Negative Cosmological Constant Research Articles

Convexity restoration from hairy black hole in Einstein-Maxwell-charged scalar system in AdS

In the Einstein-Maxwell-charged scalar system with a negative cosmological constant in arbitrary dimensions higher than three, there exists a horizonless charged soliton solution, which we construct explicitly for an arbitrary mass of the scalar in perturbative series in small charge. We find that the stability of the soliton is determined by the validity of the AdS weak gravity conjecture. The existence of a stable soliton might endanger the convexity of the (free) energy as a function of the charge because the phase transition between the soliton and the extremal Reissner-Nordstrom black hole would be discontinuous. We, however, argue that the existence of the hairy black hole solution circumvents the violation of convexity. The thermodynamic properties of the hairy black hole show that the phase transition becomes continuous irrespective of whether the AdS weak gravity conjecture holds. When it holds, the phase transition occurs between the soliton and the hairy black hole, and when it is violated, the phase transition occurs between the extremal Reissner-Nordstrom black hole and the hairy black hole.

Formula omitted] gravity theory in Einstein space background and causality violation

In this paper, we exploration a Petrov type-N vacuum solution to Einstein’s field equations, while incorporating a negative cosmological constant (Λ<0) within the framework of modified gravity theories. This solution intriguingly accommodates closed time-like curves at a particular moment in time, effectively violates the causality condition, thus acts as a time-machine model. A key observation is that the determinant of the Ricci tensor Rμν for this particular Einstein space metric differs from zero. This noteworthy finding suggests to the existence of an anti-curvature tensor defined Aμν=Rμν−1 and hence, an anti-curvature scalar A=gμνAμν, which is introduced with the Lagrangian of the system, thereby giving rise to as Ricci-inverse gravity theory. We consider class-I models of Ricci-inverse gravity, where the function f=f(R,A)=(R+κA) with κ is the coupling constant. We demonstrate that this Einstein space metric serves as a vacuum solution with a negative modified cosmological constant within the framework of Ricci-inverse gravity. Consequently, the violation of causality persists within this new gravity theory as well. Moreover, we solve the modified field equations by considering matter content other than vacuum and demonstrate that the energy-density and isotropic pressure satisfies the equation ρ=−p=3κΛ.

On the quantum Bousso bound in JT gravity

We prove the Strominger-Thompson quantum Bousso bound in the infinite class of conformal vacua in semiclassical JT gravity, with postive or negative cosmological constant. The Bousso-Fisher-Leichenauer-Wall quantum Bousso bound follows from an analogous derivation, requiring only initial quantum non-expansion. In this process, we show that the quantity \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\\pi {k}^{\\mu }{k}^{\ u }\\langle :{T}_{\\mu \ u }:\\rangle -{S}^{{\\prime}{\\prime}}-\\frac{6}{c}{\\left({S}{\\prime}\\right)}^{2}$$\\end{document} vanishes in any vacuum state, entailing a stronger version of Wall’s quantum null energy condition. We derive an entropy formula in the presence of a generic class of two reflecting boundaries, in order to apply our argument to the half reduction model of de Sitter JT gravity.

New anisotropic Gauss–Bonnet black holes in five dimensions at the critical point

We obtain new vacuum static black hole solutions with anisotropic horizons in Einstein–Gauss–Bonnet gravity with a negative cosmological constant in five dimensions. The translational invariance along one direction on the 3-dimensional horizon cross section is broken. The Gauss–Bonnet coupling α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} is at the critical point where there is one single AdS vacuum. These solutions does not appear in the form of a warped product, i.e. they lack a common warping factor, and the metric contains 2 arbitrary functions, h(r) of the radial coordinate r and H(y) of the horizon coordinate y – some degeneracy in the metric. The nontrivial horizon and the degeneracy may be closely related to the critical value of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. We introduce the process of obtaining the solutions and some of their properties, and also prove a uniqueness theorem for the case when there is a common warping factor for the rest two directions.

Cosmological constant Petrov type-N space–time in Ricci-inverse gravity

Our focus is on a specific type-N space–time that exhibits closed time-like curves in general relativity theory within the framework of Ricci-inverse gravity model. The matter-energy content is solely composed of a pure radiation field, and it adheres to the energy conditions while featuring a negative cosmological constant. One of the key findings in this investigation is the non-zero determinant of the Ricci tensor (Rμν), which implies the existence of an anti-curvature tensor (Aμν) and, as a consequence, an anti-curvature scalar (A≠R−1). Furthermore, we establish that this type-N space–time serves as a solution within modified gravity theories via the Ricci-inverse model, which involves adjustments to the cosmological constant (Λ) and the energy density (ρ) of the radiation field expressed in terms of a coupling constant. As a result, our findings suggest that causality violations remain possible within the framework of this Ricci-inverse gravity model, alongside the predictions of general relativity.

