Latest in gr-qc

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Calibrating gravitational-wave detectors with GW170817Feb 21 2019The waveform of a compact binary coalescence is predicted by general relativity. It is therefore possible to directly constrain the response of a gravitational-wave (GW) detector by analyzing a signal's observed amplitude and phase evolution as a function ... More
Nonlocal Cosmology II --- Cosmic acceleration without fine tuning or dark energyFeb 21 2019We present an improved version of our original cosmological model to explain the current phase of cosmological acceleration without resorting to a cosmological constant or any other mass scale. Like the original, this phenomenological approach is based ... More
Conformal geometry and (super)conformal higher-spin gauge theoriesFeb 21 2019We develop a manifestly conformal approach to describe linearised (super)conformal higher-spin gauge theories in arbitrary conformally flat backgrounds in three and four spacetime dimensions. Closed-form expressions in terms of gauge prepotentials are ... More
On the inexistence of solitons in Einstein-Maxwell-scalar modelsFeb 20 2019Three non-existence results are established for self-gravitating solitons in Einstein-Maxwell-scalar models, wherein the scalar field is, generically, non-minimally coupled to the Maxwell field via a scalar function $f(\Phi)$. Firstly, a trivial Maxwell ... More
The Inverse Problem for Hawking RadiationFeb 20 2019In this work we study the inverse problem related to the emission of Hawking radiation. We first show how the knowledge of greybody factors of different angular contributions $l$ can be used to constrain the width of the corresponding black hole perturbation ... More
Negative temperature in CPT-symmetic UniverseFeb 20 2019In Ref.1 (L. Boyle, K. Finn and N. Turok, CPT-Symmetric Universe, Phys. Rev. Lett. {\bf 121}, 251301 (2018)) the antispacetime Universe was suggested as the analytic continuation of our Universe across the Big Bang singularity. We extended this analytic ... More
Observational Black Hole Spectroscopy: A time-domain multimode analysis of GW150914Feb 20 2019The detection of the least damped quasi-normal mode from the remnant of the gravitational wave event GW150914 realised the long sought possibility to observationally study the properties of quasi-stationary black hole spacetimes through gravitational ... More
Conserved charges in asymptotically de Sitter spacetimesFeb 20 2019We present a covariant phase space construction of hamiltonian generators of asymptotic symmetries with `Dirichlet' boundary conditions in de Sitter spacetime, extending a previous study of J\"ager. We show that the de Sitter charges so defined are identical ... More
Charged spherically symmetric NUT and Taub-NUT black hole solutions in quadratic $f(R)$ gravityFeb 20 2019$f(R)$ theory is a modification of Einstein general relativity which has many interesting results in cosmology and astrophysics. To derive solutions for black holes solution in this theory is difficult due to the fact that it is fourth order differential ... More
Holographic Signatures of Critical CollapseFeb 19 2019Critical phenomena in gravitational collapse exhibit the universal features of self-similarity, critical scaling, and the appearance of a naked singularity. We study critical collapse in AdS, focusing on holographic field theory observables. We demonstrate ... More
Isotropic charged cosmologies in infrared-modified electrodynamicsFeb 19 2019It has long been known that the covariant formulation of quantum electrodynamics conflicts with the local description of states in the charged sector. Some of the solutions to this problem amount to modifications of the subsidiary conditions below some ... More
Novel approaches to dark-matter detection using space-time separated clocksFeb 19 2019We discuss the theoretical analysis and interpretation of space-time separated clock experiments in the context of a space-time varying scalar field that is non-universally coupled to the standard model fields. If massive, such a field is a candidate ... More
Percent-Level Test of Isotropic Expansion Using Type Ia SupernovaeFeb 19 2019We propose and implement a novel, robust, and non-parametric test of statistical isotropy of the expansion of the universe, and apply it to around one thousand type Ia supernovae from the Pantheon sample. We calculate the angular clustering of supernova ... More
Measuring gravity at cosmological scalesFeb 19 2019This paper is a pedagogical introduction to models of gravity and how to constrain them through cosmological observations. We focus on the Horndeski scalar-tensor theory and on the quantities that can be measured with a minimum of assumptions. Alternatives ... More
