6,273 research outputs found
Neutrino-Nucleus Cross Section Measurements using Stopped Pions and Low Energy Beta Beams
Two new facilities have recently been proposed to measure low energy
neutrino-nucleus cross sections, the nu-SNS (Spallation Neutron Source) and low
energy beta beams. The former produces neutrinos by pion decay at rest, while
the latter produces neutrinos from the beta decays of accelerated ions. One of
the uses of neutrino-nucleus cross section measurements is for supernova
studies, where typical neutrino energies are 10s of MeV. In this energy range
there are many different components to the nuclear response and this makes the
theoretical interpretation of the results of such an experiment complex.
Although even one measurement on a heavy nucleus such as lead is much
anticipated, more than one data set would be still better. We suggest that this
can be done by breaking the electron spectrum down into the parts produced in
coincidence with one or two neutrons, running a beta beam at more than one
energy, comparing the spectra produced with pions and a beta beam or any
combination of these.Comment: 6 pages, 6 figure
On-Off Intermittency in Time Series of Spontaneous Paroxysmal Activity in Rats with Genetic Absence Epilepsy
Dynamic behavior of complex neuronal ensembles is a topic comprising a
streamline of current researches worldwide. In this article we study the
behavior manifested by epileptic brain, in the case of spontaneous
non-convulsive paroxysmal activity. For this purpose we analyzed archived
long-term recording of paroxysmal activity in animals genetically susceptible
to absence epilepsy, namely WAG/Rij rats. We first report that the brain
activity alternated between normal states and epilepsy paroxysms is the on-off
intermittency phenomenon which has been observed and studied earlier in the
different nonlinear systems.Comment: 11 pages, 6 figure
Resipientundersøkelse av Begna, Storelva og Nordfjorden i 1997 ved Norske Skogindustrier ASA - Follum
Rapporten dokumenterer effektene av at det biologiske renseanlegget for fjerning av løst organisk stoff ble satt i drift i juni 1995. Det er også gjort sammenligninger med forholdene før og etter installeringen av kjemisk fellingsanlegg sommeren 1991. Etter installeringen av det biologiske renseanlegget, er TOC redusert fra ca 5000 tonn til ca 2000 tonn karbon pr. år. Tilførslene av fosfor er imidlertid økt fra ca 3 tonn til ca 8 tonn fordi fosfor må tilsettes til det biologiske anlegget. Follums egne og mer nøyaktige utslippsmålinger avviker noe fra elvemålingene, men trendene er de samme, klar reduksjon av organisk stoff og like klar økning av fosfor. Undersøkelse av bunndyr og begroing viser at Begna fortsatt er påvirket av utslipp av organisk stoff nedstrøms Follum. Det er en klar bedring i miljøkvalitet etter samløp med Randselva, men Storelva får igjen en redusert vannkvalitet ved Busund (nedstrøms Monserud). Forholdene i Begna (nedstrøms Monserud). Forholdene i Begna (nedstrøms Follum) er i 1997 merkbart bedre enn i 1993. Dette gir seg utslag i bedret biologisk mangfold, dvs. flere dyre- og plantegrupper (arter). Elvebunnen er også mindre dekket av bakterier og sopp, som vanligvis indikerer overbelastning av organisk stoff, noe som hovedsakelig skyldes tilførsler fra tidligere år. Hovedvannmassene i Tyrifjorden er imidlertid fortsatt i bedring, og algeinnholdet er nå på et nivå som tilsvarer miljømålet satt opp av Vannbruksplanutvalget
Enumeration of maps with self avoiding loops and the O(n) model on random lattices of all topologies
We compute the generating functions of a O(n) model (loop gas model) on a
random lattice of any topology. On the disc and the cylinder, they were already
known, and here we compute all the other topologies. We find that the
generating functions (and the correlation functions of the lattice) obey the
topological recursion, as usual in matrix models, i.e they are given by the
symplectic invariants of their spectral curve.Comment: pdflatex, 89 pages, 12 labelled figures (15 figures at all), minor
correction
Phase transitions in a frustrated XY model with zig-zag couplings
We study a new generalized version of the square-lattice frustrated XY model
