Recently Horava proposed a renormalizable gravity theory in four dimensions which reduces to Einstein gravity with a non-vanishing cosmological constant in IR but with improved UV behaviors. Here, I study an IR modification which breaks "softly" the detailed balance condition in Horava model and allows the asymptotically flat limit as well. I obtain the black hole and cosmological solutions for "arbitrary" cosmological constant that represent the analogs of the standard Schwartzschild-(A)dS solutions which can be asymptotically (A)dS as well as flat and I discuss some thermodynamical properties. I also obtain solutions for FRW metric with an arbitrary cosmological constant. I study its implication to the dark energy and find that it seems to be consistent with current observational data.
We consider linear perturbations about a homogeneous and isotropic cosmological background in the projectable version of Hořava-Lifshitz gravity. Starting from the action for cosmological perturbations, we identify the canonically normalized fluctuation variables. We find that - in contrast to what happens in the non-projectable version of the theory - the extra scalar cosmological perturbation mode is already dynamical at the level of linear perturbations. For values of the parameter $λ$ in the range $1/3 < λ< 1$, the extra mode is ghost-like, for values $1 < λ$ and $λ< 1/3$ it is tachyonic. …
We consider RFDiff invariant Horava-Lifshitz gravity action with additional Lagrange multiplier term that is a function of scalar curvature. We find its Hamiltonian formulation and we show that the constraint structure implies the same number of physical degrees of freedom as in General Relativity.
We propose a general approach for the construction of modified gravity which is invariant under foliation-preserving diffeomorphisms. Special attention is paid to the formulation of modified $F(R)$ Hořava-Lifshitz gravity (FRHL), whose Hamiltonian structure is studied. It is demonstrated that the spatially-flat FRW equations of FRHL are consistent with the constraint equations. The analysis of de Sitter solutions for several versions of FRHL indicates that the unification of the early-time inflation with the late-time acceleration is possible. It is shown that a special choice of parameters fo…
We calculate the spectrum of the relic gravitational wave due to the trans-Planckian effect in which the standard linear dispersion relations may be modified. Of the modified dispersion relations suggested in literatures which have investigated the trans-Planckian effect, we especially use the Corley-Jacobson dispersion relations. The Corley-Jacobson type modified dispersion relations can be obtained from Hořava-Lifshitz gravity which is non-relativistic and UV complete. Although it is not clear how the transitions from Hořava-Lifshitz gravity in the UV regime to Einstein gravity in the IR lim…
At the present work, it is studied the extension of F (R) gravities to the new recently proposed theory of gravity, the so-called Horava-Lifshitz gravity, which provides a way to make the theory power counting renormalizable by breaking Lorentz invariance. It is showed that dark energy can be well explained in the frame of this extension, just in terms of gravity. It is also explored the possibility to unify inflation and late-time acceleration under the same mechanism, providing a natural explanation the accelerated expansion.
We revisit gauge invariant cosmological perturbations in UV-modified, z = 3 Horava gravity with one scalar matter field, which has been proposed as a renormalizable gravity theory without the ghost problem in four dimensions. We confirm that there is no extra graviton modes and general relativity is recovered in IR, which achieves the consistency of the model. From the UV-modification terms which break the detailed balance condition in UV, we obtain scale-invariant power spectrums for non-inflationary backgrounds, like the power-law expansions, without knowing the details of early expansion hi…
We study FRW cosmology for a non-linear modified F(R) Horava-Lifshitz gravity which has a viable convenient counterpart. A unified description of early-time inflation and late-time acceleration is possible in this theory, but the cosmological dynamic details are generically different from the ones of the convenient viable F(R) model. Remarkably, for some specific choice of parameters they do coincide. The emergence of finite-time future singularities is investigated in detail. It is shown that these singularities can be cured by adding an extra, higher-derivative term, which turns out to be qu…
At the present paper, it is studied cosmological solutions and its stability in the frame of F(R) Horava-Lifshitz gravity. The perturbations around general spatially flat FRW solutions are analyzed and it is showed that the stability of those solutions will depend on the kind of theory, i.e. on the form of the action F(R), as well as on the parameters contained in any Horava-Lifshitz theory due to the breaking of Lorentz invariance. The (in)stability of a given cosmic solution can restrict the models and gives new observational predictions, and can give a natural explanation on the end of infl…
We study linear cosmological perturbations in the ``healthy extension'' of Horava-Lifshitz gravity which has recently been analyzed \cite{BPS2}. We find that there are two degrees of freedom for scalar metric fluctuations, but that one of them decouples in the infrared limit. Also, for appropriate choices of the parameters defining the Lagrangian, the extra mode can be made well-behaved even in the ultraviolet.
