Searcharxiv⌕ Search

arXiv subjects

Yan Peng

Publications and source records attributed to Yan Peng.

At least 91 records · Page 5Linked to original sources

Hair formation in the background of noncommutative reflecting stars

We investigate scalar condensations around noncommutative compact reflecting stars. We find that the neutral noncommutative reflecting star cannot support the existence of scalar field hairs. In the charged noncommutative reflecting star spacetime, we provide upper bounds for star radii. Above the bound, scalar fields cannot exist outside the star. In contrast, when the star radius is below the bound, we show that the scalar field can condense. We also obtain the largest radii of scalar hairy reflecting stars.

gr-qc↗

On instabilities of scalar hairy regular compact reflecting stars

We study the system constructed by charged scalar fields linearly coupled to asymptotically flat horizonless compact reflecting stars. We obtain bounds on the charge of the scalar field, below which the scalar hairy star is expected to suffer from nonlinear instabilities. It means that scalar hairy regular configurations are unstable for scalar fields of small charge. For the highly-charged star, there are also bounds on radii of regular compact reflecting stars. When the star radius is below the bound, the hairy star is always unstable.

gr-qc↗

Smtlink 2.0

Smtlink is an extension of ACL2 with Satisfiability Modulo Theories (SMT) solvers. We presented an earlier version at ACL2'2015. Smtlink 2.0 makes major improvements over the initial version with respect to soundness, extensibility, ease-of-use, and the range of types and associated theory-solvers supported. Most theorems that one would want to prove using an SMT solver must first be translated to use only the primitive operations supported by the SMT solver -- this translation includes function expansion and type inference. Smtlink 2.0 performs this translation using a sequence of steps performed by verified clause processors and computed hints. These steps are ensured to be sound. The final transliteration from ACL2 to Z3's Python interface requires a trusted clause processor. This is a great improvement in soundness and extensibility over the original Smtlink which was implemented as a single, monolithic, trusted clause processor. Smtlink 2.0 provides support for FTY defprod, deflist, defalist, and defoption types by using Z3's arrays and user-defined data types. We have identified common usage patterns and simplified the configuration and hint information needed to use Smtlink.

cs.LO↗

Scalar field condensation behaviors around reflecting shells in Anti-de Sitter spacetimes

We study scalar condensations around asymptotically Anti-de Sitter(AdS) regular reflecting shells. We show that the charged scalar field can condense around charged reflecting shells with both Dirichlet and Neumann boundary conditions. In particular, the radii of the asymptotically AdS hairy shells are discrete, which is similar to cases in asymptotically flat spacetimes. We also provide upper bounds for the radii of the hairy Dirichlet reflecting shells and above the bound, the scalar field cannot condense around the shell.

gr-qc↗

Scalar condensation behaviors around regular Neuman reflecting stars

We study static massive scalar field condensations in the regular asymptotically flat reflecting star background. We impose Neumann reflecting surface boundary conditions for the scalar field. We show that the no hair theorem holds in the neutral reflecting star background. For charged reflecting stars, we provide bounds for radii of hairy reflecting stars. Below the lower bound, there is no regular compact reflecting star and a black hole will form. Above the upper bound, the scalar field cannot condense around the reflecting star or no hair theorems exist. And in between the bounds, we obtain scalar configurations supported by Neumann reflecting stars.

gr-qc↗

Static scalar field condensation in regular asymptotically AdS reflecting star backgrounds

We study condensation behaviors of static scalar fields in the regular asymptotically AdS reflecting star spacetime. With analytical methods, we provide upper bounds for the radii of the scalar hairy reflecting stars. Above the bound, there is no scalar hair theorem for the star. Below the bound, we numerically obtain charged scalar hairy reflecting star solutions and in particular, the radii of the hairy stars are discrete, which is similar to known results in other reflecting object backgrounds. For every set of parameters, we search for the largest AdS hairy star radius, study effects of parameters on the largest hairy star radius and also find difference between properties in this AdS reflecting star background and those in the flat reflecting star spacetime. Moreover, we show that scalar fields cannot condense around regular AdS reflecting stars when the star charge is small or the cosmological constant is negative enough.

