Vacuum Energy Research Articles

Deconfinement transition in the revolving bag model

Based on the bag model, we revisit the deconfinement phase transition under rotation. On top of the usual rotational energy for noninteracting particles, we perturbatively analyze the revolution effect of the hadron bag, i.e., of the potential confining quarks. The revolution effect can be phenomenologically translated into the rotational correction to the QCD vacuum energy or the gluon condensate. We demonstrate that if the revolution effect is (is not) taken into account, the transition temperature increases (decreases) as the angular velocity increased. The ‘revolving bag model’ provides a feasible explanation of the recent lattice simulations showing, contrary to effective models, that rotation favors the confined phase.

Vacuum Energy, the Casimir Effect, and Newton’s Non-Constant

The idea of quantum mechanical vacuum energy contributing to the cosmological vacuum energy density is not new. However, despite the persisting cosmological constant problem, few investigations have focused on this subject. We explore the possibility that the quantum vacuum energy density contributes to the (local) gravitational energy density in the framework of a scale-dependent cosmological constant Λ and Newton’s constant G. This hypothesis has several important consequences, ranging from quantum scale-dependence to the hypothetical prospect of novel experimental insight concerning the quantum origin of cosmological energy density.

Matter accretion onto charged black holes in symmergent gravity

In astrophysics, accretion is a process where the black hole acquires matter. The gravitational energy is released as a result of the accretion and converted into radiation. Accretion onto dark compact objects, for example, neutron stars, white dwarfs, and black holes is a significant process in the astrophysical phenomenon. It is a fruitful way to examine the features of modified gravity theories by testing the analysis of their results related to dark compact objects. Here, we study the motion of a charged particle moving in near a charged symmergent black hole with Maxwell field. The symmergent gravity is a newly developed modified theory gravity within the framework of the vacuum energy VO, gravitational constant G, and quadratic curvature coefficient cO. The vacuum energy VO can be defined in terms of G and cO in the case where all the fields are degenerate in the form of mass. Further, two different choices of the parameter α provide us two different black hole spacetimes, like de Sitter for α<1 and anti-de Sitter for α>1. For this, we explore the accretion of perfect fluid onto the spherically symmetric charged symmergent black hole. Then, we get analytical results among the four-velocity and energy densities of the accreting matter. Further, we investigate it for well-known fluids flowing onto a charged symmergent black hole. Applying the Hamiltonian approach, we are able to explore the nature of accretion for these fluids such as ultra-stiff fluid, ultra-relativistic fluid, radiation fluid, and sub-relativistic fluid onto the source mass. For this study, we classified isothermal types of fluid in the context of equations of state. In addition, we introduced the application of polytropic test fluid associated with accretion disks. The accretion rate is analyzed near a charged symmergent black hole, which produced a typical behavior presented graphically by the significant parameters α and Q.

A new method that automatically regularizes scattering amplitudes

We present a new regularization procedure called autoregularization. The new procedure regularizes the divergences, encountered previously in a scattering process, using the intrinsic scale of the process. We use autoregularization to calculate the amplitudes of several scattering processes in QED and compare the calculations with experimental measurements over a broad range of center-of-momentum energies (≲MeV to ≳200 GeV). The calculated amplitudes are found to be in good agreement with experimental data. 1 1 Specifically, the O(α) correction to electron’s gyromagnetic ratio predicted by autoregularization agrees with experimental measurement to within 0.06% (Section ), which is to be compared to Schwinger’s O(α) correction which agrees with experimental measurement to within 0.15%; the O(α) estimate of the Lamb shift predicted by autoregularization agrees with the experimental measurements to within 0.33% (section ); the running fine structure constant predicted by autoregularization at O(α) agrees with the prediction of cutoff regularization to within 0.8% over one to four orders of magnitude above the electron’s mass scale (section ); the tree-level prediction of autoregularization for Compton scattering is in better agreement with experimental data than the prediction of the well-known Klein-Nishina formula by about 4.02% (section ); the tree-level predicition of autoregularization for pair annihilation at center-of-momentum energy of 206.671 GeV agrees with the experimental data about 0.67 % better than the prediction of the standard QED (section ). To test autoregularization in a non-Abelian gauge theory, we calculate the QCD coupling constant at 1-loop and show that, like the known regularization schemes, autoregularization also predicts asymptotic freedom in QCD. Finally, we show that the vacuum energy density of the free fields in the Standard Model, calculated using autoregularization, is smaller than the current estimate of the cosmic critical density.