We investigate the linear cosmological perturbations in Hořava-Lifshitz gravity with a scalar field. Starting from the most general expressions of the metric perturbations as well as that of a canonical scalar field, we decompose the scalar, vector and tensor parts of the perturbed action. By reducing the Hamiltonian, we find that there are two independent degrees of freedom for the tensor perturbations while none for the vector perturbations. For the scalar perturbations, the remaining number of degrees of freedom, which are all gauge invariant, depends on whether the projectable condition is…
We show that the cosmological phase transition from the first accelerated expansion in the early universe to the second accelerated expansion over the intermediate decelerated expansion is possible in the HL gravity without the ``detailed balance'' condition if the dark scalar energy density is assumed to be negative. Moreover, we obtain various evolutions depending on the scale factor and the expansion rate. Finally, we discuss the existence of the minimum scale in connection with the singularity free condition.
Horava-Lifshitz theory of gravity with detailed balance is plagued by the presence of a negative bare (or geometrical) cosmological constant which makes its cosmology clash with observations. We argue that adding the effects of the large vacuum energy of quantum matter fields, this bare cosmological constant can be approximately compensated to account for the small observed (total) cosmological constant. Even though we cannot address the fine-tuning problem in this way, we are able to establish a relation between the smallness of observed cosmological constant and the length scale at which dim…
We study the first law of thermodynamics in IR modified Hǒrava-Lifshitz spacetime. Based on the Bekenstein-Hawking entropy, we obtain the integral formula and the differential formula of the first law of thermodynamics for the Kehagias-Sfetsos black hole by treating $ω$ as a new state parameter and redefining a mass that is just equal to $M_{ADM}$ obtained by Myung\cite{YSM2} if we take $α=3π/8$.
We introduce conformal traceless decomposition in Lagrange Multiplier modified RFDiff invariant Horava-Lifshitz gravity. We perform Hamiltonian analysis of given action and determine the action for the physical degrees of freedom.
In Horava's theory of gravity, Lorentz symmetry is broken in exchange for renormalizability, but the original theory has been argued to be plagued with problems associated with a new scalar mode stemming from the very breaking of Lorentz symmetry. Recently, Blas, Pujolas, and Sibiryakov have proposed a healthy extension of Horava gravity, in which the behavior of the scalar mode is improved. In this paper, we study scalar modes of cosmological perturbations in extended Horava gravity. The evolution of metric and density perturbations is addressed analytically and numerically. It is shown that …
We review the effective field theory of modified gravity in which the Lagrangian involves three dimensional geometric quantities appearing in the 3+1 decomposition of space-time. On the flat isotropic cosmological background we expand a general action up to second order in the perturbations of geometric scalars, by taking into account spatial derivatives higher than two. Our analysis covers a wide range of gravitational theories-- including Horndeski theory/its recent generalizations and the projectable/non-projectable versions of Hořava-Lifshitz gravity. We derive the equations of motion for …
We investigate the Hamiltonian structure of linearized extended Hořava- Lifshitz gravity in a flat cosmological background following the Faddeev-Jackiw's Hamiltonian reduction formalism. The Hamiltonian structure of extended Hořava-Lifshitz gravity is similar to that of the projectable version of original Hořava-Lifshitz gravity, in which there is one primary constraint and so there are two physical degrees of freedom. We also find that extra scalar graviton mode in an inflationary background can be decoupled from the matter field in the infrared (IR) limit, but it is coupled to the matter fie…