gr-qc↗

Synchronous Adversarial Feature Learning for LiDAR based Loop Closure Detection

Loop Closure Detection (LCD) is the essential module in the simultaneous localization and mapping (SLAM) task. In the current appearance-based SLAM methods, the visual inputs are usually affected by illumination, appearance and viewpoints changes. Comparing to the visual inputs, with the active property, light detection and ranging (LiDAR) based point-cloud inputs are invariant to the illumination and appearance changes. In this paper, we extract 3D voxel maps and 2D top view maps from LiDAR inputs, and the former could capture the local geometry into a simplified 3D voxel format, the later could capture the local road structure into a 2D image format. However, the most challenge problem is to obtain efficient features from 3D and 2D maps to against the viewpoints difference. In this paper, we proposed a synchronous adversarial feature learning method for the LCD task, which could learn the higher level abstract features from different domains without any label data. To the best of our knowledge, this work is the first to extract multi-domain adversarial features for the LCD task in real time. To investigate the performance, we test the proposed method on the KITTI odometry dataset. The extensive experiments results show that, the proposed method could largely improve LCD accuracy even under huge viewpoints differences.

cs.RO↗

Scalar field configurations supported by charged compact reflecting stars in a curved spacetime

We study the system of static scalar fields coupled to charged compact reflecting stars through both analytical and numerical methods. We enclose the star in a box and our solutions are related to cases without box boundaries when putting the box far away from the star. We provide bottom and upper bounds for the radius of the scalar hairy compact reflecting star. We obtain numerical scalar hairy star solutions satisfying boundary conditions and find that the radius of the hairy star in a box is continuous in a range, which is very different from cases without box boundaries where the radius is discrete in the range. We also examine effects of the star charge and mass on the largest radius.

gr-qc↗

On the thermodynamics of the black hole and hairy black hole transitions in the asymptotically flat spacetime with a box

We study the asymptotically flat quasi-local black hole/hairy black hole model with nonzero mass of the scalar filed. We disclose effects of the scalar mass on transitions in a grand canonical ensemble with condensation behaviors of a parameter $ψ_{2}$, which is similar to approaches in holographic theories. We find that more negative scalar mass makes the phase transition easier to happen. We also obtain an analytical relation $ψ_{2}\varpropto(T_{c}-T)^{1/2}$ around the critical phase transition points implying a second order phase transition. Besides the parameter $ψ_{2}$, we show that metric solutions can be used to disclose properties of transitions. In this work, we observe that phase transitions in a box are strikingly similar to holographic transitions in the AdS gravity and the similarity provides insights into holographic theories.

hep-th↗

Studies of no light scalar hair behaviors for compact reflecting stars in a box

We study condensation of scalar fields around compact reflecting stars in a box. We propose no light scalar hair behaviors that the neutral compact star cannot support the existence of small single positive mass scalar field in it's exterior spacetime for very general self-interacting potentials. Moreover, we find that this no light scalar hair property can be violated by including an additional Maxwell field coupled to the scalar field in a charged compact reflecting star background.

gr-qc↗

Studies of a general flat space/boson star transition model in a box through a language similar to holographic superconductors

We study a general flat space/boson star transition model in quasi-local ensemble through approaches familiar from holographic superconductor theories. We manage to find a parameter $ψ_{2}$, which is proved to be useful in disclosing properties of phase transitions. In this work, we explore effects of the scalar mass, scalar charge and St$\ddot{u}$ckelberg mechanism on the critical phase transition points and the order of transitions mainly from behaviors of the parameter $ψ_{2}$. We mention that properties of transitions in quasi-local gravity are strikingly similar to those in holographic superconductor models. We also obtain an analytical relation $ψ_{2}\varpropto(μ-μ_{c})^{1/2}$, which also holds for the condensed scalar operator in the holographic insulator/superconductor system in accordance with mean field theories.

hep-th↗

Holographic entanglement entropy in two-order insulator/superconductor transitions

We study holographic superconductor model with two scalar fields coupled to one single Maxwell field in the AdS soliton background away from the probe limit. We disclose properties of phase transitions mostly from the holographic topological entanglement entropy approach. With different sets of parameters, we observe various types of transitions, especially a new first order phase transition between the condensation of different order parameters in the insulator/superconductor system. Our results show that the entanglement entropy is a good probe to critical phase transition points and the order of phase transitions in the two-order model. We also conclude that the entanglement entropy is useful to some extent in determining the physically supported phases. In addition, we investigate properties of the condensation through the scalar operator and the charge density in the dual theory. As a summary, we draw the complete phase diagram of the effects of the scalar charge on phase transitions. At last, we give some qualitative understanding and obtain the analytical condition for the first order phase transition to occur.

