publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
|---|---|---|---|
2021-12-08 | IGM damping wing constraints on reionisation from covariance reconstruction of two $z\gtrsim7$ QSOs | Bright, high redshift ($z>6$) QSOs are powerful probes of the ionisation
state of the intervening intergalactic medium (IGM). The detection of
Ly$\alpha$ damping wing absorption imprinted in the spectrum of high-z QSOs can
provide strong constraints on the epoch of reionisation (EoR). In this work, we
perform an indepe... | 2112.04091v1 |
2022-01-24 | A blow-up result for a Nakao-type weakly coupled system with nonlinearities of derivative-type | In this paper, we consider a weakly coupled system of a wave and damped
Klein-Gordon equation with nonlinearities of derivative type. We prove a
blow-up result for the Cauchy problem associated with this system for
nonnegative and compactly supported data by means of an iteration argument. | 2201.09462v1 |
2022-03-11 | On the small noise limit in the Smoluchowski-Kramers approximation of nonlinear wave equations with variable friction | We study the validity of a large deviation principle for a class of
stochastic nonlinear damped wave equations, of Klein-Gordon type, in the joint
small mass and small noise limit. The friction term is assumed to be state
dependent. | 2203.05923v2 |
2022-03-28 | The higher order nonlinear Schrödinger equation with quadratic nonlinearity on the real axis | The initial value problem is considered for a higher order nonlinear
Schr\"odinger equation with quadratic nonlinearity. Results on existence and
uniqueness of weak solutions are obtained. In the case of an effective at
infinity additional damping large-time decay of solutions without any smallness
assumptions is also ... | 2203.14830v1 |
2022-04-03 | Strong Solution of Modified Anistropic 3D-Navier-Stokes Equations | In this paper we study the anisotropic incompressible Navier-Stokes equations
with a logarithm damping $\alpha \log(e+|u|^2)|u|^2u$ in $H^{0.1}$, where we
used new methods, new tools and Fourier analysis. | 2204.01717v2 |
2022-04-28 | Coupling between turbulence and solar-like oscillations: A combined Lagrangian PDF/SPH approach. II - Mode driving, damping and modal surface effect | The first paper of this series established a linear stochastic wave equation
for solar-like p-modes, correctly taking the effect of turbulence thereon into
account. In this second paper, we aim at deriving simultaneous expressions for
the excitation rate, damping rate, and modal surface effect associated with any
given... | 2204.13367v1 |
2022-05-05 | Blow-up solutions of damped Klein-Gordon equation on the Heisenberg group | Inthisnote,weprovetheblow-upofsolutionsofthesemilineardamped Klein-Gordon
equation in a finite time for arbitrary positive initial energy on the
Heisenberg group. This work complements the paper [21] by the first author and
Tokmagambetov, where the global in time well-posedness was proved for the small
energy solutions... | 2205.02705v1 |
2022-05-23 | Extended random-phase-approximation study of fragmentation of giant quadrupole resonance in $^{16}$O | The damping of isoscalar giant quadrupole resonance in $^{16}$O is studied
using extended random-phase-approximation approaches derived from the
time-dependent density-matrix theory. It is pointed out that the effects of
ground-state correlations bring strong fragmentation of quadrupole strength
even if the number of t... | 2205.11654v2 |
2022-06-21 | Nonlinear Compton scattering and nonlinear Breit-Wheeler pair production including the damping of particle states | In the presence of an electromagnetic background plane-wave field, electron,
positron, and photon states are not stable, because electrons and positrons
emit photons and photons decay into electron-positron pairs. This decay of the
particle states leads to an exponential damping term in the probabilities of
single nonl... | 2206.10345v2 |
2022-06-23 | Nonlinear Landau damping for the 2d Vlasov-Poisson system with massless electrons around Penrose-stable equilibria | In this paper, we prove the nonlinear asymptotic stability of the
Penrose-stable equilibria among solutions of the $2d$ Vlasov-Poisson system
with massless electrons. | 2206.11744v2 |
2022-07-25 | Inviscid limit for the compressible Navier-Stokes equations with density dependent viscosity | We consider the compressible Navier-Stokes system describing the motion of a
barotropic fluid with density dependent viscosity confined in a
three-dimensional bounded domain $\Omega$. We show the convergence of the weak
solution to the compressible Navier-Stokes system to the strong solution to the
compressible Euler s... | 2207.12222v1 |
2022-08-25 | Polynomial energy decay rate of a 2D Piezoelectric beam with magnetic effect on a rectangular domain without geometric conditions | In this paper, we investigate the stability of coupled equations modelling a
2D piezoelectric beam with magnetic effect with only one local viscous damping
on a rectangular domain without geometric conditions. We prove that the energy
of the system decays polynomially with the rate 1/t . | 2208.12012v1 |
2022-10-12 | Backward problem for the 1D ionic Vlasov-Poisson equation | In this paper, we study the backward problem for the one-dimensional
Vlasov-Poisson system with massless electrons, and we show the Landau damping
by fixing the asymptotic behaviour of our solution. | 2210.06123v2 |
2022-10-28 | Oblique Quasi-Kink Modes in Solar Coronal Slabs Embedded in an Asymmetric Magnetic Environment: Resonant Damping, Phase and Group Diagrams | There has been considerable interest in magnetoacoustic waves in static,