Post-reionization H i 21-cm signal: a probe of negative cosmological constant

ABSTRACT In this study, we investigate a cosmological model involving a negative cosmological constant (AdS vacua in the dark energy sector). We consider a quintessence field on top of a negative cosmological constant and study its impact on cosmological evolution and structure formation. We use the power spectrum of the redshifted H i 21-cm brightness temperature maps from the post-reionization epoch as a cosmological probe. The signature of baryon acoustic oscillations (BAO) on the multipoles of the power spectrum is used to extract measurements of the angular diameter distance DA(z) and the Hubble parameter H(z). The projected errors on these are then subsequently employed to forecast the constraints on the model parameters ($H_0, \Omega _{m}, \Omega _\Lambda , w_0, w_a$) using Markov chain Monte Carlo techniques. We find that a negative cosmological constant with a phantom dark energy equation of state (EoS) and a higher value of H0 is viable from BAO distance measurements data derived from galaxy samples. We also find that BAO imprints on the 21-cm power spectrum obtained from a futuristic SKA-mid like experiment yield a 1σ error on a negative cosmological constant and the quintessence dark energy EoS parameters to be $\Omega _\Lambda =-1.030^{0.589}_{-1.712}$ and $w_0=-1.023^{0.043}_{-0.060}$, $w_a=-0.141^{0.478}_{-0.409}$ respectively.

Flat from anti de Sitter

Ricci-flat solutions to Einstein’s equations in four dimensions are obtained as the flat limit of Einstein spacetimes with negative cosmological constant. In the limiting process, the anti-de Sitter energy-momentum tensor is expanded in Laurent series in powers of the cosmological constant, endowing the system with the infinite number of boundary data, characteristic of an asymptotically flat solution space. The governing flat Einstein dynamics is recovered as the limit of the original energy-momentum conservation law and from the additional requirement of the line-element finiteness, providing at each order the necessary set of flux-balance equations for the boundary data. This analysis is conducted using a covariant version of the Newman-Unti gauge designed for taking advantage of the boundary Carrollian structure emerging at vanishing cosmological constant and its Carrollian attributes such as the Cotton tensor.

Just some simple (but nontrivial) analytical solutions for de Broglie–Bohm quantum cosmology

In this work, we provide some simple analytical solutions to the Wheeler–DeWitt equation for the minisuperspace applied to de Broglie–Bohm quantum cosmology for particular potentials of a scalar matter field ϕ. One solution describes a constantly rolling scalar field with a quadratic potential plus a negative cosmological constant. The scale factor is given by a Gaussian function. The other solution describes a flat Minkowski universe with the potential of a hilltop form.

Solving 3d gravity with Virasoro TQFT

We propose a precise reformulation of 3d quantum gravity with negative cosmological constant in terms of a topological quantum field theory based on the quantization of the Teichmüller space of Riemann surfaces that we refer to as “Virasoro TQFT”. This TQFT is similar, but importantly not equivalent, to SL(2, \mathbb{R}ℝ) Chern-Simons theory. This sharpens the folklore that 3d gravity is related to SL(2, \mathbb{R}ℝ) Chern-Simons theory into a precise correspondence, and resolves some well-known issues with this lore at the quantum level. Our proposal is computationally very useful and provides a powerful tool for the further study of 3d gravity. In particular, we explain how together with standard TQFT surgery techniques this leads to a fully algorithmic procedure for the computation of the gravity partition function on a fixed topology exactly in the central charge. Mathematically, the relation leads to many nontrivial conjectures for hyperbolic 3-manifolds, Virasoro conformal blocks and crossing kernels.

Two instabilities of Schwarzschild-AdS black holes in Einstein–Weyl-scalar theory

Stability of Schwarzschild-AdS (SAdS) black hole is investigated in Einstein–Weyl-scalar (EWS) theory with a negative cosmological constant. Here, we introduce a quadratic scalar coupling to the Weyl term, instead of the Gauss–Bonnet term. The linearized EWS theory admits the Lichnerowicz equation for Einstein tensor as well as scalar equation. The linearized Einstein-tensor carries with a regular mass term (M2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {M}}}^2$$\\end{document}), whereas the linearized scalar has a tachyonic mass term (-3r02/m2r6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-3r_0^2/m^2r^6$$\\end{document}). Two instabilities of SAdS black hole in EWS theory are found as Gregory–Laflamme and tachyonic instabilities. It shows that the correlated stability conjecture holds for small SAdS black holes obtained from EWS theory by establishing a close relation between Gregory–Laflamme and thermodynamic instabilities. On the other hand, tachyonic instability of SAdS black hole can be used for making five branches of scalarized black holes when considering proper thermodynamic quantities of EWS theory (M2>0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {M}}}^2>0$$\\end{document}).