CFTs on curved spacesFeb 19 2019We study conformal field theories (CFTs) on curved spaces including both orientable and unorientable manifolds possibly with boundaries. We first review conformal transformations on curved manifolds. We then compute the identity components of conformal ... More
How robust is the indistinguishability between quantum fluctuation seen from non-inertial frame and real thermal bathFeb 19 2019We re-advocated the conjecture of indistinguishability between the quantum fluctuation observed from a Rindler frame and a real thermal bath, for the case of a free massless scalar field. To clarify the robustness and how far such is admissible, in this ... More
Charged spherically symmetric black holes in $f(R)$ gravityFeb 18 2019A new class of analytic charged spherically symmetric black hole solutions, which behave asymptotically as flat or (A)dS spacetimes, is derived for specific classes of $f(R)$ gravity, i.e., $f(R)=R-2\alpha\sqrt{R}$ and $f(R)=R-2\alpha\sqrt{R-8\Lambda}$, ... More
ECO-like behavior in black hole analoguesFeb 18 2019Classical phenomenological aspects of acoustic perturbations on a draining bathtub geometry where a surface with reflectivity $\mathcal{R}$ is set at a small distance from the would-be acoustic horizon, which is excised, are addressed. A low-frequency ... More
Seeing in complete darkness, using the Unruh effectFeb 18 2019We present a new method by which, in principle, it is possible to "see in absolute darkness", i.e., without exchanging any real quanta through quantum fields. This is possible because objects modify the mode structure of the vacuum in their vicinity. ... More
Gravitational perturbations from oscillons and transients after inflationFeb 18 2019We study the scalar and tensor perturbations generated by the fragmentation of the inflaton condensate into oscillons or transients after inflation, using nonlinear classical lattice simulations. Without including the backreaction of metric perturbations, ... More
Does the second law hold at cosmic scales?Feb 18 2019The second law of thermodynamics is known to hold at small scales also when gravity plays a leading role, as in the case of black holes and self-gravitating radiation spheres. It has been suggested that it should as well at large scales. Here, by a purely ... More
A gauge invariant prescription to avoid $γ$-crossing instability in Galileon bounceFeb 18 2019We revisit the evolutions of scalar perturbations in a non-singular Galileon bounce. It is known that the second order differential equation governing the perturbations is numerically unstable at a point called $\gamma$-crossing. This instability is usually ... More
Entropy Generation at the Horizon Diffuses Cosmological Constant in 2d de Sitter SpaceFeb 18 2019We investigate a solution of the exactly renormalized Liouville action to foresee the fate of the 2-dimensional de Sitter space. We work in the semiclassical region with a large matter central charge $c$. Instead of de Sitter expansion, it performs a ... More
Bounce cosmology in generalized modified gravitiesFeb 18 2019We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometry. In particular, the richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom ... More
Homogeneity of the universe emerging from the Equivalence Principle and Poisson equation: A comparison between Newtonian and MONDian cosmologyFeb 18 2019A correspondence between the Equivalence principle and the homogeneity of the universe is discussed. We show that under the Newtonian gravity, translation of co-moving coordinates in a uniformly expanding universe defines a new accelerated frame. A consistency ... More
No-go theorem for asymptotically AdS static regular boson starsFeb 18 2019In a recent paper, Hod has proven no-go theorem for asymptotically flat static regular boson stars. In the present work, we extend discussions to the gravity with a negative cosmological constant. In the asymptotically AdS background, we show that spherically ... More
WdW-patches in AdS$_{3}$ and complexity change under conformal transformations IIFeb 18 2019We study the null-boundaries of Wheeler-de Witt (WdW) patches in three dimensional Poincare-AdS, when the selected boundary timeslice is an arbitrary (non-constant) function, presenting some useful analytic statements about them. Special attention will ... More
Relativistic Neutron Stars: Rheological Type Extensions of the Equations of StateFeb 18 2019Based on the Rheological Paradigm, one has extended the equations of state for relativistic spherically symmetric static neutron stars, taking into consideration the derivative of the matter pressure along the so-called director four-vector. The modified ... More