straight, field-aligned, one-dimensional equilibria where the exteriors of a
magnetic slab are different between the two sides. We focus on trapped,
transverse fundamental, oblique quasi-kink modes in pressureless setups where
the density varies c... | 2210.16091v1 |
2022-11-02 | Data-driven modeling of Landau damping by physics-informed neural networks | Kinetic approaches are generally accurate in dealing with microscale plasma
physics problems but are computationally expensive for large-scale or
multiscale systems. One of the long-standing problems in plasma physics is the
integration of kinetic physics into fluid models, which is often achieved
through sophisticated... | 2211.01021v3 |
2022-11-04 | New Clues About Light Sterile Neutrinos: Preference for Models with Damping Effects in Global Fits | This article reports global fits of short-baseline neutrino data to
oscillation models involving light sterile neutrinos. In the commonly-used 3+1
plane wave model, there is a well-known 4.9$\sigma$ tension between data sets
sensitive to appearance versus disappearance of neutrinos. We find that models
that damp the os... | 2211.02610v5 |
2022-12-07 | A recipe for orbital eccentricity damping in the type-I regime for low viscosity 2D-discs | It is known that gap opening depends on the disc's viscosity; however,
eccentricity damping formulas have only been derived at high viscosities,
ignoring partial gap opening. We aim at obtaining a simple formula to model
$e$-damping of the type-I regime in low viscosity discs, where even small
planets may start opening... | 2212.03608v1 |
2022-12-10 | Linear stabilization for a degenerate wave equation in non divergence form with drift | We consider a degenerate wave equation in one dimension, with drift and in
presence of a leading operator which is not in divergence form. We impose a
homogeneous Dirichlet boundary condition where the degeneracy occurs and a
boundary damping at the other endpoint. We provide some conditions for the
uniform exponential... | 2212.05264v1 |
2022-12-31 | On the stability of shear flows in bounded channels, II: non-monotonic shear flows | We give a proof of linear inviscid damping and vorticity depletion for
non-monotonic shear flows with one critical point in a bounded periodic
channel. In particular, we obtain quantitative depletion rates for the
vorticity function without any symmetry assumptions. | 2301.00288v2 |
2023-03-18 | Spin waves in a superconductor | Spin waves that can propagate in normal and superconducting metals are
investigated. Unlike normal metals, the velocity of spin waves becomes
temperature-dependent in a superconductor. The low frequency spin waves survive
within the narrow region below the superconducting transition temperature. At
low temperatures the... | 2303.10468v1 |
2023-04-07 | Echo disappears: momentum term structure and cyclic information in turnover | We extract cyclic information in turnover and find it can explain the
momentum echo. The reversal in recent month momentum is the key factor that
cancels out the recent month momentum and excluding it makes the echo regress
to a damped shape. Both rational and behavioral theories can explain the
reversal. This study is... | 2304.03437v1 |
2023-04-26 | Plasma echoes in graphene | Plasma echo is a dramatic manifestation of plasma damping process
reversibility. In this paper we calculate temporal and spatial plasma echoes in
graphene in the acoustic plasmon regime when echoes dominate over plasmon
emission. We show an extremely strong spatial echo response and discuss how
electron collisions redu... | 2304.13440v1 |
2023-06-01 | JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at $z=7-12$ Obtained with Ly$α$ Damping Wing Absorptions in 26 Bright Continuum Galaxies | We present volume-averaged neutral hydrogen fractions $x_{\rm \HI}$ and
ionized bubble radii $R_{\rm b}$ measured with Ly$\alpha$ damping wing
absorption of galaxies at the epoch of reionization. We combine JWST/NIRSpec
spectra taken by CEERS, GO-1433, DDT-2750, and JADES programs, and obtain a
sample containing 26 bri... | 2306.00487v2 |
2023-06-20 | New results on controllability and stability for degenerate Euler-Bernoulli type equations | In this paper we study the controllability and the stability for a degenerate
beam equation in divergence form via the energy method. The equation is clamped
at the left end and controlled by applying a shearing force or a damping at the
right end. | 2306.11851v3 |
2023-08-01 | Aerodynamics of the square-back Ahmed body under rainfall conditions | We report an experimental investigation about the aerodynamics of a
simplified road vehicle, the so-called square-back Ahmed body, under rainfall
conditions. A particular emphasis is put on the evolution of the body base
pressure distribution with respect to the operating conditions. It is found
that rainfall significa... | 2308.00276v1 |
2023-09-11 | Study of damped oscillating structures from charged and neutral K-meson electromagnetic form factors data | The damped oscillating structures (OS) were recently revealed in the proton
"effective" form factor (FF) data. For the time being they can be neither
confirmed nor disproved by investigations of timelike data on the individual
proton electric and proton magnetic FFs because their precision and reliability
(especially o... | 2309.05354v1 |
2023-10-31 | Variational principle for a damped, quadratically interacting particle chain with nonconservative forcing | A method for designing variational principles for the dynamics of a possibly
dissipative and non-conservatively forced chain of particles is demonstrated.
