Horava-Lifshitz Gravity Research Articles

Constraints on covariant Horava-Lifshitz gravity from precision measurement of planetary gravitomagnetic field

As a generalization of Einstein's theory, Horava-Lifshitz gravity has attracted significant interest owing to its healthy ultraviolet behavior. In this paper, we analyze the impact of the Horava-Lifshitz corrections on the gravitomagnetic field. We propose a new measurement method for the planetary gravitomagnetic field based on space-based laser interferometry, which is further used to constrain the Horava-Lifshitz parameters. Our analysis shows that high-precision laser gradiometers can indeed limit the parameters in Horava-Lifshitz gravity and improve the results by one or two orders of magnitude compared with the existing theories. Our novel method also provides insights into how to constrain the parameters in the modified gravitational theory to gain deeper understanding of this complex framework and pave the way for potential technological advancements in the field.

Early and late observational tension: dark energy parametrizations in horava-lifshitz gravity via baryon acoustic oscillations

We investigate late-time cosmic expansion within the Horava Lifshitz gravity framework using Barboza Alcaniz (BA) and Jassal Bagla Padmanabhan Parametrizations (JBP) as alternatives to general relativity. Anisotropic scaling is introduced at ultraviolet scales. Our aim is to constrain each cosmological parameter using the crucial Baryon Acoustic Oscillation (BAO) scale, specifically the sound horizon (r d ), by treating (r d ) as a free parameter. We employ 30 Hubble parameter measurements (H(z)) from cosmic chronometers, along with Type Ia Supernovae, Gamma-Ray Bursts, Quasars, and 24 uncorrelated BAO measurements spanning z = 0.106 to z = 2.33. The analysis includes the 2022 Hubble constant measurement by Riess (R22) as an additional prior and aims to minimize errors by simulating random correlations in the covariance matrix. In both the BA and JBP frameworks, utilizing the full dataset yields sound horizon results of r d = 146.5399 ± 2.4519 Mpc and r d = 146.4533 ± 2.4519 Mpc, respectively. When incorporating R22 results, the sound horizon values become r d = 143.4721 ± 1.8324 Mpc and r d = 142.9826 ± 1.9084 Mpc. These findings reveal a discrepancy between early and late observations, echoing the H 0 tension. Notably, excluding R22 aligns r d with Planck and SDSS results. Model predictions are evaluated against Hubble Measurements and the ΛCDM Paradigm. A comparative study between BA and JBP Models using the Cosmography test shows both models fitting seamlessly within the phantom region. Statistical analysis suggests neither model can be ruled out based on the latest observational measurements.

Primordial dust universe in the Hořava–Lifshitz theory

In this paper, we apply quantum cosmology to investigate the early moments of a Friedmann–Lemaître–Robertson–Walker (FLRW) cosmological model, using Hořava–Lifshitz (HL) as the gravitational theory. The matter content of the model is a dust perfect fluid. We start studying the classical model. Then, we write the total Hamiltonian of the model, quantize it and find the appropriate Wheeler–DeWitt equation. In order to avoid factor ordering ambiguities, in the Wheeler–DeWitt equation, we introduce a canonical transformation. We solve that equation using the Wentzel–Kramers–Brillouin (WKB) approximation and compute the tunneling probabilities for the birth of that universe ([Formula: see text]). Since the WKB wave function depends on the dust energy and the free coupling constants coming from the HL theory, we compute the behavior of [Formula: see text] as a function of all these quantities.

Cosmological test of dark energy parametrizations within the framework of Horava-Lifshitz gravity via baryon acoustic oscillation

