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4.0

Jun 30, 2018
06/18

by
Michael R. R. Good; Chi Xiong; Alvin J. K. Chua; Kerson Huang

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We consider superfluidity and quantum vorticity in rotating spacetimes. The system is described by a complex scalar satisfying a nonlinear Klein-Gordon equation. Rotation terms are identified and found to lead to the transfer of angular momentum of the spacetime to the scalar field. The scalar field responds by rotating, physically behaving as a superfluid, through the creation of quantized vortices. We demonstrate the vortex nucleation through numerical simulation.

Topics: High Energy Physics - Theory, High Energy Astrophysical Phenomena, Astrophysics, General Relativity...

Source: http://arxiv.org/abs/1407.5760

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6.0

Jun 30, 2018
06/18

by
Robert Alicki; Alejandro Jenkins

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The linear coupling of a rotating heat bath to a quantum field is studied in the framework of the Markovian master equation for the field's non-unitary time evolution. The bath's rotation induces population inversion for the field's low-energy modes. For bosons, this leads to superradiance, an irreversible process in which some of the bath's kinetic energy is extracted by spontaneous and stimulated emission. We find the energy and entropy balance for such systems and apply our results to the...

Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory, Quantum Physics

Source: http://arxiv.org/abs/1702.06231

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5.0

Jun 28, 2018
06/18

by
Adam Pound

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In general-relativistic perturbation theory, a point mass accelerates away from geodesic motion due to its gravitational self-force. Because the self-force is small, one can often approximate the motion as geodesic. However, it is well known that self-force effects accumulate over time, making the geodesic approximation fail on long timescales. It is less well known that this failure at large times translates to a failure at large distances as well. At second perturbative order, two...

Topics: Astrophysics, General Relativity and Quantum Cosmology, High Energy Astrophysical Phenomena

Source: http://arxiv.org/abs/1510.05172

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4.0

Jun 30, 2018
06/18

by
Martina Gerbino; Andrea Marchini; Luca Pagano; Laura Salvati; Eleonora Di Valentino; Alessandro Melchiorri

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We present new constraints on the spectral index n_T of tensor fluctuations from the recent data obtained by the BICEP2 experiment. We found that the BICEP2 data alone slightly prefers a positive, "blue", spectral index with n_T=1.36\pm0.83 at 68 % c.l.. However, when a TT prior on the tensor amplitude coming from temperature anisotropy measurements is assumed we get n_T=1.67\pm0.53 at 68 % c.l., ruling out a scale invariant $n_T=0$ spectrum at more than three standard deviations....

Topics: High Energy Physics - Phenomenology, Astrophysics, General Relativity and Quantum Cosmology,...

Source: http://arxiv.org/abs/1403.5732

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4.0

Jun 30, 2018
06/18

by
Guillermo Ballesteros

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We present the effective theory of fluids at next-to-leading order in derivatives, including an operator that has not been considered until now. The power-counting scheme and its connection with the propagation of phonon and metric fluctuations are emphasized. In a perturbed FLRW geometry the theory presents a set of features that make it very rich for modelling the acceleration of the Universe. These include anisotropic stress, a non-adiabatic speed of sound and modifications to the standard...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, Astrophysics, General Relativity...

Source: http://arxiv.org/abs/1410.2793

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4.0

Jun 28, 2018
06/18

by
Thomas Osburn; Niels Warburton; Charles R. Evans

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We model the inspiral of a compact stellar-mass object into a massive nonrotating black hole including all dissipative and conservative first-order-in-the-mass-ratio effects on the orbital motion. The techniques we develop allow inspirals with initial eccentricities as high as $e\sim0.8$ and initial separations as large as $p\sim 50$ to be evolved through many thousands of orbits up to the onset of the plunge into the black hole. The inspiral is computed using an osculating elements scheme...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1511.01498

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4.0

Jun 30, 2018
06/18

by
Martin Bojowald

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Quantum gravity is often expected to solve both the singularity problem and the information-loss problem of black holes. This article presents an example from loop quantum gravity in which the singularity problem is solved in such a way that the information-loss problem is made worse. Quantum effects in this scenario, in contrast to previous non-singular models, do not eliminate the event horizon and introduce a new Cauchy horizon where determinism breaks down. Although infinities are avoided,...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1409.3157

