14,949 research outputs found
On the minimal number of matrices which form a locally hypercyclic, non-hypercyclic tuple
In this paper we extend the notion of a locally hypercyclic operator to that
of a locally hypercyclic tuple of operators. We then show that the class of
hypercyclic tuples of operators forms a proper subclass to that of locally
hypercyclic tuples of operators. What is rather remarkable is that in every
finite dimensional vector space over or , a pair of
commuting matrices exists which forms a locally hypercyclic, non-hypercyclic
tuple. This comes in direct contrast to the case of hypercyclic tuples where
the minimal number of matrices required for hypercyclicity is related to the
dimension of the vector space. In this direction we prove that the minimal
number of diagonal matrices required to form a hypercyclic tuple on
is , thus complementing a recent result due to Feldman.Comment: 15 pages, title changed, section for infinite dimensional spaces
adde
Fluctuation-dissipation theorem for chiral systems in non-equilibrium steady states
We consider a three-terminal system with a chiral edge channel connecting the
source and drain terminals. Charge can tunnel between the chiral edge and a
third terminal. The third terminal is maintained at a different temperature and
voltage than the source and drain. We prove a general relation for the current
noises detected in the drain and third terminal. It has the same structure as
an equilibrium fluctuation-dissipation relation with the nonlinear response in
place of the linear conductance. The result applies to a general chiral system
and can be useful for detecting "upstream" modes on quantum Hall edges.Comment: detailed proo
Detecting non-Abelian Statistics with Electronic Mach-Zehnder Interferometer
Fractionally charged quasiparticles in the quantum Hall state with filling
factor are expected to obey non-Abelian statistics. We demonstrate
that their statistics can be probed by transport measurements in an electronic
Mach-Zehnder interferometer. The tunneling current through the interferometer
exhibits a characteristic dependence on the magnetic flux and a non-analytic
dependence on the tunneling amplitudes which can be controlled by gate
voltages.Comment: 4 pages, 2 figures; Revtex; a discussion of the asymmetry of the I-V
curve adde
Remarkable virtual SUSY effects in production at high energy hadron colliders
We present a complete 1-loop study of the electroweak corrections to the
process in MSSM and SM.
The occurrence of a number of remarkable properties in the behavior of the
helicity amplitudes at high energies is stressed, and the crucial role of the
virtual SUSY contributions in establishing them, is emphasized. The approach to
asymptopia of these amplitudes is discussed, comparing the effects of the
logarithmic and constant contributions to the mass suppressed ones, which are
relevant at lower energies. Applying crossing to , we obtain all
subprocesses needed for the 1-loop electroweak corrections to
-production at LHC. The SUSY model dependence of such a production is
then studied, and illustrations are given for the transverse momentum
distribution, as well as the angular distribution in the subprocess center of
mass.Comment: 21 pages, 12 figures, version to appear in Phys.Rev.
A Rigorous Proof of Fermi Liquid Behavior for Jellium Two-Dimensional Interacting Fermions
Using the method of continuous constructive renormalization group around the
Fermi surface, it is proved that a jellium two-dimensional interacting system
of Fermions at low temperature remains analytic in the coupling constant
for where is some numerical constant
and is the temperature. Furthermore in that range of parameters, the first
and second derivatives of the self-energy remain bounded, a behavior which is
that of Fermi liquids and in particular excludes Luttinger liquid behavior. Our
results prove also that in dimension two any transition temperature must be
non-perturbative in the coupling constant, a result expected on physical
grounds. The proof exploits the specific momentum conservation rules in two
dimensions.Comment: 4 pages, no figure
Electronic Mach-Zehnder interferometer as a tool to probe fractional statistics
We study transport through an electronic Mach-Zehnder interferometer recently
devised at the Weizmann Institute. We show that this device can be used to
probe statistics of quasiparticles in the fractional quantum Hall regime. We
calculate the tunneling current through the interferometer as the function of
the Aharonov-Bohm flux, temperature and voltage bias, and demonstrate that its
flux-dependent component is strongly sensitive to the statistics of tunneling
quasiparticles. More specifically, the flux-dependent and flux-independent
contributions to the current are related by a power law, the exponent being a
function of the quasiparticle statistics.Comment: 22 pages; 8 figure
The Fourth Positive System of Carbon Monoxide in the Hubble Space Telescope Spectra of Comets
The rich structure of the Fourth Positive System (A-X) of carbon monoxide
accounts for many of the spectral features seen in long slit HST-STIS
observations of comets 153P/Ikeya-Zhang, C/2001 Q4 (NEAT), and C/2000 WM1
(LINEAR), as well as in the HST-GHRS spectrum of comet C/1996 B2 Hyakutake. A
detailed CO fluorescence model is developed to derive the CO abundances in
these comets by simultaneously fitting all of the observed A-X bands. The model
includes the latest values for the oscillator strengths and state parameters,
and accounts for optical depth effects due to line overlap and self-absorption.
