scholarly journals Gravitational waves in neutrino plasma and NANOGrav signal

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Arun Kumar Pandey
Keyword(s):  
Lower Bound ◽  
Finite Difference ◽  
Magnetic Fields ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Length Scale ◽  
Frequency Range ◽  
Sensitivity Range

AbstractThe recent finding of the gravitational wave (GW) signal by the NANOGrav collaboration in the nHZ frequency range has opened up the door for the existence of stochastic GWs. In the present work, we have argued that in a hot dense neutrino asymmetric plasma, GWs could be generated due to the instability caused by the finite difference in the number densities of the different species of the neutrinos. The generated GWs have amplitude and frequency in the sensitivity range of the NANOGrav observation. We have shown that the GWs generated by this mechanism could be one of the possible explanations for the observed NANOGrav signal. We have also discussed generation of GWs in an inhomogeneous cosmological neutrino plasma, where GWs are generated when neutrinos enter a free streaming regime. We show that the generated GWs in an inhomogeneous neutrino plasma cannot explain the observed NANOGrav signal. We have also calculated the lower bound on magnetic fields’ strength using the NANOGrav signal and found that to explain the signal, the magnetic fields’ strength should have at least value $$\sim 10^{-12}$$ ∼ 10 - 12 G at an Mpc length scale.

scholarly journals NON-RADIAL OSCILLATIONS OF NEUTRON STARS AND THE DETECTION OF GRAVITATIONAL WAVES

2012 ◽  
Vol 18 ◽  
pp. 48-52 ◽  
Author(s):  
CECILIA CHIRENTI ◽  
PATRICK R. SILVEIRA ◽  
ODYLIO D. AGUIAR
Keyword(s):  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Sensitivity Range ◽  
Wave Emission ◽  
Spherical Detector

We study the non-radial oscillations of relativistic neutron stars, in particular the (fundamental) f-modes, which are believed to be the most relevant for the gravitational wave emission of perturbed isolated stars. The expected frequencies of the f-modes are compared to the sensitivity range of Mario Schenberg, the Brazilian gravitational wave spherical detector.

scholarly journals Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
Nancy Aggarwal ◽  
Odylio D. Aguiar ◽  
Andreas Bauswein ◽  
Giancarlo Cella ◽  
Sebastian Clesse ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
High Frequency ◽  
White Paper ◽  
Beyond The Standard Model ◽  
Frequency Range ◽  
Ultra High Frequency ◽  
The Standard Model ◽  
Challenges And Opportunities ◽  
Set Up

AbstractThe first direct measurement of gravitational waves by the LIGO and Virgo collaborations has opened up new avenues to explore our Universe. This white paper outlines the challenges and gains expected in gravitational-wave searches at frequencies above the LIGO/Virgo band, with a particular focus on Ultra High-Frequency Gravitational Waves (UHF-GWs), covering the MHz to GHz range. The absence of known astrophysical sources in this frequency range provides a unique opportunity to discover physics beyond the Standard Model operating both in the early and late Universe, and we highlight some of the most promising gravitational sources. We review several detector concepts that have been proposed to take up this challenge, and compare their expected sensitivity with the signal strength predicted in various models. This report is the summary of the workshop “Challenges and opportunities of high-frequency gravitational wave detection” held at ICTP Trieste, Italy in October 2019, that set up the stage for the recently launched Ultra-High-Frequency Gravitational Wave (UHF-GW) initiative.

scholarly journals Signatures of Noncommutativity in Bar Detectors of Gravitational Waves

2019 ◽  
Vol 64 (11) ◽  
pp. 1029 ◽  
Author(s):  
S. Gangopadhyay ◽  
S. Bhattacharyya ◽  
A. Saha
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Excited States ◽  
Ground State ◽  
Order Term ◽  
Second Order ◽  
Length Scale ◽  
Length Variation ◽  
Wave Perturbation ◽  
First Order

The comparison between the noncommutative length scale √θ and the length variation δL = hL, detected in the GW detectors, indicates that there is a strong possibility to detect the noncommutative structure of space in the GW detector setup. Therefore, we explore how the response of a bar detector gets affected due to the presence of a noncommutative structure of space keeping terms up to the second order in a gravitational wave perturbation (h) in the Hamiltonian. Interestingly, the second-order term in h shows a transition between the ground state and one of the perturbed second excited states that was absent, when the calculation was restricted only to the first order in h.

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

scholarly journals EXTENSION OF THE FREQUENCY-RANGE OF INTERFEROMETERS FOR THE "MAGNETIC" COMPONENTS OF GRAVITATIONAL WAVES?

2007 ◽  
Vol 22 (13) ◽  
pp. 2361-2381 ◽  
Author(s):  
CHRISTIAN CORDA
Keyword(s):  
Data Analysis ◽  
Frequency Dependence ◽  
Gravitational Waves ◽  
Response Functions ◽  
Frequency Range ◽  
Total Response ◽  
High Frequencies ◽  
Magnetic Components ◽  
Linear Dimensions ◽  
Dominant Part

Recently, with an enlightening treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GW's), which have to be taken into account in the context of the total response functions of interferometers for GW's propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well-known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz.

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