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200 papers

We derive a general relativistic Hamiltonian valid for both bound and scattering systems by reducing the four-component Dirac equation to a two-component Dirac-Pauli form. Unlike conventional approaches, our formulation includes first-order…

High Energy Physics - Phenomenology · Physics 2025-11-13 Abdelhamid Albaid

We present a theoretical study of the ionization dynamics of a hydrogen atom exposed to attosecond laser pulses in the extreme ultra violet region at very high intensities. The pulses are such that the electron is expected to reach…

Atomic Physics · Physics 2017-04-12 Tor Kjellsson , Sølve Selstø , Eva Lindroth

We study the reionisation of the Universe by stellar sources using a numerical approach that combines fast 3D radiative transfer calculations with high resolution hydrodynamical simulations. Ionising fluxes for the sources are derived from…

Astrophysics · Physics 2009-11-07 Aaron Sokasian , Tom Abel , Lars Hernquist , Volker Springel

Recent observations of high-redshift galaxies and quasars indicate that the hydrogen component of the intergalactic medium (IGM) must have been reionized at some redshift z>6. Prior to complete reionization, sources of ultraviolet radiation…

Astrophysics · Physics 2009-10-31 Piero Madau , Martin J. Rees

Cosmic reionization progresses as HII regions form around sources of ionizing radiation. Their average size grows continuously until they percolate and complete reionization. We demonstrate how this typical growth can be calculated around…

Astrophysics · Physics 2009-11-13 Marcelo A. Alvarez , Tom Abel

Extending the concepts of light-front field theory to quantum statistics provides a novel approach towards nuclear matter under extreme conditions. Such conditions exist, e.g., in neutron stars or in the early stage of our universe. They…

Nuclear Theory · Physics 2009-11-10 Michael Beyer

The temporal evolution of the ionizing UV background radiation field at high redshift provides a probe of the evolution of the early star formation rate. By comparing the observed levels of absorption in the highest redshift quasar spectra…

Astrophysics · Physics 2009-11-07 Renyue Cen , Patrick McDonald

We develop the new method of optimized discretization for imaging the relative source from two particle correlation functions. In this method, the source resolution depends on the relative particle separation and is adjusted to available…

Nuclear Theory · Physics 2008-11-26 David A. Brown , Pawel Danielewicz

The effects of small relativistic corrections to the off-resonant polarizability, hyperpolarizability, and second hyperpolarizability are investigated. Corrections to linear and nonlinear optical coefficients are demonstrated in the…

Quantum Physics · Physics 2015-06-22 Nathan J. Dawson

The theoretical model by Sorasio et al. (2006) for the steady state Mach number of electrostatic shocks formed in the interaction of two plasma slabs of arbitrary density and temperature is generalized for relativistic electron and…

Plasma Physics · Physics 2013-05-08 A. Stockem , E. Boella , F. Fiuza , L. O. Silva

The modeling of galaxy formation and reionization, two central issues of modern cosmology, relies on the accurate follow-up of the intergalactic medium (IGM). Unfortunately, owing to the complex nature of this medium, the differential…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-23 Alberto Manrique , Eduard Salvador-Solé

Dissipative processes in relativistic fluids are known to be important in the analyses of the hot QCD matter created in high-energy heavy-ion collisions. In this work, I consider dissipative corrections to energy and conserved charge…

Nuclear Theory · Physics 2018-10-08 Akihiko Monnai

Recently, Owen(1993) and Owen and Ledlow (1994) have shown that the dividing line between Fanaroff-Riley class~I and class~II Radio Sources is very sharp when the sources are represented as points in the radio-optical luminosity plane. It…

Astrophysics · Physics 2016-08-30 Geoffrey V. Bicknell

We study the formation and evolution of HII regions around the first stars formed at z=10-30. We use a one-dimensional Lagrangian hydrodynamics code which self-consistently incorporates radiative transfer and non-equilibrium primordial gas…

Astrophysics · Physics 2009-11-10 T. Kitayama , N. Yoshida , H. Susa , M. Umemura

Within the lowest-order relativistic approximation ($\sim v^2/c^2$) and to first order in $m_e/M$, the tensorial form of the relativistic corrections of the nuclear recoil Hamiltonian is derived, opening interesting perspectives for…

Atomic Physics · Physics 2015-05-28 E. Gaidamauskas , C. Nazé , P. Rynkun , G. Gaigalas , P. Jönsson , M. Godefroid

We compute the ionizing radiation field at low redshift, arising from Seyferts, QSOs, and starburst galaxies. This calculation combines recent Seyfert luminosity functions, extrapolated ultraviolet fluxes from our IUE-AGN database, and a…

Astrophysics · Physics 2009-10-31 J. M. Shull , D. Roberts , M. L. Giroux , S. V. Penton , M. A. Fardal

Corrections to the magnitudes of high redshift objects due to intergalactic attenuation are computed using current estimates of the properties of the intergalactic medium. The results of numerical simulations are used to estimate the…

Astrophysics · Physics 2007-05-23 Avery Meiksin

It is possible that the properties of HII regions during reionization depend sensitively on many poorly constrained quantities (the nature of the ionizing sources, the clumpiness of the gas in the IGM, the degree to which photo-ionizing…

The observed variability of BL Lac objects and Quasars on timescales <1 day (intraday variability, IDV) have revealed radio brightness temperatures up to 10^{16}-10^{20} K. These values challenge the beaming model with isotropic comoving…

Astrophysics · Physics 2007-05-23 A. R. Crusius-W"atzel , H. Lesch

QSO near-zones are an important probe of the the ionization state of the IGM at z ~ 6-7, at the end of reionization. We present here high-resolution cosmological 3D radiative transfer simulations of QSO environments for a wide range of host…

Cosmology and Nongalactic Astrophysics · Physics 2016-08-24 Laura C. Keating , Martin G. Haehnelt , Sebastiano Cantalupo , Ewald Puchwein