We conduct an investigation to explore late-time cosmic acceleration through various dark energy parametrizations (Wettrich, Efstathiou, and Ma-Zhang) within the Horava-Lifshitz gravity framework. As an alternative to general relativity, this theory introduces anisotropic scaling at ultraviolet scales. Our primary objective is to constrain the key cosmic parameters and baryon acoustic oscillation (BAO) scale, specifically the sound horizon (rd ), by utilizing 24 uncorrelated measurements of BAOs derived from recent galaxy surveys spanning a redshift range from z = 0.106 to z = 2.33. Additionally, we integrate the most recent Hubble constant measurement by Riess in 2022 (denoted as R22) as an extra prior. For the parametrizations of Wettrich, Efstathiou, and Ma-Zhang, our analysis of BAO data yields sound horizon results of rd = 148.1560 ± 2.7688 Mpc, rd = 148.6168 ± 10.2469 Mpc, and rd = 147.9737 ± 10.6096 Mpc, respectively. Incorporating the R22 prior into the BAO dataset results in rd = 139.5806 ± 3.8522 Mpc, rd = 139.728025 ± 2.7858 Mpc, and rd = 139.6001 ± 2.7441 Mpc. These outcomes highlight a distinct inconsistency between early and late observational measurements, analogous to the H 0 tension. A notable observation is that, when we do not include the R22 prior, the outcomes for rd tend to be in agreement with Planck and SDSS results. Following this, we conducted a cosmography test and comparative study of each parametrization within the Lambda Cold Dark Matter paradigm. Our diagnostic analyses demonstrate that all models fit seamlessly within the phantom region. All dark energy parametrizations predict an equation of state parameter close to = –1, indicating a behavior similar to that of a cosmological constant. The statistical analysis indicates that neither of the two models can be ruled out based on the latest observational measurements.

Thermodynamical phase transitions of AdS black hole in Horava–Lifshitz gravity

In this paper, we investigate the thermodynamical phase transitions of the spherically symmetric AdS black hole in Horava–Lifshitz (HL) gravity for the detailed balance violation parameter [Formula: see text]. First, by calculating the HP temperature [Formula: see text], the minimum temperature [Formula: see text] and the Gibbs free energy [Formula: see text] of the AdS black hole in different values of parameter [Formula: see text], we find that the HP phase transition can occur at all pressures. Comparing the HP temperature [Formula: see text] with the minimum temperature [Formula: see text], we notice that the ratio of [Formula: see text] tends to 1 when [Formula: see text]. Second, for the small–large black hole phase transition of the AdS black hole, we discover that the black hole heat capacity is divergent at the minimum temperature [Formula: see text], the small–large black hole phase transition occurs at the same time. Furthermore, the black hole entropy also exists [Formula: see text] when [Formula: see text], and [Formula: see text] when the black hole temperature has its minimum [Formula: see text], we surprisingly find that the ratio of [Formula: see text] tends to [Formula: see text] when the dimension [Formula: see text], which provides a general relation between the Hawking–Page phase transition and the small–large black hole phase transition of the AdS black hole in the large dimension. All in all, the ratios of typical temperature and entropy of two kinds of phase transitions tend to natural constant in the large dimension limit, which may imply to understand the nature of two different phase transitions.

Magnetic corrections to the fermionic Casimir effect in Horava-Lifshitz theories

In this paper, I investigate the effect of a magnetic field on the Casimir effect due to a massless and charged fermion field that violates Lorentz invariance according to the Horava-Lifshitz theory. I focus on the case of a fermion field that obeys MIT bag boundary conditions on a pair of parallel plates. I carry out this investigation using the [Formula: see text]-function technique that allows me to obtain Casimir energy and pressure in the presence of a uniform magnetic field orthogonal to the plates. I investigate the cases of the parameter associated with the violation of Lorentz invariance being even or odd and the cases of weak and strong magnetic field, examining all possible combinations of the above quantities. In all cases I obtain simple and very accurate analytic expressions of the magnetic field-dependent Casimir energy and pressure.

Probing Hořava-Lifshitz gravity using particle and photon dynamics in the presence of plasma* *This study is partly supported by Grants F-FA-2021-432, F-FA-2021-510, and MRB-2021-527 of the Ministry of Higher Education, Science and Innovations of the Republic of Uzbekistan

We study the particle motion around a black hole (BH) in Hořava-Lifshitz (HL) gravity with the Kehagias-Sfetsos (KS) parameter. First, the innermost stable circular orbit (ISCO) is obtained for massive particles around the BH in HL gravity. We find that the radii of the ISCOs decrease as the KS parameter decreases, meaning that the parameter causes the orbits of particles to move inward with respect to that of the Schwarzschild BH case. Then, the optical properties of a KS BH are studied in detail, that is, the BH shadow and gravitational weak lensing. We demonstrate that the size of the BH shadow decreases under the influence of the KS parameter.