hep-th↗

A general holographic insulator/superconductor model away from the probe limit

We investigate holographic phase transitions affected by dark matter sector in the AdS soliton background away from the probe limit. When neglecting backreaction, the scalar charge q can be scaled unity without loss of generality. While considering backreaction in this work, we obtain much more richer physics by choosing various scalar charge q. Firstly, we observe unstable retrograde condensation appears due to the dark matter sector and also derive stable conditions. For stable solutions, we find that the larger coupling parameter $α$ makes the gap of condensation shallower and the critical chemical potential keeps as a constant with a large scalar charge q, which is similar to cases in the probe limit. In contrast, the dark matter sector could affect the critical chemical potential and the order of phase transitions for very small charge q. We also arrive at the same conclusion from the holographic topological entanglement entropy approach. Moreover, we state that the entanglement entropy approach is especially powerful in studying the effects of the dark matter sector in this general insulator/superconductor system.

hep-th↗

Holographic insulator/superconductor transitions in the three dimensional AdS soliton

We investigate the holographic description of a superconductor constructed in the (2+1)-dimensional AdS soliton background in the probe limit. We study the holographic properties through both analytical and numerical methods. With analytical methods, we are the first to obtain the exact formula for critical phase transition points as $μ_{c}=1+\sqrt{1+m^2}$. Around the transition points, we find a correspondence between the value of the scalar field at the tip and the scalar operator at infinity. We also generalize the front properties to holographic models in higher dimensional AdS soliton spacetime. Moreover, we examine effects of the scalar mass on stability of phase transitions with numerical methods. With $m^{2}\in (-0.38,0]$, we arrive at the classical second order insulator/superconductor phase transition. Surprisingly, there is no stable superconducting phases in cases of $m^{2}\in (-1,-0.38]$. In other words, superconductor only exists in a certain range of the scalar mass in the (2+1)-dimensional AdS soliton spacetime, which is very different from properties in other spacetime.

hep-th↗

Extending ACL2 with SMT Solvers

We present our extension of ACL2 with Satisfiability Modulo Theories (SMT) solvers using ACL2's trusted clause processor mechanism. We are particularly interested in the verification of physical systems including Analog and Mixed-Signal (AMS) designs. ACL2 offers strong induction abilities for reasoning about sequences and SMT complements deduction methods like ACL2 with fast nonlinear arithmetic solving procedures. While SAT solvers have been integrated into ACL2 in previous work, SMT methods raise new issues because of their support for a broader range of domains including real numbers and uninterpreted functions. This paper presents Smtlink, our clause processor for integrating SMT solvers into ACL2. We describe key design and implementation issues and describe our experience with its use.

cs.LO↗

Holographic entanglement entropy in superconductor phase transition with dark matter sector

In this paper, we investigate the holographic phase transition with dark matter sector in the AdS black hole background away from the probe limit. We disclose the properties of phases mostly from the holographic topological entanglement entropy of the system. We find the entanglement entropy is a good probe to the critical temperature and the order of the phase transition in the general model. The behaviors of entanglement entropy at large strip size suggest that the area law still holds with dark matter sector. We also conclude that the holographic topological entanglement entropy is useful in detecting the stability of the phase transitions. Furthermore, we derive the complete diagram of the effects of coupled parameters on the critical temperature through the entanglement entropy and analytical methods.

hep-th↗

A general holographic metal/superconductor phase transition model

We study the scalar condensation of a general holographic superconductor model in AdS black hole background away from the probe limit. We find the model parameters together with the scalar mass and backreaction can determine the order of phase transitions completely. In addition, we observe two types of discontinuities of the scalar operator in the case of first order phase transitions. We analyze in detail the effects of the scalar mass and backreaction on the formation of discontinuities and arrive at an approximate relation between the threshold model parameters. Furthermore, we obtain superconductor solutions corresponding to higher energy states and examine the stability of these superconductor solutions.

hep-th↗

Pilot Reuse for Massive MIMO Transmission over Spatially Correlated Rayleigh Fading Channels

We propose pilot reuse (PR) in single cell for massive multiuser multiple-input multiple-output (MIMO) transmission to reduce the pilot overhead. For spatially correlated Rayleigh fading channels, we establish a relationship between channel spatial correlations and channel power angle spectrum when the base station antenna number tends to infinity. With this channel model, we show that sum mean square error (MSE) of channel estimation can be minimized provided that channel angle of arrival intervals of the user terminals reusing the pilots are non-overlapping, which shows feasibility of PR over spatially correlated massive MIMO channels with constrained channel angular spreads. Regarding that channel estimation performance might degrade due to PR, we also develop the closed-form robust multiuser uplink receiver and downlink precoder that minimize sum MSE of signal detection, and reveal a duality between them. Subsequently, we investigate pilot scheduling, which determines the PR pattern, under two minimum MSE related criteria, and propose a low complexity pilot scheduling algorithm which relies on the channel statistics only. Simulation results show that the proposed PR scheme provides significant performance gains over the conventional orthogonal training scheme in terms of net spectral efficiency.

cs.IT↗