Some qualitative features of the formulation are discussed. | 2311.00106v2 |
2024-01-30 | Linear stability analysis of the Couette flow for the 2D Euler-Poisson system | This paper is concerned with the linear stability analysis for the Couette
flow of the Euler-Poisson system for both ionic fluid and electronic fluid in
the domain $\bb{T}\times\bb{R}$. We establish the upper and lower bounds of the
linearized solutions of the Euler-Poisson system near Couette flow. In
particular, the ... | 2401.17102v1 |
2024-03-21 | Non-resonant invariant foliations of quasi-periodically forced systems | We show the existence and uniqueness of invariant foliations about invariant
tori in analytic discrete-time dynamical systems. The parametrisation method is
used prove the result. Our theory is a foundational block of data-driven model
order reduction, that can only be carried out using invariant foliations. The
theory... | 2403.14771v1 |
1999-08-09 | On the possibility of variation of the fundamental constants of physics in the static universe | A variation of fundamental constants of physics is proposed in a frame of
static universe. It is shown when the velocity of light increases (decreases)
the Planck's constant increases (decreases) and mass of bodies decreases
(increases). This variation of constants leads to the variation of dimensions
of bodies and the... | 9908082v1 |
2002-06-17 | Cosmological constant and curved 5D geometry | We study the value of cosmological constant in de Sitter brane embedded in
five dimensions with positive, vanishing and negative bulk cosmological
constant. In the case of negative bulk cosmological constant, we show that not
zero but tiny four-dimensional cosmological constant can be realized by tiny
deviation from bu... | 0206153v1 |
2003-06-30 | Convex Bodies of Constant Width and Constant Brightness | In 1926 S. Nakajima (= A. Matsumura) showed that any convex body in $\R^3$
with constant width, constant brightness, and boundary of class $C^2$ is a
ball. We show that the regularity assumption on the boundary is unnecessary, so
that balls are the only convex bodies of constant width and brightness. | 0306437v1 |
2010-07-27 | The GL-l.u.st.\ constant and asymmetry of the Kalton-Peck twisted sum in finite dimensions | We prove that the Kalton-Peck twisted sum $Z_2^n$ of $n$-dimensional Hilbert
spaces has GL-l.u.st.\ constant of order $\log n$ and bounded GL constant. This
is the first concrete example which shows different explicit orders of growth
in the GL and GL-l.u.st.\ constants. We discuss also the asymmetry constants of
$Z_2^... | 1007.4692v1 |
2019-04-02 | On geometric constants for (small) Morrey spaces | In this article, we compute Von Neumann-Jordan constant, James constant, and
Dunkl-Williams constant for small Morrey spaces. Our approach can also be seen
as an alternative way in computing the three constants for the (classical)
Morrey spaces. In addition, we prove constructively that Morrey spaces are not
uniformly ... | 1904.01712v3 |
2021-08-11 | Gravity can be caused by the difference of Coulomb's constants | Coulomb's constant is defined as a value for attraction and repulsion.
However, it is strange that only one value can be applied for both attraction
and repulsion. A very little difference between coulomb's constant for
attraction and coulomb's constant for repulsion can be the source of gravity.
The author verified if... | 2108.05114v1 |
2007-10-22 | The Hubble constant and dark energy from cosmological distance measures | We study how the determination of the Hubble constant from cosmological
distance measures is affected by models of dark energy and vice versa. For this
purpose, constraints on the Hubble constant and dark energy are investigated
using the cosmological observations of cosmic microwave background, baryon
acoustic oscilla... | 0710.3995v2 |
2016-08-19 | Kinetic stability and energetics of simulated glasses created by constant pressure cooling | We use computer simulations to study the cooling rate dependence of the
stability and energetics of model glasses created at constant pressure
conditions and compare the results with glasses formed at constant volume
conditions. To examine the stability, we determine the time it takes for a
glass cooled and reheated at... | 1608.05703v1 |
2007-04-24 | On C$^2$-smooth Surfaces of Constant Width | A number of results for C$^2$-smooth surfaces of constant width in Euclidean
3-space ${\mathbb{E}}^3$ are obtained. In particular, an integral inequality
for constant width surfaces is established. This is used to prove that the
ratio of volume to cubed width of a constant width surface is reduced by
shrinking it along... | 0704.3248v1 |
2009-05-09 | Time-like Salkowski and anti-Salkowski curves in Minkowski space $\e_1^3$ | Salkowski \cite{salkow}, one century ago, introduced a family of curves with
constant curvature but non-constant torsion (Salkowski curves) and a family of
curves with constant torsion but non-constant curvature (anti-Salkowski curves)
in Euclidean 3-space $\e^3$. In this paper, we adapt definition of such curves
to ti... | 0905.1404v1 |
2009-08-17 | The Interacting and Non-constant Cosmological Constant | We propose a time-varying cosmological constant with a fixed equation of
state, which evolves mainly through its interaction with the background during
most of the long history of the universe. However, such interaction does not
