Detection relic gravitational waves in thermal case by using Adv.LIGO data of GW150914

The thermal spectrum of relic gravitational waves causes the new amplitude that called `modified amplitude'. Our analysis shows that, there exist some chances for detection of the thermal spectrum in addition to the usual spectrum by Adv.LIGO data of GW150914 and detector based on the maser light (Dml). The behavior of the inflation and reheating stages are often known as power law expansion like $S(\eta)\propto \eta^{1+\beta}$, $S(\eta)\propto \eta^{1+\beta_s}$ respectively. The $\beta$ and $\beta_s$ have an unique effect on the shape of the spectrum. We find some upper bounds on the $\beta$ and $\beta_s$ by comparison the usual and the thermal spectrum with the Adv.LIGO and Dml. As this result modifies our information about the nature of the evolution of inflation and reheating stages.Comment: 12 pages, 4 figure

Modified Amplitude of Gravitational Waves Spectrum

The spectrum of thermal gravitational waves is obtained by including the high frequency thermal gravitons created from extra-dimensional effect and is a new feature of the spectrum. The amplitude and spectral energy density of gravitational waves in thermal vacuum state are found enhanced. The amplitude of the waves get modified in the frequency range (10$^{-16}$ -10 $^{8}$ Hz) but the corresponding spectral energy density is less than the upper bound of various estimated results. With the addition of higher frequency thermal waves, the obtained spectral energy density of the wave in thermal vacuum state does not exceed the upper bound put by nucleosynthesis rate. The existence of cosmologically originated thermal gravitational waves due to extra dimension is not ruled out.Comment: 18 pages, 4 figures, to appear in Classical and Quantum Gravity. arXiv admin note: text overlap with arXiv:astro-ph/0503162, arXiv:astro-ph/0501329 by other author

Is pulsar timing a hopeful tool for detection of relic gravitational waves by using GW150914 data?

The inflation stage has a behaviour as power law expansion like $$S(\eta )\propto \eta ^{1+\beta }$$ where $$\beta$$ constrained on the $$1+\beta <0$$. If the inflation were preceded by a radiation era, then there would be thermal spectrum of relic gravitational waves at the time of inflation. Based on this idea we find new upper bound on $$\beta$$ by comparison the thermal spectrum with strain sensitivity of single pulsar timing. Also we show that sensitivity curve of single pulsar timing may be hopeful tool for detection of the spectrum in usual and thermal case by using the GW150914 data

Further investigation about inflation and reheating stages based on the Planck and WMAP-9

The potential [Formula: see text] is responsible for the inflation of the universe as scalar field [Formula: see text] oscillates quickly around some point where [Formula: see text] has a minimum. The end of this stage has an important role on the further evolution stages of the universe. The created particles are responsible for reheating the universe at the end of this stage. The behavior of the inflation and reheating stages are often known as power law expansion [Formula: see text], [Formula: see text], respectively. The reheating temperature ([Formula: see text]) and [Formula: see text] give us valuable information about the reheating stage. Recently, people have studied about the behavior of [Formula: see text] based on slow-roll inflation and initial condition of quantum normalization. It is shown that there is some discrepancy on [Formula: see text] due to the amount of [Formula: see text] under the condition of slow-roll inflation and quantum normalization [M. Tong, Class. Quantum Grav. 30 (2013) 055013.]. Therefore, the author is believed in [M. Tong, Class. Quantum Grav. 30 (2013) 055013.] that the quantum normalization may not be a good initial condition but it seems that, we can remove this discrepancy by determining the appropriate parameter [Formula: see text] and hence the obtained temperatures based on the calculated [Formula: see text] are in favor of both mentioned conditions. Then from given [Formula: see text], we can calculate [Formula: see text], tensor-to-scalar ratio [Formula: see text] and parameters [Formula: see text] based on the Planck and WMAP-9 data. The observed results of [Formula: see text] and [Formula: see text] have consistency with their constrains. Also the results of [Formula: see text] are in agreement with its general range and special range based on the DECIGO and BBO detectors. </jats:p

B MODE CORRELATION ENHANCEMENT OF CMB FROM THERMAL SQUEEZED VACUUM STATE

The generated gravitational waves during inflation are placed in thermal squeezed vacuum state. The B mode angular power spectrum of the CMB anisotropy is found enhanced for all multipole moments l ⩾ 2 but less than the upper bound of the WMAP 7-year data. </jats:p

A new experiment for gravitational wave detection

A new experiment for gravitational waves (GWs) detection is proposed. It is shown that the effect of GWs on sound waves (SWs) in a fluid is that GWs vary the pressure of the fluid as they pass through it. This variation can be found by analysing the gauge of the local observer. It is shown that one can, in principle, detect GWs through the proposed new experiment. The variation of the pressure of the fluid, which represents detected signals, is indeed much higher than the corresponding values of GW amplitudes. The examples of rotating neutron stars (NSs) and relic GWs are discussed. Remarkably, a comparison of the proposed new method with a previous paper of Singh et al. (New J. Phys. 19, 073023 (2017). doi: 10.1088/1367-2630/aa78cb ) on a similar approach shows a possible improvement of the sensitivity concerning the potential detection of GWs. It must be emphasized that this proposed procedure may be difficult in practical experiments because of the presence of different types of noise. For this reason, a section of the paper is dedicated to the discussion of such noise. On the other hand, this paper must be considered as pioneering the new proposed approach. Thus, we hope that in future more precise studies of the noise that concerns the proposed new experiment will be done. </jats:p

Are latest detected events of gravitational waves in favor of some models of inflation based on string theory?

The general potential of power-law inflation is as [Formula: see text] with scalar field [Formula: see text]. The behavior of inflation is often known as power-law expansion like [Formula: see text] with [Formula: see text]. In this paper, the theoretical spectra of relic gravitational waves are compared with the measured strain sensitivity of Advanced LIGO and VIRGO, corresponding to the latest detected events of gravitational waves. The results show tight constraints on [Formula: see text] and [Formula: see text]. Also, the obtained constraints indicate that special types of the potential of inflation, prototype, and KKLTI models, which are originated from string theory, may be good candidates for potential of inflation. Also these results may emphasize the evidence of stochastic GWs that originated from inflation based on 12:5-year pulsar timing data set of North American Nanohertz Observatory for GWs. </jats:p

Is pulsar timing a hopeful tool for detection of relic gravitational waves by using GW150914 data?

Abstract The inflation stage has a behaviour as power law expansion like $$S(\eta )\propto \eta ^{1+\beta }$$ S(η)∝η1+β where $$\beta$$ β constrained on the $$1+\beta <0$$ 1+β<0 . If the inflation were preceded by a radiation era, then there would be thermal spectrum of relic gravitational waves at the time of inflation. Based on this idea we find new upper bound on $$\beta$$ β by comparison the thermal spectrum with strain sensitivity of single pulsar timing. Also we show that sensitivity curve of single pulsar timing may be hopeful tool for detection of the spectrum in usual and thermal case by using the GW150914 data