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3.0

Jun 30, 2018
06/18

by
Chris D. A. Blair; Emanuel Malek

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We use a geometric approach to construct a flux formulation for the SL(5) U-duality manifest exceptional field theory. The resulting formalism is well-suited for studying gauged supergravities with geometric and non-geometric fluxes. Here we describe all such fluxes for both M-theory and IIB supergravity including the Ramond-Ramond fields for compactifications to seven dimensions. We define the locally non-geometric "R-flux" and globally non-geometric "Q-flux" for M-theory...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.0635

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7.0

Jun 28, 2018
06/18

by
Massimo Giovannini

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We investigate the production of the hypermagnetic gyrotropy when the electric and magnetic gauge couplings evolve at different rates, as it happens in the the relativistic theory of the Van der Waals forces. If a pseudo-scalar interaction breaks the duality symmetry of the corresponding equations, the gyrotropic configurations of the hypermagnetic fields can be amplified from the vacuum during an inflationary stage of expansion. After charting the parameter space of the model in terms of the...

Topics: High Energy Physics - Theory, Cosmology and Nongalactic Astrophysics, Astrophysics, General...

Source: http://arxiv.org/abs/1511.00138

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Jun 29, 2018
06/18

by
Marios Christodoulou; Carlo Rovelli; Simone Speziale; Ilya Vilensky

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A gravitationally collapsed object can bounce-out from its horizon via a tunnelling process that violates the classical equations in a finite region. Since tunnelling is a non-perturbative phenomenon, it cannot be described in terms of quantum fluctuations around a classical solution and a background-free formulation of quantum gravity is needed to analyze it. Here we use Loop Quantum Gravity to compute the amplitude for this process, in a first approximation. The amplitude determines the...

Topics: High Energy Physics - Theory, Astrophysics, High Energy Astrophysical Phenomena, Cosmology and...

Source: http://arxiv.org/abs/1605.05268

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3.0

Jun 30, 2018
06/18

by
Adam Moss; Levon Pogosian

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Scaling networks of cosmic defects, such as strings and textures, actively generate scalar, vector and tensor metric perturbations throughout the history of the universe. In particular, {\em vector} modes sourced by defects are an efficient source of the CMB B-mode polarization. We use the recently released BICEP2 and POLARBEAR B-mode polarization spectra to constrain properties of a wide range of different types of cosmic strings networks. We find that in order for strings to provide a...

Topics: High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology, Cosmology and...

Source: http://arxiv.org/abs/1403.6105

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4.0

Jun 30, 2018
06/18

by
Jonathan Ganc; Martin S. Sloth

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The damping of a non-uniform magnetic field between the redshifts of about $10^4$ and $10^6$ injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called $\mu$-distortion. We can calculate the correlation $\langle\mu T\rangle$ of this distortion with the temperature anisotropy $T$ of the CMB to search for a correlation $\langle B^2\zeta\rangle$ between the magnetic field $B$ and the curvature perturbation $\zeta$; knowing...

Topics: High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology, Cosmology and...

Source: http://arxiv.org/abs/1404.5957

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6.0

Jun 30, 2018
06/18

by
Davood Momeni; Ratbay Myrzakulov

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Motivated by the newly proposal for gravity as the effect of the torsion scalar $T$ and trace of the energy momentum tensor $\mathcal{T}$,we investigate the cosmological reconstruction of different models of the Universe. Our aim here is to show that how this modified gravity model, $f(T,\mathcal{T})$ is able to reproduce different epoches of the cosmological history. We explicitly show that $f(T,\mathcal{T})$ can be reconstructed for $\Lambda $CDM as the most popular and consistent model. Also...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1405.5863