Galaxy rotation curve in hyperconical universes: a natural relativistic MOND

Abstract Modified Newtonian dynamics (MOND) and similar proposals can (at least partially) explain the excess rotation of galaxies or the equivalent mass-discrepancy acceleration, without (or by reducing) the requirement of dark matter halos. This paper develops a modified gravity model to obtain local limit to the general relativity (GR) compatible with a cosmological metric different to the standard Friedmann–Lemaître–Robertson–Walker metric. Specifically, the paper uses a distorted stereographic projection of hyperconical universes, which are 4D hypersurfaces embedded into 5D Minkowski spacetime. This embedding is a key in the MOND effects found in galactic scales. To adequately describe the mass-discrepancy acceleration relation, centrifugal force would present a small time-like contribution at large-scale dynamics due to curvature of the Universe. Therefore, the Lagrangian density is very similar to the GR but with subtracting the background curvature (or vacuum energy density) of the perturbed hyperconical metric. Results showed that the proposed model adjusts well to 123 galaxy rotation curves obtained from the Spitzer Photometry and Accurate Rotation Curves database, using only a free parameter.

Vacuum energy with nonideal boundary conditions via an approximate functional equation

Vacuum energy with nonideal boundary conditions via an approximate functional equation

Insight of charge injection barrier at the copper/epoxy resin interface with cross-linking molecules: First-principles calculation and experimental verification

Understanding charge injection at a metal/cross-linking epoxy resin (EP) interface facilitates the design and application of high-power electric and electronic devices. This paper focuses on the charge injection barrier at the metal/EP interfaces using first-principles calculation. Two fragmentary structures, obtained from cross-linking EP with amine and anhydride curing agent, were selected to construct interface models on a Cu(111) slab. The injection barrier, dipole moment, charge transfer, and vacuum energy level shift (Δ) at the interfaces were examined. The model with the anhydride groups produced higher electron and hole injection barriers than the interface model with the amine groups. The model with the amine groups had a higher Δ, which was derived from molecule dipole and charge transfer. An increase in the work function and Δ caused by an electric field caused an increase in the electron injection barrier and a decrease in the hole injection barrier. Experimental results of the methyl tetrahydrophthalic anhydride cross-linking EP showed a higher charge injection than that of m-phenylenediamine cross-linking EP, providing experimental verification of the theoretical calculation.

Fayet–Iliopoulos D-term in non-supersymmetric heterotic string orbifolds

The Fayet–Iliopoulos D-term is a common feature in N=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {N}}=1$$\\end{document} string vacua that contain an anomalous U(1) gauge symmetry, and arises from a one-loop diagram in string perturbation theory. The same diagram is generated in string vacua in which supersymmetry is broken directly at the string scale, either via spontaneous Scherk–Schwarz breaking, in which case the gravitino mass is determined by the radius of the circle used in the Scherk–Schwarz mechanism, or via explicit supersymmetry breaking by the GSO projections. We analyse the resulting would-be Fayet–Illiopoulos D-term in the non-supersymmetric string vacua and its contribution to the vacuum energy. A numerical estimate in an explicit tachyon-free string-derived model suggests that the would-be D-term contribution may uplift the vacuum energy to a positive value.

