Gravitational-Wave Background  

In General > s.a. gravitational-wave analysis; quantum-gravity effects.
* Idea: A stochastic background, supposed to be roughly uniform between frequencies of 10–5 sec and 100 yr, isotropic, stationary over long periods, and Gaussian, because it comes from many uncorrelated sources.
* Sources: In order of increasing likelihood of detection, Parametric amplification of 0-point fluctuations during inflation (flat spectrum in huge f range, including LIGO and LISA sensitivity); Cosmic strings (relatively flat); Collisions of vacuum bubbles in reheating after phase transitions (peak at 10–7 Hz × Ept/GeV; Unresolved isolated sources.
* And inflation: There were three different production processes at work in the inflationary era – Waves stemming from the inflationary expansion of space itself (which arise from the quantum properties of the gravitational field); Waves from the collision of bubble-like clumps of new matter at reheating after inflation; and Waves from the turbulent fluid mixing of the early pools of matter and radiation, before equilibrium among them (thermalization) had been achieved; Gravity waves would never have been in equilibrium with matter (since gravity is such a weak force there wouldn't be time to mingle adequately); Consequently the GWB will not appear to a viewer now to be at a single overall temperature.
* Bounds: 1995, At some frequencies we can already get bounds from the absence of δT/T s in the COBE data (~ 10–18 Hz) or timing residuals in msec pulsars (~ 10–8 Hz = (8 yrs)–1); 2005, LIGO results, Ωgwb < 8.4 × 10–4 for flat spectrum 69–156 Hz.
@ General references: Alpher et al PR(53); Michelson MNRAS(87); ApJ(94)428, p713; Polnarev & Roxburgh GRG(95); Grishchuk gq/98 [estimates], LNP(01)gq/00 [rev]; Astone et al IJMPD(00); Maggiore PRP(00)gq/99, gq/00-ln [rev]; de Araujo et al PRD(00)ap [theory]; news pw(07)jan; Mitra et al PRD(08)-a0711 [mapping]; Camerini et al PRD(08)-a0802 [blue waves and cosmology]; Giovannini PMCPA(10)-a0901 [relic gravitons, theoretical appraisal]; Su & Zhang PRD(12) [relic waves, energy-momentum pseudotensor]; Mandic et al PRL(12) [parameter estimation]; Romano & Cornish LRR(17)-a1608 [detection methods].
@ Spectrum: Hawking et al PRD(00)ht [in open de Sitter]; Phinney ap/01/MNRAS; Farmer & Phinney MNRAS(03)ap [cosmological binaries]; Zhang et al CQG(05)ap, CQG(06)ap [in accelerating universe]; Seto & Cooray PRD(06)ap/05 [very low f, constraints]; Lasky et al PRX(16)-a1511 [constraints].
@ Anisotropies: Allen & Ottewill PRD(97)gq/96; Olmez et al JCAP(12)-a1106; Mingarelli et al PRD(13) [using pulsar timing arrays]; Kuroyanagi et al PRD(17)-a1604 [and the cosmic string network].
@ And astrophysics: Mazumder et al PRD(14)-a1401; Callister et al a1604/PRX [limits of astrophysics].
@ Theoretical bounds: Cooray et al PRD(05)ap [cmb-galaxy cross-correlation]; Smith et al PRL(06), Corda MPLA(07) [cmb]; Pshirkov & Baskarán PRD(09)-a0903 [large-scale magnetic fields]; Giblin & Thrane PRD(14)-a1410 [detectability].
@ Experimental bounds: Coughlin & Harms PRL(14)-a1401 [from seismic measurements]; Siegel & Roth ApJ(14)-a1401 [from helioseismology]; Aasi et al PRL(14)-a1406 [from 2009-2010 LIGO and Virgo Data]; Pagano et al PLB(16)-a1508 [from Planck 2015]; > s.a. interferometers.
@ Bending of light: Faraoni ap/96-proc; Kaiser & Jaffe ApJ(97)ap/96; LSC & Virgo a1612 [from Advanced LIGO data]..
@ Back-reaction, and universal expansion: Dautcourt PRD(99)gq; Garrison AIP(09)-a0808; Chevalier et al PhyA(09); > s.a. cosmological expansion.
@ Other effects: Kosenko & Postnov A&A-ap/99 [fluctuations]; Grishchuk PU(05)gq-conf [cosmology and cmb]; de Araujo & Miranda PRD(05)ap [and star formation rate]; Mangilli et al PRD(08) [and cosmic neutrinos]; Zhao PRD(09); Rotti & Souradeep PRL(12)-a1112 [cmb lensing]; > s.a. types of black holes [primordial].