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4.0

Jun 28, 2018
06/18

by
N. Malsawmtluangi; P K Suresh

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Gravitational waves are placed in the squeezed vacuum state and obtained its spectrum for the expanding flat FLRW universe. The gravitational wave spectrum gets enhanced due to the squeezing effect and is likely to be detected with the Einstein Telescope. The spectral energy density of gravitational waves in the squeezed vacuum state does not exceed the nucleosynthesis upper bound.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1511.07120

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3.0

Jun 29, 2018
06/18

by
Phongpichit Channuie; Peeravit Koad

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We investigate the particle production due to parametric resonances in model of inflation where the lightest composite state stemming from the minimal walking technicolor theory plays the role of the inflaton. For model of inflation, the effective theory couples non-minimally to gravity. Regarding the preheating, we study in details a model of a composite inflaton field $\phi$ coupled to another scalar field $\chi$ with the interaction term $g^{2}\phi^{2}\chi^{2}$. Particularly, in the...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, General Relativity and Quantum...

Source: http://arxiv.org/abs/1603.06875

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4.0

Jun 29, 2018
06/18

by
Po-Ning Chen; Mu-Tao Wang; Ye-Kai Wang; Shing-Tung Yau

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This article considers the quasi-local energy in reference to a general static spacetime. We follow the approach developed by the authors in [19, 20, 7, 9] and define the quasi-local energy as a difference of surface Hamiltonians, which are derived from the Einstein-Hilbert action. The new quasi-local energy provides an effective gauge independent measurement of how far a spacetime deviates away from the reference static spacetime on a finitely extended region.

Topics: Differential Geometry, General Relativity and Quantum Cosmology, Mathematics

Source: http://arxiv.org/abs/1604.02983

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3.0

Jun 29, 2018
06/18

by
Nahomi Kan; Kiyoshi Shiraishi

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In this paper, we study rotating boson stars in the large coupling limit as well as in the Newtonian limit. We investigate the equilibrium solutions in four and five dimensions by adopting some analytical approximations. We show that the relations among the radius, angular momentum, Newtonian energy and quadrupole moment (for the four-dimensional solution) of the boson star can be qualitatively realized for the minimal number of boson star parameters.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1605.02846

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4.0

Jun 28, 2018
06/18

by
Benjamin E. Niehoff; Jorge E. Santos; Benson Way

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Numerical evidence suggests that the superradiant instability of Kerr-AdS black holes and "black resonators" evolves to smaller and smaller scales towards a "limiting" black resonator. Using $AdS_4$ supergravity, we argue that this putative endpoint to the superradiant instability does not exist.

Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory

Source: http://arxiv.org/abs/1510.00709

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3.0

Jun 30, 2018
06/18

by
Michael Pürrer

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Black-hole binary coalescences are one of the most promising sources for the first detection of gravitational waves. Fast and accurate theoretical models of the gravitational radiation emitted from these coalescences are highly important for the detection and extraction of physical parameters. Spinning effective-one-body (EOB) models for binaries with aligned spins have been shown to be highly faithful, but are slow to generate and thus have not yet been used for parameter estimation studies. I...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1402.4146

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4.0

Jun 29, 2018
06/18

by
V. K. Oikonomou

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We study the gravitational shock wave generated by a massless high energy particle in the context of higher order gravities of the form $F(R,R_{\mu \nu}R^{\mu \nu},R_{\mu \nu \alpha \beta}R^{\mu \nu \alpha \beta})$. In the case of $F(R)$ gravity, we investigate the gravitational shock wave solutions corresponding to various cosmologically viable gravities, and as we demonstrate the solutions are rescaled versions of the Einstein-Hilbert gravity solution. Interestingly enough, other higher order...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1605.08404

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6.0

Jun 29, 2018
06/18

by
Saoussen Mbarek; Robert B. Mann

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We present explicit expressions of the thermodynamic volume inside and outside the cosmological horizon of Eguchi-Hanson solitons in general odd dimensions. These quantities are calculable and well-defined regardless of whether or not the regularity condition for the soliton is imposed. For the inner case, we show that the reverse isoperimetric inequality is not satisfied for general values of the soliton parameter $a$, though a narrow range exists for which the inequality does hold. For the...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1611.01131

