Recently, several theoretical and experimental studies have been undertaken to probe the effect of stochasticity on gene expression (GE). In experiments, the GE response to an inducing signal in a ...cell, measured by the amount of mRNAs/proteins synthesized, is found to be either graded or binary. The latter type of response gives rise to a bimodal distribution in protein levels in an ensemble of cells. One possible origin of binary response is cellular bistability achieved through positive feedback or autoregulation. In this paper, we study a simple, stochastic model of GE and show that the origin of binary response lies exclusively in stochasticity. The transitions between the active and inactive states of the gene are random in nature. Graded and binary responses occur in the model depending on the relative stability of the activated and deactivated gene states with respect to that of mRNAs/proteins. The theoretical results on binary response provide a good description of the 'all-or-none' phenomenon observed in an eukaryotic system.
Time dependent gravitational background is well known as a theoretical laboratory for quantum mechanical particle production. In this submission, we explore such production in a time dependent analog ...system. This is the follow up of our earlier study on the Sonoluminescence phenomenon which is modelled in terms of analog geometry coupled with the electromagnetic field exhibiting quantum production. In the same analog geometry, we studied neutrino production. Like the photons, we showed that such a system can also produce a repeated flux of neutrinos via the parametric resonance from a quantum vacuum. Our analysis seems to suggest that in the laboratory setup time dependent analog systems could be an interesting playground where phenomena of quantum mechanical particle production can be observed.
Sonoluminescence is a well known laboratory phenomenon where an oscillating gas bubble in the appropriate environment periodically emits a flash of light in the visible frequency range. In this ...submission, we study the system in the framework of analog gravity. We model the oscillating bubble in terms of analog geometry and propose a non-minimal coupling prescription of the electromagnetic field with the geometry. The geometry behaves as an analogous oscillating time dependent background in which repeated flux of photons are produced in a wide frequency range through parametric resonance from quantum vacuum. Due to our numerical limitation, we could reach the frequency up to \(\sim 10^5 ~\mbox{m}^{-1}\). However, we numerically fit the spectrum in a polynomial form including the observed frequency range around \(\sim 10^7 ~\mbox{m}^{-1}\). Our current analysis seems to suggest that parametric resonance in analog background may play a fundamental role in explaining such phenomena in the quantum field theory framework.
Detection of gravitational waves (GWs) paves the beginning of a new era of gravitational wave astronomy. Black holes (BHs) in their ringdown phase provide the cleanest signal of emitted GWs that ...imprint the fundamental nature of BHs under low energy perturbation. Apart from GWs, any complementary signature of ringing BHs can be of paramount importance. Motivated by this we analyzed the scattering of electromagnetic waves in such a background and demonstrated that the absorption cross section of a ringing Schwarzschild BH can be superradiant. Moreover, we have found out that such superradiant phenomena are transient in nature with a characteristic time scale equal to the GW oscillation time scale. We further point out that the existing ground-based Low Frequency Array (LOFAR), radio telescopes, may be able to detect such transient signals from BHs of mass range \(M\sim 10^{-1} - 10^{-2} M_{\odot}\), which should necessarily be of primordial origin. Our present result opens up an intriguing possibility of observing the black hole merging phenomena through electromagnetic waves.
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