Exploring models of running vacuum energy with viscous dark matter from a dynamical system perspective

Running vacuum models and viscous dark matter scenarios beyond perfect fluid idealization are two appealing theoretical strategies that have been separately studied as alternatives to solve some problems rooted in the ΛCDM cosmological model. In this paper, we combine these two notions in a single cosmological setting and investigate their cosmological implications, paying particular attention in the interplay between these two constituents in different cosmological periods. Specifically, we consider a well-studied running vacuum model inspired by renormalization group, and a recently proposed general parameterization for the bulk viscosity ξ. By employing dynamical system analysis, we explore the physical aspects of the new phase space that emerges from the combined models and derive stability conditions that ensure complete cosmological dynamics. We identify four distinct classes of models and find that the critical points of the phase space are non-trivially renewed compared to the single scenarios. We then proceed, in a joint and complementary way to the dynamical system analysis, with a detailed numerical exploration to quantify the impact of both the running parameter and the bulk viscosity coefficient on the cosmological evolution. Thus, for some values of the model parameters, numerical solutions show qualitative differences from the ΛCDM model, which is phenomenologically appealing in light of cosmological observations.

Probability thermodynamics and probability quantum field

We introduce probability thermodynamics and probability quantum fields. By probability we mean that there is an unknown operator, physical or nonphysical, whose eigenvalues obey a certain statistical distribution. Eigenvalue spectra define spectral functions. Various thermodynamic quantities in thermodynamics and effective actions in quantum field theory are all spectral functions. In the scheme, eigenvalues obey a probability distribution, so a probability distribution determines a family of spectral functions in thermodynamics and quantum field theory. This leads to probability thermodynamics and probability quantum fields determined by a probability distribution. In constructing spectral functions, we encounter a problem. The conventional definition of spectral functions applies only to lower bounded spectra. In our scheme, however, there are two types of spectra: lower bounded spectra, corresponding to the probability distribution with nonnegative random variables, and the lower unbounded spectra, corresponding to probability distributions with negative random variables. To take the lower unbounded spectra into account, we generalize the definition of spectral functions by analytical continuation. In some cases, we encounter divergences. We remove the divergence by a renormalization procedure. In virtue of spectral theory in physics, we generalize some concepts in probability theory. For example, the moment-generating function in probability theory does not always exist. We redefine the moment-generating function as the generalized heat kernel introduced in this paper, which makes the concept definable when the definition in probability theory fails. We construct examples corresponding to some probability distributions. Thermodynamic quantities, vacuum amplitudes, one-loop effective actions, and vacuum energies for various probability distributions are presented.

Comparative Evaluation of PSA, PVSA, and Twin PSA Processes for Biogas Upgrading: The Purity, Recovery, and Energy Consumption Dilemma

The current challenges of commercial cyclic adsorption processes for biogas upgrading are associated with either high energy consumption or low recovery. To address these challenges, this work evaluates the performance of a range of configurations for biogas separations, including pressure swing adsorption (PSA), pressure vacuum swing adsorption (PVSA), and twin double-bed PSA, by dynamic modelling. Moreover, a sensitivity analysis was performed to explore the effect of various operating conditions, including adsorption time, purge-to-feed ratio, biogas feed temperature, and vacuum level, on recovery and energy consumption. It was found that the required energy for a twin double-bed PSA to produce biomethane with 87% purity is 903 kJ/kg CH4 with 90% recovery, compared to 961 kJ/kg CH4 and 76% recovery for a PVSA process. With respect to minimum purity requirements, increasing product purity from 95.35 to 99.96% resulted in a 32% increase in energy demand and a 23% drop in recovery, illustrating the degree of loss in process efficiency and the costly trade-off to produce ultra-high-purity biomethane. It was concluded that in processes with moderate vacuum requirements (&gt;0.5 bar), a PVSA should be utilised when a high purity biomethane product is desirable. On the other hand, to minimise CH4 loss and enhance recovery, a twin double-bed PSA should be employed.

