GRBs and fundamental physics

Gamma-ray bursts (GRBs) are short and intense flashes at the cosmological distances, which are the most luminous explosions in the Universe. The high luminosities of GRBs make them detectable out to the edge of the visible universe. So, they are unique tools to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal evolution of the Universe. First, they can be used to constrain the history of cosmic acceleration and the evolution of dark energy in a redshift range hardly achievable by other cosmological probes. Second, long GRBs are believed to be formed by collapse of massive stars. So they can be used to derive the high-redshift star formation rate, which can not be probed by current observations. Moreover, the use of GRBs as cosmological tools could unveil the reionization history and metal evolution of the Universe, the intergalactic medium (IGM) properties and the nature of first stars in the early universe. But beyond that, the GRB high-energy photons can be applied to constrain Lorentz invariance violation (LIV) and to test Einstein's Equivalence Principle (EEP). In this paper, we review the progress on the GRB cosmology and fundamental physics probed by GRBs.Comment: 38 pages, 18 figures, Review based on ISSI workshop "Gamma-Ray Bursts: a Tool to Explore the Young Universe" (2015, Beijing, China), accepted for publication in Space Science Review

Conditioning of BPM pickup signals for operations of the Duke storage ring with a wide range of single-bunch current

The Duke storage ring is a dedicated driver for the storage ring based oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source (HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA per bunch for various operations and accelerator physics studies. High performance operations of the FEL and gamma-ray source require a stable electron beam orbit, which has been realized by the global orbit feedback system. As a critical part of the orbit feedback system, the electron beam position monitors (BPMs) are required to be able to precisely measure the electron beam orbit in a wide range of the single-bunch current. However, the high peak voltage of the BPM pickups associated with high single-bunch current degrades the performance of the BPM electronics, and can potentially damage the BPM electronics. A signal conditioning method using low pass filters is developed to reduce the peak voltage to protect the BPM electronics, and to make the BPMs capable of working with a wide range of single-bunch current. Simulations and electron beam based tests are performed. The results show that the Duke storage ring BPM system is capable of providing precise orbit measurements to ensure highly stable FEL and HIGS operations

Strong decays of heavy baryons in Bethe-Salpeter formalism

In this paper we study the properties of diquarks (composed of $u$ and/or $d$ quarks) in the Bethe-Salpeter formalism under the covariant instantaneous approximation. We calculate their BS wave functions and study their effective interaction with the pion. Using the effective coupling constant among the diquarks and the pion, in the heavy quark limit $m_Q\to\infty$, we calculate the decay widths of $\Sigma_Q^{(*)}$ ($Q=c,b$) in the BS formalism under the covariant instantaneous approximation and then give predictions of the decay widths $\Gamma(\Sigma_b^{(*)}\to\Lambda_b+\pi)$.Comment: 41 pages, 1 figure, LaTex2e, typos correcte

Quasiparticle Interference on the Surface of the Topological Insulator Bi2_2Te3_3

The quasiparticle interference of the spectroscopic imaging scanning tunneling microscopy has been investigated for the surface states of the large gap topological insulator Bi$_2$Te$_3$ through the T-matrix formalism. Both the scalar potential scattering and the spin-orbit scattering on the warped hexagonal isoenergy contour are considered. While backscatterings are forbidden by time-reversal symmetry, other scatterings are allowed and exhibit strong dependence on the spin configurations of the eigenfunctions at k points over the isoenergy contour. The characteristic scattering wavevectors found in our analysis agree well with recent experiment results.Comment: 5 pages, 2 figures, Some typos are correcte

Research on the Integration Characteristics of Cooling Energy Recovery from Room Exhausting Cool Air in Summer

