publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
|---|---|---|---|
2001-10-16 | A simple analytical model for the abundance of damped Ly-α absorbers | A simple analytical model for estimating the fraction (\Omega_{gas}) of
matter in gaseous form within the collapsed dark matter (DM) haloes is
presented. The model is developed using (i) the Press-Schechter formalism to
estimate the fraction of baryons in DM haloes, and (ii) the observational
estimates of the star form... | 0110359v2 |
2001-10-16 | Unusual Metal Abundances in a Pair of Damped Lyman Alpha Systems at z~2 | We present high resolution spectroscopic observations of two neighbouring
damped Lya systems (DLAs) along the same line of sight towards B2314-409. Due
to their separation (v ~ 2000 km/s) and the high spectral resolution of the
data, it is possible to fit not only the weak metal transitions, but also the
separate HI ab... | 0110391v2 |
2001-12-18 | NICMOS Snapshot Survey of Damped Lyman Alpha Quasars | We image 19 quasars with 22 damped Lyman alpha (DLA) systems using the F160W
filter and the Near-Infrared Camera and Multiobject Spectrograph aboard the
Hubble Space Telescope, in both direct and coronagraphic modes. We reach 5
sigma detection limits of ~H=22 in the majority of our images. We compare our
observations t... | 0112416v1 |
2002-02-19 | Saturation of the R-mode Instability | Rossby waves (r-modes) in rapidly rotating neutron stars are unstable because
of the emission of gravitational radiation. We study saturation of this
instability by nonlinear transfer of energy to stellar "inertial" oscillation
modes. We present detailed calculations of stellar inertial modes in the WKB
limit, their li... | 0202345v2 |
2002-04-05 | HI 21cm imaging of a nearby Damped Lyman-alpha system | We present Giant Metrewave Radio Telescope (GMRT) HI 21cm emission images of
the z=0.009 damped Lyman-alpha (DLA) absorber towards the QSO HS 1543+5921. The
DLA has been earlier identified as a low surface brightness galaxy SBS 1543+593
at an impact parameter of ~ 400 pc to the QSO line of sight. The extremely low
reds... | 0204094v1 |
2002-08-26 | Damped Lyman alpha systems and disk galaxies: number density, column density distribution and gas density | We present a comparison between the observed properties of damped Lyman alpha
systems (DLAs) and the predictions of simple models for the evolution of
present day disk galaxies, including both low and high surface brightness
galaxies. We focus in particular on the number density, column density
distribution and gas den... | 0208457v1 |
2002-09-10 | A search for molecules in damped Lyman-alpha absorbers occulting millimetre-loud quasars | We have used the SEST 15-metre and Onsala 20-metre telescopes to perform deep
(r.m.s. >~ 30 mJy) integrations of various molecular rotational transitions
towards damped Lyman-alpha absorption systems (DLAs) known to occult
millimetre-loud quasars. We have observed 6 new systems and improved the
existing limits for 11 t... | 0209175v1 |
2002-11-13 | Strong Absorption-line Systems at Low Redshift: MgII and Damped Lyman Alpha | We detail a powerful indirect method for the study of damped Lyman alpha
systems (DLAs) at low redshift. We increase the probability of finding a
low-redshift DLA to nearly 50% by targeting QSOs that are known to have strong
low-redshift MgII and FeII absorption lines in their spectra. We are using
Sloan Digital Sky Su... | 0211295v1 |
2002-11-22 | On the Origin of Nitrogen in Damped Ly-alpha Systems | Recent measurements of nitrogen and alpha elements in over 20 damped Ly-alpha
systems (DLA) are compared with similar measurements for numerous emission line
objects and stars. It is found that the DLA distribution in the N/alpha-alpha/H
plane is bimodal, where most sample DLAs fall along the N/alpha plateau defined
at... | 0211512v1 |
2002-12-16 | Fragmentation and Collapse of Turbulent Molecular Clouds | We performed simulations of self-gravitating hydrodynamic turbulence to model
the formation of filaments, clumps and cores in molecular clouds. We find that
when the mass on the initial computational grid is comparable to the Jeans
mass, turbulent pressure is able to prevent gravitational collapse. When the
turbulence ... | 0212359v1 |
2003-02-20 | One-Armed Spiral Instability in Differentially Rotating Stars | We investigate the dynamical instability of the one-armed spiral m=1 mode in
differentially rotating stars by means of 3+1 hydrodynamical simulations in
Newtonian gravitation. We find that both a soft equation of state and a high
degree of differential rotation in the equilibrium star are necessary to excite
a dynamica... | 0302436v2 |
2003-03-21 | Molecular Hydrogen in Damped Ly-alpha Systems: Spatial Distribution | To interpret H_2 quasar absorption line observations in Damped Ly-alpha
clouds (DLAs), we model the H_2 spatial distribution within a DLA. Based on
numerical simulations of disk structures with parameters similar to those
derived for such absorbers, we calculate the H_2 distribution as a function of
ultraviolet backgro... | 0303495v1 |
2003-05-01 | Scalar perturbation spectra from warm inflation | We present a numerical integration of the cosmological scalar perturbation
equations in warm inflation. The initial conditions are provided by a
discussion of the thermal fluctuations of an inflaton field and thermal