Scattering approach for calculating one-loop effective action and vacuum energy

Scattering approach for calculating one-loop effective action and vacuum energy

Nonlocal Fractional Quantum Field Theory and Converging Perturbation Series

The main purpose of this paper is to derive a new perturbation theory (PT) that has converging series. Such series arise in the nonlocal scalar quantum field theory (QFT) with fractional power potential. We construct a PT for the generating functional (GF) of complete Green functions (including disconnected parts of functions) Zj as well as for the GF of connected Green functions Gj=lnZj in powers of coupling constant g. It has infrared (IR)-finite terms. We prove that the obtained series, which has the form of a grand canonical partition function (GCPF), is dominated by a convergent series—in other words, has majorant, which allows for expansion beyond the weak coupling g limit. Vacuum energy density in second order in g is calculated and researched for different types of Gaussian part S0[ϕ] of the action S[ϕ]. Further in the paper, using the polynomial expansion, the general calculable series for Gj is derived. We provide, compare and research simplifications in cases of second-degree polynomial and hard-sphere gas (HSG) approximations. The developed formalism allows us to research the physical properties of the considered system across the entire range of coupling constant g, in particular, the vacuum energy density.

Perils of towers in the swamp: dark dimensions and the robustness of EFTs

Recently there has been an interesting revival of the idea to use large extra dimensions to address the dark energy problem, exploiting the (true) observation that towers of states with masses split, by MN2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {M}_N^2 $$\\end{document} = f(N)m2, with f an unbounded function of the integer N, sometimes contribute to the vacuum energy only an amount of order mD in D dimensions. It has been argued that this fact is a consequence of swampland conjectures and may require a departure from Effective Field Theory (EFT) reasoning. We test this claim with calculations for Casimir energies in extra dimensions. We show why the domain of validity for EFTs ensures that the tower spacing scale m is always an upper bound on the UV scale for the lower-energy effective theory; use of an EFT with a cutoff part way up a tower is not a controlled approximation. We highlight the role played by the sometimes-suppressed contributions from towers in extra-dimensional approaches to the cosmological constant problem, old and new, and point out difficulties encountered in exploiting it. We compare recent swampland realizations of these arguments with earlier approaches using standard EFT examples, discussing successes and limitations of both.

UV completion of extradimensional Yang-Mills theory for Gauge-Higgs unification

The SU(N)SU(N) Yang-Mills theory in \mathbb R^4\times S^1ℝ4×S1 spacetime is studied as a simple toy model of Gauge-Higgs unification. The theory is perturbatively nonrenormalizable but could be formulated as an asymptotically safe theory, namely a nonperturbatively renormalizable theory. We study the fixed point structure of the Yang-Mills theory in \mathbb R^4\times S^1ℝ4×S1 by using the functional renormalization group in the background field approximation. We derive the functional flow equations for the gauge coupling and the background gauge-field potential. There exists a nontrivial fixed point for both couplings at finite compactification radii. At the fixed point, gauge coupling and vacuum energy are both relevant. The renormalization group flow of the gauge coupling describes the smooth transition between the ultraviolet asymptotically safe regime and the strong interacting infrared limit.

Primordial black holes from strong first-order phase transitions

We study the formation of primordial black holes (PBHs) in strongly super-cooled first-order phase transitions. The mechanism is based on the presence of remnants dominated by the false vacuum that scale slower with the expansion of the Universe than their surroundings where this energy was already converted into radiation. We compute the PBH formation from these remnants including the contribution from the false vacuum and the bubble walls, by estimating the collapse using the hoop conjecture and by considering both regions collapsing immediately when entering the horizon and sub-horizon regions that collapse as their compactness grows. We show that for exponential bubble nucleation rate, Γ ∝ eβt, the primordial black hole formation implies β/H ≳ 3.8, where H denotes the Hubble rate, if the potential energy of the false vacuum is ∆V ≲ (1012 GeV)4, as otherwise a too large abundance of long-lived PBHs forms. The observed dark matter abundance can be formed in asteroid mass PBHs if β/H ≃ 3.8 and 105 GeV ≲ ∆V1/4 ≲ 108 GeV. Finally, we consider also the effect of the second order correction to the exponential nucleation rate showing that the PBH abundance is mainly determined by the average radius of the true vacuum bubbles.