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3.0

Jun 30, 2018
06/18

by
Alessandra Buonanno; B. S. Sathyaprakash

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Gravitational-wave astronomy will soon become a new tool for observing the Universe. Detecting and interpreting gravitational waves will require deep theoretical insights into astronomical sources. The past three decades have seen remarkable progress in analytical and numerical computations of the source dynamics, development of search algorithms and analysis of data from detectors with unprecedented sensitivity. This Chapter is devoted to examine the advances and future challenges in...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1410.7832

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10.0

Jun 26, 2018
06/18

by
Hiroyuki Nakano

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In previous works, we developed a perturbative extrapolation formula to obtain gravitational waves at infinity from binary black hole simulations, based on the Regge-Wheeler-Zerilli formalism. In practice, this formula was basically derived in a background flat spacetime. We derive here an estimation of errors and an improved extrapolation formula by using the Teukolsky perturbative equation for a background Kerr spacetime. The improved formula requires knowledge about a mass and spin of the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.02890

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Jun 27, 2018
06/18

by
Thomas Bäckdahl; Juan A. Valiente Kroon

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We develop a frame and dyad gauge-independent formalism for the calculus of variations of functionals involving spinorial objects. As part of this formalism we define a modified variation operator which absorbs frame and spin dyad gauge terms. This formalism is applicable to both the standard spacetime (i.e. SL(2,C)) 2-spinors as well as to space (i.e. SU(2,C)) 2-spinors. We compute expressions for the variations of the connection and the curvature spinors.

Topics: Differential Geometry, General Relativity and Quantum Cosmology, Mathematics

Source: http://arxiv.org/abs/1505.03770

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3.0

Jun 29, 2018
06/18

by
Casey Cartwright; Alex Flournoy

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We consider topological constraints that must be satisfied by formulations of gravitation as a gauge theory. To facilitate the analysis we review and further justify the composite bundle formalism of Tresguerres as a consistent underlying structure capable of incorporating both the local Lorentz and translational degrees of freedom. Identifying an important global structure required by the composite construction, we translate this into conditions on the underlying manifold. We find that in...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1604.03980

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3.0

Jun 29, 2018
06/18

by
Jean-Baptiste Fouvry; Christophe Pichon; John Magorrian

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We derive the kinetic equation that describes the secular evolution of a large set of particles orbiting a dominant massive object, such as stars bound to a supermassive black hole or a proto-planetary debris disc encircling a star. Because the particles move in a quasi-Keplerian potential, their orbits can be approximated by ellipses whose orientations remain fixed over many dynamical times. The kinetic equation is obtained by simply averaging the BBGKY equations over the fast angle that...

Topics: Astrophysics, Astrophysics of Galaxies, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1606.05501

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7.0

Jun 28, 2018
06/18

by
Gabriel German; Alfredo Herrera-Aguilar; Juan Carlos Hidalgo; Roberto A. Sussman

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We take a pragmatic, model independent approach to single field slow-roll canonical inflation by imposing conditions, not on the potential, but on the slow-roll parameter $\epsilon(\phi)$ and its derivatives $\epsilon^{\prime }(\phi)$ and $\epsilon^{\prime\prime }(\phi)$, thereby extracting general conditions on the tensor-to-scalar ratio $r$ and the running $n_{sk}$ at $\phi_{H}$ where the perturbations are produced, some $50$ $-$ $60$ $e$-folds before the end of inflation. We find quite...

Topics: Cosmology and Nongalactic Astrophysics, Astrophysics, General Relativity and Quantum Cosmology,...

Source: http://arxiv.org/abs/1512.03105

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3.0

Jun 30, 2018
06/18

by
Fotis Farakos; Rikard von Unge

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We study the embedding of the quadratic model of chaotic inflation into the 4D, N=1 minimal theories of supergravity by the use of massive vector multiplets and investigate its robustness against higher order corrections. In particular, we investigate the criterion of technical naturalness for the inflaton potential. In the framework of the new-minimal formulation the massive vector multiplet is built in terms of a real linear multiplet coupled to a vector multiplet via the 4D analog of the...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1404.3739

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3.0

Jun 30, 2018
06/18

by
Georgios Kofinas; Emmanuel N. Saridakis

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We investigate the cosmological applications of $F(T,T_G)$ gravity, which is a novel modified gravitational theory based on the torsion invariant $T$ and the teleparallel equivalent of the Gauss-Bonnet term $T_{G}$. $F(T,T_{G})$ gravity differs from both $F(T)$ theories as well as from $F(R,G)$ class of curvature modified gravity, and thus its corresponding cosmology proves to be very interesting. In particular, it provides a unified description of the cosmological history from early-times...