radiation using a combination of thermal field theory and thermodynamics. The
perturbation equations in... | 0305015v3 |
2003-05-02 | The Critical Rotation of Strange Stars and Rapidly Rotating Pulsars | We utilize the bulk viscosity of interacting strange quark matter to
reevaluate the damping time scale. The presence of medium effect of bulk
viscosity leads to a stronger damping of r-modes, which can be over an order of
magnitude for realistic parameters. We find that the r-mode instability window
is narrowed due to ... | 0305034v1 |
2003-06-02 | Chemical Evolution of Damped Lyman Alpha Systems | By means of detailed chemical evolution models for galaxies of different
morphological types (i.e. spirals, irregular/starburst galaxies and
ellipticals) we study the nature of Damped Lyman-Alpha systems. Our concern is
to infer which systems represent likely candidates for the DLA population and
which do not. By focus... | 0306037v1 |
2003-07-01 | Clustering of galaxies at z=3 around the probable Damped Ly-alpha absorber towards QSO APM 08279+5255 | [Abridged] We present results on the clustering og Lyman break galaxies
(LBGs) around a probable damped Ly-alpha absorption (DLA) line cloud at
z_DLA=2.974 from deep UBVI images of the field containing the quasar APM
08279+5255 (z=3.91). The large area covered by our images, 0.31 deg^2 or 40x40
Mpc co-moving at z=3, an... | 0307033v1 |
2003-08-11 | Imaging and spectroscopy of galaxies associated with two z~0.7 damped Lyman-alpha absorption systems | We have identified galaxies near two quasars which are at the redshift of
damped Lyman-alpha (DLA) systems in the UV spectra of the quasars. Both
galaxies are actively forming stars. One galaxy has a luminosity close to the
break in the local galaxy luminosity function, L*, the other is significantly
fainter than L* an... | 0308193v1 |
2003-09-03 | The Thermal Stability of Mass-Loaded Flows | We present a linear stability analysis of a flow undergoing
conductively-driven mass-loading from embedded clouds. We find that
mass-loading damps isobaric and isentropic perturbations, and in this regard is
similar to the effect of thermal conduction, but is much more pronounced where
many embedded clumps exist. The s... | 0309086v1 |
2003-09-22 | Hierarchical Structure Formation and Chemical Evolution of Damped Ly alpha Systems | We present a model for chemical evolution of damped Ly alpha systems
considering production of metals by SNe II and infall associated with
hierarchical structure formation. The growth of metallicity in these systems is
a reflection of the competition between astration and infall. The apparent late
turn-on of these syst... | 0309600v1 |
2003-09-29 | A common trend in the chemical evolution of Local Group dwarf spheroidals and Damped Ly-alpha systems | We compare chemical abundances of Local Group dwarf spheroidals, obtained
from recent UVES/VLT observations, and of high redshift Damped Lyman alpha
systems (DLAs), corrected for dust effects. We focus, in particular, on the
abundance ratio between alpha-capture elements and iron, alpha/Fe, a well known
indicator of ch... | 0309765v1 |
2003-10-15 | H_2-bearing damped Lyman-alpha systems as tracers of cosmological chemical evolution | The chemical abundances in damped Lyman-alpha systems (DLAs) show more than 2
orders of magnitude variation at a given epoch, possibly because DLAs arise in
a wide variety of host galaxies. This could significantly bias estimates of
chemical evolution. We explore the possibility that DLAs in which H_2
absorption is det... | 0310409v2 |
2004-01-21 | Constraints on Early Nucleosynthesis from the Abundance Pattern of a Damped Ly-alpha System at z = 2.626 | We have investigated chemical evolution in the young universe by analysing
the detailed chemical enrichment pattern of a metal-rich galaxy at high
redshift. The recent detection of over 20 elements in the gas-phase of a damped
Lyman-alpha absorber (DLA) at z = 2.626 represents an exciting new avenue for
exploring early... | 0401413v1 |
2004-03-23 | The clustering of galaxies around three damped Ly-alpha absorbers at Redshift Three | [Abridged] We present out results on the cross-correlation of Lyman break
galaxies (LBGs) around three damped \Ly absorbers (DLAs) at redshift three from
deep multi-band MOSAIC images obtained at the KPNO 4m. The large area of the
MOSAIC images, 0.31 $\deg^2$ allows us to probe the clustering of LBGs on
scales up to 20... | 0403544v2 |
2004-03-31 | Cold Neutral Gas in a z=4.2 Damped Lyman-alpha System: The Fuel for Star Formation | We discuss interstellar temperature determinations using the excitation
equilibrium of the ^2P levels of Si II and C II. We show how observations of
the ^2P_3/2 fine structure levels of Si II and C II (which have significantly
different excitation energies, corresponding to ~413 and 92 K, respectively)
can be used to l... | 0404005v2 |
2004-04-27 | Molecular fraction limits in damped Lyman-alpha absorption systems | We have used the Green Bank Telescope (GBT) and Berkeley-Illinois-Maryland
Association (BIMA) array to search for redshifted millimetre absorption in a
sample of damped Lyman-alpha absorption systems (DLAs). This brings the number
of published systems searched from 18 to 30. In 17 cases we reach $3\sigma$
limits of $\t... | 0404516v1 |
