Dark Matter at the Center and in the Halo of the Galaxy

All presently known stellar-dynamical constraints on the size and mass of the supermassive compact dark object at the Galactic center are consistent with a ball of self-gravitating, nearly non-interacting, degenerate fermions with mass between 76 and 491 keV, for degeneracy factor g=2. Sterile neutrinos of 76 keV mass, which are mixed with at least one of the active neutrinos with a mixing angele ~10^{-7}, are produced in about the right amount in the early Universe by incoherent resonant and non-resonant scattering of active neutrinos having asymmetry of ~0.01. The former process yields sterile neutrinos with a quasi-degenerate spectrum while the latter leads to a thermal spectrum. As the production mechanism of the sterile neutrino is consistent with the constraints from large scale structure formation, core collapse supernovae, and diffuse X-ray background, it could be the dark matter particle of the Universe.Comment: 6 pages, to appear in the Beyond 2003 conference proceeding

A renormalized large-n solution of the U(n) x U(n) linear sigma model in the broken symmetry phase

Dyson-Schwinger equations for the U(n) x U(n) symmetric matrix sigma model reformulated with two auxiliary fields in a background breaking the symmetry to U(n) are studied in the so-called bare vertex approximation. A large n solution is constructed under the supplementary assumption so that the scalar components are much heavier than the pseudoscalars. The renormalizability of the solution is investigated by explicit construction of the counterterms.Comment: RevTeX4, 14 pages, 2 figures. Version published in Phys. Rev.

Phase Transitions and Critical Behavior for Charged Black Holes

We investigate the thermodynamics of a four-dimensional charged black hole in a finite cavity in asymptotically flat and asymptotically de Sitter space. In each case, we find a Hawking-Page-like phase transition between a black hole and a thermal gas very much like the known transition in asymptotically anti-de Sitter space. For a ``supercooled'' black hole--a thermodynamically unstable black hole below the critical temperature for the Hawking-Page phase transition--the phase diagram has a line of first-order phase transitions that terminates in a second order point. For the asymptotically flat case, we calculate the critical exponents at the second order phase transition and find that they exactly match the known results for a charged black hole in anti-de Sitter space. We find strong evidence for similar phase transitions for the de Sitter black hole as well. Thus many of the thermodynamic features of charged anti-de Sitter black holes do not really depend on asymptotically anti-de Sitter boundary conditions; the thermodynamics of charged black holes is surprisingly universal.Comment: LaTeX, 14 pages, 9 eps figures; higher resolution figures available on reques

Empirical Analyses of the Relationship between Trade and Budget Deficit of FYR of Macedonia

The purpose of this article is to analyze the evidence of twin deficits hypothesis by empirically examining the relationship between trade deficit and budget deficit for the case of FYR of Macedonia. The study employs a vector autoregression (VAR) model as well as a Granger causality test in order to investigate the causal relationship between trade and budget deficit variables using quarterly data for the time period 1998Q1–2017Q4. The econometric results of VAR model disclose that there exists a short term relationship between these two variables, implying that higher trade deficits are associated with higher fiscal deficits. Moreover, the causality test shows a unidirectional relationship, revealing that trade deficit causes budget deficit, whereas budget deficit doesn't cause trade deficit.     Keywords: trade deficit, budget deficit, causality analysi

Academic integrity: An educative and equitable approach in enabling pathway programs

This paper unpacks the key components of an educative approach to academic integrity and applies them to enabling pathway programs. Enabling programs progress high numbers of students from recognised equity groups into undergraduate studies and are recognised for supporting and encouraging students and fostering a sense of belonging (Burke, Bennett, Burgess, Gray, & Southgate, 2016; Hellmundt & Baker, 2017; Lane & Sharp, 2014). University measures to support academic integrity can, on the other hand, be perceived as procedure-based and punitive (Dalal, 2015). In this paper, we provide an integrative review of literature on the common features of an educative approach to academic integrity and enabling programs and introduce exemplars from two universities of enabling pedagogies applied to academic integrity

Phase transition(s) in finite density QCD

The Grand Canonical formalism is generally used in numerical simulations of finite density QCD since it allows free mobility in the chemical potential $\mu$. We show that special care has to be used in extracting numerical results to avoid dramatic rounding effects and spurious transition signals. If we analyze data correctly, with reasonable statistics, no signal of first order phase transition is present and results using the Glasgow prescription are practically coincident with the ones obtained using the modulus of the fermionic determinant.Comment: 6 pages, 5 ps figs. To appear in Proceedings of "QCD at Finite Baryon Density" workshop, Bielefeld, 27-30 April 199

Does an educative approach work? A reflective case study of how two Australian higher education Enabling programs support students and staff uphold a responsible culture of academic integrity

Introduction Enabling education programs, otherwise known as Foundation Studies or Preparatory programs, provide pathways for students typically under-represented in higher education. Students in Enabling programs often face distinct challenges in their induction to academic culture which can implicate them in cases of misconduct. This case study addresses a gap in the enabling literature reporting on how a culture of academic integrity can be developed for students and staff in these programs through an educative approach. Case description This paper outlines how an educative approach to academic integrity is implemented within the Enabling programs of two Australian universities. Discussion and reflection This case study reflects upon an approach which makes specific reference to the key elements of ‘support’, ‘approach’ and ‘responsibility’ as highlighted in Bretag and Mahmud’s seminal paper. The paper reports a reduction in misconduct cases at the two institutions suggesting a positive correlation between the interventions and students’ understanding of ethical academic practice. This study reflects upon practitioner experiences with academic integrity investigations to evaluate the effectiveness of this approach. Conclusions The authors show that it is possible to ensure academic integrity practices and values are upheld within a supportive learning environment appropriate to a students’ level of study

Dark Energy vs. Dark Matter: Towards a Unifying Scalar Field?

The standard model of cosmology suggests the existence of two components, "dark matter" and "dark energy", which determine the fate of the Universe. Their nature is still under investigation, and no direct proof of their existences has emerged yet. There exist alternative models which reinterpret the cosmological observations, for example by replacing the dark energy/dark matter hypothesis by the existence of a unique dark component, the dark fluid, which is able to mimic the behaviour of both components. After a quick review of the cosmological constraints on this unifying dark fluid, we will present a model of dark fluid based on a complex scalar field and discuss the problem of the choice of the potential.Comment: 6 pages, 2 figures, contribution to the proceedings of the July 2008 CRAL-IPNL conference "Dark Energy and Dark Matter

A field theory approach to cosmological density perturbations

Adiabatic perturbations propagate in the expanding universe like scalar massless fields in some effective Robertson-Walker space-time

The motion of stars near the Galactic center: A comparison of the black hole and fermion ball scenarios

After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the stars S0-1 and S0-2, which have the smallest projected distances to Sgr A*, in the supermassive black hole as well as in the fermion ball scenarios of the Galactic center. It is shown that both scenarios are consistent with the data, as measured during the last six years by Genzel et al. and Ghez et al. The free parameters of the projected orbit of a star are the unknown components of its velocity v_z and distance z to Sgr A* in 1995.4, with the z-axis being in the line of sight. We show, in the case of S0-1 and S0-2, that the z-v_z phase-space which fits the data, is much larger for the fermion ball than for the black hole scenario. Future measurements of the positions or radial velocities of S0-1 and S0-2 could reduce this allowed phase-space and eventually rule out one of the currently acceptable scenarios. This may shed some light into the nature of the supermassive compact dark object, or dark matter in general at the center of our Galaxy.Comment: 30 pages, 12 figures, Latex, aasms4 styl