Vacuum Phase Transition Research Articles

Cosmological first-order vacuum phase transitions in an expanding anisotropic universe

We examine the anisotropy originated from a first-order vacuum phase transitions through three-dimensional numerical simulations. We apply Bianchi Type-I metric to our model that has one scalar field minimally coupled to the gravity. We calculate the time evolution of the energy density for the shear scalar and the directional Hubble parameters as well as the power spectra for the scalar field and the gravitational radiation although there are a number of caveats for the tensor perturbations in Bianchi Type-I universe. We run simulations with different mass scales of the scalar field, therefore, in addition to investigation of anisotropy via the shear scalar, we also determine at which mass scale the phase transition completes successfully, hence, neglecting the expansion of the Universe does not significantly affect the results. Finally, we showed that such an event may contribute to the total anisotropy depending on the mass scale of the scalar field and the initial population of nucleated bubbles.

Thin and thick bubble walls. Part I. Vacuum phase transitions

This is the first in a series of papers where we study the dynamicsof a bubble wall beyond usual approximations, such as the assumptionsof spherical bubbles and infinitely thin walls. In this paper, weconsider a vacuum phase transition. Thus, we describe a bubble asa configuration of a scalar field whose equation of motion depends onlyon the effective potential.The thin-wall approximation allows obtaining bothan effective equation of motion for the wall position anda simplified equation for the field profile inside the wall.Several different assumptions are involved in this approximation.We discuss the conditions for the validity of each of them.In particular, the minima of the effective potential musthave approximately the same energy, and we discuss the correct implementation of this approximation.We consider different improvements to the basic thin-wall approximation,such as an iterative method for finding the wall profileand a perturbative calculation in powers of the wall width.We calculate the leading-order corrections.Besides, we derive an equation of motion for the wall without any assumptions about its shape.We present a suitable method to describe arbitrarily deformed walls from the spherical shape.We consider concrete examples and compare our approximations with numericalsolutions. In subsequent papers, we shall consider higher-order finite-width corrections,and we shall take into account the presence of the fluid.

The effect of non-minimally coupled scalar field on gravitational waves from first-order vacuum phase transitions

We investigate first-order vacuum phase transitions in the presence of a non-minimally coupled scalar field starting with the coupling effect on the initial dynamics of phase transitions by defining an effective potential for the scalar field and then performing three dimensional numerical simulations to observe any possible distinction in gravitational wave power spectrum. Although we give a description of the model with the expanding background, in this particular paper, we exclude the scale factor contribution since we primarily focus on the immediate impact of the non-minimal coupling at initial phases of the transition. Even in this case we found that this modification has discernible effect on the power spectrum of the gravitational wave energy density.

The Emergence of Quarks/Anti-Quarks

In clarifying the entirety of the universe, the most important processes are the emergence of the universe and the ‎formation of quarks/anti-quarks. The entirety of the universe has emerged in a causal and consecutive manner. ‎According to the Standard Model, from the dawn of the universe, particles such as 3 pairs of neutrinos (v_µ ⁄ v ̅_µ , ‎v_e ⁄ v ̅_e , v_τ ⁄ v ̅_τ ) and 6 pairs of quarks (U/U ̅,d/d ̅ , s/s ̅ , c/c ̅ , b/b ̅ , t/t ̅ ) suddenly emerged with different ‎components not due to causality but due to "vacuum phase transitions" with no space existing in the universe. In ‎this research paper, we must first assume that quarks/anti-quarks are formed inextricably linked with the ‎organization of space-time/anti-space-time and in cooperation with 2 pairs of neutrinos (v_µ ⁄ v ̅_µ , v_e ⁄ v ̅_e ) in ‎the acting of the "strong interaction" and "weak interaction." We must also assume that quarks/anti-quarks are the ‎main body that composes the π- on group ( π^+, π^-, π^±, π^0 ) and the nucleon group ( P, P ̅, n , n ̅ ), and ‎that they play the leading role to compose not only 120 types of atomic nuclei, but also all the ‎particles/antiparticles that exist in the entire universe. In other words, the formed quarks/anti-quarks must clear any ‎and all problems in the above series without any contradictions. This research paper will make clear details such as ‎the fact that only 2 pairs of quarks (U/U ̅ , d ⁄ d ̅ ), were formed; that in the entirety of the universe, only these 2 ‎pairs of quarks were given electrical charges; and that the raw materials of space-time/anti-space-time are the same ‎as quarks/anti-quarks.‎

