Related papers: Gravitational Waves from Primordial Magnetic Field…
We study the graviton-photon conversion in the magnetic fields of the Earth, the Milky Way Galaxy, and intergalactic regions. Requiring that the photon flux converted from gravitons does not exceed the observed photon flux with telescopes,…
High-Frequency Gravitational Waves (HFGWs) constitute a unique window on the early Universe as well as exotic astrophysical objects. If the current gravitational wave experiments are more dedicated to the low frequency regime, the graviton…
First-order phase transitions in the early Universe are a well-motivated source of gravitational waves (GWs). In this Letter, we identify a previously overlooked GW production mechanism: gravitational transition radiation, arising from…
Dark gauge fields have been discussed as candidates for dark matter recently. If they existed, primordial dark magnetic fields during inflation would have existed. It is believed that primordial gravitational waves (PGWs) arise out of…
High-frequency gravitational waves ($f \gtrsim 1$ MHz) may provide a unique signature for the existence of exotic physics. The lack of current and future gravitational-wave experiments sensitive at those frequencies leads to the need of…
We calculate the gravitational waves (GWs) produced by primordial black holes (PBHs) in the presence of the inflaton condensate in the early Universe. Combining the GW production from the evaporation process, the gravitational scattering of…
We study graviton-photon conversion in the presence of stochastic magnetic fields. Assuming Gaussian magnetic fields that may possess nontrivial helicity, and unpolarized gravitational waves (GWs) as the initial state, we obtain expressions…
The primordial gravitational waves (\textbf{PGW}) have been generated by inflationary amplification of the primordial (quantum) fluctuations. It is true that they have not been recorded directly so far, but their spectrum can help a lot in…
While photons and gravitons do not interact significantly, photons can be converted to gravitons in a background magnetic field -- a phenomenon known as the Gertsenshtein effect. In this paper, we investigate whether chiral electromagnetic…
A variety of mechanisms in the early Universe lead to the generation of gravitational waves (GWs). We introduce here a novel source of GWs generated by vacuum fluctuations after inflation. Given that gravitons are minimally coupled…
First order phase transitions in the early Universe generate gravitational waves, which may be observable in future space-based gravitational wave observatiories, e.g. the European eLISA satellite constellation. The gravitational waves…
In this paper we analyze in detail a rarely discussed question of gravity wave production from evaporating primordial black holes. These black holes emit gravitons which are, at classical level, registered as gravity waves. We use the…
We show that photon spheres of supermassive black holes generate high-frequency stochastic gravitational waves through the photon-graviton conversion. Remarkably, the frequency is universally determined as $m_e\sqrt{m_e /m_p} \simeq 10^{20}…
Gravitational waves (GW) can constitute a unique probe of the primordial universe. In many cases, the characteristic frequency of the emitted GW is directly related to the energy scale at which the GW source is operating in the early…
Conversion of the CMB photons into gravitational waves at the post recombination epoch is considered. We calculate the probability of transformation of the CMB photons into gravitons in the presence of a large scale magnetic field. Based on…
High-frequency gravitational waves, particularly in the range $f \gtrsim 10^{10}~\mathrm{Hz}$, represent a compelling probe of physics beyond the Standard Model. Due to the absence of direct detection methods in this frequency regime,…
Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic…
High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth…
We study graviton-photon conversion in magnetosphere of a pulsar and explore the possibility of detecting high frequency gravitational waves with pulsar observations. It is shown that conversion of one polarization mode of photons can be…
Compared to primordial perturbations on large scales, roughly larger than $1$ megaparsec, those on smaller scales are not severely constrained. We revisit the issue of probing small-scale primordial perturbations using gravitational waves…