2004-08-07 | Metals and Dust in Intermediate-redshift Damped Ly-alpha Galaxies | We report spectroscopic observations with the Multiple Mirror Telescope for
11 damped Lyman-alpha absorbers (DLAs) or strong DLA candidates at 0.1 < z <
1.5, including several absorbers discovered in the Sloan Digital Sky Survey. In
particular, we have measured absorption lines of Zn II, Cr II, Ni II, Fe II, Mn
II, Ti ... | 0408139v1 |
2004-09-22 | On Detecting the X-ray Silhouette of a Damped Lyman alpha System | We explore the possibility of resolving an image of a damped Lyman alpha
(DLA) system in absorption against an extended, diffuse background X-ray
source. Typical columns of neutral hydrogen in DLAs are high enough to block
out up to ~30% of the soft X-ray flux at an observed photon energy of 0.5 keV,
and we find that ~... | 0409516v2 |
2004-10-11 | Is the solar corona nonmodally self-heated? | Recently it was pointed out that nonmodally (transiently and/or
adiabatically) pre-amplified waves in shear flows, undergoing subsequent
viscous damping, can ultimately heat the ambient flow. The key ingredient of
this process is the ability of waves to grow, by extracting energy from the
spatially inhomogeneous mean f... | 0410279v1 |
2004-10-23 | Extended Neutral Gas Around z ~ 0.5 Galaxies: Properties of Damped Lya Absorbing Galaxies | I review current results from searching for galaxies giving rise to damped
Lya absorbers (DLAs) at z<1. Using 14 confirmed DLA galaxies, I further show
that intermediate-redshift galaxies possess large HI envelope out to 24-30
h^{-1} kpc radius. The photometric and spectral properties of these galaxies
confirm that DLA... | 0410558v1 |
2004-11-25 | Survey for Galaxies Associated with z~3 Damped Lyman alpha Systems I: Spectroscopic Calibration of u'BVRI Photometric Selection | We present a survey for z~3 Lyman break galaxies (LBGs) associated with
damped Lyman alpha systems (DLAs) with the primary purpose of determining the
DLA-LBG cross-correlation. This paper describes the acquisition and analysis of
imaging and spectroscopic data of 9 quasar fields having 11 known z~3 DLAs
covering an are... | 0411681v1 |
2005-01-06 | Observations of Solar Flare Doppler Shift Oscillations with the Bragg Crystal Spectrometer on Yohkoh | Oscillations in solar coronal loops appear to be a common phenomenon.
Transverse and longitudinal oscillations have been observed with both the
Transition Region and Coronal Explorer and Extreme Ultraviolet Imaging
Telescope imaging experiments. Damped Doppler shift oscillations have been
observed in emission lines fro... | 0501093v1 |
2005-03-09 | Abundances in Damped Ly-alpha Galaxies | Damped Ly_alpha galaxies provide a sample of young galaxies where chemical
abundances can be derived throughout the whole universe with an accuracy
comparable to that for the local universe. Despite a large spread in redshift,
HI column density and metallicity, DLA galaxies show a remarkable uniformity in
the elemental... | 0503214v1 |
2005-03-10 | Pulsar: repeatable Lagrangian singularity | In general, the interior of radially symmetric self-gravitating sphere is
considered in terms of hydrostatic equilibrium (HSE). This approach implies the
possibility of the static being of a body. Such a static state is assumed to be
the result of asymptotic damping of the process of formation. It is shown here
that th... | 0503231v2 |
2005-03-14 | Quasi-Periodic Oscillations in Relativistic Tori | Motivated by recent interesting work on p-mode oscillations in axisymmetric
hydrodynamic black-hole tori by Rezzolla, Zanotti, and collaborators, I explore
the robustness of these oscillations by means of two and three-dimensional
relativistic hydrodynamic and MHD simulations. The primary purpose of this
investigation ... | 0503305v1 |
2005-03-17 | The first observed stellar X-ray flare oscillation: Constraints on the flare loop length and the magnetic field | We present the first X-ray observation of an oscillation during a stellar
flare. The flare occurred on the active M-type dwarf AT Mic and was observed
with XMM-Newton. The soft X-ray light curve (0.2-12 keV) is investigated with
wavelet analysis. The flare's extended, flat peak shows clear evidence for a
damped oscilla... | 0503384v1 |
2005-04-25 | Emission-line spectroscopy of Damped Lyman Alpha Systems: The case of SBS 1543+593/HS 1543+5921 | We report HST/STIS spectroscopy and Gemini/GMOS-N imaging of the Damped Lyman
Alpha (DLA) system toward HS 1543+5921 caused by the host star-forming galaxy
(SFG) SBS 1543+593. The Gemini image shows new morphological details of this
well resolved DLA galaxy. In combination with previous optical spectra, the new
UV spec... | 0504556v1 |
2005-04-27 | Self-consistent radiative effect on relativistic electromagnetic particle acceleration | We study the radiation damping effect on the relativistic acceleration of
electron-positron plasmas with two-and-half-dimensional particle-in-cell (PIC)
simulation. Particles are accelerated by Poynting flux via the diamagnetic
relativistic pulse accelerator (DRPA), and decelerated by the self-consistently
solved radia... | 0504612v2 |
2005-07-13 | UHE neutrino damping in a thermal gas of relic neutrinos | We present a calculation of the damping of an ultra-energetic (UHE) cosmic
neutrino travelling through the thermal gas of relic neutrinos, using the