Using the dynamical system approach, properties of cosmological models based on the Horava-Lifshitz gravity are systematically studied. In particular, the cosmological phase space of the Horava-Lifshitz model is characterized. The analysis allows to compare some key physical consequences of the imposition (or not) of detailed balance. A result of the investigation is that in the detailed balance case one of the attractors in the theory corresponds to an oscillatory behavior. Such oscillations can be associated to a bouncing universe, as previously described by Brandenberger, and will prevent a…
In this work, a minisuperspace model for the projectable Hořava-Lifshitz (HL) gravity without the detailed balance condition is investigated. The Wheeler-deWitt equation is derived and its solutions are studied and discussed for some particular cases where, due to HL gravity, there is a "potential barrier" nearby $a=0$. For a vanishing cosmological constant, it is found a normalizable wave function of the universe. When the cosmological constant is non-vanishing, the WKB method is used to obtain solutions for the wave function of the universe. Using the Hamilton-Jacobi equation, one discusses …
This note is devoted to the study of Hamiltonian formalism of modified F(R) Horava-Lifshitz theories of gravity that were proposed recently in arXiv:1001.4102[hep-th]. We also study Hamiltonian formulation of the healthy extended Horava-Lifshitz gravities and show that these theories have many unusual and interesting properties.
We discuss the cosmology of recently proposed Horava-Lifshitz f(R) gravity. In particular, we derive the modified Hubble equation that reduces to the standard HL gravity case in appropriate limit. We show how the bounce solutions in this theory are modified due to nonlinear effect of f(R) gravity. We also show that in principle, the Universe in this set-up can show cyclic behavior.
We consider gauge invariant cosmological perturbations in UV-modified, z=3 Horava gravity with one scalar matter field, which has been proposed as a renormalizable gravity theory without the ghost problem in four dimensions. In order to exhibit its dynamical degrees of freedom, we consider the Hamiltonian reduction method and find that, by solving "all" the constraint equations, the degrees of freedom are the same as those of Einstein gravity: One scalar and two tensor (graviton) modes when a scalar matter field presents. However, we confirm that there is no extra graviton modes and general re…
We show that the Kerr metric does not exist as a fully rotating black hole solution to the modified Hořava-Lifshitz (HL) gravity with $Λ_W=0$ and $λ=1$ case. We perform it by showing that the Kerr metric does not satisfy full equations derived from the modified HL gravity.
In the framework of Horava-Lifshitz theory, we study the eigenvalues associated with the Wheeler-DeWitt equation representing the vacuum expectation values associated with the cosmological constant. The explicit calculation is performed with the help of a variational procedure with trial wave functionals of the Gaussian type. We analyze both the case with the detailed balanced condition and the case without it. In the case without the detailed balance, we find the existence of an eigenvalue depending on the set of coupling constants (g2,g3) and (g4,g5,g6), respectively, and on the physical sca…
We study cosmological perturbations in Hořava-Lifshitz Gravity. We consider scalar metric fluctuations about a homogeneous and isotropic space-time. Starting from the most general metric, we work out the complete second order action for the perturbations. We then make use of the residual gauge invariance and of the constraint equations to reduce the number of dynamical degrees of freedom. After introducing the Sasaki-Mukhanov variable, the combination of spatial metric fluctuation and matter inhomogeneity for which the action in General Relativity has canonical form, we find that this variable…
The partial Hamiltonian analysis of the Hořava-type action presented in the paper by M. Chaichian, S. Nojiri, S. D. Odintsov, M. Oksanen, A. Tureanu (Class. Quant. Grav. 27 (2011) 185021) is incorrect; for the authors' choice of variables, a covariant shift, instead of a contravariant shift which is the one usually used in General Relativity (GR) in ADM variables, the true algebra of constraints differs from what they presented. The algebra of constraints for their choice of variables is explicitly given for GR and compared with the standard algebra.