where unequal ferromagnetic and antiferromagnetic couplings are arranged in a
zig-zag pattern. The ratio between the couplings can be used to tune the
system, continuously, from the isotropic square-lattice to the
triangular-lattice frustrated XY model. The model can be physically realized as
a Josephson-junction array with two different couplings, in a magnetic field
corresponding to half-flux quanta per plaquette. Mean-field approximation,
Ginzburg-Landau expansion and finite-size scaling of Monte Carlo simulations
are used to study the phase diagram and critical behavior. Depending on the
value of , two separate transitions or a transition line in the
universality class of the XY-Ising model, with combined and U(1)
symmetries, takes place. In particular, the phase transitions of the standard
square-lattice and triangular-lattice frustrated XY models correspond to two
different cuts through the same transition line. Estimates of the chiral
() critical exponents on this transition line deviate significantly from
the pure Ising values, consistent with that along the critical line of the
XY-Ising model. This suggests that a frustrated XY model or Josephson-junction
array with a zig-zag coupling modulation can provide a physical realization of
the XY-Ising model critical line.Comment: 11 pages, 9 figures, RevTex, to appear in Phys. Rev.
On the Properties of Two Pulses Propagating Simultaneously in Different Dispersion Regimes in a Nonlinear Planar Waveguide
Properties of two pulses propagating simultaneously in different dispersion
regimes, anomalous and normal, in a Kerr-type planar waveguide are studied in
the framework of the nonlinear Schroedinger equation. Catastrophic
self-focusing and spatio-temporal splitting of the pulses is investigated. For
the limiting case when the dispersive term of the pulse propagating in the
normal dispersion regime can be neglected an indication of a possibility of a
stable self-trapped propagation of both pulses is obtained.Comment: 18 pages (including 15 eps figures
Sfermion Pair Production in Polarized and Unpolarized Collisions
We calculate total and differential cross sections for the production of
sfermion pairs in photon-photon collisions, including contributions from
resolved photons and arbitrary photon polarization. Sfermion production in
photon collisions depends only on the sfermion mass and charge. It is thus
independent of the details of the SUSY breaking mechanism, but highly sensitive
to the sfermion charge. We compare the total cross sections for bremsstrahlung,
beamstrahlung, and laser backscattering photons to those in
annihilation. We find that the total cross section at a polarized photon
collider is larger than the annihilation cross section up to the
kinematic limit of the photon collider.Comment: 19 pages, Latex, 18 (e)ps-figure
Two-Center Integrals for r_{ij}^{n} Polynomial Correlated Wave Functions
All integrals needed to evaluate the correlated wave functions with
polynomial terms of inter-electronic distance are included. For this form of
the wave function, the integrals needed can be expressed as a product of
integrals involving at most four electrons
Using network-flow techniques to solve an optimization problem from surface-physics
The solid-on-solid model provides a commonly used framework for the
description of surfaces. In the last years it has been extended in order to
investigate the effect of defects in the bulk on the roughness of the surface.
The determination of the ground state of this model leads to a combinatorial
problem, which is reduced to an uncapacitated, convex minimum-circulation
problem. We will show that the successive shortest path algorithm solves the
problem in polynomial time.Comment: 8 Pages LaTeX, using Elsevier preprint style (macros included
Noise Induced Intermittency in a Superconducting Microwave Resonator
We experimentally and numerically study a NbN superconducting stripline
resonator integrated with a microbridge. We find that the response of the
system to monochromatic excitation exhibits intermittency, namely,
noise-induced jumping between coexisting steady-state and limit-cycle
responses. A theoretical model that assumes piecewise linear dynamics yields
partial agreement with the experimental findings
- …