Gauge-invariant gravitational wave modes in pre-big bang cosmology

In this paper we will discuss exoplanets in the habitable zone of the Milky Way, the origin of terrestrial life, and what 'intelligent' humanity is doing, in order to complete the excursion on <i>The Bridge between the Big Bang and Biology</i>, started with the paper I (Giovannelli & Sabau-Graziati, 2020).

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Modifications to Plane Gravitational Waves from Minimal Lorentz Violation

Symmetry ◽

10.3390/sym11101318 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1318 ◽

Cited By ~ 2

Author(s):

Rui Xu

Keyword(s):

General Relativity ◽

Gravitational Wave ◽

Gravitational Waves ◽

Lorentz Invariance ◽

Lorentz Violation ◽

First Order ◽

Test Particles ◽

Violation Of Lorentz Invariance ◽

Plane Gravitational Waves ◽

Wave Modes

General Relativity predicts two modes for plane gravitational waves. When a tiny violation of Lorentz invariance occurs, the two gravitational wave modes are modified. We use perturbation theory to study the detailed form of the modifications to the two gravitational wave modes from the minimal Lorentz-violation coupling. The perturbation solution for the metric fluctuation up to the first order in Lorentz violation is discussed. Then, we investigate the motions of test particles under the influence of the plane gravitational waves with Lorentz violation. First-order deviations from the usual motions are found.

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Gravitational wave detection in space

International Journal of Modern Physics D ◽

10.1142/s0218271816300019 ◽

2016 ◽

Vol 25 (14) ◽

pp. 1630001 ◽

Cited By ~ 9

Author(s):

Wei-Tou Ni

Keyword(s):

Black Holes ◽

Gravitational Wave ◽

Frequency Band ◽

Low Frequency ◽

Big Bang ◽

Mass Ratio ◽

Intermediate Mass ◽

Compact Binaries ◽

Laser Interferometer Space Antenna ◽

Deployment Time

Gravitational Wave (GW) detection in space is aimed at low frequency band (100[Formula: see text]nHz–100[Formula: see text]mHz) and middle frequency band (100[Formula: see text]mHz–10[Formula: see text]Hz). The science goals are the detection of GWs from (i) Supermassive Black Holes; (ii) Extreme-Mass-Ratio Black Hole Inspirals; (iii) Intermediate-Mass Black Holes; (iv) Galactic Compact Binaries and (v) Relic GW Background. In this paper, we present an overview on the sensitivity, orbit design, basic orbit configuration, angular resolution, orbit optimization, deployment, time-delay interferometry (TDI) and payload concept of the current proposed GW detectors in space under study. The detector proposals under study have arm length ranging from 1000[Formula: see text]km to [Formula: see text][Formula: see text]km (8.6[Formula: see text]AU) including (a) Solar orbiting detectors — (ASTROD Astrodynamical Space Test of Relativity using Optical Devices (ASTROD-GW) optimized for GW detection), Big Bang Observer (BBO), DECi-hertz Interferometer GW Observatory (DECIGO), evolved LISA (e-LISA), Laser Interferometer Space Antenna (LISA), other LISA-type detectors such as ALIA, TAIJI etc. (in Earthlike solar orbits), and Super-ASTROD (in Jupiterlike solar orbits); and (b) Earth orbiting detectors — ASTROD-EM/LAGRANGE, GADFLI/GEOGRAWI/g-LISA, OMEGA and TIANQIN.

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Gravitational Waves from the Cosmological Quark-Hadron Phase Transition Revisited

Universe ◽

10.3390/universe7080304 ◽

2021 ◽

Vol 7 (8) ◽

pp. 304

Author(s):

Pauline Lerambert-Potin ◽

José Antonio de Freitas Pacheco

Keyword(s):

Phase Transition ◽

Gravitational Wave ◽

Equations Of State ◽

Wave Spectrum ◽

Gluon Plasma ◽

Big Bang ◽

Einstein Equations ◽

Black Hole Binaries ◽

Hadron Phase ◽

Gravitational Wave Background

The recent claim by the NANOGrav collaboration of a possible detection of an isotropic gravitational wave background stimulated a series of investigations searching for the origin of such a signal. The QCD phase transition appears as a natural candidate and in this paper the gravitational spectrum generated during the conversion of quarks into hadrons is calculated. Here, contrary to recent studies, equations of state for the quark-gluon plasma issued from the lattice approach were adopted. The duration of the transition, an important parameter affecting the amplitude of the gravitational wave spectrum, was estimated self-consistently with the dynamics of the universe controlled by the Einstein equations. The gravitational signal generated during the transition peaks around 0.28 μHz with amplitude of h02Ωgw≈7.6×10−11, being unable to explain the claimed NANOGrav signal. However, the expected QCD gravitational wave background could be detected by the planned spatial interferometer Big Bang Observer in its advanced version for frequencies above 1.0 mHz. This possible detection assumes that algorithms recently proposed will be able to disentangle the cosmological signal from that expected for the astrophysical background generated by black hole binaries.

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Gauge invariant treatment of the energy carried by a gravitational wave

Physical Review D ◽

10.1103/physrevd.74.024019 ◽

2006 ◽

Vol 74 (2) ◽

Cited By ~ 4

Author(s):

Philip D. Mannheim

Keyword(s):

Gravitational Wave ◽

Gauge Invariant

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On Gauge Invariant Cosmological Perturbations in UV-modified Hořava Gravity: A Brief Introduction

EPJ Web of Conferences ◽

10.1051/epjconf/201816808003 ◽

2018 ◽

Vol 168 ◽

pp. 08003 ◽

Cited By ~ 1

Author(s):

Mu-In Park

Keyword(s):

Detailed Balance ◽

Big Bang ◽

Matter Field ◽

Cosmological Perturbations ◽

Scale Invariant ◽

Gauge Invariant ◽

Four Dimensions ◽

Detailed Balance Condition ◽

Scalar Matter ◽

Horava Gravity

We revisit gauge invariant cosmological perturbations in UV-modified, z = 3 Hořava 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 history of Universe. This could provide a new framework for the Big Bang cosmology.

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