formalism of finite-temperature field theory. From the self-energy diagram due
to Z exchange, we obtain the annihilation cross section for an UHE neutrino
interacting with... | 0507333v2 |
2005-07-25 | Post-inflation increase of the cosmological tensor-to-scalar perturbation ratio | We investigate the possibility that the amplitude of scalar density
perturbations may be damped after inflation. This would imply that CMB
anisotropies do not uniquely fix the amplitude of the perturbations generated
during inflation and that the present tensor-to-scalar ratio might be larger
than produced in inflation... | 0507573v3 |
2005-09-08 | Possible Detection of Lyman-alpha Fluorescence from a Damped Lyman Alpha system at Redshift z=2.8 | We have detected Lyman-alpha emission from a damped Lyman-alpha system (DLA)
that lies near the bright quasar HS1549+1919. The DLA has the same redshift as
HS1549+1919 and was discovered in the spectrum of a faint QSO that lies 49"
away (380 proper kpc). The emission line's luminosity, double-peaked profile,
and small ... | 0509229v1 |
2005-11-17 | Measurement of the Spatial Cross-Correlation Function of Damped Lyman Alpha Systems and Lyman Break Galaxies | We present the first spectroscopic measurement of the spatial
cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman
break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with
11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5
photometrically selected z > 2 LBGs.... | 0511509v1 |
2006-01-29 | Relative abundance pattern along the profile of high redshift Damped Lyman-alpha systems | We investigated abundance ratios along the profiles of six high-redshift
Damped Lyman-alpha systems, three of them associated with H2 absorption, and
derived optical depths in each velocity pixel. The variations of the pixel
abundance ratios were found to be remarkably small and usually smaller than a
factor of two wit... | 0601664v1 |
2006-02-14 | VLT/UVES constraints on the carbon isotope ratio 12C/13C at z=1.15 toward the quasar HE 0515-4414 | We analyzed the CI lines associated with the damped Ly-alpha system observed
at zabs = 1.15 in the spectrum of HE 0515-4414 to derive the 12C/13C ratio. The
spectrum was obtained by means of the UV-Visual Echelle Spectrograph (UVES) at
the ESO Very Large Telescope (VLT). The obtained lower limit 12C/13C > 80
(2sigma C.... | 0602303v1 |
2006-06-08 | The detectability of HI 21-cm absorption in damped Lyman-alpha systems | In this paper we investigate the possible reasons why HI 21-cm absorption in
damped Lyman-alpha systems (DLAs) has only been detected at low redshift... We
suggest that the lack of 21-cm absorption detections at high redshift arises
from the fact that these DLAs are at similar angular diameter distances to the
backgrou... | 0606180v1 |
2006-07-15 | Damping and excitation variations of the solar acoustic modes using LOWL observations | We have used observations made with the helioseismic instrument LOWL
collected over $\sim$ 6 years to carry out an independent study of the
variations of the p-mode damping and excitation rates with solar activity. We
observe significant variations in the mode height, mode width and mode velocity
power over a wide rang... | 0607346v1 |
2006-09-01 | A line profile analysis of the pulsating red giant star epsilon Ophiuchi (G9.5III) | So far, solar-like oscillations have been studied using radial velocity
and/or light curve variations, which reveal frequencies of the oscillation
modes. Line-profile variations, however, are also a valuable diagnostic to
characterise radial and non-radial oscillations, including frequencies,
amplitudes, the spherical ... | 0609043v1 |
2006-10-11 | Determining the neutron star equation of state using the narrow-band gravitational wave detector Schenberg | We briefly review the properties of quasi-normal modes of neutron stars and
black holes. We analyse the consequences of a possible detection of such modes
via the gravitational waves associated with them, especially addressing our
study to the Brazilian spherical antenna, on which a possible detection would
occur at 3.... | 0610335v1 |
2006-12-14 | Three dimensional numerical simulations of acoustic wave field in the upper convection zone of the Sun | Results of numerical 3D simulations of propagation of acoustic waves inside
the Sun are presented. A linear 3D code which utilizes realistic OPAL equation
of state was developed by authors. Modified convectively stable standard solar
model with smoothly joined chromosphere was used as a background model. High
order dis... | 0612364v1 |
2006-12-21 | Accretion of Terrestrial Planets from Oligarchs in a Turbulent Disk | We have investigated the final accretion stage of terrestrial planets from
Mars-mass protoplanets that formed through oligarchic growth in a disk
comparable to the minimum mass solar nebula (MMSN), through N-body simulation
including random torques exerted by disk turbulence due to
Magneto-Rotational-Instability. For t... | 0612619v1 |
2007-01-18 | Models of the Collisional Damping Scenario for Ice Giant Planets and Kuiper Belt Formatio | Chiang et al. 2006, hereafter C06 have recently proposed that the observed
structure of the Kuiper belt could be the result of a dynamical instability of
a system of ~5 primordial ice giant planets in the outer Solar System.