exist in the very early and the late-time universe and produces the
acceleration during the... | 0908.2303v1 |
2012-06-04 | The Yamabe constant on noncompact manifolds | We prove several facts about the Yamabe constant of Riemannian metrics on
general noncompact manifolds and about S. Kim's closely related "Yamabe
constant at infinity". In particular we show that the Yamabe constant depends
continuously on the Riemannian metric with respect to the fine C^2-topology,
and that the Yamabe... | 1206.0610v2 |
2018-10-01 | Three geometric constants for Morrey spaces | In this paper we calculate three geometric constants, namely the von
Neumann-Jordan constant, the James constant, and the Dunkl-Williams constant,
for Morrey spaces and discrete Morrey spaces. These constants measure uniformly
nonsquareness of the associated spaces. We obtain that the three constants are
the same as th... | 1810.00963v3 |
2019-09-03 | Maximal Chow constant and cohomologically constant fibrations | Motivated by the study of rationally connected fibrations (and the MRC
quotient) we study different notions of birationally simple fibrations. We say
a fibration of smooth projective varieties is Chow constant if pushforward
induces an isomorphism on the Chow group of 0-cycles. Likewise we say a
fibration is cohomologi... | 1909.01483v1 |
2020-04-08 | On Seshadri constants and point-curve configurations | In the note we study the multipoint Seshadri constants of
$\mathcal{O}_{\mathbb{P}^{2}_{\mathbb{C}}}(1)$ centered at singular loci of
certain curve arrangements in the complex projective plane. Our first aim is to
show that the values of Seshadri constants can be approximated with use of a
combinatorial invariant which... | 2004.04043v1 |
2021-10-07 | Biconservative hypersurfaces with constant scalar curvature in space forms | Biconservative hypersurfaces are hypersurfaces which have conservative
stress-energy tensor with respect to the bienergy, containing all minimal and
constant mean curvature hypersurfaces. The purpose of this paper is to study
biconservative hypersurfaces $M^n$ with constant scalar curvature in a space
form $N^{n+1}(c)$... | 2110.03438v1 |
2008-03-15 | Constant-Rank Codes and Their Connection to Constant-Dimension Codes | Constant-dimension codes have recently received attention due to their
significance to error control in noncoherent random linear network coding. What
the maximal cardinality of any constant-dimension code with finite dimension
and minimum distance is and how to construct the optimal constant-dimension
code (or codes) ... | 0803.2262v7 |
1994-02-17 | Power Spectrum Constraints from Spectral Distortions in the Cosmic Microwave Background | %The content of this replacement paper is identical to the original. %We have
attempted to fix the postscript so that it will print out on %a larger number
of printers. Using recent experimental limits on $\mu$ distortions from COBE
FIRAS, and the large lever-arm spanning the damping of sub-Jeans scale
fluctuations to ... | 9402045v2 |
1995-06-01 | The epoch of structure formation in blue mixed dark matter models | Recent data on the high--redshift abundance of damped Ly$\alpha$ systems are
compared with theoretical predictions for `blue' (i.e. $n>1$) Mixed Dark Matter
models. The results show that decreasing the hot component fraction
$\Omega_\nu$ and/or increasing the primordial spectral index $n$ implies an
earlier epoch of co... | 9506003v2 |
1996-04-16 | Cosmic Emissivity and Background Intensity from Damped Lyman-Alpha Galaxies | We present a new method to compute the cosmic emissivity $\E_\nu$ and
background intensity $J_\nu$. Our method is based entirely on data from quasar
absorption-line studies, namely, the comoving density of HI and the mean
metallicity and dust-to-gas ratio in damped Ly$\alpha$ galaxies. These
observations, when combined... | 9604091v1 |
1996-05-24 | Identification of a Galaxy Responsible for a High-Redshift Damped Ly-alpha Absorption System | Galaxies believed to be responsible for damped Ly-alpha absorption (DLA)
systems in the spectra of high-redshift quasars represent a viable population
of progenitors of normal disk galaxies. They appear to contain a substantial
fraction of the baryons known to exist in normal galaxies today. Here we report
on the detec... | 9605154v1 |
1996-10-18 | The absorbers towards Q0836+113 | We have performed RIJHK_S imaging of the field around the z=2.67 quasar
Q0836+113, which presents several metal line and a damped Ly\alpha absorption
systems in its spectrum. The images reveal the existence of a red K_S=18.9
object \approx 11 arcsec from the quasar. On the basis of the empirical
relationships between a... | 9610141v1 |
1996-12-13 | The 67 Hz Feature in the Black Hole Candidate GRS 1915+105 as a Possible ``Diskoseismic'' Mode | The Rossi X-ray Timing Explorer (RXTE) has made feasible for the first time
the search for high-frequency (~ 100 Hz) periodic features in black hole
candidate (BHC) systems. Such a feature, with a 67 Hz frequency, recently has
been discovered in the BHC GRS 1915+105 (Morgan, Remillard, & Greiner). This
feature is weak ... | 9612142v2 |
1997-01-15 | Gravitational Lensing of Quasars by Spiral Galaxies | Gravitational lensing by a spiral galaxy occurs when the line-of-sight to a
background quasar passes within a few kpc from the center of the galactic disk.