Dark energy in light of the early JWST observations: case for a negative cosmological constant?

Early data from the James Webb Space Telescope (JWST) has uncovered the existence of a surprisingly abundant population of very massive galaxies at extremely high redshift, which are hard to accommodate within the standard ΛCDM cosmology. We explore whether the JWST observations may be pointing towards more complex dynamics in the dark energy (DE) sector. Motivated by the ubiquity of anti-de Sitter vacua in string theory, we consider a string-inspired scenario where the DE sector consists of a negative cosmological constant (nCC) and a evolving component with positive energy density on top, whose equation of state is allowed to cross the phantom divide. We show that such a scenario can drastically alter the growth of structure compared to ΛCDM, and accommodate the otherwise puzzling JWST observations if the dynamical component evolves from the quintessence-like regime in the past to the phantom regime today: in particular, we demonstrate that the presence of a nCC (which requires a higher density for the evolving component) plays a crucial role in enhancing the predicted cumulative comoving stellar mass density. Our work reinforces the enormous potential held by observations of the abundance of high-z galaxies in probing cosmological models and new fundamental physics, including string-inspired ingredients.

More on pure gravity with a negative cosmological constant

We identify an ambiguity in the Chern-Simons formulation of three-dimensional gravity with negative cosmological constant that originates in an outer automorphism of the Lie algebra sl\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathfrak{sl} $$\\end{document}(2, ℝ). It has important consequences for the stability of the theory in a space-time with boundary. We revisit the classical equivalence of three-dimensional gravity with a boundary Liouville theory both on and off the mass shell. Moreover, we provide further details on the quantum equivalence, the gauge symmetry that renders the spectrum diagonal, as well as the relation between asymptotically AdS3 metrics and polar boundary conditions. We thus set the proposal that the Liouville conformal field theory serves as a definition of a unitary theory of pure gravity in three dimensions with negative cosmological constant on a more stable footing.

Small black string thermodynamics

We consider a cylindrically symmetric solution for the field equations of Einstein-Hilbert action with a negative cosmological constant in four dimensions. The small statistical fluctuation in the equilibrium thermodynamics of the black string solution is investigated. The small black string under the influence of small statistical fluctuation also follows the first law of thermodynamics. The behaviour of equation of states for black string changes significantly due to the fluctuation. The fluctuation causes instability to the small-sized black string only. Assuming the black string is fluid, the compressibility of the black string is inversely proportional to the fluctuation parameter.

Asymptotically locally flat and AdS higher-dimensional black holes of Einstein–Horndeski–Maxwell gravity in the light of EHT observations: shadow behavior and deflection angle

Unification of gravity with other interactions, achieving the ultimate framework of quantum gravity, and fundamental problems in particle physics and cosmology motivate to consider extra spatial dimensions. The impact of these extra dimensions on the modified theories of gravity has attracted a lot of attention. One way to examine how extra dimensions affect the modified gravitational theories is to analytically investigate astrophysical phenomena, such as black hole shadows. In this study, we aim to investigate the behavior of the shadow shapes of higher-dimensional charged black hole solutions including asymptotically locally flat (ALF) and asymptotically locally AdS (ALAdS) in Einstein–Horndeski–Maxwell (EHM) gravitational theory. We utilize the Hamilton–Jacobi method to find photon orbits around these black holes as well as the Carter approach to formulate the geodesic equations. We examine how extra dimensions, negative cosmological constant, electric charge, and coupling constants of the EHM gravity affect the shadow size of the black hole. Then, we constrain these parameters by comparing the shadow radius of these black holes with the shadow size of M87* supermassive black hole captured by the Event Horizon Telescope (EHT) collaborations. We discover that generally the presence of extra dimensions within the EHM gravity results in reducing the shadow size of higher-dimensional ALF and ALAdS charged black holes, whereas the impact of electric charge on the shadow of these black holes is suppressible. Interestingly, we observe that decreasing the negative cosmological constant, i.e., increasing its absolute value, leads to increase the shadow size of the ALAdS charged higher-dimensional black hole in the EHM gravity. Surprisingly, based on the constraints from EHT observations, we discover that only the shadow size of the four dimensional ALF charged black hole lies in the confidence levels of EHT data, whereas owing to the presence of the negative cosmological constant, the shadow radius of the four, five, and seven dimensional ALAdS charged black holes lie within the EHT data confidence levels.