Currently, the design and construction of buildings and building energy systems are far from reasonable. The requirement and consumption of primary energy resources is aggravated, the use of building energy is free and wasteful, and pollution of the earth's atmosphere from building energy consumption is also aggravated. Therefore, the research and applications of energy efficiency and environmentally benign building energy systems are very important and urgent. Until now, much work on building energy conservation methods, measures and evaluations have been done by people in many countries. Some theoretical achievements have been already put into practice, but most of them put undue emphasis on some parts of the whole system. The complete idea of building energy conservation by integrating the building energy systems has not been put forward, and unequivocal guidance and a complete evaluation index and theoretical system for building energy consumption and its impact on the environment have not been formed. In this paper, we make further suggestions for improvement, and present some new concepts such as building energy flow, building mass flow, couple recovering of building discharge energy, integrated system of building energy , factor of building energy integration I, and effect factor on atmospheric environment of building energy F. The positive effects of these new concepts and methods on traditional approaches are also predicted. Theoretical research on an energy recovery unit that recovers cooling energy from indoor exhausting cool air in summer has been done in this paper, and demonstrates great advantages of its integration characteristics of building thermal systems

Full Hydrodynamic Model of Nonlinear Electromagnetic Response in Metallic Metamaterials

Applications of metallic metamaterials have generated significant interest in recent years. Electromagnetic behavior of metamaterials in the optical range is usually characterized by a local-linear response. In this article, we develop a finite-difference time-domain (FDTD) solution of the hydrodynamic model that describes a free electron gas in metals. Extending beyond the local-linear response, the hydrodynamic model enables numerical investigation of nonlocal and nonlinear interactions between electromagnetic waves and metallic metamaterials. By explicitly imposing the current continuity constraint, the proposed model is solved in a self-consistent manner. Charge, energy and angular momentum conservation laws of high-order harmonic generation have been demonstrated for the first time by the Maxwell-hydrodynamic FDTD model. The model yields nonlinear optical responses for complex metallic metamaterials irradiated by a variety of waveforms. Consequently, the multiphysics model opens up unique opportunities for characterizing and designing nonlinear nanodevices.Comment: 11 pages, 14 figure

Luby Transform Coding Aided Iterative Detection for Downlink SDMA Systems

A Luby Transform (LT) coded downlink Spatial Division Multiple Access (SDMA) system using iterative detection is proposed, which invokes a low-complexity near-Maximum-Likelihood (ML) Sphere Decoder (SD). The Ethernet-based Internet section of the transmission chain inflicts random packet erasures, which is modelled by the Binary Erasure Channel (BEC), which the wireless downlink imposes both fading and noise. A novel log-Likelihood Ratio based packet reliability metric is used for identifying the channel-decoded packets, which are likely to be error-infested. Packets having residual errors must not be passed on to the KT decoder for the sake of avoiding LT-decoding –induced error propagation. The proposed scheme is capable of maintaining an infinitesimally low packet error ratio in the downlink of the wireless Internet for Eb/n0 values in excess of about 3dB

Allocation of tie-line costs in power exchange scheduling using amulti-agent approach

After deregulations in power industries, the original boundary lines have been removed and how to support optimal cross-border electricity trade planning has become an important issue. Decentralization, or all market participants have the rights to participate in decision making, is one of the directions. In this paper a decentralized structure is suggested to solve the problem using multi-agent technology. In this structure the information centralization is prevented and each market participant behaves rationally based on local information. Although the market participants make decisions to protect its own benefits, the minimum production and transmission cost of the whole system can be finally reached. This structure is based on the method proposed in another paper by the authors and implemented on computer via a multi-agent system using Java programming language. A demonstration on a 5-area test system shows that the suggested new approach is effective and promising.published_or_final_versio

A decentralized approach for optimal wholesale cross-border trade planning using multi-agent technology

Over the past decade, power industry has been undergoing deregulations to introduce competitions among market participants. Once centralized decision making must now adapt to the new market structure. The optimal cross-border electricity trade planning is an important issue in interconnected power systems under transmission open access. In this paper a decentralized approach is suggested to solve the problem using multi-agent technology. In the new approach rational market participants make decisions based on their own benefits, in the meantime the minimum production and transmission cost of the whole system can be reached without a central coordination except necessary information exchange through media like the Internet. A relevant lemma has been proven. The approach is implemented via a multi-agent system using Java programming language. Computer tests on a 5-area test system show that the suggested new approach is effective and promising.published_or_final_versio