A Wheeler-DeWitt equation for the Kantowski-Sachs model is derived within the framework of the minimal quantum gravity theory proposed by Hořava. We study the solution to this equation in the ultraviolet limit for the specific case where the λ parameter of the theory takes its relativistic value λ = 1. It is observed that the minisuperspace variables switch their role compared with their usual infrared (General Relativity) behavior.
In this note we search for large distance solutions of Horava gravity. In the case of the "detailed balance" action, gravity solutions asymptote to IR only above the cosmological constant ($\sim$horizon) scale. However, if one adds IR dominant terms $αR^{(3)}+βΛ_W$, one can recover general relativity solutions on usual scales in the real Universe, provided one fine-tunes the cosmological constant, reobtaining the usual cosmological constant problem. We comment on pp wave solutions, in order to gain insight into the relativistic properties of the theory.
We study stability of singularity-free cosmological solutions with positive cosmological constant based on projectable Hořava-Lifshitz (HL) theory. In HL theory, the isotropic and homogeneous cosmological solutions with bounce can be realized if spacial curvature is non-zero. By performing perturbation analysis around non-flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime, we derive a quadratic action and discuss the stability, i.e, ghost and tachyon-free conditions. Although the squared effective mass of scalar perturbation must be negative in infrared regime, we can avoid tachyon inst…
In order to allow the asymptotically flat, we consider Hořava-Lifshitz gravity theory with a soft violation of the detailed balance condition and obtain various solutions. In particular, we find that such theory coupled to a global monopole leads to a solution representing a space with deficit solid angle, which is well matched with genuine feature of GR.
We study thermodynamics of cosmological models in the Horava-Lifshitz theory of gravity, and systematically investigate the evolution of the universe filled with a perfect fluid that has the equation of state $p=wρ$, where $p$ and $ρ$ denote, respectively, the pressure and energy density of the fluid, and $w$ is an arbitrary real constant. Depending on specific values of the free parameters involved in the models, we classify all of them into various cases. In each case the main properties of the evolution are studied in detail, including the periods of deceleration and/or acceleration, and th…
Brane world scenarios offer a way of setting the cosmological constant to zero after supersymmetry breaking provided there is a sufficient number of adjustable integration constants/parameters. In the case of the Horava-Witten theory compactified on a Calabi-Yau threefold, we argue that it is difficult to find enough freedom to get a zero (or small) cosmological constant after supersymmetry breaking.
We study a version of the recently proposed modified $F(R)$ Hořava-Lifshitz gravity that abandons the projectability condition of the lapse variable. We discovered that the projectable version of this theory has a consistent Hamiltonian structure, and that the theory has interesting cosmological solutions which can describe the eras of accelerated expansion of the universe in a unified manner. The usual Hořava-Lifshitz gravity is a special case of our theory. Hamiltonian analysis of the non-projectable theory, however, shows that this theory has serious problems. These problems are compared wi…
In the Horava-Lifshitz theory of quantum gravity, two conditions -- detailed balance and projectability -- are usually assumed. The breaking of projectability simplifies the theory, but it leads to serious problems with the theory. The breaking of detailed balance leads to a more complicated form of the theory, but it appears to resolve some of the problems. Sotiriou, Visser and Weinfurtner formulated the most general theory of Horava-Lifshitz type without detailed balance. We compute the linear scalar perturbations of the FRW model in this form of HL theory. We show that the higher-order curv…
In this paper we show that by considering a slightly modified Horava-Lifshitz gravity one can find self-tuning cosmological scenarios. Since in the proposed model the cosmological constant cancels out, then regardless of its value it cannot produce any gravitational effect. As a consequence this removes the gravitational effect of the vacuum energy on the expansion of the Universe. Accelerating scenarios, however, can be found through the presence of conventional and non-conventional fluids.
