2,616 research outputs found
LSD and AMAZE: the mass-metallicity relation at z>3
We present the first results on galaxy metallicity evolution at z>3 from two
projects, LSD (Lyman-break galaxies Stellar populations and Dynamics) and AMAZE
(Assessing the Mass Abundance redshift Evolution). These projects use deep
near-infrared spectroscopic observations of a sample of ~40 LBGs to estimate
the gas-phase metallicity from the emission lines. We derive the
mass-metallicity relation at z3 and compare it with the same relation at
lower redshift. Strong evolution from z=0 and z=2 to z=3 is observed, and this
finding puts strong constrains on the models of galaxy evolution. These
preliminary results show that the effective oxygen yields does not increase
with stellar mass, implying that the simple outflow model does not apply at
z>3.Comment: 5 pages, to appear in the IAUS 255 conference proceedings:
"Low-Metallicity Star Formation: from the First Stars to Dwarf Galaxies",
L.K. Hunt, S. Madden and R. Schneider ed
Eigenvalue statistics of the real Ginibre ensemble
The real Ginibre ensemble consists of random matrices formed
from i.i.d. standard Gaussian entries. By using the method of skew orthogonal
polynomials, the general -point correlations for the real eigenvalues, and
for the complex eigenvalues, are given as Pfaffians with explicit
entries. A computationally tractable formula for the cumulative probability
density of the largest real eigenvalue is presented. This is relevant to May's
stability analysis of biological webs.Comment: 4 pages, to appear PR
Semiclassical Approach to Parametric Spectral Correlation with Spin 1/2
The spectral correlation of a chaotic system with spin 1/2 is universally
described by the GSE (Gaussian Symplectic Ensemble) of random matrices in the
semiclassical limit. In semiclassical theory, the spectral form factor is
expressed in terms of the periodic orbits and the spin state is simulated by
the uniform distribution on a sphere. In this paper, instead of the uniform
distribution, we introduce Brownian motion on a sphere to yield the parametric
motion of the energy levels. As a result, the small time expansion of the form
factor is obtained and found to be in agreement with the prediction of
parametric random matrices in the transition within the GSE universality class.
Moreover, by starting the Brownian motion from a point distribution on the
sphere, we gradually increase the effect of the spin and calculate the form
factor describing the transition from the GOE (Gaussian Orthogonal Ensemble)
class to the GSE class.Comment: 25 pages, 2 figure
Chaotic Transport in the Symmetry Crossover Regime with a Spin-orbit Interaction
We study a chaotic quantum transport in the presence of a weak spin-orbit
interaction. Our theory covers the whole symmetry crossover regime between
time-reversal invariant systems with and without a spin-orbit interaction. This
situation is experimentally realizable when the spin-orbit interaction is
controlled in a conductor by applying an electric field. We utilize a
semiclassical approach which has recently been developed. In this approach, the
non-Abelian nature of the spin diffusion along a classical trajectory plays a
crucial role. New analytical expressions with one crossover parameter are
semiclassically derived for the average conductance, conductance variance and
shot noise. Moreover numerical results on a random matrix model describing the
crossover from the GOE (Gaussian Orthogonal Ensemble) to the GSE (Gaussian
Symplectic Ensemble) are compared with the semiclassical expressions.Comment: 13 pages, 7 figure
Is there any evidence that ionised outflows quench star formation in type 1 quasars at z<1?
The aim of this paper is to test the basic model of negative AGN feedback.
