2,093 research outputs found
One-dimensional space-discrete transport subject to Levy perturbations
In this paper we study a one-dimensional space-discrete transport equation
subject to additive Levy forcing. The explicit form of the solutions allows
their analytic study. In particular we discuss the invariance of the covariance
structure of the stationary distribution for Levy perturbations with finite
second moment. The situation of more general Levy perturbations lacking the
second moment is considered as well. We moreover show that some of the
properties of the solutions are pertinent to a discrete system and are not
reproduced by its continuous analogue
Modified Dispersion Relations from the Renormalization Group of Gravity
We show that the running of gravitational couplings, together with a suitable
identification of the renormalization group scale can give rise to modified
dispersion relations for massive particles. This result seems to be compatible
with both the frameworks of effective field theory with Lorentz invariance
violation and deformed special relativity. The phenomenological consequences
depend on which of the frameworks is assumed. We discuss the nature and
strength of the available constraints for both cases and show that in the case
of Lorentz invariance violation, the theory would be strongly constrained.Comment: revtex4, 9 pages, updated to match published versio
Performance Cycle Analysis of a Two-Spool, Separate-Exhaust Turbofan With Interstage Turbine Burner
This paper presents the performance cycle analysis of a dual-spool, separate-exhaust turbofan engine, with an Interstage Turbine Burner serving as a secondary combustor. The ITB, which is located at the transition duct between the high- and the low-pressure turbines, is a relatively new concept for increasing specific thrust and lowering pollutant emissions in modern jet engine propulsion. A detailed performance analysis of this engine has been conducted for steady-state engine performance prediction. A code is written and is capable of predicting engine performances (i.e., thrust and thrust specific fuel consumption) at varying flight conditions and throttle settings. Two design-point engines were studied to reveal trends in performance at both full and partial throttle operations. A mission analysis is also presented to assure the advantage of saving fuel by adding ITB
The Photon Dispersion as an Indicator for New Physics ?
We first comment on the search for a deviation from the linear photon
dispersion relation, in particular based on cosmic photons from Gamma Ray
Bursts. Then we consider the non-commutative space as a theoretical concept
that could lead to such a deviation, which would be a manifestation of Lorentz
Invariance Violation. In particular we review a numerical study of pure U(1)
gauge theory in a 4d non-commutative space. Starting from a finite lattice, we
explore the phase diagram and the extrapolation to the continuum and infinite
volume. These simultaneous limits - taken at fixed non-commutativity - lead to
a phase of broken Poincare symmetry, where the photon appears to be IR stable,
despite a negative IR divergence to one loop.Comment: 8 pages, 4 figures, talk presented at the VI International Workshop
on the Dark Side of the Universe, Leon (Mexico), June 1-6, 2010. References
adde
Top Arc Seam Weld Shear Strength and Stiffness for Sheet-to-sheet Connections
The North American Specification for the Design of Cold-Formed Steel Structural Members does not provide specific design guidance for sheet-to-sheet top arc seam welds in shear. A collaborative industry study has developed design guidance for both strength and stiffness of the connection to facilitate analytical evaluation of floor and roof diaphragm assemblies and wall assemblies. The test program was performed per AISI S905 and addressed material ductility, weld length, sheet thickness and the distribution of the force being transferred by the weld connection
Performance (Off-Design) Cycle Analysis for a Turbofan Engine With Interstage Turbine Burner
This report presents the performance of a steady-state, dual-spool, separate-exhaust turbofan engine, with an interstage turbine burner (ITB) serving as a secondary combustor. The ITB, which is located in the transition duct between the high- and the low-pressure turbines, is a relatively new concept for increasing specific thrust and lowering pollutant emissions in modern jet-engine propulsion. A detailed off-design performance analysis of ITB engines is written in Microsoft(Registered Trademark) Excel (Redmond, Washington) macrocode with Visual Basic Application to calculate engine performances over the entire operating envelope. Several design-point engine cases are pre-selected using a parametric cycle-analysis code developed previously in Microsoft(Registered Trademark) Excel, for off-design analysis. The off-design code calculates engine performances (i.e. thrust and thrust-specific-fuel-consumption) at various flight conditions and throttle settings
The Casimir Force in a Lorentz Violating Theory
We study the effects of the minimal extension of the standard model including
Lorentz violation on the Casimir force between two parallel conducting plates
in vacuum. We provide explicit solutions for the electromagnetic field using
scalar field analogy, for both the cases in which the Lorentz violating terms
come from the CPT-even or CPT-odd terms. We also calculate the effects of the
Lorentz violating terms for a fermion field between two parallel conducting
plates and analyze the modifications of the Casimir force due to the
modifications of the Dirac equation. In all cases under consideration, the
standard formulas for the Casimir force are modified by either multiplicative
or additive correction factors, the latter case exhibiting different dependence
on the distance between the plates.Comment: 20 pages, no figures, references added, accepted for publication in
Phys. Rev.
Nontrivial, Asymptotically Non-free Gauge Theories and Dynamical Unification of Couplings
An evidence for nontriviality of asymptotically non-free (ANF) Yang-Mills
theories is found on the basis of optimized perturbation theory. It is argued
that these theories with matter couplings can be made nontrivial by means of
the reduction of couplings, leading to the idea of dynamical unification of
couplings (DUC) The second-order reduction of couplings in the ANF
-gauged Higgs-Yukawa theory, which is assumed to be nontrivial here, is
carried out to motivate independent investigations on its nontriviality and
DUC
Footprints of Statistical Anisotropies
We propose and develop a formalism to describe and constrain statistically
anisotropic primordial perturbations. Starting from a decomposition of the
primordial power spectrum in spherical harmonics, we find how the temperature
fluctuations observed in the CMB sky are directly related to the coefficients
in this harmonic expansion. Although the angular power spectrum does not
discriminate between statistically isotropic and anisotropic perturbations, it
is possible to define analogous quadratic estimators that are direct measures
of statistical anisotropy. As a simple illustration of our formalism we test
for the existence of a preferred direction in the primordial perturbations
using full-sky CMB maps. We do not find significant evidence supporting the
existence of a dipole component in the primordial spectrum.Comment: 26 pages, 5 double figures. Uses RevTeX
- …