal, though opposite, contributions to the pressure on the plates. We calculate the magnitude of the splitting effect, in a simple one-dimensional model.

hep-ph↗

arXiv2022

Electric Current and Heat Production by a Neutral Carrier: An Effect of the Axion

A general axion-electrodynamic formalism is presented on the phenomenological level when the environment is dielectric (permittivity and permeability assumed to be constants). Thereafter, a strong and uniform magnetic field is considered in the $z$ direction, the field region having the form of a long material cylinder (which corresponds to the haloscope setup). If the axion amplitude depends on time only, the axions give rise to an oscillating electric current in the $z$ direction. We estimate the magnitudes of the azimuthal magnetic fields and the accompanying Joule heating in the cylinder, taking the cylinder to have ordinary dissipative properties. We evaluate and calculate the electric current and the heat production separately, without using the effective approximation, both when there is a strong magnetic field and when there is a strong electric one, showing that with the magnetic field there is a heat production, while with the electric field there is not. The heat generation that we consider, is a nontrivial effect as it is generated by the electrically neutral axions, and has obvious consequences for axion thermodynamics. The heat production can moreover have an additional advantage, since the effect is accumulative and so grows with time. The boundary conditions (in a classical sense) are explained and the use of them in a quantum mechanical context is discussed. This point is nontrivial, accentuated in particular in connection with the Casimir effect. For comparison purposes, we present finally some results for heat dissipation taken from the theory of viscous cosmology.

hep-ph↗

arXiv2021

Self-preserving ice layers on CO2 clathrate particles: implications for Enceladus, Pluto and similar ocean worlds

Under both engineering and natural conditions on Earth and in the Universe, some gas hydrates are found to be stabilised outside their window of thermodynamic stability by the formation of an ice layer-a phenomenon termed self-preservation. Low occupancy surface regions on type I CO2 clathrate structures together with the self-preserving ice layer lead to an effective buoyancy for these structures which restricts the size range of particles that float in the ocean on Enceladus, Pluto and similar oceanic worlds. Our goal here is to investigate the implications of Lifshitz forces and low occupancy surface regions on clathrate structures for their self-preservation through ice layer formation, presenting a plausible model based on multilayer interactions through dispersion forces. We predict that the growth of an ice layer between 0.01 and 0.2 $\mu$m thick on CO2 clathrate surfaces depends on the presence of surface regions in the gas hydrates with low occupancy. The effective particle density is estimated delimiting a range of particles that would be buoyant in different oceans. Over geological time, deposition of floating CO2 hydrates could result in the accumulation of kilometre-thick hydrate layers above liquid water reservoirs, and below the water ice crusts of their respective ocean worlds. On Enceladus, destabilisation of near-surface hydrate deposits could lead to increased gas pressures that both drive plumes and entrain stabilised hydrates to be redeposited on the surface of Enceladus or ejected into the E-ring of Saturn. On ocean worlds such as Enceladus and particularly Pluto, the accumulation of thick CO2 hydrate deposits could insulate its ocean against freezing. In preventing the freezing of liquid water reservoirs in ocean worlds, the presence of CO2 hydrate layers could enhance the habitability of ocean worlds in our solar systems and on the exoplanets and exomoons beyond.

astro-ph.EP↗

arXiv2021

Premelting and formation of ice due to Casimir-Lifshitz interactions: Impact of improved parameterization for materials

Recently, the premelting and formation of ice due to the Casimir-Lifshitz interaction, proposed in early 1990s by Elbaum and Schick [Phys. Rev. Lett. 66, 1713-1716 (1991)], have been generalized to diverse practical scenarios, yielding novel physical intuitions and possibilities of application for those phenomena. The properties of materials, in particular, the electrical permittivity and permeability, exert significant influences on the Casimir-Cifshitz energies and forces, and hence on the corresponding premelting and formation of ice. To address these influences in detail and explore the resulting physics, here we revisit and extend the analyses of previous work, with both the dielectric data utilized there and the latest dielectric functions for ice and cold water. While our previous results are rederived, an error there has also been spotted. For the four-layer cases considered by some of us, the existence of stable configurations depending on the initial conditions has been confirmed, and different types of stability corresponding to minima of the Casimir-Lifshitz free energy are demonstrated. As the new dielectric functions for ice and cold water deviate considerably from those used by Elbaum and Schick, their vital impacts on three- and four-layer configurations are therefore being reconsidered.

cond-mat.mtrl-sci↗