Quasi-isotropic cycles and non-singular bounces in a Mixmaster cosmologyFeb 18 2019A Bianchi IX Mixmaster spacetime is the most general spatially homogeneous solution of Einstein's equations and it can represent the space-averaged Universe. We introduce two novel mechanisms resulting in a Mixmaster Universe with non-singular bounces ... More
Scalar Clouds and Quasinormal ModesFeb 16 2019In this thesis, Maggiore's method (MM), which evaluates the transition frequency that appears in the adiabatic invariant from the highly damped quasinormal mode frequencies (QNMFs), is used to investigate the entropy and area spectra of the Garfinkle-Horowitz-Strominger ... More
Spinning Cosmic Strings in Conformal GravityFeb 16 2019We investigate the spacetime of a spinning cosmic string in conformal invariant gravity, where the interior consists of a gauged scalar field. We find an exact solutions of the exterior of a stationary spinning cosmic string, where we write the metric ... More
Comment on "Astrophysical gravitational waves in conformal gravity"Feb 15 2019Recently, in Phys. Rev. D 98, 084002 (2018), an investigation was carried out on the gravitational radiation from binary systems in conformal gravity and massive conformal gravity. According to the authors of the paper, these two theories differ only ... More
Five-dimensional scale-dependent black holes with constant curvature and Solv horizonsFeb 15 2019In this work, we investigate five--dimensional scale--dependent black hole solutions by modelling their event horizon with some of the eight Thurston three--dimensional geometries. Specifically, we construct constant curvature scale--dependent black holes ... More
Viable inflationary magnetogenesis with helical couplingFeb 15 2019We consider helical coupling to electromagnetism and present a simple model of evolution of the coupling function leading to a viable inflationary magnetogenesis. In this scenario, helical magnetic fields of any desirable strength of order up to $10^{- ... More
Limits on $f(R,T)$ Gravity from Earth's AtmosphereFeb 15 2019Feb 20 2019We investigate changes in Earth's atmospheric models coming from the $f(R,T)$ modified theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the stress-energy tensor. We obtain ... More
Limits on $f(R,T)$ Gravity from Earth's AtmosphereFeb 15 2019We investigate changes in Earth's atmospheric models coming from the $f(R,T)$ modified theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the stress-energy tensor. We obtain ... More
Boson and Dirac stars in $D\geq 4$ dimensionsFeb 15 2019We present a comparative study of spherically symmetric, localized, particle-like solutions for spin $s=0,1/2$ and $1$ gravitating fields in a $D$-dimensional, asymptotically flat spacetime. These fields are massive, possessing a harmonic time dependence ... More
Anisotropic $2$-form dark energyFeb 15 2019We study the dynamics of dark energy in the presence of a 2-form field coupled to a canonical scalar field $\phi$. We consider the coupling proportional to $e^{-\mu \phi/M_{\rm pl}} H_{\alpha \beta \gamma}H^{\alpha \beta \gamma}$ and the scalar potential ... More
The $8Pmmn$ borophene sheet: A solid-state platform for space-time engineeringFeb 15 2019We construct the most generic Hamiltonian of the $8Pmmn$ structure of borophene sheet in presence of spin-orbit, as well as background electric and magnetic fields. In addition to spin and valley Hall effects, this structure offers a framework to conveniently ... More
Spontaneous scalarization of charged black holes at the approach to extremalityFeb 15 2019We study static, spherically symmetric and electrically charged black hole solutions in a quadratic Einstein-scalar-Gauss-Bonnet gravity model. Very similar to the uncharged case, black holes undergo spontaneous scalarization for sufficiently large scalar-tensor ... More
Wormhole as a possible accelerator of high-energy cosmic-ray particlesFeb 15 2019We present the simplest topological classification of wormholes and demonstrate that in open Friedmann models the genus $n\geq 1$ wormholes are stable and do not require the presence of exotic forms of matter, or any modification of general relativity. ... More
Quantum Geometry I : Basics of Loop Quantum Gravity. The Quantum PolyhedraFeb 15 2019General Relativity describes gravity in geometrical terms. This suggests that quantizing such theory is the same as quantizing geometry. The subject can therefore be called quantum geometry and one may think that mathematicians are responsible of this ... More
Quantum Information Capsule in Multiple-Qudit Systems and Continuous-Variable SystemsFeb 15 2019Quantum correlations in an entangled many-body system are capable of storing information. Even when the information is injected by a local unitary operation to the system, the entanglement delocalizes it. In a recent study on multiple-qubit systems, it ... More