According to this scenario, before the instability occurred, these giants were
growing in a hig... | 0701544v1 |
2007-02-05 | Ion Charge States in the Fast Solar Wind: New Data Analysis and Theoretical Refinements | We present a further investigation into the increased ionization observed in
element charge states in the fast solar wind compared to its coronal hole
source regions. Once ions begin to be perpendicularly heated by ion cyclotron
waves and execute large gyro-orbits, density gradients in the flow can excite
lower hybrid ... | 0702131v1 |
1995-10-11 | Multiple Transitions to Chaos in a Damped Parametrically Forced Pendulum | We study bifurcations associated with stability of the lowest stationary
point (SP) of a damped parametrically forced pendulum by varying $\omega_0$
(the natural frequency of the pendulum) and $A$ (the amplitude of the external
driving force). As $A$ is increased, the SP will restabilize after its
instability, destabil... | 9510003v1 |
1996-03-04 | Period Doublings in Coupled Parametrically Forced Damped Pendulums | We study period doublings in $N$ $(N=2,3,4, \dots)$ coupled parametrically
forced damped pendulums by varying $A$ (the amplitude of the external driving
force) and $c$ (the strength of coupling). With increasing $A$, the stationary
point undergoes multiple period-doubling transitions to chaos. We first
investigate the ... | 9603002v1 |
1996-12-05 | Fractal Basins of Attraction Associated with a Damped Newton's Method | An intriguing and unexpected result for students learning numerical analysis
is that Newton's method, applied to the simple polynomial z^3 - 1 = 0 in the
complex plane, leads to intricately interwoven basins of attraction of the
roots. As an example of an interesting open question that may help to stimulate
student int... | 9612010v1 |
1999-01-28 | Intrinsically localized chaos in discrete nonlinear extended systems | The phenomenon of intrinsic localization in discrete nonlinear extended
systems, i.e. the (generic) existence of discrete breathers, is shown to be not
restricted to periodic solutions but it also extends to more complex (chaotic)
dynamical behaviour. We illustrate this with two different forced and damped
systems exhi... | 9901030v1 |
1995-03-27 | Dynamics of a Strongly Damped Two-Level System: Beyond the DBGA | Dynamics of a dissipative two-level system is studied using quantum
relaxation theory. This calculation for the first time goes beyond the commonly
used dilute bounce gas approximation (DBGA), even for strong damping. The new
results obtained here deviate from the DBGA results at low temperatures,
however, the DBGA for... | 9503133v1 |
1995-05-23 | The phase-dependent linear conductance of a superconducting quantum point contact | The exact expression for the phase-dependent linear conductance of a weakly
damped superconducting quantum point contact is obtained. The calculation is
performed by summing up the complete perturbative series in the coupling
between the electrodes. The failure of any finite order perturbative expansion
in the limit of... | 9505102v1 |
1996-02-27 | Quasiparticle properties of a coupled quantum wire electron-phonon system | We study leading-order many-body effects of longitudinal optical (LO) phonons
on electronic properties of one-dimensional quantum wire systems. We calculate
the quasiparticle properties of a weakly polar one dimensional electron gas in
the presence of both electron-phonon and electron-electron interactions. The
leading... | 9602143v1 |
1996-02-29 | Dynamical response of a one dimensional quantum wire electron system | We provide a self-contained theoretical analysis of the dynamical response of
a one dimensional electron system, as confined in a semiconductor quantum wire,
within the random phase approximation. We carry out a detailed comparison with
the corresponding two and three dimensional situations, and discuss the
peculiariti... | 9602157v1 |
1996-08-24 | New Universality Class at the Superconductor--Insulator Transition | We study dynamic properties of thin films near the superconductor - insulator
transition. We formulate the problem in a phase representation. The key new
feature of our model is the assumption of a {\it local} ohmic dissipative
mechanism. Coarse graining leads to a Ginzburg-Landau description, with
non-ohmic dynamics f... | 9608115v1 |
1996-10-07 | Supersymmetric Fokker-Planck strict isospectrality | I report a study of the nonstationary one-dimensional Fokker-Planck solutions
by means of the strictly isospectral method of supesymmetric quantum mechanics.
