655 research outputs found
Symmetry breaking perturbations and strange attractors
The asymmetrically forced, damped Duffing oscillator is introduced as a
prototype model for analyzing the homoclinic tangle of symmetric dissipative
systems with \textit{symmetry breaking} disturbances. Even a slight fixed
asymmetry in the perturbation may cause a substantial change in the asymptotic
behavior of the system, e.g. transitions from two sided to one sided strange
attractors as the other parameters are varied. Moreover, slight asymmetries may
cause substantial asymmetries in the relative size of the basins of attraction
of the unforced nearly symmetric attracting regions. These changes seems to be
associated with homoclinic bifurcations. Numerical evidence indicates that
\textit{strange attractors} appear near curves corresponding to specific
secondary homoclinic bifurcations. These curves are found using analytical
perturbational tools
Adaptive Sampling Approach to the Negative Sign Problem in the Auxiliary Field Quantum Monte Carlo Method
We propose a new sampling method to calculate the ground state of interacting
quantum systems. This method, which we call the adaptive sampling quantum monte
carlo (ASQMC) method utilises information from the high temperature density
matrix derived from the monte carlo steps. With the ASQMC method, the negative
sign ratio is greatly reduced and it becomes zero in the limit
goes to zero even without imposing any constraint such like the constraint path
(CP) condition. Comparisons with numerical results obtained by using other
methods are made and we find the ASQMC method gives accurate results over wide
regions of physical parameters values.Comment: 8 pages, 7 figure
Approximating multi-dimensional Hamiltonian flows by billiards
Consider a family of smooth potentials , which, in the limit
, become a singular hard-wall potential of a multi-dimensional
billiard. We define auxiliary billiard domains that asymptote, as
to the original billiard, and provide asymptotic expansion of
the smooth Hamiltonian solution in terms of these billiard approximations. The
asymptotic expansion includes error estimates in the norm and an
iteration scheme for improving this approximation. Applying this theory to
smooth potentials which limit to the multi-dimensional close to ellipsoidal
billiards, we predict when the separatrix splitting persists for various types
of potentials
Plan de negocio para la viabilidad comercial, operativa y econ?mica de crear un instituto para diagnosticar y tratar problemas de lenguaje y aprendizaje en ni?os entre 3 y 12 a?os en Lima Moderna
Instituto de lenguaje y aprendizaje que atienda a ni?os entre 3 y 12 a?os de Lima Moderna ? Zona 7 para los distritos de La Molina, Miraflores, San Borja, San Isidro y Surco de los NSE B1, B2 y C1, que ofrece servicio de: Evaluaci?n y diagn?stico, donde se aplicar? una serie de pruebas al ni?o con la finalidad de identificar si presenta alg?n problema de lenguaje y aprendizaje, Terapias de lenguaje, ayudan a mejorar las condiciones de comunicaci?n, Terapias de habla, para mejorar la movilidad y tonicidad de los ?rganos relacionados con el habla, Terapias de aprendizaje, con la finalidad de mejorar los problemas de lectura, concentraci?n, escritura y c?lculo, Terapias sensoriales, con la finalidad de estimular el sistema nervioso central y establecer la adaptaci?n con el entorno, Terapias ocupacionales, para ayudar a mejorar a procesar la informaci?n que los ni?os reciben a trav?s de los sentidos, Terapias de psicomotricidad, para potenciar las habilidades corporales de los ni?os, Asesor?as psicol?gicas. El cliente tambi?n contar? con la posibilidad de atenci?n del ni?o a domicilio, como servicio complementario, donde un terapista asistir? a la casa del paciente, para iniciar o continuar con el tratamiento
On measuring the covariance matrix of the nonlinear power spectrum from simulations
We show how to estimate the covariance of the power spectrum of a
statistically homogeneous and isotropic density field from a single periodic
simulation, by applying a set of weightings to the density field, and by
measuring the scatter in power spectra between different weightings. We
recommend a specific set of 52 weightings containing only combinations of
fundamental modes, constructed to yield a minimum variance estimate of the
covariance of power. Numerical tests reveal that at nonlinear scales the
variance of power estimated by the weightings method substantially exceeds that
estimated from a simple ensemble method. We argue that the discrepancy is
caused by beat-coupling, in which products of closely spaced Fourier modes
couple by nonlinear gravitational growth to the beat mode between them.
Beat-coupling appears whenever nonlinear power is measured from Fourier modes
with a finite spread of wavevector, and is therefore present in the weightings
method but not the ensemble method. Beat-coupling inevitably affects real
galaxy surveys, whose Fourier modes have finite width. Surprisingly, the
beat-coupling contribution dominates the covariance of power at nonlinear
scales, so that, counter-intuitively, it is expected that the covariance of
nonlinear power in galaxy surveys is dominated not by small scale structure,
but rather by beat-coupling to the largest scales of the survey.Comment: 19 pages, 4 figures. To appear in Monthly Notices of the Royal
Astronomical Society. Revised to match accepted versio
An SU(N) Mott insulator of an atomic Fermi gas realized by large-spin Pomeranchuk cooling
The Hubbard model, containing only the minimum ingredients of nearest
neighbor hopping and on-site interaction for correlated electrons, has
succeeded in accounting for diverse phenomena observed in solid-state
materials. One of the interesting extensions is to enlarge its spin symmetry to
SU(N>2), which is closely related to systems with orbital degeneracy. Here we
report a successful formation of the SU(6) symmetric Mott insulator state with
an atomic Fermi gas of ytterbium (173Yb) in a three-dimensional optical
lattice. Besides the suppression of compressibility and the existence of charge
excitation gap which characterize a Mott insulating phase, we reveal an
important difference between the cases of SU(6) and SU(2) in the achievable
temperature as the consequence of different entropy carried by an isolated
spin. This is analogous to Pomeranchuk cooling in solid 3He and will be helpful
for investigating exotic quantum phases of SU(N) Hubbard system at extremely
low temperatures.Comment: 20 pages, 6 figures, to appear in Nature Physic
Spontaneous CP Violation in Non-Minimal Supersymmetric Models
We study the possibilities of spontaneous CP violation in the Next-to-Minimal
Supersymmetric Standard Model with an extra singlet tadpole term in the scalar
potential. We calculate the Higgs boson masses and couplings with radiative
corrections including dominant two loop terms. We show that it is possible to
satisfy the LEP constraints on the Higgs boson spectrum with non-trivial
spontaneous CP violating phases. We also show that these phases could account
for the observed value of epsilonK.Comment: 21 pages, 7 Figures in Encapsulated Postscrip
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