Configuration entropy and instability of accelerating black hole in AdS

We consider the accelerating black hole with a negative cosmological constant in four-dimensional spacetime. There are two configurations such as a black string (BS) phase when a mass parameter is zero and a black hole (BH) phase when a mass parameter is nonzero. We investigate their stability via a configuration entropy (CE). It is found that the BS is not always stable but the BH has a thermally stable range below the critical mass of the BH, which is consistent with thermodynamic instability.

New regular 2+1 black hole solutions in bilocal gravity

We obtain new regular black hole solutions for an action in 2+1 dimensions with a bilocal Ricci scalar and a negative cosmological constant. Besides their connection to the cosmological constant, these solutions depend on a fundamental length due to their nonlocal nature. The effective profile densities that result from the nonlocal geometries have quasi-localized mass/energy since they are finite at the origin and their integration in all space is convergent. The black holes obtained are free of singularities and present one, two, or none horizons depending on the values of the involved parameters. The new solutions can have either an AdS, dS, or even a flat core. In the case of a de-Sitter core, it could represent a repulsive force coming from quantum effects. Although the resulting (effective) cosmological constant is positive near the origin, the classical (naked) counterpart is still negative thus precluding a cosmological horizon. We investigate the energy conditions of the effective source and determine the region where exotic energy should be found. Thermodynamic quantities are also computed. On the one hand, the Gibbs’s potential shows that both solutions are globally unstable, as in the BTZ case. On the other hand, we show that for small values of the horizon radius the Hawking temperature is negatively divergent but a finite size remnant can be defined where [Formula: see text] crosses zero. At this point, the heat capacity sign changes from negative to positive, indicating that the black holes are locally stable while irradiating. Thus, such a quantity, along with [Formula: see text] presents crucial differences with the BTZ black hole for small horizon radii where quantum effects become relevant. Finally, we analyze the bilocal black hole geodesics and find stable circular orbits for massless and massive particles, another feature absent in the BTZ case.

Topological classes of thermodynamics of rotating AdS black holes

In this paper, we extend our previous work [D. Wu, Phys. Rev. D 107, 024024 (2023)] to the more general cases with a negative cosmological constant, and investigate the topological numbers for the singly rotating Kerr-AdS black holes in all dimensions and the four-dimensional Kerr-Newman-AdS black hole as well as the three-dimensional Ba\~nados-Teitelboim-Zanelli black hole. We find that the topological numbers of black holes are remarkably influenced by the cosmological constant. In addition, we also demonstrate that the dimension of spacetimes has an important effect on the topological number for rotating anti--de Sitter (AdS) black holes. Furthermore, it is interesting to observe that the difference between the topological number of the AdS black hole and that of its corresponding asymptotically flat black hole is always unity. This new observation leads us to conjure that it might be valid also for other black holes. Of course, this novel conjecture needs to be further verified by examining the topological numbers of many other black holes and their AdS counterparts in the future work.

Uniform rate inflation

In this work, I consider an inflation model with a quadratic potential and a negative cosmological constant. An analytical solution of the equation of motion for the inflaton field is found without slow-roll approximation. The result is that the inflation field is rolling at a constant speed. The prediction for cosmological perturbation is calculated.

Thermodynamic overview and heat engine efficiency of Kerr–Sen–AdS black hole

This paper reflects a study on the thermodynamic features of charged rotating Kerr–Sen–AdS black holes discussed with an extended phase space, where the negative cosmological constant is accounted for pressure. Thermal stability/instability and dependency of the phase transition points on the parameters of a black hole have been discussed further. The authors have systematically studied the throttling process of the black hole considering its mass is identified by its enthalpy. Moreover, the phenomenon of Joule–Thomson expansion has been explored, and inversion temperature for the black hole has been investigated using a numerical approach. Next, a heat engine is constructed by considering the black hole as a working object and subsequently, its efficiency is calculated by considering a rectangular heat cycle in the [Formula: see text]–[Formula: see text] plane. Then the effects of the black hole parameters on its efficiency and their respective roles are studied, followed by a careful comparison of the efficiency with that of a Carnot engine so that the second law of thermodynamics holds true.

Phase transitions and stability of Eguchi-Hanson-AdS solitons

The Eguchi-Hanson-AdS5 family of spacetimes are a class of static, geodesically complete asymptotically locally AdS5 soliton solutions of the vacuum Einstein equations with negative cosmological constant. They have negative mass and are parameterized by an integer p ≥ 3 with a conformal boundary with spatial topology L(p, 1). We investigate mode solutions of the scalar wave equation on this background and show that, similar to AdS5, the geometry admits a normal mode spectrum (i.e. solutions that neither grow or decay in time). In addition, we also discuss other geometric properties of these soliton spacetimes, including the behaviour of causal geodesics and their thermodynamic properties. We also point out a surprising connection with the AdS soliton.