Numerical initial data deformation exploiting a gluing construction: I. Exterior asymptotic SchwarzschildFeb 15 2019In this work a new numerical technique to prepare Cauchy data for the initial value problem (IVP) formulation of Einstein's field equations is presented. Directly inspired by the exterior asymptotic gluing (EAG) result of Corvino (2000) our (pseudo)-spectral ... More
First loosely coherent all-sky search for periodic gravitational waves in the O1 LIGO dataFeb 14 2019A new loosely coherent analysis improves sensitivity to continuous gravitational waves by more than 30%, with order of magnitude gains in computational efficiency. Results of all-sky search in 20-200 Hz frequency band are provided including outlier lists ... More
Dark sector unifications: dark matter-phantom energy, dark matter - constant $w$ dark energy, dark matter-dark energy-dark matterFeb 14 2019The paper brings a novel approach to unification of dark matter and dark energy in terms of a cosmic fluid. A model is introduced in which the cosmic fluid speed of sound squared is defined as a function of its equation of state (EoS) parameter. It is ... More
Cosmic Inflation: Trick or Treat?Feb 14 2019Discovered almost forty years ago, inflation has become the leading paradigm for the early universe. Originally invented to avoid the fine-tuning puzzles of the standard model of cosmology, the so-called hot Big Bang phase, inflation has always been the ... More
Cosmic Evolution of Holographic Dark Energy in f(\mathcal{G},T) GravityFeb 14 2019The aim of this paper is to analyze the cosmological evolution of holographic dark energy in $f(\mathcal{G},T)$ gravity ($\mathcal{G}$ and $T$ represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively). We reconstruct ... More
No-go theorem for static boson starsFeb 14 2019It is proved that self-gravitating static scalar fields whose self-interaction potential $V(\psi^2)$ is a monotonically increasing function of its argument cannot form spherically symmetric asymptotically flat bound matter configurations. Our compact ... More
Reduced thin-sandwich equations on manifolds euclidean at infinity and on closed manifolds: existence and multiplicityFeb 14 2019The reduced thin-sandwich equations (RTSE) appear within Wheeler's thin-sandwich approach towards the Einstein constraint equations (ECE) of general relativity. It is known that these equations cannot be well-posed in general, but, on closed manifolds, ... More
Greybody factor for black string in dRGT massive gravityFeb 14 2019The greybody factor from the black string in the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory is investigated in this study. The dRGT massive gravity theory is one of the modified gravity theories used in explaining the current acceleration ... More
On Scalaron Decay via the Trace of Energy-Momentum TensorFeb 14 2019In some inflation scenarios such as $R^{2}$ inflation, a gravitational scalar degrees of freedom called scalaron is identified as inflaton. Scalaron linearly couples to matter via the trace of energy-momentum tensor. We study scenarios with a sequestered ... More
Hawking radiation from not-extremal and extremal Reissner-Nordstrom black holesFeb 14 2019We consider the non-extremal Reissner-Nordstrom black hole and construct a wave packet that exhibits the Hawking radiation. We find the average of the number of the created particles with respect to the in-vacuum state and with respect to Unruh type vacuum ... More
Well-posed Cauchy formulation for Einstein-æther theoryFeb 13 2019We study the well-posedness of the initial value (Cauchy) problem of vacuum Einstein-aether theory. The latter is a Lorentz-violating gravitational theory consisting of General Relativity with a dynamical timelike 'aether' vector field, which selects ... More
Boundary Orbits in Static SpacetimesFeb 13 2019The study of circular orbits in spacetime is of astrophysical importance. The identification and classification of circular orbits in both static spherically (and axially) symmetric and also stationary spacetimes remains an active area of interest. Even ... More
Realism and causality I: Pilot wave and retrocausal models as possible facilitatorsFeb 13 2019Of all basic principles of classical physics, realism should arguably be the last to be given up when seeking a better interpretation of quantum mechanics. We examine the de Broglie-Bohm pilot wave theory as a well developed example of a realistic theory. ... More
Energy in Gravitation and Noether's TheoremsFeb 13 2019I exhibit the conflicting roles of Noether's two great theorems in defining conserved quantities, especially Energy in General Relativity and its extensions: It is the breaking of coordinate invariance through boundary conditions that removes the barrier ... More