The main conclusion is that this technique can lead to a space-dependent
(modulational) damping of the spatial part of the nonstationary Fokker-Planck
solutions, ... | 9610049v2 |
1997-04-03 | Quasiparticle Many-Body Dynamics of Highly Correlated Electronic Systems | The self-consistent theory of the correlation effects in Highly Correlated
Systems(HCS) is presented. The novel Irreducible Green's Functions(IGF) method
is discused in detail for the Hubbard model and random Hubbard model. The
interpolative solution for the quasiparticle spectrum, which is valid for both
the atomic an... | 9704028v1 |
1997-12-17 | Detecting flux creep in superconducting YBCO thin films via damping of the oscillations of a levitating permanent magnet | The damping of the oscillations of a small permanent magnet (spherical shape,
radius 0.1 mm) levitating between two parallel epitaxial YBCO films is measured
as a function of oscillation amplitude and temperature. At small amplitudes the
dissipation is found to be orders of magnitude lower than in bulk YBCO,
Q-factors ... | 9712199v1 |
1998-02-06 | Spin polaron damping in the spin-fermion model for cuprate superconductors | A self-consistent, spin rotational invariant Green's function procedure has
been developed to calculate the spectral function of carrier excitations in the
spin-fermion model for the CuO2 plane. We start from the mean field description
of a spin polaron in the Mori-Zwanzig projection method. In order to determine
the s... | 9802074v1 |
1998-05-09 | The resonance peak in cuprate superconductors | We pursue the consequences of a theory in which the resonance peak observed
in inelastic neutron scattering (INS) experiments on underdoped and optimally
doped YBa$_2$Cu$_3$O$_{6+x}$ compounds arises from a spin-wave excitation. We
find that it is heavily damped, and thus almost not observable, in the normal
state, but... | 9805107v1 |
1998-05-22 | On the driven Frenkel-Kontorova model: I. Uniform sliding states and dynamical domains of different particle densities | The dynamical behavior of a harmonic chain in a spatially periodic potential
(Frenkel-Kontorova model, discrete sine-Gordon equation) under the influence of
an external force and a velocity proportional damping is investigated. We do
this at zero temperature for long chains in a regime where inertia and damping
as well... | 9805287v1 |
1999-01-29 | Acoustic radiation controls friction: Evidence from a spring-block experiment | Brittle failures of materials and earthquakes generate acoustic/seismic waves
which lead to radiation damping feedbacks that should be introduced in the
dynamical equations of crack motion. We present direct experimental evidence of
the importance of this feedback on the acoustic noise spectrum of
well-controlled sprin... | 9901350v2 |
1999-03-02 | d_{x^2-y^2}-Wave Pairing Fluctuations and Pseudo Spin Gap in Two-Dimensional Electron Systems | Pseudogap phenomena of high-T_c cuprates are examined. In terms of AFM
(antiferromagnetic) and dSC (d_{x^2-y^2}-wave superconducting) auxiliary fields
introduced to integrate out the fermions, the effective action for 2D electron
systems with AFM and dSC fluctuations is considered. By the self-consistent
renormalizatio... | 9903030v2 |
1999-04-19 | Numerical analysis of the dissipative two-state system with the density-matrix Hilbert-space-reduction algorithm | Ground state of the dissipative two-state system is investigated by means of
the Lanczos diagonalization method. We adopted the Hilbert-space-reduction
scheme proposed by Zhang, Jeckelmann and White so as to reduce the overwhelming
reservoir Hilbert space to being tractable in computers. Both the
implementation of the ... | 9904260v1 |
1999-05-02 | Finite Temperature Time-Dependent Effective Theory For The Goldstone Field In A BCS-Type Superfluid | We extend to finite temperature the time-dependent effective theory for the
Goldstone field (the phase of the pair field) $ \theta $ which is appropriate
for a superfluid containing one species of fermions with s-wave interactions,
described by the BCS Lagrangian. We show that, when Landau damping is
neglected, the eff... | 9905008v2 |
1999-06-29 | Simulation of I-V Hysteresis Branches in An Intrinsic Stack of Josephson Junctions in High $T_c$ Superconductors | I-V characteristics of the high T$_c$ superconductor
Bi$_2$Sr$_2$Ca$_1$C$_2$O$_8$ shows a strong hysteresis, producing many
branches. The origin of hysteresis jumps is studied by use of the model of
multi-layered Josephson junctions proposed by one of the authors (T. K.). The
charging effect at superconducting layers p... | 9906422v1 |
1999-07-05 | The interplay between flattening and damping of single particle spectra in strongly correlated Fermi systems | The self-consistent theory of the fermion condensation, a specific phase
transition which results in a rearrangement of the single particle degrees of
freedom in strongly correlated Fermi systems is developed. Beyond the phase
transition point, the single particle spectra are shown to be flat. The
interplay between the... | 9907061v1 |
1999-10-19 | Zener transitions between dissipative Bloch bands. II: Current Response at Finite Temperature | We extend, to include the effects of finite temperature, our earlier study of
the interband dynamics of electrons with Markoffian dephasing under the
influence of uniform static electric fields. We use a simple two-band
tight-binding model and study the electric current response as a function of
field strength and the ... | 9910290v1 |
