Thermodynamics of acoustic black holes in two dimensions

It is well-known that the thermal Hawking-like radiation can be emitted from the acoustic horizon, but the thermodynamic-like understanding for acoustic black holes was rarely made. In this paper, we will show that the kinematic connection can lead to the dynamic connection at the horizon between the fluid and gravitational models in two dimension, which implies that there exists the thermodynamic-like description for acoustic black holes. Then, we discuss the first law of thermodynamics for the acoustic black hole via an intriguing connection between the gravitational-like dynamics of the acoustic horizon and thermodynamics. We obtain a universal form for the entropy of acoustic black holes, which has an interpretation similar to the entropic gravity. We also discuss the specific heat, and find that the derivative of the velocity of background fluid can be regarded as a novel acoustic analogue of the two-dimensional dilaton potential, which interprets why the two-dimensional fluid dynamics can be connected to the gravitational dynamics but difficult for four-dimensional case. In particular, when a constraint is added for the fluid, the analogue of a Schwarzschild black hole can be realized

Infinite Volume of Noncommutative Black Hole Wrapped by Finite Surface

The volume of a black hole under noncommutative spacetime background is found to be infinite, in contradiction with the surface area of a black hole, or its Bekenstein-Hawking (BH) entropy, which is well-known to be finite. Our result rules out the possibility of interpreting the entropy of a black hole by counting the number of modes wrapped inside its surface if the final evaporation stage can be properly treated. It implies the statistical interpretation for the BH entropy can be independent of the volume, provided spacetime is noncommutative. The effect of radiation back reaction is found to be small and doesn't influence the above conclusion

A protocol of potential advantage in the low frequency range to gravitational wave detection with space based optical atomic clocks

A recent proposal describes space based gravitational wave (GW) detection with optical lattice atomic clocks [Kolkowitz et. al., Phys. Rev. D 94, 124043 (2016)] [1]. Based on their setup, we propose a new measurement method for gravitational wave detection in low frequency with optical lattice atomic clocks. In our method, n successive Doppler signals are collected and the summation for all these signals is made to improve the sensitivity of the low-frequency GW detection. In particular, the improvement is adjustable by the number of Doppler signals, which is equivalent to that the length between two atomic clocks is increased. Thus, the same sensitivity can be reached but with shorter distance, even though the acceleration noises lead to failing to achieve the anticipated improvement below the inflection point of frequency which is determined by the quantum projection noise. Our result is timely for the ongoing development of space-born observatories aimed at studying physical and astrophysical effects associated with low-frequency GW