According to this model, once the central black hole accretes at the Eddington
limit and reaches a certain critical mass, AGN driven outflows blow out gas,
suppressing star formation in the host galaxy and self-regulating black hole
growth. We consider a sample of 224 quasars selected from the SDSS at z<1
observed in the infrared band by Herschel. We evaluate the star formation rate
in relation to several outflow signatures traced by the [OIII]4959,5007 and
[OII]3726,3729 emission lines in about half of the sample with high quality
spectra. Most of the quasars show asymmetric and broad wings in [OIII], which
we interpret as outflow signatures. We separate the quasars in two groups,
``weakly'' and ``strongly'' outflowing, using three different criteria. When we
compare the mean star formation rate in five redshift bins in the two groups,
we find that the SFRs are comparable or slightly larger in the strongly
outflowing quasars. We estimate the stellar mass from SED fitting and the
quasars are distributed along the star formation main sequence, although with a
large scatter. The scatter from this relation is uncorrelated with respect to
the kinematic properties of the outflow. Moreover, for quasars dominated in the
infrared by starburst or by AGN emission, we do not find any correlation
between the star formation rate and the velocity of the outflow, a trend
previously reported in the literature for pure starburst galaxies. We conclude
that the basic AGN negative feedback scenario seems not to agree with our
results. Although we use a large sample of quasars, we did not find any
evidence that the star formation rate is suppressed in the presence of AGN
driven outflows on large scale. A possibility is that feedback is effective
over much longer timescales than those of single episodes of quasar activity.Comment: 18 pages, new version that implements the suggestions of the referee
and matches the AA published versio
Symmetry of matrix-valued stochastic processes and noncolliding diffusion particle systems
As an extension of the theory of Dyson's Brownian motion models for the
standard Gaussian random-matrix ensembles, we report a systematic study of
hermitian matrix-valued processes and their eigenvalue processes associated
with the chiral and nonstandard random-matrix ensembles. In addition to the
noncolliding Brownian motions, we introduce a one-parameter family of
temporally homogeneous noncolliding systems of the Bessel processes and a
two-parameter family of temporally inhomogeneous noncolliding systems of Yor's
generalized meanders and show that all of the ten classes of eigenvalue
statistics in the Altland-Zirnbauer classification are realized as particle
distributions in the special cases of these diffusion particle systems. As a
corollary of each equivalence in distribution of a temporally inhomogeneous
eigenvalue process and a noncolliding diffusion process, a stochastic-calculus
proof of a version of the Harish-Chandra (Itzykson-Zuber) formula of integral
over unitary group is established.Comment: LaTeX, 27 pages, 4 figures, v3: Minor corrections made for
publication in J. Math. Phy
Crossover from Fermi Liquid to Non-Fermi Liquid Behavior in a Solvable One-Dimensional Model
We consider a quantum moany-body problem in one-dimension described by a
Jastrow type, characterized by an exponent and a parameter .
We show that with increasing , the Fermi Liquid state (
crosses over to non-Fermi liquid states, characterized by effective
"temperature".Comment: 8pp. late
An Intermediate-band imaging survey for high-redshift Lyman Alpha Emitters: The Mahoroba-11
We present results of our intermediate-band optical imaging survey for
high- Ly emitters (LAEs) using the prime focus camera, Suprime-Cam,
on the 8.2m Subaru Telescope. In our survey, we use eleven filters; four
broad-band filters (, , , and ) and seven
intermediate-band filters covering from 500 nm to 720 nm; we call this imaging
program as the Mahoroba-11. The seven intermediate-band filters are selected
from the IA filter series that is the Suprime-Cam intermediate-band filter
system whose spectral resolution is . Our survey has been made in a
sky area in the Subaru XMM Newton Deep Survey
field. We have found 409 IA-excess objects that provide us a large photometric
sample of strong emission-line objects. Applying the photometric redshift
method to this sample, we obtained a new sample of 198 LAE candidates at . We found that there is no evidence for evolution of the number density
and the star formation rate density for LAEs with between and 5.Comment: 46 pages, 15 figures, PASJ, Vol.57, No.6, in pres
Random Matrix Theory for the Hermitian Wilson Dirac Operator and the chGUE-GUE Transition
We introduce a random two-matrix model interpolating between a chiral
Hermitian (2n+nu)x(2n+nu) matrix and a second Hermitian matrix without
symmetries. These are taken from the chiral Gaussian Unitary Ensemble (chGUE)
and Gaussian Unitary Ensemble (GUE), respectively. In the microscopic large-n
limit in the vicinity of the chGUE (which we denote by weakly non-chiral limit)
this theory is in one to one correspondence to the partition function of Wilson
chiral perturbation theory in the epsilon regime, such as the related two
matrix-model previously introduced in refs. [20,21]. For a generic number of
flavours and rectangular block matrices in the chGUE part we derive an
eigenvalue representation for the partition function displaying a Pfaffian
structure. In the quenched case with nu=0,1 we derive all spectral correlations
functions in our model for finite-n, given in terms of skew-orthogonal
polynomials. The latter are expressed as Gaussian integrals over standard
Laguerre polynomials. In the weakly non-chiral microscopic limit this yields
all corresponding quenched eigenvalue correlation functions of the Hermitian
Wilson operator.Comment: 27 pages, 4 figures; v2 typos corrected, published versio
Functional central limit theorems for vicious walkers
We consider the diffusion scaling limit of the vicious walker model that is a
system of nonintersecting random walks. We prove a functional central limit
theorem for the model and derive two types of nonintersecting Brownian motions,
in which the nonintersecting condition is imposed in a finite time interval
for the first type and in an infinite time interval for
the second type, respectively. The limit process of the first type is a
temporally inhomogeneous diffusion, and that of the second type is a temporally
homogeneous diffusion that is identified with a Dyson's model of Brownian
motions studied in the random matrix theory. We show that these two types of
processes are related to each other by a multi-dimensional generalization of
Imhof's relation, whose original form relates the Brownian meander and the
three-dimensional Bessel process. We also study the vicious walkers with wall
restriction and prove a functional central limit theorem in the diffusion
scaling limit.Comment: AMS-LaTeX, 20 pages, 2 figures, v6: minor corrections made for
publicatio
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