The Effect of Nonminimally Coupled Scalar Field on Gravitational Waves from First-Order Vacuum Phase Transitions

The Effect of Nonminimally Coupled Scalar Field on Gravitational Waves from First-Order Vacuum Phase Transitions

The well-tempered cosmological constant: fugue in B♭

Zero point fluctuations of quantum fields should generate a large cosmological constant energy density in any spacetime. How then can we have anything other than de Sitter space without fine tuning? Well tempering—dynamical cancellation of the cosmological constant using degeneracy within the field equations— can replace a large cosmological constant with a much lower energy state. Here we give an explicit mechanism to obtain a Minkowski solution, replacing the cosmological constant with zero, and testing its attractor nature and persistence through a vacuum phase transition. We derive the general conditions that Horndeski scalar-tensor gravity must possess, and evolve in a fugue of functions, to deliver nothing and make the universe be flat.

On catalyzed vacuum decay around a radiating black hole and the crisis of the electroweak vacuum

False vacuum decay is a key feature in quantum field theories and exhibits a distinct signature in the early Universe cosmology. It has recently been suggested that the false vacuum decay is catalyzed by a black hole (BH), which might cause the catastrophe of the Standard Model Higgs vacuum if primordial BHs are formed in the early Universe. We investigate vacuum phase transition of a scalar field around a radiating BH with taking into account the effect of Hawking radiation. We find that the vacuum decay rate slightly decreases in the presence of the thermal effect since the scalar potential is stabilized near the horizon. However, the stabilization effect becomes weak at the points sufficiently far from the horizon. Consequently, we find that the decay rate is not significantly changed unless the effective coupling constant of the scalar field to the radiation is extremely large. This implies that the change of the potential from the Hawking radiation does not help prevent the Standard Model Higgs vacuum decay catalyzed by a BH.

Strongly magnetized quantum vacuum and ferromagnetic phase transition

AbstractQuantum vacuum in large fields of the order of twice or greater than the critical Schwinger field 2Bc shows strong anisotropic properties: virtual photons as well as electrons and positrons tend to propagate in a parallel direction to the magnetic field. The photon self‐energy acquires an imaginary part, which suggests an instability. In order to overcome this anisotropic behavior, we propose an heuristic model based on fermion pairing of boson‐vacuum n in the form of virtual para‐positronium, a chiral noninvariant electron‐positron bound state leading to a ferromagnetic quantum phase transition of the vacuum for fields of order of twice the critical Schwinger field 2Bc.

Thermodynamic Geometry of Yang–Mills Vacua

We study vacuum fluctuation properties of an ensemble of S U ( N ) gauge theory configurations, in the limit of many colors, viz. N c → ∞ , and explore the statistical nature of the topological susceptibility by analyzing its critical behavior at a non-zero-vacuum parameter θ and temperature T. We find that the system undergoes a vacuum phase transition at the chiral symmetry restoration temperature as well as at an absolute value of θ . On the other hand, the long-range correlation length solely depends on θ for the theories with critical exponent e = 2 or T = T d + 1 , where T d is the decoherence temperature. Furthermore, it is worth noticing that the unit-critical exponent vacuum configuration corresponds to a non-interacting statistical basis pertaining to a constant mass of η ′ .

Hot medium effects on pseudotensor K2(1820) meson

The investigation of mesons in hot medium can give valuable information about the nature of QCD vacuum and deconfinement phase transitions. In this study, thermal properties of pseudotensor K2(1820) meson is examined via QCD sum rules at finite temperature. The mass and the decay constant of K2(1820) are estimated up to dimension-five by considering the new operators emerging at finite temperature. It is seen that after a certain temperature, the decay constant and the mass decrease significantly due to the hot medium effects.