Cosmological perturbations in the Regge-Wheeler formalismFeb 13 2019We study linear perturbations of the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model in the Regge-Wheeler formalism which is a standard framework to study perturbations of spherically-symmetric black holes. In particular, we show that the ... More
$R_h=ct$ and the eternal coasting cosmological modelFeb 13 2019We point out that the nonempty $R_h=ct$ cosmological model has some known antecedents in the literature. Some of those eternal coasting models are published even before the discovery of the accelerated expansion of the universe and were shown to have ... More
Realism and Causality II: Retrocausality in Energetic Causal SetsFeb 13 2019We describe a new form of retrocausality, which is found in the behaviour of a class of causal set theories, called energetic causal sets (ECS). These are discrete sets of events, connected by causal relations. They have three orders: (1) a birth order, ... More
Spontaneous scalarisation of charged black holes: coupling dependence and dynamical featuresFeb 13 2019Spontaneous scalarisation of electrically charged, asymptotically flat Reissner-Nordstr\"om black holes (BHs) has been recently demonstrated to occur in Einstein-Maxwell-Scalar (EMS) models. EMS BH scalarisation presents a technical simplification over ... More
Constraining the neutron star equation of state using multi-band independent measurements of radii and tidal deformabilitiesFeb 13 2019Using a Bayesian approach, we combine measurements of neutron star macroscopic observables obtained by astrophysical and gravitational observations, to derive joint constraints on the equation of state (EoS) of matter at supranuclear density. In our analysis ... More
A quasi-matter bounce equivalent to Starobinsky inflationFeb 13 2019In this paper we construct a bounce model that mimics the Starobinsky inflationary model. Our construction relies on Wands' duality, which shows that the Mukhanov-Sasaki equation has a symmetry transformation by changing appropriately its time-dependent ... More
Operational causality in spacetimeFeb 13 2019We consider the general evolution of binary statistics in a, possibly curved, spacetime with the help of the optimal transport theory. It covers a wide range of models including classical statistics, quantum wave-packets and general, possibly non-linear, ... More
Hair-dressing Horndeski: an approach to hairy solutions in cubic Horndeski gravityFeb 13 2019In obtaining exact solutions in gravitational theories containing arbitrary model functions, such as Horndeski gravity, one usually starts by prescribing the model functions of the theory and then goes on to solving their corresponding field equations. ... More
Effective field theory for gravitational radiation in scalar-tensor gravityFeb 13 2019A light scalar degree of freedom, as the one possibly responsible for the accelerated expansion of the Universe, could leave observable traces in the inspiral gravitational wave signal of binary systems. In order to study these effects, we extend the ... More
Accelerating parameter inference with graphics processing unitsFeb 13 2019Gravitational wave Bayesian parameter inference involves repeated comparisons of GW data to generic candidate predictions. Even with algorithmically efficient methods like RIFT or reduced-order quadrature, the time needed to perform these calculations ... More
Acceleration of particles in Schwarzschild and Kerr geometriesFeb 13 2019The Landau-Lifshitz decomposition of spacetime, or (1+3)\,-split, determines the three-dimensional velocity and acceleration as measured by static observers. We use these quantities to analyze the geodesic particles in Schwarzschild and Kerr spacetimes. ... More
Thermodynamics of $f(R)$ Gravity with Disformal TransformationFeb 13 2019We study thermodynamics in $f(R)$ gravity with the disformal transformation. The transformation applied to the matter Lagrangian has the form of $\g_{\m\n} = A(\phi,X)g_{\m\n} + B(\phi,X)\pa_\m\f\pa_\n\f$ with the assumption of the Minkowski matter metric ... More
Gravitational phase transition of self-gravitating systems of fermions in General RelativityFeb 13 2019The Thomas-Fermi model is extended at finite temperature, to describe the gravitational phase transition occurring in massive fermionic systems in a general-relativistic framework. It is shown that, when a nondegenerate fermionic gas (for $N < N_{OV}$, ... More
On the dynamical instability of self-gravitating systemsFeb 13 2019We study the dynamical stability of self-gravitating systems in presence of anisotropy. In particular, we introduce a stability criterion, in terms of the adiabatic local index, that generalizes the stability condition $<\gamma> \geq 4/3$ of the isotropic ... More