Rotating Lifshitz-like black holes in F(R) gravity

Abstract One of the alternative theories of gravitation with a possible UV completion of general relativity is Horava–Lifshitz gravity. Regarding a particular class of pure F(R) gravity in three dimensions, we obtain an analytical rotating Lifshitz-like black hole solution. We first investigate some geometrical properties of the obtained solution that reduces to a charged rotating Banados–Teitelboim–Zanelli black hole in a special limit. Then, we study the optical features of such a black hole, like the photon orbit and the energy emission rate, and discuss how electric charge, angular momentum, and exponents affect them. To have acceptable optical behavior, we should apply some constraints on the exponents. We continue our investigation by studying the thermodynamic behavior of solutions in the extended phase space and explore the validity of the first law of thermodynamics as well as local thermal stability using heat capacity. Evaluating the existence of van der Waals-like phase transition, we obtain critical quantities and show how they change under the variation of black hole parameters. Finally, we construct a holographic heat engine of such a black hole and obtain its efficiency in a cycle. Comparing the obtained results with the well-know Carnot heat engine efficiency, we examine the second law of thermodynamics.

Resolution of Cosmological Singularity in Hořava–Lifshitz Cosmology

The standard ΛCDM model, despite its agreement with observational data, still has some issues unaddressed, such as the problem of initial singularity. Solving that problem usually requires modifications of general relativity. However, there appeared the Hořava–Lifshitz (HL) theory of gravity, in which equations governing cosmological evolution include a new term scaling similarly as the dark radiation term in the Friedmann equations, enabling a bounce of the universe instead of initial singularity. This review describes past works on the stability of such a bounce in different formulations of HL theory, an initial detailed balance scenario, and further projectable versions containing higher than quadratic terms to the original action.

Charged AdS black holes with finite electrodynamics in 4D Einstein-Gauss-Bonnet gravity

Using a modified expression for the electric potential in the context of T-duality [Gaete and Nicolini, Phys. Lett. B, 2022], we obtained an exact charged solution within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. We show that the solution also exists in the regularized 4D EGB theory. Moreover, we point out a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava–Lifshitz theory. The black hole solution is regular and free from singularity. As a special case, we derive a class of well known solutions in the literature.

Weak gravity conjecture, black branes and violations of universal thermodynamics relation

The universal thermodynamic relations between corrections to entropy and extremality for various black hole solutions, like rotating-AdS black holes, charged black holes, rotating black holes in massive gravity, etc., have been studied by modifying general relativity. In this paper, we consider a number of the black brane in different structures, such as black brane solution in Rastall AdS massive gravity, Einstein–Yang–Mills AdS black brane solution in massive gravity, and general anisotropic black brane in Horava–Lifshitz gravity. Then, we study universal thermodynamic relations by using a small constant correction added to the action. We conclude that black brane violates the universal thermodynamic relations. In other words, these universal thermodynamic relations are not valid in the black brane structure.

DeWitt wave function in Hořava-Lifshitz cosmology with tensor perturbation

We present a well-tempered DeWitt wave function, which vanishes at the classical big-bang singularity, in Hořava-Lifshitz (HL) cosmology with tensor perturbation, both analytically and numerically. In general relativity, the DeWitt wave function is ill-behaved once the tensor perturbation is taken into account. This is essential because the amplitude of the perturbation diverges at the singularity and the perturbative expansion completely breaks down. On the other hand, in HL gravity it is known that the higher dimensional operators required by the perturbative renormalizability render the tensor perturbation scale-invariant and regular all the way up to the singularity. In this paper we analytically show that in d+1 dimensional HL gravity, the DeWitt wave function for tensor perturbation is indeed well-defined around the classical big-bang singularity. Also, we numerically demonstrate the well-behaved DeWitt wave function for tensor perturbation from the singularity to the finite size of the Universe.

Thermodynamics and shadow images of charged black holes in Horava–Lifshitz gravity

Thermodynamics and shadow images of charged black holes in Horava–Lifshitz gravity

Chaos in spatially homogeneous Hořava–Lifshitz subcritical cosmologies

We consider spatially homogeneous models in Hořava–Lifshitz (HL) gravity that perturbs general relativity (GR) by a parameter v ∈ (0, 1) such that GR occurs at v = 1/2. We prove that the induced Kasner map is chaotic for a broad class of modified HL gravity models, when v ∈ (0, 1/2), despite the fact that the Kasner map is multi-valued in such subcritical regime.