Stable gravastars: Guilfoyle’s electrically charged solutions

Compelling alternatives to black holes, namely, gravitational vacuum stars (gravastars), which are multilayered compact objects, have been proposed to avoid a number of theoretical problems associated with event horizons and singularities. In this work, we construct a spherically symmetric thin-shell charged gravastar model where the vacuum phase transition between the de Sitter interior and the external Reissner–Nordström spacetime (RN) are matched at a junction surface, by using the cut-and-paste procedure. Gravastar solutions are found among the Guilfoyle exact solutions where the gravitational potential W2 and the electric potential field ϕ obey a particular relation in a simple form a(b−ϵϕ)2 + b1, where a, b and b1 are arbitrary constants. The simplest ansatz of Guilfoyle’s solution is implemented by the following assumption: that the total energy density is constant, where Q(r) is the electric charge up to a certain radius r. We show that, for certain ranges of the parameters, we can avoid the horizon formation, which allows us to study the linearized spherically symmetric radial perturbations around static equilibrium solutions. To lend our solution theoretical support, we also analyze the physical and geometrical properties of gravastar configurations.

Gravitational waves from vacuum first-order phase transitions: From the envelope to the lattice

We conduct large scale numerical simulations of gravitational wave production at a first order vacuum phase transition. We find a power law for the gravitational wave power spectrum at high wavenumber which falls off as $k^{-1.5}$ rather than the $k^{-1}$ produced by the envelope approximation. The peak of the power spectrum is shifted to slightly lower wave numbers from that of the envelope approximation. The envelope approximation reproduces our results for the peak power less well, agreeing only to within an order of magnitude. After the bubbles finish colliding the scalar field oscillates around the true vacuum. An additional feature is produced in the UV of the gravitational wave power spectrum, and this continues to grow linearly until the end of our simulation. The additional feature peaks at a length scale close to the bubble wall thickness and is shown to have a negligible contribution to the energy in gravitational waves, providing the scalar field mass is much smaller than the Planck mass.

P−Vcriticality in the extended phase space of black holes in massive gravity

We study the P-V criticality and phase transition in the extended phase space of charged anti-de Sitter black holes in canonical ensemble of ghost-free massive gravity, where the cosmological constant is viewed as a dynamical pressure of the black hole system. We give the generalized thermodynamic first law and the Smarr relation with massive gravity correction. We find that not only when the horizon topology is spherical but also in the Ricci flat or hyperbolic case, there appear the P-V criticality and phase transition up to the combination k+c02c2m2 in the four-dimensional case, where k characterizes the horizon curvature and c2m2 is the coefficient of the second term of massive potential associated with the graviton mass. The positivity of such combination indicate the van der Waals-like phase transition. When the spacetime dimension is larger then four, the Maxwell charge there seems unnecessary for the appearance of critical behavior, but a infinite repulsion effect needed, which can also be realized through negative valued c3m2 or c4m2, which is third or fourth term of massive potential. When c3m2 is positive, a Hawking-Page-like black hole to vacuum phase transition is shown in the five-dimensional chargeless case. For the van der Waals-like phase transition in four and five spacetime dimensions, we calculate the critical exponents near the critical point and find they are the same as those in the van der Waals liquid-gas system.

Late-time vacuum phase transitions: Connecting sub-eV scale physics with cosmological structure formation

We show that a particular class of postrecombination phase transitions in the vacuum can lead to localized overdense regions on relatively small scales, roughly 10^6 to 10^10 M_sun, potentially interesting for the origin of large black hole seeds and for dwarf galaxy evolution. Our study suggests that this mechanism could operate over a range of conditions which are consistent with current cosmological and laboratory bounds. One byproduct of phase transition bubble-wall decay may be extra radiation energy density. This could provide an avenue for constraint, but it could also help reconcile the discordant values of the present Hubble parameter (H_0) and sigma_8 obtained by cosmic microwave background (CMB) fits and direct observational estimates. We also suggest ways in which future probes, including CMB considerations (e.g., early dark energy limits), 21-cm observations, and gravitational radiation limits, could provide more stringent constraints on this mechanism and the sub-eV scale beyond-standard-model physics, perhaps in the neutrino sector, on which it could be based. Late phase transitions associated with sterile neutrino mass and mixing may provide a way to reconcile cosmological limits and laboratory data, should a future disagreement arise.

