arXiv subjects

Ruifeng Zheng

Publications and source records attributed to Ruifeng Zheng.

23 records · Page 2Linked to original sources

arXiv2023

Generation of primordial black holes from an inflation model with modified dispersion relation

A primordial black hole (PBH) is interesting to people for its ability of explaining dark matter as well as supermassive astrophysical objects. In the normal inflation scenario, the generation of PBHs usually requires an enhanced power spectrum of scalar perturbation at the end of inflation era, which is expected when the dispersion relation of the inflaton field gets modified. In this work, we study a kind of inflation model called {the \it Dirac-Born-Infeld-inspired nonminimal kinetic coupling (DINKIC)} model, where the dispersion relation is modified by a square root existing in the field Lagrangian. We discuss the enhancement of scalar power spectrum due to the modified dispersion relation, as well as the abundance of PBHs produced by the Press-Schechter collapse mechanism. We also discuss the formation of scalar-induced gravitational waves by linear scalar perturbations.

astro-ph.CO↗

arXiv2022

On Primordial Black Holes and secondary gravitational waves generated from inflation with solo/multi-bumpy potential

It is well known that a primordial black hole (PBH) can be generated in the inflation process of the early universe, especially when the inflation field has a number of non-trivial features that could break the slow-roll condition. In this study, we investigate a toy model of inflation with bumpy potential, which has one or several bumps. We determined that the potential with multi-bump can generate power spectra with multi-peaks in small-scale region, which can in turn predict the generation of primordial black holes in various mass ranges. We also consider the two possibilities of PBH formation by spherical and elliptical collapses. Finally, we discuss the scalar-induced gravitational waves(SIGWs)generated by linear scalar perturbations at second order.

astro-ph.CO↗

arXiv2022

Filters for ISI Suppression in Molecular Communication via Diffusion

Molecular communication via diffusion (MCvD) is considered as one of the most feasible communication paradigms for nanonetworks, especially for bio-nanonetworks which are usually in water-rich biological environments. Two effects that deteriorates the signal in MCvD are noise and inter-symbol interference (ISI). The expected channel impulse response of MCvD has a long and slow attenuating tail due to molecular diffusion which causes ISI and further limits the slow data rate of MCvD. The extent that ISI and noise are suppressed in an MCvD system determines its effectiveness, especially at a high data rate. Although ISI-suppression approaches have been investigated, most of them are addressed as non-essential parts in other topics, such as signal detection or modulation. Furthermore, most of the state-of-the-art ISI-suppression approaches are performed by subtracting the estimated ISI from the total signal. In this work, we investigate ISI-suppression from a new perspective of filters to filter ISI out without any ISI estimation. The principles for a good design of ISI-suppression filters in MCvD are investigated. Based on the principles, an ISI-suppression filter with good anti-noise capability and an associated signal detection scheme is proposed for MCvD scenarios with both ISI and noise. We compare the proposed scheme with the state-of-the-art ISI-suppression approaches. The result manifests that the proposed ISI-suppression scheme could recover signals deteriorated severely by both ISI and noise, which could not be effectively detected by the state-of-the-art ISI-suppression approaches.

eess.SP↗

arXiv2022

Can the Quantization of Black Hole be detected?

As a mysterious celestial body predicted by General Relativity, black holes have been confirmed by observations in recent years. But there are still many unknown properties waiting for us to discover, one of the famous problems is the quantization of black holes. The quantization of black holes gives new research significance to black holes, but the quantization of black holes is difficult to prove. Here we propose a new method to verify the quantization of black holes: Carnot cycle. Our results show that if the black holes have quantized energy levels, the work W they impose to us via the Carnot cycle should also be quantized. We indirectly verify the quantization of black holes by detecting the quantization of W, and contrast it with the classic Carnot cycle. In addition, we have also verified the correctness of the second law of thermodynamics under the premise of considering the quantization of black holes.

gr-qc↗

arXiv2021

New Insights on the Thermodynamic Equilibrium of Black Hole and Thermal Radiation

The thermal balance between the black hole and surrounding thermal radiation is an interesting topic. The primordial black hole is a type of black hole formed in the early universe, especially during the thermal radiation period of the early universe. Driven by gravity, thermal radiation will collapse to form a black hole. Because of the complexity of the actual situation, we use the simplest model for simulation under the premise of only considering the thermodynamic properties of the system: in the classic case, an isolated box full of thermal radiation, by adjusting the initial temperature within a reasonable range, the results show that the collapse of part of the thermal radiation to form a black hole and finally achieve thermal equilibrium is an inevitable result of the second law of thermodynamics. We then introduced the quantization of black holes and the number of microscopic states of thermal radiation into the thermal equilibrium system and came to a surprising conclusion: if both the quantization of black holes and the number of microscopic states of thermal radiation are considered at the same time, the fluctuation of thermodynamics is inevitable. When only one of them is considered, the law of conservation of energy and the second law of thermodynamics can be satisfied at the same time, and the fluctuation of thermodynamics can be avoided. This provides a new way of thinking for us to understand the microscopic origin of thermodynamic fluctuations.

gr-qc↗