Time orientability and particle production from universal horizons

We discuss particle production in spacetimes endowed with a universal horizon in Einstein--Aether and Horava gravity. We argue that continuity and differentiability of the lapse function require the orientation of the foliation in the interior of the horizon to be reversed with respect to the exterior one. Unless this is allowed, interaction of gravitating scalar fields with the universal horizon leads to unitarity violations in the quantum theory. This property is responsible for particle production by the universal horizon, as we show by computing explicitly its Hawking temperature for all stationary and spherically symmetric spacetimes. We particularize our result to known analytic solutions, including those compatible with observational constraints.

Constructions of entropy and modified Friedmann equations in gravity theories

The FRW universe is considered a thermodynamical system. We assume that the universe filled in a perfect fluid. So, we obtain apparent horizon radius, surface gravity, and temperature. Using the unified first law as well as the first law of thermodynamics and Friedmann equations, we obtain the entropy-area relation on the apparent horizon in Einstein’s gravity. In Horava–Lifshitz gravity, scalar–tensor gravity, f(R) gravity and f(T) gravity theories, using corresponding Friedmann equations, we obtain the corresponding entropies in integration forms. Next, for a power law, future singularity, and de Sitter expansions, we obtain the general entropy function F(A) in terms of horizon area A on different IR cutoffs like Hubble, apparent, particle, event, (m, n)-type event, conformal age, and Ricci horizons. Moreover, by considering general entropy, we determine the modified Friedmann equations for Horava–Lifshitz gravity, scalar–tensor gravity, f(R) gravity and f(T) gravity theories.

Resolving the information loss paradox from the five-dimensional minimal supergravity black hole

In this paper, we study the Hawking tunneling radiation of the charged rotating black hole in five-dimensional minimal supergravity theory by using the semiclassical Hamilton-Jacobi equation. By using two separated ways we obtain the corrected entropy of the black hole. Equality of results gives us a special condition that may solve the information loss paradox. Then, we focus on the phase transitions, and the results show that if the effects of thermal fluctuations are incorporated in the entropy, the black hole is unstable, while there are phase transitions according to the sign-changing behavior of the black hole specific heat. We find that, in presence of thermal fluctuations, the black holes of five-dimensional minimal supergravity behave like the black holes in Horava-Lifshitz gravity hence the second-order phase transition is possible.

Charged Black Holes in Ads Spaces in Horava-Lifshitz Gravity

Charged Black Holes in Ads Spaces in Horava-Lifshitz Gravity

Finite action principle and Hořava-Lifshitz gravity: Early universe, black holes, and wormholes

The destructive interference of the neighbouring field configurations with infinite classical action in the gravitational path integral approach serves as a dynamical mechanism resolving the black hole singularity problem. It also provides an isotropic and homogeneous early universe without the need of inflation. In this work, we elaborate on the finite action in the framework of Horava-Lifshitz gravity -- a ghost-free QFT. Assuming the mixmaster chaotic solutions in the projectable H-L theory, we show that the beginning of the universe is homogeneous and isotropic. Furthermore, we show that the H-L gravity action selects only the regular black-hole spacetimes. We also comment on possibility of traversable wormholes in theories with higher curvature invariants.

Shadows and rings of the Kehagias-Sfetsos black hole surrounded by thin disk accretion

In this paper, under the illumination of thin disk accretion, we have employed the ray-tracing method to carefully investigate shadows and rings of the Kehagias-Sfetsos(KS) black hole in deformed Hořava-Lifshitz(HL) gravity.The results show that the event horizon r+, the radius r_p and impact parameter bp of photon sphere are all decreased with the increase of the HL parameter ω, but the effective potential increases. And, it also turns out that the trajectories of light rays emitted from the north pole direction are defined as the direct emission, lensing ring and photon ring of KS black hole, on the basis of orbits n = ϕ/2π.As black hole surrounded by thin disk accretion, we show that the corresponding transfer functions have their values increased with the parameter ω. More importantly, we also find that the direct emissions always dominate the total observed intensity, while lensing rings as a thin ring make a very small contribution and photon ring as a extremely narrow ring make a negligible contribution, for all three toy-model functions. In view of this, the results finally imply that shadows and rings as the observational appearance of KS black hole exhibit some obvious interesting features, which might be regarded as an effective way to distinguish black holes in HL gravity from the Schwarzschild black hole.