16931057
A Statistical Analysis of Point-like Sources in the Chandra Galactic Center Survey ∗
The Chandra Galactic Center Survey detected similar to 800 X-ray point-like sources in the 2 degrees x 0.8 degrees sky region around the Galactic Center. We study the spatial and luminosity distributions of these sources according to their spectral properties. Fourteen bright sources detected are used to fit jointly an absorbed power-law model, from which the power-law photon index is determined to be similar to 2.5. Assuming that all other sources have the same power-law form, the relation between hardness ratio and HI column density N-H is used to estimate the NH values for all sources. Monte Carlo simulations show that these sources are more likely concentrated in the Galactic center region, rather than distributed throughout the Galactic disk. We also find that the luminosities of the sources are positively correlated with their HI column densities, i.e., a more luminous source has a higher HI column density. From this relation, we suggest that the X-ray luminosity comes from the interaction between an isolated old neutron star and interstellar medium (mainly dense molecular clouds). Using the standard Bondi accretion theory and the statistical information of molecular clouds in the Galactic center, we confirm this positive correlation and calculate the luminosity range in this scenario, which is consistent with the observation (10(32)-10(35) erg s(-1)).
17924332
HARDNESS RATIO ESTIMATION IN LOW COUNTING X-RAY PHOTOMETRY
Hardness ratios are commonly used in X-ray photometry to roughly indicate spectral properties. They are usually defined as the ratio of counts in two different wave bands. This definition, however, is problematic when the counts are very limited. Here we instead define the hardness ratio using the lambda-parameter of Poisson processes and develop an estimation method via Bayesian statistics. Our Monte Carlo simulations show the validity of our method. Based on this new definition we can estimate the hydrogen column density for the photoelectric absorption of X-ray spectra in the case of low counting statistics.
119316237
Fermionization, Triangularization and Integrability
In this article, we derive the fermionic formalism of Hamiltonians as well as corresponding excitation spectrums and states of Calogero-Sutherland(CS), Laughlin and Halperin systems, respectively. In addition, we study the triangular property of these Hamiltonians and prove the integrability in these three cases.
116901981
Further evidence for the Sigma* resonance with J**P = 1/2- around 1380-MeV
The unquenched quark models predict the new particle $\Sigma^*$ with spin parity $J^P=1/2^-$ and its mass is around the well established $\Sigma^*(1385)$ with $J^P=3/2^+$. Here by using the effective Lagrangian approach we study \kp\ reaction at the range of $\Lambda^{*}(1520)$ peak, comparing the resulting total cross section, and $\pi^+\pi^-$, $\Lambda\pi^+$, $\Lambda\pi^-$ invariant squared mass distributions for various incident $K^-$ momenta, as well as the production angular distribution of the $\Lambda$ with the data from the Lawrence Berkeley Laboratory 25-inch hydrogen bubble chamber, we find that, apart from the existing resonance $\Sigma^{*}(1385)$ with $J^P=3/2^+$, there is a strong evidence for the existence of the new resonance $\Sigma^{*}$ with $J^P=1/2^-$ around 1380 MeV. Higher statistic data on relevant reactions are needed to clarify the situation.
119192598
Evidence for a new Sigma* resonance with J**P = 1/2- in the old data of K- p ---> Lambda pi+ pi- reaction
Distinctive patterns are predicted by quenched quark models and unquenched quark models for the lowest SU(3) baryon nonet with spin parity J P = 1/2 - . While the quenched quark models predict the lowest 1/2- ∑* resonance to be above 1600 MeV, the unquenched quark models predict it to be around ∑*(1385) energy. Here we reexamine some old data of the K - p → ∧π + π - reaction and find that besides the well-established ∑*(1385) with J p = 3/2 + , there is indeed some evidence for the possible existence of a new ∑* resonance with J P = 1/2- around the same mass but with broader decay width. Higher statistic data on relevant reactions are needed to clarify the situation.
120073554
Emergence of gap from holographic fermions on charged Lifshitz background
A bstractWe report a dynamical formation of a gap from holographic fermions with dipole coupling on charged Lifshitz background. For a large enough dipole coupling, a gap opens as that found in RN-AdS background. By studying the density of states A(ω), one shows that the onset of the gap is near p ≃ 4.8 for the case of q = 2 and mζ = 0 and the width of the gap becomes larger as the strength of the interaction keeps increasing. Similar with that found in RN-AdS black hole, there are also a transfer of spectral weight over all energy scales by tuning the dipole coupling. Finally, a brief discussion on the effect of the dynamical exponent z is also presented.
119222618
Spin-3 topologically massive gravity
Abstract In this Letter, we study the spin-3 topologically massive gravity (TMG), paying special attention to its properties at the chiral point. We propose an action describing the higher spin fields coupled to TMG. We discuss the traceless spin-3 fluctuations around the AdS 3 vacuum and find that there is an extra local massive mode, besides the left-moving and right-moving boundary massless modes. At the chiral point, such extra mode becomes massless and degenerates with the left-moving mode. We show that at the chiral point the only degrees of freedom in the theory are the boundary right-moving graviton and spin-3 field. We conjecture that spin-3 chiral gravity with generalized Brown–Henneaux boundary condition is holographically dual to 2D chiral CFT with classical W 3 algebra and central charge c R = 3 l / G .
121148227
The charged Lifshitz black brane geometry and the bulk dipole coupling
Abstract We study the fermionic response including the bulk dipole coupling on the charged Lifshitz black brane from Einstein–Dilaton–Maxwell model. For fixed Lifshitz dynamical critical exponent z , by tuning the dipole coupling parameter p , we can realize the phase transitions from Fermi liquid, to marginal Fermi liquid, to non-Fermi liquid and finally to Mott insulator. The Lifshitz dynamical critical exponent z plays the role of making the phase transition point from Fermi liquid to non-Fermi liquid or to Mott insulator decrease with the increase of z for fixed dipole coupling p .