Improved calculation of the gravitational wave spectrum from kinks on infinite cosmic strings

Abstract A metastable cosmic-string network is a generic consequence of many grand unified theories (GUTs) when combined with cosmic inflation. Metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of GUT monopoles. This leads to a network consisting of metastable long strings on superhorizon scales as well as of string loops and segments on subhorizon scales. We compute for the first time the complete stochastic gravitational-wave background (SGWB) arising from all these network constituents, including several technical improvements to both the derivation of the loop and segment contributions. We find that the gravitational waves emitted by string loops provide the main contribution to the gravitational-wave spectrum in the relevant parameter space. The resulting spectrum is consistent with the tentative signal observed by the NANOGrav and Parkes pulsar timing collaborations for a string tension of G μ ∼ 10-11…-7 and has ample discovery space for ground- and space-based detectors. For GUT-scale string tensions, G μ ∼ 10-8…-7, metastable strings predict a SGWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.

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Primordial monopoles and strings, inflation, and gravity waves

Journal of High Energy Physics ◽

10.1007/jhep02(2021)114 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Joydeep Chakrabortty ◽

George Lazarides ◽

Rinku Maji ◽

Qaisar Shafi

Keyword(s):

Symmetry Breaking ◽

Gravity Waves ◽

Cosmic Strings ◽

Wave Spectrum ◽

Gauge Coupling ◽

String Tension ◽

Magnetic Monopoles ◽

Intermediate Scale ◽

Tension Parameter ◽

The Universe

Abstract We consider magnetic monopoles and strings that appear in non-supersymmetric SO(10) and E6 grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter Gμ spans the range 10−6− 10−30, where G is Newton’s constant and μ is the string tension. We show how intermediate scale monopoles with mass ∼ 1013− 1014 GeV and flux ≲ 2.8 × 10−16 cm−2s−1sr−1, and cosmic strings with Gμ ∼ 10−11− 10−10 survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio r lies between 0.06 and 0.003 depending on the details of the inflationary scenario.

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Searching for gravitational-wave bursts from cosmic string cusps with the Parkes Pulsar Timing Array

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3721 ◽

2020 ◽

Vol 501 (1) ◽

pp. 701-712

Author(s):

N Yonemaru ◽

S Kuroyanagi ◽

G Hobbs ◽

K Takahashi ◽

X-J Zhu ◽

...

Keyword(s):

False Alarm ◽

Gravitational Wave ◽

Cosmic String ◽

Cosmic Strings ◽

False Alarm Probability ◽

String Tension ◽

Detection Algorithm ◽

Pulsar Timing ◽

Upper Limits ◽

Pulsar Timing Array

ABSTRACT Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1 per cent. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of Gμ ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array.

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General properties of the gravitational wave spectrum from phase transitions

Physical Review D ◽

10.1103/physrevd.79.083519 ◽

2009 ◽

Vol 79 (8) ◽

Cited By ~ 99

Author(s):

Chiara Caprini ◽

Ruth Durrer ◽

Thomas Konstandin ◽

Géraldine Servant

Keyword(s):

Phase Transitions ◽

Gravitational Wave ◽

Wave Spectrum ◽

General Properties

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Stochastic gravitational wave background from light cosmic strings

Physical Review D ◽

10.1103/physrevd.75.125006 ◽

2007 ◽

Vol 75 (12) ◽

Cited By ~ 61

Author(s):

Matthew R. DePies ◽

Craig J. Hogan

Keyword(s):

Gravitational Wave ◽

Cosmic Strings ◽

Gravitational Wave Background

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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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