We perform the phase space analysis in terms of the linearization technique in the Hořava-Lifshitz gravity with the softly broken detailed balance condition. It can be shown that the bouncing universe appears only for the positive spatial curvature of $k=+1$, and it is possible to obtain oscillating universe with the help of the negative dark radiation and the negative cosmological constant.
It is well known that by applying the first law of thermodynamics to the apparent horizon of a Friedmann-Robertson-Walker universe, one can derive the corresponding Friedmann equations in Einstein, Gauss-Bonnet, and more general Lovelock gravity. Is this a generic feature of any gravitational theory? Is the prescription applicable to other gravities? In this paper we would like to address the above questions by examining the same procedure for Horava-Lifshitz gravity. We find that in Horava-Lifshitz gravity, this approach does not work and we fail to reproduce a corresponding Friedmann equatio…
Based on the renormalizable theory of gravitation recently proposed by Horava, we present a simple scenario to generate almost scale-invariant, super-horizon curvature perturbations. The anisotropic scaling with dynamical critical exponent z=3 implies that the amplitude of quantum fluctuations of a free scalar field generated in the early epoch of the expanding universe is insensitive to the Hubble expansion rate and, thus, scale-invariant. Those fluctuations are later converted to curvature perturbations by the curvaton mechanism or/and the modulated decay of heavy particles/oscillating field…
We study the Hawking radiation of the spherically symmetric, asymptotically flat black holes in the infrared modified Horava-Lifshitz gravity by applying the methods of covariant anomaly cancellation and effective action, as well as the approach of Damour-Ruffini-Sannan's. These black holes behave as the usual Schwarzschild ones of the general relativity when the radial distance is very large. We also extend the method of covariant anomaly cancellation to derive the Hawking temperature of the spherically symmetric, asymptotically AdS black holes that represent the analogues of the Schwarzschil…
The cosmological solutions of Horava-Witten theory discovered by Lukas, Ovrut and Waldram are generalized to allow non vanishing spatial curvature. The solution with closed spatial sections has initial and final curvature singularities. We find two solutions with open spatial sections, both of which evolve from an initial curvature singularity to the supersymmetric domain wall solution at late times. We also present a solution with open spatial sections and a non-zero Ramond-Ramond scalar. The behaviour of the solutions in eleven dimensions is discussed.
We study anisotropic cosmology in Hořava's gravity theory and obtain Kasner type solutions, valid for any number d of spatial dimensions. The corresponding exponents satisfy two relations, one involving the marginal coupling λ. Also, Hořava's (super)renormalisable theory predicts (super)stiff matter whose equation of state is p = w ρwith w \ge 1. We discuss briefly the implications of these results for the nature of cosmological collapse.