Topics: High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology, Cosmology and...

Source: http://arxiv.org/abs/1408.0107

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5.0

Jun 30, 2018
06/18

by
K. Surya Kiran; Chethan Krishnan; Ayush Saurabh; Joan Simon

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We study the null orbifold singularity in 2+1 d flat space higher spin theory as well as string theory. Using the Chern-Simons formulation of 2+1 d Einstein gravity, we first observe that despite the singular nature of this geometry, the eigenvalues of its Chern-Simons holonomy are trivial. Next, we construct a resolution of the singularity in higher spin theory: a Kundt spacetime with vanishing scalar curvature invariants. We also point out that the UV divergences previously observed in the...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1408.3296

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5.0

Jun 30, 2018
06/18

by
F. Belgiorno; S. L. Cacciatori; F. Dalla Piazza

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We set up a tunneling approach to the analogue Hawking effect in the case of models of analogue gravity which are affected by dispersive effects. An effective Schroedinger-like equation for the basic scattering phenomenon IN->P+N*, where IN is the incident mode, P is the positive norm reflected mode, and N* is the negative norm one, signalling particle creation, is derived, aimed to an approximate description of the phenomenon. Horizons and barrier penetration play manifestly a key-role in...

Topics: Quantum Physics, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1411.7871

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Jun 29, 2018
06/18

by
Jerzy Lewandowski; Adam Szereszewski; Piotr Waluk

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The theory of non-expanding horizons (NEH) geometry and the theory of near horizon geometries (NHG) are two mathematical relativity frameworks generalizing the black hole theory. From the point of view of the NEHs theory, a NHG is just a very special case of a spacetime containing an NEH of many extra symmetries. It can be obtained as the Horowitz limit of a neighborhood of an arbitrary extremal Killing horizon. An unexpected relation between the two of them, was discovered in the study of...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1605.07038

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3.0

Jun 29, 2018
06/18

by
Ernesto F. Eiroa; Emilio Rubin de Celis; Claudio Simeone

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In this article we present a theoretical construction of spacetimes with a thin shell that joins two different local cosmic string geometries. We study two types of global manifolds, one representing spacetimes with a thin shell surrounding a cosmic string or an empty region with Minkowski metric, and the other corresponding to wormholes which are not symmetric across the throat located at the shell. We analyze the stability of the static configurations under perturbations preserving the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1608.04729

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2.0

Jun 30, 2018
06/18

by
C. García-Meca; S. Carloni; C. Barceló; G. Jannes; J. Sánchez-Dehesa; A. Martínez

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We apply a homogenization process to the acoustic velocity potential wave equation. The study of various examples shows that the resulting effective properties are different from those of the homogenized pressure wave equation for the same underlying acoustic parameters. A careful analysis reveals that a given set of inhomogeneous parameters represents an entirely different physical system depending on the considered equation. Our findings unveil a different way of tailoring acoustic properties...

Topics: Physics, General Relativity and Quantum Cosmology, Mesoscale and Nanoscale Physics, Classical...

Source: http://arxiv.org/abs/1409.5773

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3.0

Jun 30, 2018
06/18

by
Gautam Mandal; Ritam Sinha; Nilakash Sorokhaibam

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We present the complete family of solutions of 3D gravity (Lambda

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1405.6695

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3.0

Jun 30, 2018
06/18

by
S. H. Hendi

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Generalizing of the Maxwell field to nonlinear electrodynamics theories, we look for the magnetic solutions. In initial approximation these models give the usual linear electrodynamics. We consider a suitable metric and investigate the properties of the solutions. Also, we use the cut-and-paste method to construct wormhole structure. We generalize the static solutions to rotating spacetime and obtain conserved quantities.

