Astronomy

Inflationary cosmology from quantum Conformal Gravity
We analyze the functional integral for quantum Conformal Gravity and showthat with the help of a Hubbard-Stratonovich transformation, the action can bebroken into a local quadratic-curvature theory coupled to a scalar field. Aone-loop effective action calculation reveals that strong fluctuations of themetric field are capable of spontaneously generating a dimensionally transmutedparameter which...


Effect of squeezing on parameter estimation of gravitational waves emitted by compact binary systems
The LIGO gravitational wave (GW) detectors will begin collecting data in2015, with Virgo following shortly after. The use of squeezing has beenproposed as a way to reduce the quantum noise without increasing the laserpower, and has been successfully tested at one of the LIGO sites and at GEO inGermany. When used in Advanced LIGO without a filter cavity, the squeezerimproves the performances of ...
Critical Behavior in a Massless Scalar Field Collapse with Self-interaction Potential
We examine a one-parameter family of analytical solutions representingspherically symmetric collapse of a nonlinear massless scalar field withself-interaction in an asymptotically flat spacetime. The time evolutionexhibits a type of critical behavior. Depending on the scalar charge parameter$q$ as compared to a critical value $q^*$, the incoming scalar wave collapseseither to a globally naked c...


A cosmographic analysis of holographic dark energy models
The present work deals with a detailed study of interacting holographic darkenergy model for three common choices of the interaction term. Also, twostandard choices of IR cut-off, namely, Ricci length scale and radius of theevent horizon are considered here. Finally, the cosmographic parameters arepresented both analytically and graphically.
A Dynamical Systems Analysis of Axisymmetric Accretion in a Schwarzschild Black Hole
Stationary, inviscid, axi-symmetric, rotating, transonic accretion flow hasbeen studied in a general relativistic framework, in the Schwarzschild metric;for three different flow geometries - under both polytropic and isothermalconditions. The equilibrium points of the underlying fluid system have beenlocated and an eigenvalue based linear dynamical systems analysis of thesecritical points has b...


Quantum Riemannian geometry of phase space and nonassociativity
Noncommutative or `quantum' differential geometry has emerged in recent yearsas a process for quantizing not only a classical space into a noncommutativealgebra (as familiar in quantum mechanics) but also differential forms, bundlesand Riemannian structures at this level. The data for the algebra quantisationis a classical Poisson bracket, the data for the quantum differential forms isa Poisson...
Statistical Study of Reconnection Exhausts in the Solar Wind
Magnetic reconnection is a fundamental process that changes magnetic field configuration and converts a magnetic energy to flow energy and plasma heating. This paper presents a survey of the plasma and magnetic field parameters inside 418 reconnection exhausts identified in the WIND data from 1995-2012. The statistical analysis is oriented on the re-distribution of the magnetic energy released ...

Soft X-Ray Extended Emissions of Short Gamma-Ray Bursts as Electromagnetic Counterparts of Compact Binary Mergers: Possible Origin and Detectability
We investigate the possible origin of extended emissions (EEs) of short gamma-ray bursts with an isotropic energy of ~10 50-51 erg and a duration of a few 10 s to ~100 s, based on a compact binary (neutron star (NS)-NS or NS-black hole (BH)) merger scenario. We analyze the evolution of magnetized neutrino-dominated accretion disks of mass ~0.1 M ☉ around BHs formed after the mergers and estim...
Solar Photospheric Network Properties and Their Cycle Variation
We present a numerical simulation of the formation and evolution of the solar photospheric magnetic network over a full solar cycle. The model exhibits realistic behavior as it produces large, unipolar concentrations of flux in the polar caps, a power-law flux distribution with index –1.69, a flux replacement timescale of 19.3 hr, and supergranule diameters of 20 Mm. The polar behavior is esp...

On the Area Expansion of Magnetic Flux Tubes in Solar Active Regions
We calculated the three-dimensional (3D) distribution of the area expansion factors in a potential magnetic field, extrapolated from the high-resolution Hinode /SOT magnetogram of the quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the distribution of area expansion factors show significant structure. Loop-like structures characterized ...
Lower Limits on the Anisotropy of the Extragalactic Gamma-Ray Background Implied by the 2FGL and 1FHL Catalogs
In principle, the angular anisotropy in the extragalactic gamma-ray background (EGRB) places severe constraints upon putative populations of unresolved gamma-ray point sources. Existing estimates of the EGRB anisotropy have been constructed by excising known point sources, e.g., taken from the First or Two Year Fermi -LAT Source Catalog (1FGL or 2FGL, respectively) and statistically analyzing ...

Electron Densities and Alkali Atoms in Exoplanet Atmospheres
We describe a detailed study on the properties of alkali atoms in extrasolar giant planets, and specifically focus on their role in generating the atmospheric free electron densities, as well as their impact on the transit depth observations. We focus our study on the case of HD 209458b, and we show that photoionization produces a large electron density in the middle atmosphere that is about tw...
Ultrafaint Dwarfs—Star Formation and Chemical Evolution in the Smallest Galaxies
In earlier work, we showed that a dark matter halo with a virial mass of 10 7 M ☉ can retain a major part of its baryons in the face of the pre-ionization phase and supernova (SN) explosion from a25 M ☉ star. Here, we expand on the results of that work, investigating the star formation and chemical evolution of the system beyond the first SN. In a galaxy with a mass M vir = 10 7 M ☉ , s...
Numerical Simulations of Optically Thick Accretion onto a Black Hole. II. Rotating Flow
In this paper, we report on recent upgrades to our general relativistic radiation magnetohydrodynamics code, Cosmos++ , including the development of a new primitive inversion scheme and a hybrid implicit-explicit solver with a more general M 1 closure relation for the radiation equations. The new hybrid solver helps stabilize the treatment of the radiation source terms, while the new closure al...
Diffuse γ-Ray Emission from Galactic Pulsars
Millisecond pulsars (MSPs) are old fast-spinning neutron stars that represent the second most abundant source population discovered by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope ( Fermi ). As guaranteed γ-ray emitters, they might contribute non-negligibly to the diffuse emission measured at high latitudes by Fermi -LAT (i.e., the Isotropic Diffuse γ-Ray (IDGRB...