Optimizing CuFeS2 Chalcopyrite Thin Film Synthesis: A Comprehensive Three-Step Approach Using Ball-Milling, Thermal Evaporation, and Sulfurization Applied for Thermoelectric Generation

CuFeS2 (CFS) stands out as a promising narrow band-gap semiconductor for thermoelectric (TE) applications. However, its high lattice thermal conductivity is one of the factors hampering its potential for TE generation. A common strategy for tackling this problem is to produce this material in thin film form. Thus, this study aims to practically understand and optimize the synthesis of CFS 2D materials using a simple three-step approach of ball-milling, thermal evaporation, and sulfurization of the CuFe metallic precursors. The tools for thin film characterization employ X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), and Hall-effect measurements. DFT phase diagrams are also used to understand the energy of formation of the secondary phases present in the film. Here, we highlight that the ball-milling mechanisms, allied with high vacuum and high energy density during evaporation, are essential for the interdiffusion of Cu and Fe during the evaporation process. The film presented a flower-like morphology and p-type semiconducting behavior. A proof-of-concept Thermoelectric Generator (TEG) was designed in an in-plane geometry, showing a power output per unit active area of 114 nW cm−2 (ΔT = 180 °C), comparable to other Cu-based materials, thus demonstrating the feasibility of this method of synthesis for TE applications.

Reflections on bubble walls

We discuss the dynamics of expanding bubble walls in the presence of massive dark photons whose mass changes as they cross the wall. For sufficiently thin walls, we show that there exists a transient kinematic regime characterized by a constant reflection probability of longitudinal — but not transverse — modes. This effect can have important implications for the dynamics of expanding vacuum bubbles in the early Universe. Most notably, it leads to a new source of pressure on the expanding interface, featuring a non-monotonic dependence on the γ-factor of the bubble walls and reaching a peak at intermediate γ-factors that we dub Maximum Dynamic Pressure. When this pressure is large enough to halt the acceleration of the bubble walls, the difference in vacuum energy densities goes into making a fraction of the dark photons relativistic, turning them into dark radiation. If the dark radiation remains relativistic until late times, an observable contribution to ∆Neff is possible for phase transitions with strength α ∼ 10−2− 10−1.

Anisotropic Segre [(11)(1,1)] dark energy following a particular equation of state

A generally anisotropic equation of state originally derived in the context of Newman-Janis rotating systems allows for vacuum energy at a specific density. In this paper we examine the possibility of using that equation of state for cosmological dark energy. We treat the case of large scale ordering of the directions of the energy-momentum tensor eigenvectors with a Bianchi cosmological model, and treat the case where the ordering is random on small scales with an effectively isotropic FLRW system. We find particular spacetimes which evolve towards a vacuum energy/ de Sitter like configuration in either case. In the anisotropic Bianchi case, the system can have behavior reminiscent of big bounce cosmologies, in which the matter content approaches vacuum energy at large scale factor and can behave in a variety of ways at small scale factor. For particular conditions in the effectively isotropic case, we can evolve between true and false vacuum configurations, or between radiation like and vacuum energy configurations. We also show how some simpler equations of state behave under the same assumptions to elucidate the methods for analysis.

Time-symmetric quantization of relativistic fields. 2. Electroweak theory. Observable effects of TSQ

In the method of time-symmetric quantization (TSQ) of relativistic systems, based on the Stückelberg-Feynman interpretation, the creation-annihilation operators of quanta of complex fields and massless gauge fields, are automatically normally ordered, and there is no vacuum energy and charge (Z. Zakir 2023, article 1). In this second article the application of TSQ to massive bosonic fields of electroweak theory and the observational consequences of TSQ are considered. It is shown that the vacuum of these fields is free of zero-point energy and zero-point charge, and thus a contribution of these fields to the cosmological constant is absent. A direct observational consequence of TSQ is crossing symmetry in particle physics. The observable effects, which were attributed to the zero-point energy of the vacuum, are actually generated by the fields of real charges, and there is no evidence of the existence of zero-point energy of fundamental fields. This fact contradicts the prediction of the standard formulation of quantum field theory, but indirectly confirms TSQ.