122431079
Massive photons in General Relativity
In order to avoid a speed-of-light catastrophe in General Relativity with an electromagnetic source, gauge invariance with respect to the electric charge is broken with the photon acquiring mass. The general equations for the Einstein-Maxwell system are derived for the case with massive photons. Nonminimal couplings which might compete with the small minimal photon mass term are included.
121902881
Unified SL(8,C) model of spin-2 gluons and gravitons
A unified version of $f\ensuremath{-}g$ gravity models with Higgs field has been constructed using the SL(8, $C$) group. Leptons and quarks are represented in a four-color scheme using the SU(4) group. When the Higgs fields exhibit a spontaneous breakdown of symmetry in the tree approximation, the spin-2 gluons ($f$) and fermions acquire mass while the graviton ($g$) remains massless. The Higgs-fermion interaction is renormalizable in contrast to the $\mathrm{SL}(2,C)\ensuremath{\bigotimes}\mathrm{SL}(6,C)$ gravity models. The spin-2 gluons include the three-color gluon, an exotic gluon which mixes leptons with hadrons, and a weak gluon which mediates only between leptons.
122395245
Chiral symmetry breaking in QED for weak coupling
The authors examine the procedure for studying chiral symmetry breaking for weak coupling in QED. They note that while the lowest non-trivial order calculations using numerical solutions to the Schwinger-Dyson equation indicate a breaking of chiral symmetry, the neglected higher-order contributions to the effective potential have imaginary values which can indicate possible instabilities in the theory.
121494708
Requirements for scattering solutions and the causal Green's function of the Bethe--Salpeter equation
We investigate the conditions necessary for the existence of scattering solutions to the Bethe-Salpeter equation. We work with the causal Green's function in both timelike and spacelike regions of $x\ensuremath{-}{x}^{\ensuremath{'}}$. Our results indicate that high-momentum or small-relative-time limits must be taken. In the small-relative-time limit, suitable restrictions on the interaction $I(x)$ must also be considered.
121710663
SPIN-2 GLUON - GRAVITON MODEL WITH BARYON NUMBER NONCONSERVATION
We have shown how a weak-strong gravity model with Higgs fields can contain a baryon-number-violating mechanism. If more than one set of Higgs particles are allowed, the Higgs-fermion coupling will generate the violation of baryon-number symmetry spontaneously. To illustrate our point, we present some numerical examples on quark and nucleon decay. We find that some of the quarks can decay into leptons, antileptons, and pions with very short lifetimes. The proton is found to be much more stable than the neutron and both have possible baryon-number-violating modes of decay with very long lifetimes.
122685473
Ladder approximation, scalar-exchange mesons, and Bethe--Salpeter scattering states
123106274
Seyfert 2 Galaxies with Spectropolarimetric Observations
117991499
Zero and one jet combined next-to-leading order analysis of the top quark forward-backward asymmetry
We present an analysis of the forward{backward asymmetry in the production of top quark pairs at the Tevatron collider. We use novel Monte Carlo methods for merging matrix elements and parton showers to combine NLO QCD predictions fort t andt t+jet production. Theoretical uncertainties are quantied in detail. We nd agreement with experimental data on the transverse momentum dependence of the asymmetry. t t events with large invariant mass, mt t 450 GeV. The inclusive parton-level asymmetry was measured as 0:164 0:047 considering all pair masses, and 0:295 0:067 for mt t 450 GeV. This needs to be compared to theoretical predictions from various event generators in the unrestricted and high t t mass region: 0:067 0:020 and 0:089 0:027 from MC@NLO (6, 7), 0:066 0:020 and 0:100 0:030 from POWHEG (8, 9), and 0:073 0:022 and 0:110 0:033 from MCFM (4, 10). In all cases, electroweak corrections had been applied. The linear behavior of AFB with increasing y and mt t persists,
118242012
Multi-TeV gamma-ray emission from the Crab Nebula observed with the new Tibet-III air-shower array
Using a high density air-shower array (Tibet-HD array), we succeeded in detecting multi-TeV -ray signals from the Crab Nebula in 1999. In the late fall of 1999, the HD array was enlarged from 5175 m up to 22000 m (TibetIII array). Using the 316 live-day data taken between 1999 November and 2001 May with this enlarged new array, we studied the emission of TeV -rays from the Crab Nebula. A preliminary analysis gives the excess -ray signal at the statistical significance of 4.8 . The energy spectrum of rays observed is consistent with the previous observation. We report the result on the study of the Crab flux.
14163496
The nuclear starburst activity in the Seyfert 2 galaxy NGC 7679
We present our recent spectrophotometric results of the infrared luminous Seyfert 2 galaxy NGC 7679. We nd compelling evidence for the presence of a recent nuclear starburst, revealed by the observations of a) the spectral features of high order Balmer absorption lines, b) the weak equivalent widths for CaIIK 3933, CN 4200, G-band 4300 and MgIb 5173, and c) the suggested UV stellar wind resonance lines (N V 1240, Si IV 1400 and C IV 1550) in the IUE spectrum. Using the simple stellar population synthesis model, we nd that in the nuclear 2" 2" region, the contributions from the old, intermediate and young components are 21.7%, 42.9% and 35.4%, respectively. These nuclear starburst activities might have been triggered by the close encounter with NGC 7682, as suggested by recent numerical simulations.
121270760
The complex EAS hybrid arrays in Tibet
The Tibet hybrid experiment is an extensive air shower experiment that operated at Yangbajing (E90°31', N30°06'; 4300 m above sea level) in Tibet, China, since 1996. This multi-detector system is used to observe air showers of high energy celestial gamma-ray origin and that of nuclear-component origin. Both observations aim to investigate the origin of cosmic rays using different methods. In this paper, based on the energy spectrum of the nuclear component and its chemical composition around the knee, we would like to discuss whether they could be described by the theoretical picture of the diffusive shock acceleration at SNRs. The consistency of the experimental data with rigidity dependent cutoff spectrum of CRs is examined using Tibet data and KASCADE data. It is found that both experimental data cannot be fully interpreted by such a simple approach. The sharp knee observed by Tibet experiment suggests the contribution of nearby source(s).