LIGO Signals from the Mirror WorldFeb 13 2019We want to explain non-observation of electromagnetic counterpart of currently confirmed ten gravitational wave signals from the black hole mergers assuming their existence in the hidden mirror universe. Mirror matter, which interacts with our world only ... More
Emergence and expansion of cosmic space in an accelerating BIonFeb 13 2019We generalize the Padmanabhan [arXiv:hep-th/1206.4916] mechanism to an accelerating BIon and show that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated ... More
New coordinates for a simpler canonical derivation of the Hawking effectFeb 13 2019In order to achieve a Hamiltonian-based canonical derivation of the Hawking effect, one usually faces multiple hurdles. Firstly, the spacetime foliation using Schwarzschild time does not lead to hyper-surfaces which are always spacelike. Secondly, the ... More
Observational constraints on the oscillating dark energy cosmologiesFeb 13 2019In this study we combine the background and the growth rate data in order to study the ability of the two oscillating dark energy parameterizations, to fit the observational data. Using the likelihood and MCMC method we try to explore the posterior space ... More
The impact of the crust equation of state on the analysis of GW170817Feb 12 2019The detection of GW170817, the first neutron star-neutron star merger observed by Advanced LIGO and Virgo, and its following analyses represent the first contributions of gravitational wave (GW) data to understanding dense matter. Parameterizing the high ... More
Gravitational Waves from Compact Dark Objects in Neutron StarsFeb 12 2019Dark matter could be composed of compact dark objects (CDOs). We find that the oscillation of CDOs inside neutron stars can be a detectable source of gravitational waves (GWs). The GW strain amplitude depends on the mass of the CDO, and its frequency ... More
Inferring Neutron Star Properties from GW170817 with Universal RelationsFeb 12 2019Because all neutron stars share a common equation of state, tidal deformability constraints from the compact binary coalescence GW170817 have implications for the properties of neutron stars in other systems. Using equation-of-state insensitive relations ... More
An alternative way to locally measure the Hubble constant using Gravitational Waves and PTAFeb 12 2019Recent research show that the cosmological components of the Universe should influence on the propagation and observation of Gravitational Waves. Furthermore, it has been proposed a new way to measure the cosmological constant using Pulsar Timing Arrays ... More
Effective Quantum Extended Spacetime of Polymer Schwarzschild Black HoleFeb 12 2019The physical interpretation and eventual fate of gravitational singularities in a theory surpassing classical general relativity are puzzling questions that have generated a great deal of interest among various quantum gravity approaches. In the context ... More
Are quantum corrections on horizon scale physically motivated?Feb 12 2019The aim of this note is to give an overview to non-specialists of recent arguments from fundamental physics in favor and disfavor of quantum corrections to black hole horizons. I will mainly discuss the black hole information paradox, its possible resolutions ... More
Deriving Hawking Radiation via Gauss-Bonnet Theorem: An Alternative WayFeb 12 2019Feb 13 2019In this paper, we apply the recently found topological method of Robson, Villari and Biancalana (RVB) [1, 2] to the various black holes to derive their Hawking temperature. We show that the RVB method can easily be employed to compute the Hawking temperature ... More
Deriving Hawking Radiation via Gauss-Bonnet Theorem: An Alternative WayFeb 12 2019In this paper, we apply the recently found topological method of Robson, Villari and Biancalana (RVB) [1, 2] to the various black holes to derive their Hawking temperature. We show that the RVB method can easily be employed to compute the Hawking temperature ... More
Scale-invariant in inflation with 1-loop quantum correctionsFeb 12 2019We study quantum corrections to an inflationary model, which has the attractive feature of being classically scale-invariant. In this model, quadratic gravity plays along a scalar field in such a way that inflation begins near the unstable point of the ... More
Scale-invariant inflation with 1-loop quantum correctionsFeb 12 2019Feb 13 2019We study quantum corrections to an inflationary model, which has the attractive feature of being classically scale-invariant. In this model, quadratic gravity plays along a scalar field in such a way that inflation begins near the unstable point of the ... More
Science with TianQin: Preliminary Results on Massive Black Hole BinariesFeb 12 2019We investigate the prospects of detecting gravitational waves from coalescing massive black hole binaries in the Universe with the TianQin observatory, a space-based gravitational wave interferometer proposed to be launched in the 2030s. To frame the ... More