1999-11-02 | Shifts and widths of collective excitations in trapped Bose gases by the dielectric formalism | We present predictions for the temperature dependent shifts and damping
rates. They are obtained by applying the dielectric formalism to a simple model
of a trapped Bose gas. Within the framework of the model we use lowest order
perturbation theory to determine the first order correction to the results of
Hartree-Fock-... | 9911018v1 |
2000-06-13 | Characteristic features of anharmonic effects in the lattice dynamics of fcc metals | The dispersion in the entire Brillouin zone and the temperature dependence
(right up to the melting temperature) of the anharmonic frequency shift and
phonon damping in a number of fcc metals is investigated on the basis of
microscopic calculations. It is found that the anharmonic effects depend
sharply on the wave vec... | 0006205v1 |
2000-06-20 | Collisional damping of the collective oscillations of a trapped Fermi gas | We consider a Fermi gas confined by a harmonic trapping potential and we
highlight the role of the Fermi-Dirac statistics by studying frequency and
damping of collective oscillations of quadrupole type in the framework of the
quantum Boltzmann equation, in which statistical corrections are taken into
account in the col... | 0006305v2 |
2000-06-21 | Resonances in the dynamics of $φ^4$ kinks perturbed by ac forces | We study the dynamics of $\phi^4$ kinks perturbed by an ac force, both with
and without damping. We address this issue by using a collective coordinate
theory, which allows us to reduce the problem to the dynamics of the kink
center and width. We carry out a careful analysis of the corresponding ordinary
differential e... | 0006313v1 |
2000-07-11 | Quantum phase transitions in d-wave superconductors | Motivated by the strong, low temperature damping of nodal quasiparticles
observed in some cuprate superconductors, we study quantum phase transitions in
d_{x^2-y^2} superconductors with a spin-singlet, zero momentum, fermion
bilinear order parameter. We present a complete, group-theoretic classification
of such transit... | 0007170v3 |
2000-07-12 | Frequencies and Damping rates of a 2D Deformed Trapped Bose gas above the Critical Temperature | We derive the equation of motion for the velocity fluctuations of a 2D
deformed trapped Bose gas above the critical temperature in the hydrodynamical
regime. From this equation, we calculate the eigenfrequencies for a few
low-lying excitation modes. Using the method of averages, we derive a
dispersion relation in a def... | 0007210v2 |
2000-09-01 | The Broad Brillouin Doublet and CP of Ktao_3 : Second Sound vs. Two-Phonon Difference Scattering | Low-T Brillouin spectra of the incipient ferroelectric KTaO3 exhibit a broad
central peak (CP), and additional Brillouin doublets (BD), that can both be
related to phonon-density fluctuations. On the basis of new high-resolution
neutron data obtained of low-lying phonon branches, we analysed the
phonon-kinetics mechani... | 0009011v1 |
2000-09-21 | Landau-Khalatnikov two-fluid hydrodynamics of a trapped Bose gas | Starting from the quantum kinetic equation for the non-condensate atoms and
the generalized Gross-Pitaevskii equation for the condensate, we derive the
two-fluid hydrodynamic equations of a trapped Bose gas at finite temperatures.
We follow the standard Chapman-Enskog procedure, starting from a solution of
the kinetic ... | 0009333v1 |
2000-12-29 | Finite Temperature Time-Dependent Effective Theory for the Phase Field in two-dimensional d-wave Neutral Superconductor | We derive finite temperature time-dependent effective actions for the phase
of the pairing field, which are appropriate for a 2D electron system with both
non-retarded d- and s-wave attraction. As for s-wave pairing the d-wave
effective action contains terms with Landau damping, but their structure
appears to be differ... | 0012511v4 |
2001-01-23 | Ginzburg-Landau theory for the time-dependent phase field in a two-dimensional d-wave superconductor | We derive a finite temperature time-dependent effective theory for the phase
$\theta$ of the pairing field, which is appropriate for a 2D conducting
electron system with non-retarded d-wave attraction. As for s-wave pairing the
effective action contains terms with Landau damping, but their structure
appears to be diffe... | 0101353v1 |
2001-03-30 | Thermal magnetization fluctuations in thin films and a new physical form for magnetization damping | The effect of thermal fluctuations on a thin film magnetoresistive element
has been calculated. The technique involves adding to the basic spin dynamics a
general form of interaction with a thermal bath. For a general anisotropic
magnetic system the resulting equation can be written as a Langevin equation
for a harmoni... | 0103624v3 |
2001-06-05 | Damping and frequency shift in the oscillations of two colliding Bose-Einstein condensates | We have investigated the center-of-mass oscillations of a Rb87 Bose-Einstein
condensate in an elongated magneto-static trap. We start from a trapped
condensate and we transfer part of the atoms to another trapped level, by
applying a radio-frequency pulse. The new condensate is produced far from its
equilibrium positio... | 0106072v1 |
2001-07-12 | Ferromagnetism in the Hubbard model | We investigate the possibility and stability of bandferromagnetism in the
single-band Hubbard model. This model poses a highly non-trivial many-body
problem the general solution of which has not been found up to now.