The model fits yield radial profiles of CO column density that are consistent
with a predominantly native source for all the comets observed by STIS. The
derived CO abundances relative to water in these comets span a wide range, from
0.44% for C/2000 WM1 (LINEAR), 7.2% for 153P/Ikeya-Zhang, 8.8% for C/2001 Q4
(NEAT) to 20.9% for C/1996 B2 (Hyakutake). The subtraction of the CO spectral
features using this model leads to the first identification of a molecular
hydrogen line pumped by solar HI Lyman-beta longward of 1200A in the spectrum
of comet 153P/Ikeya-Zhang. (Abridged)Comment: 12 pages, 11 figures, ApJ accepte
Multipair approach to pairing in nuclei
The ground state of a general pairing Hamiltonian for a finite nuclear system
is constructed as a product of collective, real, distinct pairs. These are
determined sequentially via an iterative variational procedure that resorts to
diagonalizations of the Hamiltonian in restricted model spaces. Different
applications of the method are provided that include comparisons with exact and
projected BCS results. The quantities that are examined are correlation
energies, occupation numbers and pair transfer matrix elements. In a first
application within the picket-fence model, the method is seen to generate the
exact ground state for pairing strengths confined in a given range. Further
applications of the method concern pairing in spherically symmetric mean fields
and include simple exactly solvable models as well as some realistic
calculations for middle-shell Sn isotopes. In the latter applications, two
different ways of defining the pairs are examined: either with J=0 or with no
well-defined angular momentum. The second choice reveals to be more effective
leading, under some circumstances, to solutions that are basically exact.Comment: To appear in Physical Review
LHC discovery potential for models with continuously distributed mass
We study the Large Hadron Collider (LHC) discovery potential for models
with continuously distributed mass for and 14 TeV
centre-of-mass energies. One of possible LHC signatures for such models is the
existence of broad resonance in Drell-Yan reaction .Comment: 14 pages, some references and formula adde
Comparison of Alternative Safety Net Programs for the 2000 Farm Bill
As Congress begins its debate for the 2002 farm bill, there have been calls for a counter cyclical safety net that will provide a better basis for targeting longer term planning than exists with ad hoc emergency assistance. Further subsidization of the multi-peril crop insurance (MPCI) program has been proposed, as well as reliance on a farm and ranch risk management (FARRM) account to help farmers. A whole farm revenue income support program and several variations of national income supplement programs have been put forward. A comprehensive analysis of different safety net alternatives using a common methodology is needed so farmers and policy makers can make objective comparisons. The objective of this paper is to quantitatively analyze the economic effects of alternative safety net/insurance programs on farmers in the Southern United States. The objective is accomplished by simulating representative crop farms in the South over the 2001-2005 planning horizon for alternative safety net options. The simulated net present value distributions for the farms are compared using certainty equivalents to determine the value of alternative safety net options to feed grain, cotton and rice farms in the South.Agricultural and Food Policy,
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