34,157 research outputs found
Optimization problems involving the first Dirichlet eigenvalue and the torsional rigidity
We present some open problems and obtain some partial results for spectral
optimization problems involving measure, torsional rigidity and first Dirichlet
eigenvalue.Comment: 18 pages, 4 figure
On the torsion function with Robin or Dirichlet boundary conditions
For and the -torsion function with
Robin boundary conditions associated to an arbitrary open set \Om \subset
\R^m satisfies formally the equation in \Om and on \partial \Om. We
obtain bounds of the norm of {\it only} in terms of the bottom
of the spectrum (of the Robin -Laplacian), and the dimension of the
space in the following two extremal cases: the linear framework (corresponding
to ) and arbitrary , and the non-linear framework (corresponding to
arbitrary ) and Dirichlet boundary conditions (). In the
general case, and our bounds involve also
the Lebesgue measure of \Om.Comment: 19 page
High resolution angular sensor
Specifications for the pointing stabilization system of the large space telescope were used in an investigation of the feasibility of reducing ring laser gyro output quantization to the sub-arc-second level by the use of phase locked loops and associated electronics. Systems analysis procedures are discussed and a multioscillator laser gyro model is presented along with data on the oscillator noise. It is shown that a second order closed loop can meet the measurement noise requirements when the loop gain and time constant of the loop filter are appropriately chosen. The preliminary electrical design is discussed from the standpoint of circuit tradeoff considerations. Analog, digital, and hybrid designs are given and their applicability to the high resolution sensor is examined. the electrical design choice of a system configuration is detailed. The design and operation of the various modules is considered and system block diagrams are included. Phase 1 and 2 test results using the multioscillator laser gyro are included
Higgs diphoton rate enhancement from supersymmetric physics beyond the MSSM
We show that supersymmetric "new physics" beyond the MSSM can naturally
accommodate a Higgs mass near 126 GeV and enhance the signal rate in the Higgs
to diphoton channel, while the signal rates in all the other Higgs decay
channels coincide with Standard Model expectations, except possibly the Higgs
to Z-photon channel. The "new physics" that corrects the relevant Higgs
couplings can be captured by two supersymmetric effective operators. We provide
a simple example of an underlying model in which these operators are
simultaneously generated. The scale of "new physics" that generates these
operators can be around 5 TeV or larger, and outside the reach of the LHC.Comment: 24 pages, 4 figure
Wind speed statistics for Goldstone, California, anemometer sites
An exploratory wind survey at an antenna complex was summarized statistically for application to future windmill designs. Data were collected at six locations from a total of 10 anemometers. Statistics include means, standard deviations, cubes, pattern factors, correlation coefficients, and exponents for power law profile of wind speed. Curves presented include: mean monthly wind speeds, moving averages, and diurnal variation patterns. It is concluded that three of the locations have sufficiently strong winds to justify consideration for windmill sites
On the minimization of Dirichlet eigenvalues of the Laplace operator
We study the variational problem \inf \{\lambda_k(\Omega): \Omega\
\textup{open in}\ \R^m,\ |\Omega| < \infty, \ \h(\partial \Omega) \le 1 \},
where is the 'th eigenvalue of the Dirichlet Laplacian
acting in , \h(\partial \Omega) is the - dimensional
Hausdorff measure of the boundary of , and is the Lebesgue
measure of . If , and , then there exists a convex
minimiser . If , and if is a minimiser,
then is also a
minimiser, and is connected. Upper bounds are
obtained for the number of components of . It is shown that if
, and then has at most components.
Furthermore is connected in the following cases : (i) (ii) and (iii) and (iv) and
. Finally, upper bounds on the number of components are obtained for
minimisers for other constraints such as the Lebesgue measure and the torsional
rigidity.Comment: 16 page
Large deviations for ideal quantum systems
We consider a general d-dimensional quantum system of non-interacting
particles, with suitable statistics, in a very large (formally infinite)
container. We prove that, in equilibrium, the fluctuations in the density of
particles in a subdomain of the container are described by a large deviation
function related to the pressure of the system. That is, untypical densities
occur with a probability exponentially small in the volume of the subdomain,
with the coefficient in the exponent given by the appropriate thermodynamic
potential. Furthermore, small fluctuations satisfy the central limit theorem.Comment: 28 pages, LaTeX 2
Bose-Einstein Condensation in Geometrically Deformed Tubes
We show that Bose-Einstein condensate can be created in quasi-one-dimensional
systems in a purely geometrical way, namely by bending or other suitable
deformation of a tube.Comment: RevTex, 4pages, no figure
Density of states and Fisher's zeros in compact U(1) pure gauge theory
We present high-accuracy calculations of the density of states using
multicanonical methods for lattice gauge theory with a compact gauge group U(1)
on 4^4, 6^4 and 8^4 lattices. We show that the results are consistent with weak
and strong coupling expansions. We present methods based on Chebyshev
interpolations and Cauchy theorem to find the (Fisher's) zeros of the partition
function in the complex beta=1/g^2 plane. The results are consistent with
reweighting methods whenever the latter are accurate. We discuss the volume
dependence of the imaginary part of the Fisher's zeros, the width and depth of
the plaquette distribution at the value of beta where the two peaks have equal
height. We discuss strategies to discriminate between first and second order
transitions and explore them with data at larger volume but lower statistics.
Higher statistics and even larger lattices are necessary to draw strong
conclusions regarding the order of the transition.Comment: 14 pages, 16 figure
String Loop Corrections to Kahler Potentials in Orientifolds
We determine one-loop string corrections to Kahler potentials in type IIB
orientifold compactifications with either N=1 or N=2 supersymmetry, including
D-brane moduli, by evaluating string scattering amplitudes.Comment: 80 pages, 4 figure
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