Since galactic disks are rich in neutral hydrogen, the quasar spectrum will
likely be marked by a damped Lyman-alpha absorption trough at the lens
redshift. Therefo... | 9701100v1 |
1997-02-27 | Interacting Hot Dark Matter | We discuss the viability of a light particle ($\sim 30$ eV neutrino) with
strong self-interactions as a dark matter candidate. The interaction prevents
the neutrinos from free-streaming during the radiation dominated regime so
galaxy sized density perturbations can survive. Smaller scale perturbations are
damped due to... | 9702236v1 |
1997-05-20 | Detection of the First Star Clusters With NGST | We calculate the observable signatures of the first generation of stars at
high redshift (5<z<100). To determine the cosmic star-formation history, we use
an extension of the Press-Schechter formalism for Cold Dark Matter (CDM)
cosmologies that incorporates gas pressure. We calibrate the fraction of gas
converted into ... | 9705144v1 |
1997-09-04 | Cosmic-Ray Momentum Diffusion In Magnetosonic Versus Alfvenic Turbulent Field | Energetic particle transport in a finite amplitude magnetosonic and Alfvenic
turbulence is considered using Monte Carlo particle simulations, which involve
an integration of particle equation of motion. We show that in a low-Betha
plasma cosmic ray can be the most important damping process for magnetosonic
waves. Assum... | 9709039v2 |
1997-09-12 | Baryonic Features in the Matter Transfer Function | We provide scaling relations and fitting formulae for adiabatic cold dark
matter cosmologies that account for all baryon effects in the matter transfer
function to better than 10% in the large-scale structure regime. They are based
upon a physically well-motivated separation of the effects of acoustic
oscillations, Com... | 9709112v1 |
1997-09-23 | Nonlinear spherical Alfven waves | We present an one-dimensional numerical study of Alfven waves propagating
along a radial magnetic field. Neglecting losses, any spherical Alfven wave, no
matter how small its initial amplitude is, becomes nonlinear at sufficiently
large radii. From previous simulations of Alfven waves in plane parallel
atmospheres we d... | 9709222v1 |
1997-12-10 | Effects of Disks on Gravitational Lensing by Spiral Galaxies | Gravitational lensing of a quasar by a spiral galaxy should often be
accompanied by damped Lyman-alpha absorption and dust extinction due to the
intervening gaseous disk. In nearly edge-on configurations, the surface mass
density of the gas and stars in the disk could by itself split the quasar image
and contribute sig... | 9712138v1 |
1998-03-20 | HI 21cm absoprtion in two low redshift damped Ly-alpha systems | We report the discovery of two low redshift HI 21cm absorbers, one at z =
0.2212 towards the z_{em} = 0.630 quasar OI 363 (B0738+313), and the other at z
= 0.3127 towards PKS B1127-145 (z_{em} = 1.187). Both were found during a
survey of MgII selected systems at redshifts 0.2 < z < 1 using the new UHF-high
system at th... | 9803243v1 |
1998-05-08 | Infrared emission-line galaxies associated with damped Lyman-alpha and strong metal absorber redshifts | Eighteen candidates for emission line galaxies were discovered in a
narrow-band infrared survey that targeted the redshifts of damped Lyman-alpha
or metal lines in the spectra of quasars. The presence of emission lines is
inferred from the photometric magnitudes in narrow and broad band interference
filters, correspond... | 9805103v1 |
1998-05-12 | Resonant Thickening of Disks by Small Satellite Galaxies | We study the vertical heating and thickening of galaxy disks due to accretion
of small satellites. Our simulations are restricted to axial symmetry, which
largely eliminates numerical evolution of the target galaxy but requires the
trajectory of the satellite to be along the symmetry axis of the target. We
find that di... | 9805145v1 |
1998-09-14 | Collisionless Relaxation of Stellar Systems | The objective of the work summarised here has been to exploit and extend
ideas from plasma physics and accelerator dynamics to formulate a unified
description of collisionless relaxation that views violent relaxation, Landau
damping, and phase mixing as (manifestations of) a single phenomenon. This
approach embraces th... | 9809178v1 |
1998-09-30 | Discovery of a z=0.808 damped Lyman-alpha system candidate in a UV selected quasar spectrum | We present the observation of a new intermediate redshift damped Lyman-alpha
absorption system candidate, discovered in the course of a spectroscopic
follow-up for identifying the sources detected in a 150 A wide bandpass
UV-imaging survey at 2000 A. The system displays very strong MgII and FeII
lines and a high FeII/M... | 9809402v1 |
1998-10-02 | Gravity-modes in ZZ Ceti Stars. II. Effects of Turbulent Dissipation | We investigate dynamical interactions between turbulent convection and g-mode
pulsations in ZZ Ceti variables (DAVs). Since our understanding of turbulence
is rudimentary, we are compelled to settle for order of magnitude results. A
key feature of these interactions is that convective response times are much
shorter th... | 9810038v1 |
1999-02-11 | Element Abundances at High Redshifts | I review measurements of element abundances in different components of the
high redshift universe, including the Lyman alpha forest, damped Lyman alpha
systems, and Lyman break galaxies. Although progress is being made in all three