Approximations are still unavoidable. Starting from a simple two-pole ansatz
for the spectral density o... | 0107255v1 |
2001-09-10 | Finite temperature theory of the scissors mode in a Bose gas using the moment method | We use a generalized Gross-Pitaevskii equation for the condensate and a
semi-classical kinetic equation for the noncondensate atoms to discuss the
scissors mode in a trapped Bose-condensed gas at finite temperatures. Both
equations include the effect of $C_{12}$ collisions between the condensate and
noncondensate atoms... | 0109149v1 |
2002-01-24 | Dynamic light scattering from colloidal fractal monolayers | We address experimentally the problem of how the structure of a surface
monolayer determines the visco-elasticity of the interface. Optical microscopy
and surface quasi--elastic light scattering have been used to characterize
aggregation of CaCO$_3$ particles at the air--water interface. The structures
formed by cluste... | 0201438v1 |
2002-08-06 | Spin pumping and magnetization dynamics in metallic multilayers | We study the magnetization dynamics in thin ferromagnetic films and small
ferromagnetic particles in contact with paramagnetic conductors. A moving
magnetization vector causes \textquotedblleft pumping\textquotedblright of
spins into adjacent nonmagnetic layers. This spin transfer affects the
magnetization dynamics sim... | 0208091v2 |
2002-08-08 | Excitation and damping of collective modes of a Bose-Einstein condensate in a one-dimensional lattice | The mode structure of a Bose-Einstein condensate non-adiabatically loaded
into a one-dimensional optical lattice is studied by analyzing the visibility
of the interference pattern as well as the radial profile of the condensate
after a time-of-flight. A simple model is proposed that predicts the short-time
decrease of ... | 0208162v1 |
2002-08-12 | Spectral Properties of the Generalized Spin-Fermion Models | In order to account for competition and interplay of localized and itinerant
magnetic behaviour in correlated many body systems with complex spectra the
various types of spin-fermion models have been considered in the context of the
Irreducible Green's Functions (IGF) approach. Examples are generalized d-f
model and Ko... | 0208227v1 |
2002-08-13 | Itinerant Antiferromagnetism of Correlated Lattice Fermions | The problem of finding of the ferromagnetic and antiferromagnetic "symmetry
broken" solutions of the correlated lattice fermion models beyond the
mean-field approximation has been investigated. The calculation of the
quasiparticle excitation spectra with damping for the single- and multi-orbital
Hubbard model has been ... | 0208242v1 |
2003-01-21 | Zero temperature damping of Bose-Einstein condensate oscillations by vortex-antivortex pair creation | We investigate vortex-antivortex pair creation in a supersonically expanding
and contracting quasi-2D Bose-Einstein condensate at zero temperature. For
sufficiently large amplitude condensate oscillations, pair production provides
the leading dissipation mechanism. The condensate oscillations decay in a
nonexponential ... | 0301397v3 |
2003-02-10 | Damped orbital excitations in the titanates | A possible mechanism for the removal of the orbital degeneracy in RTiO3
(where R=La, Y, ...) is considered. The calculation is based on the
Kugel-Khomskii Hamiltonian for electrons residing in the t2g orbitals of the Ti
ions, and uses a self-consistent pe rturbation expansion in the interaction
between the orbital and ... | 0302182v1 |
2003-03-20 | Energies and damping rates of elementary excitations in spin-1 Bose-Einstein condensed gases | Finite temperature Green's function technique is used to calculate the
energies and damping rates of elementary excitations of the homogeneous,
dilute, spin-1 Bose gases below the Bose-Einstein condensation temperature both
in the density and spin channels. For this purpose the self-consistent
dynamical Hartree-Fock mo... | 0303424v3 |
2003-04-17 | Non-Fermi liquid behavior from two-dimensional antiferromagnetic fluctuations: a renormalization-group and large-N analysis | We analyze the Hertz-Moriya-Millis theory of an antiferromagnetic quantum
critical point, in the marginal case of two dimensions (d=2,z=2). Up to
next-to-leading order in the number of components (N) of the field, we find
that logarithmic corrections do not lead to an enhancement of the Landau
damping. This is in agree... | 0304415v1 |
2003-05-21 | The path-coalescence transition and its applications | We analyse the motion of a system of particles subjected a random force
fluctuating in both space and time, and experiencing viscous damping. When the
damping exceeds a certain threshold, the system undergoes a phase transition:
the particle trajectories coalesce. We analyse this transition by mapping it to
a Kramers p... | 0305491v2 |
2003-06-16 | Infrared Spectroscopy of Quantum Crossbars | Infrared (IR) spectroscopy can be used as an important and effective tool for
probing periodic networks of quantum wires or nanotubes (quantum crossbars,
QCB) at finite frequencies far from the Luttinger liquid fixed point. Plasmon
excitations in QCB may be involved in resonance diffraction of incident
electromagnetic ... | 0306409v1 |
2003-06-19 | Superradiant light scattering from a moving Bose-Einstein condensate | We investigate the interaction of a moving BEC with a far detuned laser beam.
Superradiant Rayleigh scattering arises from the spontaneous formation of a
matter-wave grating due to the interference of two wavepackets with different
momenta. The system is described by the CARL-BEC model which is a
generalization of the ... | 0306500v2 |
2003-07-25 | Finite temperature excitations of a trapped Bose-Fermi mixture | We present a detailed study of the low-lying collective excitations of a
spherically trapped Bose-Fermi mixture at finite temperature in the
collisionless regime. The excitation frequencies of the condensate are
calculated self-consistently using the static Hartree-Fock-Bogoliubov theory
within the Popov approximation.... | 0307638v1 |
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