2,142 research outputs found
Sharp values for the constants in the polynomial Bohnenblust-Hille inequality
In this paper we prove that the complex polynomial Bohnenblust-Hille constant
for -homogeneous polynomials in is exactly
. We also give the exact value of the real polynomial
Bohnenblust-Hille constant for -homogeneous polynomials in .
Finally, we provide lower estimates for the real polynomial Bohnenblust-Hille
constant for polynomials in of higher degrees.Comment: 16 page
Finite-size scaling study of the d=4 site-diluted Ising
We study the four dimensional site-diluted Ising model using finite-size
scaling techniques. We explore the whole parameter space (density-coupling) in
order to determine the Universality Class of the transition line. Our data are
compatible with Mean Field behavior plus logarithmic corrections.Comment: Contribution to LATTICE 9
Spin splitting in a polarized quasi-two-dimensional exciton gas
We have observed a large spin splitting between "spin" and
heavy-hole excitons, having unbalanced populations, in undoped GaAs/AlAs
quantum wells in the absence of any external magnetic field. Time-resolved
photoluminescence spectroscopy, under excitation with circularly polarized
light, reveals that, for high excitonic density and short times after the
pulsed excitation, the emission from majority excitons lies above that of
minority ones. The amount of the splitting, which can be as large as 50% of the
binding energy, increases with excitonic density and presents a time evolution
closely connected with the degree of polarization of the luminescence. Our
results are interpreted on the light of a recently developed model, which shows
that, while intra-excitonic exchange interaction is responsible for the spin
relaxation processes, exciton-exciton interaction produces a breaking of the
spin degeneracy in two-dimensional semiconductors.Comment: Revtex, four pages; four figures, postscript file Accepted for
publication in Physical Review B (Rapid Commun.
Polynomial Inequalities on the Ï/4-Circle Sector
A number of sharp inequalities are proved for the space P (2D (Ï/4)) of 2-homogeneous polynomials on â2 endowed with the supremum norm on the sector D (Ï/4) := {eiΞ : Ξ â [0, Ï/4]}. Among the main results we can find sharp Bernstein and Markov inequalities and the calculation of the polarization constant and the unconditional constant of the canonical basis of the space P (2D (Ï/4))
Characterizing SL2S galaxy groups using the Einstein radius
We analyzed the Einstein radius, , in our sample of SL2S galaxy
groups, and compared it with (the distance from the arcs to the center of
the lens), using three different approaches: 1.- the velocity dispersion
obtained from weak lensing assuming a Singular Isothermal Sphere profile
(), 2.- a strong lensing analytical method ()
combined with a velocity dispersion-concentration relation derived from
numerical simulations designed to mimic our group sample, 3.- strong lensing
modeling () of eleven groups (with four new models presented in
this work) using HST and CFHT images. Finally, was analyzed as a function
of redshift to investigate possible correlations with L, N, and the
richness-to-luminosity ratio (N/L). We found a correlation between
and , but with large scatter. We estimate = (2.2 0.9)
+ (0.7 0.2), = (0.4 1.5) + (1.1
0.4), and = (0.4 1.5) + (0.9 0.3) for
each method respectively. We found a weak evidence of anti-correlation between
and , with Log = (0.580.06) - (0.040.1), suggesting
a possible evolution of the Einstein radius with , as reported previously by
other authors. Our results also show that is correlated with L and N
(more luminous and richer groups have greater ), and a possible
correlation between and the N/L ratio. Our analysis indicates that
is correlated with in our sample, making useful to
characterize properties like L and N (and possible N/L) in galaxy groups.
Additionally, we present evidence suggesting that the Einstein radius evolves
with .Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte
Brief Results of a Trawl Experimental Survey at NW Atlantic
An experimental survey was carried out in NAFO Regulatory Area (Div. 6EFGH and 4XWVs) and adjacent
international Southern waters during last Quarter of year 2004, with one polyvalent Spanish trawler, using "Gloria"
pelagic gear and bottom gear, with the aim to obtain data on distribution and biology on pelagic and demersal
species in non-habitual grounds for the Spanish fleet. A scientific observer was on board to collect the information
on fishing activity (effort, depth, etc.) and biological data (length distributions, length-weight relationships, etc.). A
total of 119 hauls were carried out. Samplings were conducted in a wide geographical and bathymetrical range.
During the survey, Alfonsino (Beryx splendens) was the main caught species
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