Fidelity susceptibility, scaling, and universality in quantum critical phenomena

We study fidelity susceptibility in one-dimensional asymmetric Hubbard model, and show that the fidelity susceptibility can be used to identify the universality class of the quantum phase transitions in this model. The critical exponents are found to be 0 and 2 for cases of half-filling and away from half-filling respectively.Comment: 4 pages, 4 figure

The Submillimeter Array

The Submillimeter Array (SMA), a collaborative project of the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), has begun operation on Mauna Kea in Hawaii. A total of eight 6-m telescopes comprise the array, which will cover the frequency range of 180-900 GHz. All eight telescopes have been deployed and are operational. First scientific results utilizing the three receiver bands at 230, 345, and 690 GHz have been obtained and are presented in the accompanying papers.Comment: 10 pages, 4 figure

Quantum criticality of the Lipkin-Meshkov-Glick Model in terms of fidelity susceptibility

We study the critical properties of the Lipkin-Meshkov-Glick Model in terms of the fidelity susceptibility. By using the Holstein-Primakoff transformation, we obtain explicitly the critical exponent of the fidelity susceptibility around the second-order quantum phase transition point. Our results provide a rare analytical case for the fidelity susceptibility in describing the universality class in quantum critical behavior. The different critical exponents in two phases are non-trivial results, indicating the fidelity susceptibility is not always extensive.Comment: 3 figure

Fokker-Planck equation with variable diffusion coefficient in the Stratonovich approach

We consider the Langevin equation with multiplicative noise term which depends on time and space. The corresponding Fokker-Planck equation in Stratonovich approach is investigated. Its formal solution is obtained for an arbitrary multiplicative noise term given by $g(x,t)=D(x)T(t)$, and the behaviors of probability distributions, for some specific functions of $D(x)$% , are analyzed. In particular, for $D(x)\sim | x| ^{-\theta /2}$, the physical solutions for the probability distribution in the Ito, Stratonovich and postpoint discretization approaches can be obtained and analyzed.Comment: 6 pages in LATEX cod

Current-voltage characteristic and stability in resonant-tunneling n-doped semiconductor superlattices

We review the occurrence of electric-field domains in doped superlattices within a discrete drift model. A complete analysis of the construction and stability of stationary field profiles having two domains is carried out. As a consequence, we can provide a simple analytical estimation for the doping density above which stable stable domains occur. This bound may be useful for the design of superlattices exhibiting self-sustained current oscillations. Furthermore we explain why stable domains occur in superlattices in contrast to the usual Gunn diode.Comment: Tex file and 3 postscript figure

Effect of age on the prognostic value of left ventricular function in patients with acute coronary syndrome:a prospective registry study

Objective: This study aims to study the prognostic impact of LV function on mortality and examine the effect of age on the prognostic value of left ventricular function.  Methods: We examined the Myocardial Ischaemia National Audit Project (MINAP) registry (2006-2010) data with a mean follow up of 2.1 years. LV function was categorized into good (ejection fraction (EF) ≥50%), moderate (EF 30-49%) and poor (EF <30%) categories. Cox-proportional hazards models were constructed to examine the prognostic significance of LV function in different age groups (<65, 65-74, 75-84 and ≥85 years) on all-cause mortality adjusting for baseline variables.  Results: Of 424,848 patients, LV function data available for 123,609. Multiple imputations were used to impute missing values of LV function and the final sample for analyses were drawn from 414,305. After controlling for confounders, 339,887 participants were included in the regression models. For any age group, mortality was higher with worsening degree of LV impairment. Increased age reduced the adverse prognosis associated with reduced LV function (hazard ratios (HRs) of death comparing poor LV function to good LV function were 2.11 95%CI 1.88-2.37 for age <65 years and 1.28 95%CI 1.20-1.36 for age ≥85 years. Older patients had a high mortality risk even in those with good LV function. HRs of mortality for ≥85 compared to <65 years (HR=1.00) within good, moderate and poor ejection fractions groups were 5.89, 4.86 and 3.43, respectively.  Conclusions: In patients with ACS, clinicians should interpret the prognostic value of LV function taking into account patient’s age

Mid Infrared Photometry of Mass-Losing AGB Stars

We present ground-based mid-infrared imaging for 27 M-, S- and C-type Asymptotic Giant Branch (AGB) stars. The data are compared with those of the database available thanks to the IRAS, ISO, MSX and 2MASS catalogues. Our goal is to establish relations between the IR colors, the effective temperature $T_{eff}$, the luminosity $L$ and the mass loss rate $\dot M$, for improving the effectiveness of AGB modelling. Bolometric (absolute) magnitudes are obtained through distance compilations, and by applying previously-derived bolometric corrections; the variability is also studied, using data accumulated since the IRAS epoch. The main results are: i) Values of $L$ and $\dot M$ for C stars fit relations previously established by us, with Miras being on average more evolved and mass losing than Semiregulars. ii) Moderate IR excesses (as compared to evolutionary tracks) are found for S and M stars in our sample: they are confirmed to originate from the dusty circumstellar environment. iii) A larger reddening characterizes C-rich Miras and post-AGBs. In this case, part of the excess is due to AGB models overestimating $T_{eff}$ for C-stars, as a consequence of the lack of suitable molecular opacities. This has a large effect on the colors of C-rich sources and sometimes disentangling the photospheric and circumstellar contributions is difficult; better model atmospheres should be used in stellar evolutionary codes for C stars. iv) The presence of a long-term variability at mid-IR wavelengths seems to be limited to sources with maximum emission in the 8 -- 20 $\mu$m region, usually Mira variables (1/3 of our sample). Most Semiregular and post-AGB stars studied here remained remarkably constant in mid-IR over the last twenty years.Comment: Accepted for publication in the Astronomical Journal - 35 pages (in preprint), 9 figures, 5 table