Sources and Other References > s.a. numerical relativity; sources of gravitational radiation [including phase transitions].
@ Reviews: Hogan AIP(06)ap [LISA and inflation and other new physics], pw(07)jun; Schneider et al a1005/CQG-proc [extragalactic].
@ Cosmic strings: Hawking PLB(90); Battye & Shellard ap/96-GRF, CQG(96)ap; Martin & Vilenkin PRL(96)ap [hybrid defects]; Damour & Vilenkin PRL(00)gq, PRD(01)gq [non-Gaussian]; Allen & Ottewill PRD(01) [waveforms]; Siemens & Olum NPB(01); Siemens et al PRL(07)ap/06; DePies & Hogan PRD(07)ap [light cosmic strings]; Kleidis et al PRD(08)-a0806; Sousa & Avelino PRD(13)-a1304 [power spectrum], PRD(14)-a1403.
@ Quantum, primordial: Soares-Santos & Gouveia Dal Pino ap/06; Gogoberidze et al PRD(07)-a0705 [turbulence]; Krauss et al Sci(10)may-a1004 + news SA(10)may [and cosmology]; Freitas & Gonçalves a1102 [in Brans-Dicke theory]; Henrot-Versillé et al CQG(15)-a1408 [constraints]; > s.a. loop quantum cosmology.
@ Inflation: Lyth PRL(97); Bucher & Cohn PRD(97); Gleiser & Roberts PRL(98) [collapsing vacuum domains]; Allen et al PRD(00)gq/99; Giovannini hp/99; Hertog & Turok PRD(00)ap/99 [instantons]; Langlois et al PLB(00) [on the brane]; Pilo et al PRL(04)ap; Sahoo MPLA(05)gq/04 [Brans-Dicke, spectrum]; Alexander & Martin PRD(05)ht/04 [birefringence]; Siegel & Fry PLB(05)ap [extra dimensions, thermal spectrum]; Zhao ap/05 [model dependence of spectrum]; Easther & Lim JCAP(06)ap; Smith et al PRD(06)ap [cmb vs direct detection]; Osano et al JCAP(07)gq/06 [second-order effects]; García & Figueroa PRL(07), a0801-proc [hybrid preheating]; Dufaux et al PRD(07)-a0707 [preheating after inflation]; Easther et al PRL(07), PRD(08)-a0712; Smith et al PRD(08)-a0802; Kuroyanagi et al PRD(09)-a0804; Ashoorioon & Freese a0811 [chain inflation]; Shafi & Wickman PLB(11)-a1009 [supersymmetric hybrid inflation, and cmb]; Kuroyanagi et al PRD(11)-a1010 [future prospects of detection]; Brandenberger a1104 [spectrum and inflation]; Wu et al PRD(11) [quantum stress tensor fluctuations]; Senatore et al JCAP(14)-a1109; Jinno et al PLB(12) [and cosmic phase transition]; López & Freese JCAP(15)-a1305 [and Advanced LIGO]; Guzzetti et al RNC(16)-a1605 [rev]; > s.a. sources of gravitational radiation [lqc].
@ Other early universe: Kosowsky et al PRD(02)ap/01 [from turbulence]; Grishchuk gq/02-in; Buonanno gq/03-ln; Boyle et al PRD(04)ht/03 [cyclic universe]; Santos et al AIP(05)gq; Izquierdo PhD(05)gq/06 [expanding universe]; Mandic & Buonanno PRD(06)ap/05 [pre-big-bang and LIGO]; Ananda et al PRD(07) [from primordial density perturbations]; Zhao et al PLB(09)-a0907 [detection]; Figueroa & Meriniemi JHEP(13)-a1306 [out-of-equilibrium fermions]; Caprini JPCS(15)-a1501 [cosmological sources]; > s.a. cmb; propagation effects [conversion into photons].
@ Particles and fields: Del Campo & Ford PRD(88) [thermal γs]; Brodin et al PRD(00)ap [magnetized plasmas]; Enqvist et al PRD(12) [fermions].
@ Binaries: Regimbau & Chauvineau CQG(07)-a0707-proc [extragalactic ns-ns]; Rosado PRD(11)-a1106; Evangelista & de Araujo MPLA(13)-a1504, BJP(14)-a1504, BJP(15)-a1504; NANOGrav Collaboration a1602 [on the upper limit from the Parkes Pulsar Timing Array]; Abbott et al PRL(16) [implications from GW150914]; Nakazato et al ApJ(16)-a1605 [and galaxy metallicity]; Cholis a1609; > s.a. black-hole binaries.
@ Other sources: Carbone et al PRD(06)ap/05 [cold dark matter halos]; Buonanno et al PRD(05) [supernovae]; Sigl JCAP(06) [phase transitions in neutron stars]; Sivaram & Arun OAJ(11)-a0708 [thermal sources]; Regimbau & Mandic CQG(08)-a0806 [astrophysical vs primordial]; Toonen et al MNRAS(09)-a0902 [stars around massive black holes]; Marassi et al MNRAS(10)-a1009 [magnetars]; Regimbau RAA(11)-a1101 [astrophysical]; Rosado PRD(12)-a1206 [rotating neutron stars]; Crocker et al a1701 [stellar core collapse].
@ Other theories: Capozziello et al MPLA(07)-a0707 [scalar-tensor gravity, scalar waves], APP(08)-a0712 [higher-order gravity]; Corda OAJ(09)-a0901 [in f(R) gravity, rev]; Nishizawa & Hayama PRD(13)-a1307 [massive gravity]; Maselli et al PRL(16)-a1606; > s.a. higher-dimensional gravity; Steady-State Cosmology; string phenomenology; tests of general relativity.

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