areas, recent work has also produced some surprises and shown that established
ideas abo... | 9902173v1 |
1999-03-09 | Numerical simulation of prominence oscillations | We present numerical simulations, obtained with the Versatile Advection Code,
of the oscillations of an inverse polarity prominence. The internal prominence
equilibrium, the surrounding corona and the inert photosphere are well
represented. Gravity and thermodynamics are not taken into account, but it is
argued that th... | 9903128v1 |
1999-03-26 | Nature and evolution of Damped Lyman alpha systems | The main properties of Damped Lyman alpha (DLA) systems are briefly reviewed
with the aim of studying the nature and evolution of the galaxies associated
with this class of QSO absorbers. Candidate DLA galaxies identified at z </= 1
in the fields of background QSOs show a variety of morphological types without
a predom... | 9903406v1 |
1999-11-09 | Viscous Boundary Layer Damping of R-Modes in Neutron Stars | Recent work has raised the exciting possibility that r-modes (Rossby waves)
in rotating neutron star cores might be strong gravitational wave sources. We
estimate the effect of a solid crust on their viscous damping rate and show
that the dissipation rate in the viscous boundary layer between the oscillating
fluid and ... | 9911155v1 |
1999-11-30 | The formation and evolution of supermassive black holes and their host galaxies | We discuss constraints on the assembly history of supermassive black holes
from the observed remnant black holes in nearby galaxies and from the emission
caused by accretion onto these black holes. We also summarize the results of a
specific model for the evolution of galaxies and their central black holes
which traces... | 9911514v1 |
1999-12-06 | The Metallicity evolution of Damped Lyman-alpha systems | We have collected data for 69 Damped Lyman-alpha (DLA) systems, to
investigate the chemical evolution of galaxies in the redshift interval 0.0 < z
< 4.4. In doing that, we have adopted the most general approach used so far to
correct for dust depletion. The best solution, obtained through chi^2
minimization, gives as o... | 9912112v2 |
1999-12-22 | Alfvenic Heating of Protostellar Accretion Disks | We investigate the effects of heating generated by damping of Alfven waves on
protostellar accretion disks. Two mechanisms of damping are investigated,
nonlinear and turbulent, which were previously studied in stellar winds
(Jatenco-Pereira & Opher 1989a, b). For the nominal values studied, f=delta
v/v_{A}=0.002 and F=... | 9912478v1 |
2000-01-18 | Metallicity in damped Lyman-alpha systems: evolution or bias? | Assuming that damped Lyman-alpha(DLA) systems are galactic discs, we
calculate the corresponding evolution of metal abundances. We use detailed
multi-zone models of galactic chemical evolution (reproducing successfully the
observed properties of disc galaxies) and appropriate statistics (including
geometrical propabili... | 0001313v1 |
2000-02-24 | Optical Counterparts to Damped Lyman Alpha Systems | Previously we have shown (Maller et al, 1998) that the kinematics of Damped
Lyman Alpha Systems (DLAS) as measured by Prochaska and Wolfe (1998) can be
reproduced in a multiple disk model (MDM) if the gaseous disks are of
sufficient radial extent. Here we discuss this model's predictions for the
relationship between DL... | 0002452v1 |
2000-02-24 | Damped Ly-alpha Systems in Semi-Analytic Models: Sensitivity to dynamics, disk properties, and cosmology | Previously we have shown that it is possible to account for the kinematic
properties of damped Lyman alpha systems (DLAS) in the context of semi-analytic
models. In these models, hierarchical structure formation is approximated by
constructing a merger tree for each dark matter halo. A natural consequence is
that every... | 0002454v1 |
2000-07-31 | UVES observations of QSO 0000-2620: Molecular hydrogen abundance in the damped Ly-alpha system at z_abs = 3.3901 | We have discovered molecular hydrogen in a fourth quasar damped Ly-alpha
system (hereafter DLA). The UVES spectrograph on the 8.2m ESO Kueyen telescope
has allowed the detection of H2 in gas with low metallicity, Z/Z_solar ~=
10^{-2}, and high neutral hydrogen column density, N(HI) ~= 2.6*10^{21}
cm^{-2}, at redshift z... | 0007472v1 |
2000-08-11 | The Evolution and Space Density of Damped Lyman-alpha Galaxies | The results of a new spectroscopic survey of 66 $z \simgt 4$ quasars for
Damped Lyman-alpha absorption systems are presented. The search led to the
discovery of 30 new DLA candidates which are analysed in order to compute the
comoving mass density of neutral gas in a non-zero lambda Universe. The
possible sources of un... | 0008172v1 |
2000-09-06 | Damped Lyman-Alpha Galaxies | Some results from an imaging program to identify low-redshift (0.09<z<1.63)
damped Lyman-alpha (DLA) galaxies are presented. The standard paradigm that was
widely accepted a decade ago, that DLA galaxies are the progenitors of luminous
disk galaxies, is now being seriously challenged. The indisputable conclusion
from i... | 0009096v2 |
2000-09-07 | On ionisation effects and abundance ratios in damped Lyman-alpha systems | The similarity between observed velocity structures of Al III and singly
ionised species in damped Lyman-alpha systems (DLAs) suggests the presence of
ionised gas in the regions where most metal absorption lines are formed.