Topics: Physics, General Physics, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1405.6997

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3.0

Jun 30, 2018
06/18

by
Amit Ghosh; Daniele Pranzetti

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A quantum isolated horizon can be modeled by an SU(2) Chern-Simons theory on a punctured 2-sphere. We show how a local 2-dimensional conformal symmetry arises at each puncture inducing an infinite set of new observables localized at the horizon which satisfy a Kac-Moody algebra. By means of the isolated horizon boundary conditions, we represent the gravitational fluxes degrees of freedom in terms of the zero modes of the Kac-Moody algebra defined on the boundary of a punctured disk. In this...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1405.7056

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2.0

Jun 30, 2018
06/18

by
Pankaj Jain; Gopal Kashyap

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We show that a theory with conformal invariance, which is explicitly broken by small terms, provides a solution to the fine tuning problem of the cosmological constant. In the absence of the symmetry breaking terms, the cosmological constant is zero. Its value in the full theory is controlled by the symmetry breaking terms. The symmetry breaking terms also provide the slow roll conditions, which may be useful in constructing a model of inflation.

Topics: High Energy Physics - Phenomenology, Astrophysics, General Relativity and Quantum Cosmology,...

Source: http://arxiv.org/abs/1405.7775

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3.0

Jun 30, 2018
06/18

by
Daniele Bertacca; Roy Maartens; Chris Clarkson

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We present a detailed derivation of the observed galaxy number over-density on cosmological scales up to second order in perturbation theory. We include all relativistic effects that arise from observing on the past lightcone. The derivation is in a general gauge, and applies to all dark energy models (including interacting dark energy) and many modified gravity models. The result will be important for accurate cosmological parameter estimation, including non-Gaussianity, since all projection...

Topics: High Energy Physics - Phenomenology, Astrophysics, General Relativity and Quantum Cosmology,...

Source: http://arxiv.org/abs/1406.0319

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2.0

Jun 30, 2018
06/18

by
Shaon Ghosh; Gijs Nelemans

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Neutron star binaries, which are among the most promising sources for the direct detection of gravitational waves (GW) by ground based detectors, are also potential electromagnetic (EM) emitters. Gravitational waves will provide a new window to observe these events and hopefully give us glimpses of new astrophysics. In this paper, we discuss how EM information of these events can considerably improve GW parameter estimation both in terms of accuracy and computational power requirement. And then...

Topics: High Energy Astrophysical Phenomena, Astrophysics, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1406.0343

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2.0

Jun 30, 2018
06/18

by
Daniel N. Blaschke; Raúl Carballo-Rubio; Emil Mottola

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We analyze the phenomenon of fermion pairing into an effective boson associated with anomalies and the anomalous commutators of currents bilinear in the fermion fields. In two spacetime dimensions the chiral bosonization of the Schwinger model is determined by the axial current anomaly of massless Dirac fermions. A similar bosonized description applies to the 2D conformal trace anomaly of the fermion stress tensor. For both the chiral and conformal anomalies, correlation functions involving...

Topics: High Energy Physics - Theory, Mathematics, Mathematical Physics, General Relativity and Quantum...

Source: http://arxiv.org/abs/1407.8523

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2.0

Jun 30, 2018
06/18

by
G. S. Khadekar

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We consider the brane Kantowski-Sachs universe when bulk space is five dimensional anti-de Sitter obeying a linear equation of state of the form $p=(\gamma -1)\rho +p_{0}$, where $ \gamma,\:p_{0}$ are a parameters. In this framework we discuss the brane Kantowski-Sachs cosmology and compare it with standard Kantowski-Sachs cosmology in Einstein theory for some specific matter choice. For several specific choice of relation between energy and pressure, the behavior of the scale factors at early...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.1583