In this paper, the issue how to introduce matter in Hořava-Lifshitz theories of gravity is addressed. This is a key point in order to complete the proper definition of these theories and, what is very important, to study their possible phenomenological implications. As is well known, in Hořava-Lifshitz gravity the breakdown of Lorentz invariance invalidates the usual notion of minimally coupled matter. Two different approaches to bypass this problem are here described. One is based on a Kaluza-Klein reinterpretation of the 3+1 decomposition of the gravity degrees of freedom, what naturally lea…
Hořava gravity has been proposed as a renormalizable, higher-derivative gravity without ghost problems, by considering different scaling dimensions for space and time. In the non-relativistic higher-derivative generalization of Einstein gravity, the meaning and physical properties of black hole and membrane space-times are quite different from the conventional ones. Here, we study the singularity and horizon structures of such geometries in IR-modified Hořava gravity, where the so-called "detailed balance" condition is softly broken in IR. We classify all the viable static solutions without na…
By combining analytical and numerical methods we find that the solutions of the complete Horava theory with negative cosmological constant that satisfy the conditions of staticity, spherical symmetry and vanishing of the shift function are two kinds of geometry: (i) a wormhole-like solution with two sides joined by a throat and (ii) a single side with a naked singularity at the origin. We study the second-order effective action. We consider the case when the coupling constant of the (partial ln N)^2 term, which is the unique deviation from general relativity in the effective action, is small. …
We investigate static spherically symmetric vacuum solutions in the IR limit of projectable nonrelativistic quantum gravity, including the renormalisable quantum gravity recently proposed by Hořava. It is found that the projectability condition plays an important role. Without the cosmological constant, the spacetime is uniquely given by the Schwarzschild solution. With the cosmological constant, the spacetime is uniquely given by the Kottler (Schwarzschild-(anti) de Sitter) solution for the entirely vacuum spacetime. However, in addition to the Kottler solution, the static spherical and hyper…
Orbifold branes are studied in the framework of the 11-dimensional Horava-Witten heterotic M-Theory. It is found that the effective cosmological constant can be easily lowered to its current observational value by the mechanism of large extra dimensions. The domination of this constant over the evolution of the universe is only temporarily. Due to the interaction of the bulk and the branes, the universe will be in its decelerating expansion phase again in the future, whereby all problems connected with a far future de Sitter universe are resolved.
In this paper, we investigate the fermions Hawking radiation and quasinormal modes in infra-red modified Ho$\check{r}$ava-Lifshitz gravity under tunneling and perturbation perspectives.Firstly, through the fermions tunneling in IR modified Ho$\check{r}$ava-Lifshitz gravity,we obtain the Hawking radiation emission rate, tunneling temperature and entropy for the Kehagias-Sfetsos black hole. It is found that the results of fermions tunneling are in consistence with the thermodynamics results obtained by calculating surface gravity.Secondly, we numerically calculate the lowing quasinormal modes fr…
In this paper, we take cosmological constant as a thermodynamical pressure and it's conjugate quantity as a thermodynamical volume. This expression help us to investigate the phase transition and holographic heat engine. So, in order to have Van der Waals fluid behaviour in Horava -Lifshitz (HL) black hole, we modified the solution of such black hole with some cosmology ansatz. Also from holographic heat engine, we obtain Carnot efficiency for the HL black hole. The phase transition of the system lead us to investigate the stability condition for the corresponding black hole. In that case, we …
We investigate the linear cosmological perturbations of Hořava-Lifshitz gravity in a FRW universe without any matter. Our results show that a new gauge invariant dynamical scalar mode emerges, due to the gauge transformation under the "foliation-preserving" diffeomorphism and "projectability condition", and it can produce a scale invariant power spectrum. In the infrared regime with $λ=1$, the dynamical scalar degree of freedom turns to be a non-dynamical one at the linear order level.
In this work, we will analyze a noncommutative (NC) version of the Friedmann-Robert-Walker cosmological models within the gravitational Hořava-Lifshitz theory. The matter content of the models is described by a perfect fluid and the constant curvature of the spatial sections may be positive, negative or zero. In order to obtain this theory, we will use the Faddeev-Jackiw symplectic formalism to introduce, naturally, space-time noncommutativity inside the equations that provide the dynamics of the theory. We will investigate, in details, the classical field equations of a particular version of …
We calculate the Casimir energy of a massless scalar field confined between two nearby parallel plates formed by ideal uncharged conductors, placed tangentially to the surface of a sphere with mass M and radius R. To this end, we take into account a static and spherically symmetric solution of Hořava-Lifshitz (HL) gravity, with a cosmological constant term, in lower orders of approximation, considering both weak-field and infrared limits. We show that the Casimir energy, just in the second order weak-field approximation, is modified due to the parameter of the HL gravity as well as to the cosm…
We find stable singularity-free cosmological solutions in non-flat Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime in the context of Hořava-Lifshitz (HL) theory. Although we encounter the negative squared effective masses of the scalar perturbations in the original HL theory, the behaviors can be remedied by relaxing the projectability condition. In our analysis, the effects from the background dynamics are taken into account as well as the sign of the coefficients in the quadratic action for perturbations. More specifically, we give further classification of the gradient stability/instab…
We find spherically symmetric solutions in the modified Hořava-Lifshitz gravity proposed recently by Blas, Pujolas and Sibiryakov. The non-linear equations of the two derivative action turn out to be similar to those stemming from the four-derivative action explored recently. We analyze the solutions and derive constraints on the relevant new coupling constant. We also analyze the case where the cosmological constant is non-zero. We derive the large distance expansion of solutions and show that the power of the standard Newton's law is modified in the presence of a cosmological constant.