To explore the possible implications of ionisation effects we construct a
simplified two-regio... | 0009107v1 |
2000-10-20 | An Imaging and Spectroscopic Study of the z=3.38639 Damped Lyman Alpha System in Q0201+1120: Clues to Star Formation Rate at High Redshift | We present the results of a series of imaging and spectroscopic observations
aimed at identifying and studying the galaxy responsible for the z = 3.38639
damped lya system in the z = 3.61 QSO Q0201+1120. We find that the DLA is part
of a concentration of matter which includes at least four galaxies (probably
many more)... | 0010427v1 |
2000-10-31 | Non-Linear Evolution of the r-Modes in Neutron Stars | The evolution of a neutron-star r-mode driven unstable by gravitational
radiation (GR) is studied here using numerical solutions of the full non-linear
fluid equations. The amplitude of the mode grows to order unity before strong
shocks develop which quickly damp the mode. In this simulation the star loses
about 40% of... | 0010653v2 |
2000-11-07 | Damped Lyman-alpha absorption from a nearby Low Surface Brightness galaxy | Ground-based & HST images of the nearby galaxy SBS 1543+593 (z=0.009) show it
to be a Low Surface Brightness (LSB) galaxy with a central surface brightness
of mu_B(0)=23.2 mag/arcsec-2 and scale length 0.9 h-1 kpc, values typical for
the local LSB galaxy population. The galaxy lies directly in front of the QSO
HS 1543+... | 0011134v1 |
2000-11-25 | Molecular hydrogen abundance in the dust-free damped Ly-alpha galaxy at z = 3.4 | New results from the search for H2 absorption in the damped Ly-alpha galaxy
at redshift z = 3.4 toward QSO 0000-2620 (z_em = 4.1) are reported. The
high-resolution (lambda/Delta lambda = 48,000) spectra of Q0000-2620 were
obtained using the Ultraviolet - Visual Echelle Spectrograph (UVES) on the 8.2m
ESO Kueyen telesco... | 0011470v1 |
2000-11-25 | The Metallicity Evolution of Damped Lyman-alpha Systems | According to Pei, Fall & Hauser (1999), the global metallicity evolution of
the Universe can be represented by the ratio of the total metal content to the
total gas content measured in Damped Lyman-alpha (DLA) systems (the ``column
density weighted metallicity'' `a la Pettini). To minimize dust obscuration
effects, a D... | 0011473v1 |
2000-12-04 | ATCA search for 21 cm emission from a candidate damped Ly-$α$ absorber at z = 0.101 | We report a deep search for 21 cm emission/absorption from the $z \sim 0.101$
candidate damped Lyman-$\alpha$ system towards PKS 0439-433, using the
Australia Telescope Compact Array (ATCA). The spectrum shows a weak absorption
feature --- at the $3.3 \sigma$ level --- which yields a lower limit of 730 K
on the spin te... | 0012079v1 |
2000-12-05 | Lost and Found: The Damped Lyman Alpha Absorbers in the QSO OI 363 | The galaxy giving rise to the damped Ly$\alpha$ absorbing system in the QSO
OI 363 with z=0.221 has been found. A galaxy which is probably associated with
the second DLA in this same QSO at z=0.0912 has also been found. Neither galaxy
is very luminous, and neither galaxy shows signs of extensive current star
formation,... | 0012109v1 |
2001-01-05 | Constraints from the damping tail | The detection of anisotropy in the cosmic microwave background on arcminute
scales by the Cosmic Background Imager (CBI) provides us with our first
measurement of the damping tail and closes one chapter in the CMB story. We now
have experimental verification for all of the features in the temperature
anisotropy spectru... | 0101086v2 |
2001-01-10 | Magnetized gravitational waves | We investigate the influence of cosmic magnetic fields on gravitational wave
perturbations, and find exact solutions on large scales. We show that a
large-scale magnetic field can generate large-scale non-decaying gravitational
waves. In the general case where gravitational waves are generated by other
mechanisms, a la... | 0101151v3 |
2001-01-15 | Damping time and stability of density fermion perturbations in the expanding universe | The classic problem of the growth of density perturbations in an expanding
Newtonian universe is revisited following the work of Bisnovatyi-Kogan and
Zel'dovich. We propose a more general analytical approach: a system of free
particles satisfying semi-degenerate Fermi-Dirac statistics on the background
of an exact expa... | 0101222v1 |
2001-02-09 | A new deuterium abundance measurement from a damped Ly-alpha system at z_abs = 3.025 | We present the first D/H measurement in a damped Ly-alpha system at z_abs =
3.025 towards QSO 0347-3819 obtained from the UVES-VLT spectra. The DLA