Minkowski domain walls in hyperbolic metamaterials

Abstract Minkowski domain walls are being actively considered in gravitation theory. They may form during a vacuum phase transition, or as a result of braneworld collision. Despite having interesting physical properties, Minkowski domain walls had remained in the theoretical domain only since their first introduction a few decades ago. Here we demonstrate how to make an electromagnetic analogue of a Minkowski domain wall using hyperbolic metamaterials. We analyze electromagnetic field behavior at the wall, and present a simple experimental model of “Minkowski domain wall” formation due to “collision” of two Minkowski spaces.

SCALAR MODULI, WALL CROSSING AND PHENOMENOLOGICAL PREDICTIONS

We present the scalar moduli stabilization from the perspective of the real intrinsic geometry. In this paper, we describe the physical nature of the vacuum moduli fluctuations of an arbitrary Fayet configuration. For finitely many Abelian scalar fields, we show that the framework of the real intrinsic geometry investigates the mixing between the marginal and threshold vacua. Interestingly, we find that the phenomena of wall crossing and the search of the stable vacuum configurations, pertaining to D-term and F-term scalar moduli, can be accomplished for the Abelian charges. For given vacuum expectation values of the moduli scalars, we provide phenomenological aspects of the vacuum fluctuations and phase transitions in the supersymmetry breaking configurations.

Evolution of vacuum states and phase transitions in the two Higgs doublet model during cooling of the Universe

We consider the evolution of the ground state in the two Higgs doublet model during cooling down of the Universe after the big bang. Different regions in the space of free parameters of this model correspond to different sequences of thermal phase transitions. We discuss different paths of thermal evolution and corresponding evolution of physical properties of the system for different modern values of the parameters.

Gravastar energy conditions revisited

We consider the gravastar model where the vacuum phase transition between the de Sitter interior and the Schwarzschild or Schwarzschild–de Sitter exterior geometries takes place at a single spherical δ-shell. We derive sharp analytic bounds on the surface compactness (2m/r) that follow from the requirement that the dominant energy condition (DEC) holds at the shell. In the case of Schwarzschild exterior, the highest surface compactness is achieved with the stiff shell in the limit of vanishing (dark) energy density in the interior. In the case of Schwarzschild–de Sitter exterior, in addition to the gravastar configurations with the shell under surface pressure, gravastar configurations with vanishing shell pressure (dust shells), as well as configurations with the shell under surface tension, are allowed by the DEC. Respective bounds on the surface compactness are derived for all cases. We also consider the speed of sound on the shell as derived from the requirement that the shell is stable against the radial perturbations. The causality requirement (sound speed not exceeding that of light) further restricts the space of allowed gravastar configurations.

Vacuum phase transition at nonzero baryon density

It is argued that the dominant contribution to the interaction of quark–gluon plasma at moderate T⩾Tc is given by the nonperturbative vacuum field correlators. Basing on that nonperturbative equation of state of quark–gluon plasma is computed and in the lowest approximation expressed in terms of absolute values of Polyakov lines for quarks and gluons Lfund(T),Ladj(T)=(Lfund)9/4 known from lattice and analytic calculations. Phase transition at any μ is described as a transition due to vanishing of one of correlators, DE(x), which implies the change of gluonic condensate ΔG2. Resulting transition temperature Tc(μ) is calculated in terms of ΔG2 and Lfund(Tc). The phase curve Tc(μ) is in a good agreement with lattice data. In particular Tc(0)=0.27; 0.19; 0.17 GeV for nf=0,2,3 and fixed ΔG2=0.0035 GeV4.

False vacuum bubble nucleation due to a nonminimally coupled scalar field

We study the possibility of forming the false vacuum bubble nucleated within the true vacuum background via the true-to-false vacuum phase transition in curved spacetime. We consider a semiclassical Euclidean bubble in the Einstein theory of gravity with a nonminimally coupled scalar field. In this paper we present the numerical computations as well as the approximate analytical computations. We mention the evolution of the false vacuum bubble after nucleation.