Four-wave mixing and enhanced analogue Hawking effect in a nonlinear optical waveguideFeb 12 2019We study the scattering of light on a soliton propagating in a waveguide. When not applying the rotating wave approximation, we show that the linearized wave equation governing perturbations has the same structure as that governing phonon propagation ... More
Implications of JLA data for $k-$essence model of dark energy with given equation of stateFeb 12 2019We perform a comprehensive analysis of recently released `Joint Light-curve Analysis' SNe Ia data to investigate its implications for different dark energy models with varying equation of state parameter $w(z)$, $z$ is the redshift. Observational constraints ... More
Constraints on axionlike dark matter with masses down to $10^{-23}$ eV/c$^2$Feb 12 2019We analyzed an 6.7-year span of data from a rotating torsion-pendulum containing $\approx 10^{23}$ polarized electrons to search for the "wind" arising from ultralight, axionlike dark matter with masses between $10^{-23}$ and $10^{-18}$ eV/c$^2$. Over ... More
Vaidya spacetimes, black-bounces, and traversable wormholesFeb 12 2019We consider a non-static evolving version of the regular "black-bounce"/traversable wormhole geometry recently introduced in arXiv:1812.07114 [gr-qc]. We first re-write the static metric using Eddington-Finkelstein coordinates, and then allow the mass ... More
Time's Arrow in a Quantum Universe: On the Status of Statistical Mechanical ProbabilitiesFeb 12 2019In a quantum universe with a strong arrow of time, it is standard to postulate that the initial wave function started in a particular macrostate--the special low-entropy macrostate selected by the Past Hypothesis. Moreover, there is an additional postulate ... More
Inflying perspectives of reduced phase spaceFeb 12 2019There is widespread disagreement about how the general covariance of a theory affects its quantization. Without a complete quantum theory of gravity, one can examine quantum consequences of coordinate choices only in highly idealized `toy' models. In ... More
Test of Einstein equivalence principle near the Galactic center supermassive black holeFeb 12 2019During its orbit around the four million solar mass black hole Sagittarius A* the star S2 experiences significant changes in gravitational potential. We use this change of potential to test one part of the Einstein equivalence principle: the local position ... More
Primordial Black Holes and Co-Decaying Dark MatterFeb 11 2019Models of Co-Decaying dark matter lead to an early matter dominated epoch -- prior to BBN -- which results in an enhancement of the growth of dark matter substructure. If these primordial structures collapse further they can form primordial black holes ... More
A note on the Hamiltonian as a polymerisation parameterFeb 11 2019In effective models of loop quantum gravity, the onset of quantum effects is controlled by a so-called polymerisation scale. It is sometimes necessary to make this scale phase space dependent in order to obtain sensible physics. A particularly interesting ... More
On the general relativistic framework of the Sagnac effectFeb 11 2019The Sagnac effect is usually considered as being a relativistic effect produced in an interferometer when the device is rotating. General relativistic explanations are known and already widely explained in many papers. Such general relativistic approaches ... More
Inflation after Planck: Judgment DayFeb 11 2019Inflation is considered as the best theory of the early universe by a very large fraction of cosmologists. However, the validity of a scientific model is not decided by counting the number of its supporters and, therefore, this dominance cannot be taken ... More
Horndeski in the SwamplandFeb 11 2019We investigate the implications of string Swampland criteria for alternative theories of gravity. Even though this has not rigorously been proven, there is some evidence that exact de-Sitter solutions with a positive cosmological constant cannot be successfully ... More
Interstellar Travels On Board of Photon RocketsFeb 11 2019By using Kinnersley's solution of general relativity, we model relativistic deep space flights and local celestial sphere on board of rockets that are thrusted by anisotropic absorption or emission of radiation. Relativistic kinematics of the photon rocket ... More
Weak and strong deflection gravitational lensings by a charged Horndeski black holeFeb 11 2019A charged black hole was predicted by the Einstein--Horndeski--Maxwell theory. In order to provide its observational signatures, we investigate its weak and strong deflection gravitational lensings. We find its weak deflection lensing observables, including ... More