absorber has a metallicity of [Zn/H] = -1.25 and a relatively simple velocity
structure, with two dominating components detected in several metal lines. The
hydrogen Lyman ... | 0102162v1 |
2001-03-19 | Fluctuations in the Cosmic Microwave Background I: Form Factors and their Calculation in Synchronous Gauge | It is shown that the fluctuation in the temperature of the cosmic microwave
background in any direction may be evaluated as an integral involving scalar
and dipole form factors, which incorporate all relevant information about
acoustic oscillations before the time of last scattering. A companion paper
gives asymptotic ... | 0103279v2 |
2001-04-24 | 21-cm H I emission from the Damped Lyman-alpha absorber SBS 1543+593 | We detect 21-cm emission from the Low Surface Brightness (LSB) galaxy SBS
1543+593, which gives rise to a Damped Lyman-alpha (DLA) absorption line in the
spectrum of the background QSO HS 1543+5921 (z=0.807). We obtain an accurate
measure of the velocity of the H I gas in the LSB galaxy, v=2868 km/s, and
derive a mass ... | 0104396v1 |
2001-05-23 | Mapping the Dark Matter through the CMB Damping Tail | The lensing of CMB photons by intervening large-scale structure leaves a
characteristic imprint on its arcminute-scale anisotropy that can be used to
map the dark matter distribution in projection on degree scales or ~100 Mpc/h
comoving. We introduce a new algorithm for mass reconstruction which optimally
utilizes info... | 0105424v2 |
2001-06-30 | Chandra Detection of X-ray Absorption Associated with a Damped Lyman Alpha System | We have observed three quasars, PKS 1127-145, Q 1331+171 and Q0054+144, with
the ACIS-S aboard the Chandra X-ray Observatory, in order to measure soft X-ray
absorption associated with intervening 21-cm and damped Ly$\alpha$ absorbers.
For PKS 1127-145, we detect absorption which, if associated with an intervening
z_{ab... | 0107003v1 |
2001-08-08 | The Evolution of Neutral Gas in the Universe as Traced by Damped Lyman Alpha Systems | We discuss our recent results on the statistical properties of damped Lyman
alpha systems (DLAs) at low redshift (z<1.65) (Rao & Turnshek 2000). Contrary
to expectations, we found that the cosmological neutral gas mass density as
traced by DLAs, $\Omega_{DLA}$, does not evolve from redshifts $z \approx 4$ to
$z \approx... | 0108141v1 |
2001-08-08 | Properties of Low-Redshift Damped Lyman Alpha Galaxies | Images of five QSO fields containing six damped Lyman alpha (DLA) systems at
redshifts 0.09<z<0.53 are presented. Identifications for the DLA galaxies
giving rise to the DLA systems are made. The observed and modeled
characteristics of the DLA galaxies are discussed. The DLA galaxies have impact
parameters ranging from... | 0108146v1 |
2001-08-29 | The impact of dust and ionization effects on abundance measurements of Damped Ly alpha systems | Studies of elemental abundances are a fundamental tool for unveiling the
nature of the high-redshift (proto-)galaxies associated to Damped Ly alpha
systems (DLAs). The present contribution analyses the impact of dust and
ionization effects on abundance measurements in DLAs. The behaviour of the
alpha/Fe abundance ratio... | 0108466v2 |
2001-08-30 | Reconciling Damped Ly-alpha Statistics and 21cm Studies at z=0 | Blind 21cm surveys in the local universe have shown that the local HI mass
density, Omega_HI, is dominated by luminous, high surface brightness, spiral
galaxies. On the other hand, surveys for host galaxies of damped Ly-alpha
systems have not always been successful in finding bright spiral galaxies. From
an analysis of... | 0108498v1 |
2001-09-03 | GRB 000301C: a possible short/intermediate duration burst connected to a DLA system | We discuss two main aspects of the GRB 000301C afterglow (Fynbo et al. 2000,
Jensen et al. 2000); its short duration and its possible connection with a
Damped Ly-alpha Absorber (DLA). GRB 000301C falls in the short class of bursts,
though it is consistent with belonging to the proposed intermediate class or
the extreme... | 0109020v1 |
2001-10-16 | The UCSD HIRES/KeckI Damped Lya Abundance Database: I. The Data | We present new chemical abundance measurements of 16 damped Lya systems at
z>1.5 and update our previous abundance analyses. The entire database presented
here was derived from HIRES observations on the Keck I telescope, reduced with
the same software package, and analysed with identical techniques. Altogether,
we pres... | 0110350v1 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.