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Jun 30, 2018
06/18

by
S. Habib Mazharimousavi; M. Halilsoy

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We consider Einstein-Maxwell-self-interacting scalar field theory described by a potential $V\left( \phi \right) $ in $2+1-$dimensions. The self-interaction potential is chosen to be a highly non-linear double-Liouville type. Exact solutions, including chargeless black holes and singularity-free non-black hole solutions are obtained in this model.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.4002

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Jun 30, 2018
06/18

by
Peter K. F. Kuhfittig

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This paper addresses the following issues: (1) the possible existence of macroscopic traversable wormholes, given a noncommutative-geometry background, and (2) the possibility of allowing zero tidal forces, given a known density. It is shown that whenever the energy density describes a classical wormhole, the resulting solution is incompatible with quantum field theory. If the energy density originates from noncommutative geometry, then zero tidal forces are allowed. Also attributable to the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.4267

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Jun 30, 2018
06/18

by
Miguel Campiglia; Madhavan Varadarajan

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We construct a quantum kinematics for asymptotically flat spacetimes based on the Koslowski-Sahlmann (KS) representation. The KS representation is a generalization of the representation underlying Loop Quantum Gravity (LQG) which supports, in addition to the usual LQG operators, the action of `background exponential operators' which are connection dependent operators labelled by `background' $su(2)$ electric fields. KS states have, in addition to the LQG state label corresponding to 1...

Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.5527

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Jun 30, 2018
06/18

by
Koichi Hamaguchi; Takeo Moroi; Takahiro Terada

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Motivated by the recent observation of the B-mode signal in the cosmic microwave background by BICEP2, we stuty the Starobinsky-type inflation model in the framework of old-minimal supergravity, where the inflaton field in the original (non-supersymmetric) Starobinsky inflation model becomes a complex field. We study how the inflaton evolves on the two-dimensional field space, varying the initial condition. We show that (i) one of the scalar fields has a very steep potential once the trajectory...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, Astrophysics, General Relativity...

Source: http://arxiv.org/abs/1403.7521

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Jun 30, 2018
06/18

by
Ran Li; Zhaojun Kun; Yanming Zhang

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We analytically study the superradiant instability of a charged massless scalar field in the background of D-dimensional Reissner-Nordstr\"{o}m (RN) black hole caused by the mirror's boundary condition. By using the asymptotic matching method to solve the Klein-Gordon equation that govern the dynamics of the scalar field, we have derived the expressions of the complex parts of the boxed quasinormal frequencies, and shown they are positive in the regime of superradiance. This indicates the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1404.6309

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Jun 30, 2018
06/18

by
Cedric Deffayet; Gilles Esposito-Farese; Richard P. Woodard

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We consider a class of nonlocal, pure-metric modified gravity models which were developed to reproduce the Tully-Fisher relation without dark matter and without changing the amount of weak lensing predicted by general relativity. Previous work gave only the weak field limiting form of the field equations specialized to a static and spherically symmetric geometry. Here we derive the full field equations and specialize them to a homogeneous, isotropic and spatially flat geometry. We also discuss...

Topics: Astrophysics, General Relativity and Quantum Cosmology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1405.0393

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Jun 30, 2018
06/18

by
Angnis Schmidt-May

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Recently, the construction of ghost-free nonlinear massive spin-2 interactions solved a long outstanding problem in classical field theory. The consistent formulation requires a second rank-two tensor (or metric) and therefore has the form of a bimetric theory. Besides providing the solution to an old problem in field theory, ghost-free bimetric theory also has an interesting phenomenology: Its homogeneous and isotropic background solutions can reproduce the expansion history of the universe...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1405.1208

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Jun 30, 2018
06/18

by
Jens Chluba

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In the expanding Universe, the average temperature of the cosmic microwave background (CMB) is expected to depend like TCMB~(1+z) on redshift z. Adiabatic photon production (or destruction) or deviations from isotropy and homogeneity could modify this scaling and several observational tests have been carried out in response. Here, we explain why `adiabatic' conditions are extremely difficult to establish in the redshift range targeted by these tests. Thus, instead of leading to a simple...

Topics: High Energy Physics - Theory, Astrophysics, General Relativity and Quantum Cosmology, Cosmology and...

Source: http://arxiv.org/abs/1405.1277