We explore a connection between generalized uncertainty principle (GUP) and modified Hořava-Lifshitz (HL) gravity. The GUP density function may be replaced by the cutoff function for the renormalization group of modified Hořava-Lifshitz gravity. We find the GUP-corrected graviton propagators and compare these with tensor propagators in the HL gravity. Two are qualitatively similar, but the $p^5$-term arisen from Cotton tensor is missed in the GUP-corrected graviton propagator.
The functional renormalization group equation for projectable Hořava-Lifshitz gravity is used to derive the non-perturbative beta functions for the Newton's constant, cosmological constant and anisotropy parameter. The resulting coupled differential equations are studied in detail and exemplary RG trajectories are constructed numerically. The beta functions possess a non-Gaussian fixed point and a one-parameter family of Gaussian fixed points. One of the Gaussian fixed points corresponds to the Einstein-Hilbert action with vanishing cosmological constant and constitutes a saddle point with one…
In Horava-Lifshitz gravity, the extra dynamical scalar mode could play significant role in cosmology. However it has been pointed out that such a scalar may suffer from the strong coupling problem in IR. We address this issue in this paper. Our analysis shows that the scalar mode could decouple naturally at λ=1 due to the extra gauge symmetry. On the other hand, the fact that the scalar mode becomes ghost when 1/3<λ<1 is a real challenge to the theory. We try to overcome this problem by modifying the action such that the RG flow lies outside the problematic region. We discuss the cosmological …
We consider Horava gravity within the framework of the effective field theory (EFT) of dark energy and modified gravity. We work out a complete mapping of the theory into the EFT language for an action including all the operators which are relevant for linear perturbations with up to sixth order spatial derivatives. We then employ an updated version of the EFTCAMB/EFTCosmoMC package to study the cosmology of the low-energy limit of Horava gravity and place constraints on its parameters using several cosmological data sets. In particular we use cosmic microwave background (CMB) temperature-temp…
We attempt a critical reconsideration of "detailed balance" as a principle that can be used to restrict the proliferation of couplings in Horava-Lifshitz gravity. We re-examine the shortcomings that have been usually associated with it in the literature and we argue that easy remedies can be found for all of them within the framework of detailed balance, and that the most persistent of them are actually related to projectability. We show that, once projectability is abandoned, detailed balance reduces the number of independent couplings by roughly an order of magnitude and imposes only one res…
We study quantum corrections to projectable Horava gravity with $z = 2$ scaling in 2+1 dimensions. Using the background field method, we utilize a non-singular gauge to compute the anomalous dimension of the cosmological constant at one loop, in a normalization adapted to the spatial curvature term.
We study possible links between quantum gravity phenomenology encoding Lorentz violations as nonlinear dispersions, the Einstein-Finsler gravity models, EFG, and nonholonomic (non-integrable) deformations to Hořava-Lifshitz, HL, and/or Einstein's general relativity, GR, theories. EFG and its scaling anisotropic versions formulated as Hořava-Finsler models, HF, are constructed as covariant metric compatible theories on (co) tangent bundle to Lorentz manifolds and respective anisotropic deformations. Such theories are integrable in general form and can be quantized following standard methods of …
