31,567 research outputs found
Classical mappings of the symplectic model and their application to the theory of large-amplitude collective motion
We study the algebra Sp(n,R) of the symplectic model, in particular for the
cases n=1,2,3, in a new way. Starting from the Poisson-bracket realization we
derive a set of partial differential equations for the generators as functions
of classical canonical variables. We obtain a solution to these equations that
represents the classical limit of a boson mapping of the algebra. The
relationship to the collective dynamics is formulated as a theorem that
associates the mapping with an exact solution of the time-dependent Hartree
approximation. This solution determines a decoupled classical symplectic
manifold, thus satisfying the criteria that define an exactly solvable model in
the theory of large amplitude collective motion. The models thus obtained also
provide a test of methods for constructing an approximately decoupled manifold
in fully realistic cases. We show that an algorithm developed in one of our
earlier works reproduces the main results of the theorem.Comment: 23 pages, LaTeX using REVTeX 3.
Microscopic Conductivity of Lattice Fermions at Equilibrium - Part I: Non-Interacting Particles
We consider free lattice fermions subjected to a static bounded potential and
a time- and space-dependent electric field. For any bounded convex region
() of space, electric fields
within drive currents. At leading order, uniformly
with respect to the volume of and
the particular choice of the static potential, the dependency on
of the current is linear and described by a conductivity distribution. Because
of the positivity of the heat production, the real part of its Fourier
transform is a positive measure, named here (microscopic) conductivity measure
of , in accordance with Ohm's law in Fourier space. This finite
measure is the Fourier transform of a time-correlation function of current
fluctuations, i.e., the conductivity distribution satisfies Green-Kubo
relations. We additionally show that this measure can also be seen as the
boundary value of the Laplace-Fourier transform of a so-called quantum current
viscosity. The real and imaginary parts of conductivity distributions satisfy
Kramers-Kronig relations. At leading order, uniformly with respect to
parameters, the heat production is the classical work performed by electric
fields on the system in presence of currents. The conductivity measure is
uniformly bounded with respect to parameters of the system and it is never the
trivial measure . Therefore, electric fields generally
produce heat in such systems. In fact, the conductivity measure defines a
quadratic form in the space of Schwartz functions, the Legendre-Fenchel
transform of which describes the resistivity of the system. This leads to
Joule's law, i.e., the heat produced by currents is proportional to the
resistivity and the square of currents
A very brief introduction to quantum computing and quantum information theory for mathematicians
This is a very brief introduction to quantum computing and quantum
information theory, primarily aimed at geometers. Beyond basic definitions and
examples, I emphasize aspects of interest to geometers, especially connections
with asymptotic representation theory. Proofs of most statements can be found
in standard references
On Dimensional Degression in AdS(d)
We analyze the pattern of fields in d+1 dimensional anti-de Sitter space in
terms of those in d dimensional anti-de Sitter space. The procedure, which is
neither dimensional reduction nor dimensional compactification, is called
dimensional degression. The analysis is performed group-theoretically for all
totally symmetric bosonic and fermionic representations of the anti-de Sitter
algebra. The field-theoretical analysis is done for a massive scalar field in
AdS(d+d) and massless spin one-half, spin one, and spin two fields in
AdS(d+1). The mass spectra of the resulting towers of fields in AdS(d) are
found. For the scalar field case, the obtained results extend to the shadow
sector those obtained by Metsaev in [1] by a different method.Comment: 30 page
Transient Nucleation near the Mean-Field Spinodal
Nucleation is considered near the pseudospinodal in a one-dimensional
model with a non-conserved order parameter and long-range
interactions. For a sufficiently large system or a system with slow relaxation
to metastable equilibrium, there is a non-negligible probability of nucleation
occurring before reaching metastable equilibrium. This process is referred to
as transient nucleation. The critical droplet is defined to be the
configuration of maximum likelihood that is dynamically balanced between the
metastable and stable wells. Time-dependent droplet profiles and nucleation
rates are derived, and theoretical results are compared to computer simulation.
The analysis reveals a distribution of nucleation times with a distinct peak
characteristic of a nonstationary nucleation rate. Under the quench conditions
employed, transient critical droplets are more compact than the droplets found
in metastable equilibrium simulations and theoretical predictions.Comment: 7 Pages, 5 Figure
Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders
Several models predict the existence of heavy colored resonances decaying to
top quarks in the TeV energy range that might be discovered at the LHC. In some
of those models, moreover, a sizable charge asymmetry of top versus antitop
quarks might be generated. The detection of these exotic resonances, however,
requires selecting data samples where the top and the antitop quarks are highly
boosted, which is experimentally very challenging. We asses that the
measurement of the top quark charge asymmetry at the LHC is very sensitive to
the existence of excited states of the gluon with axial-vector couplings to
quarks. We use a toy model with general flavour independent couplings, and show
that a signal can be detected with relatively not too energetic top and antitop
quarks. We also compare the results with the asymmetry predicted by QCD, and
show that its highest statistical significance is achieved with data samples of
top-antitop quark pairs of low invariant masses.Comment: 20 page
High-temperature signatures of quantum criticality in heavy fermion systems
We propose a new criterion for distinguishing the Hertz-Millis (HM) and the
local quantum critical (LQC) mechanism in heavy fermion systems with a magnetic
quantum phase transition (QPT). The criterion is based on our finding that the
spin screening of Kondo ions can be completely suppressed by the RKKY coupling
to the surrounding magnetic ions even without magnetic ordering and that,
consequently, the signature of this suppression can be observed in
spectroscopic measurements above the magnetic ordering temperature. We apply
the criterion to high-resolution photoemission (UPS) measurements on
CeCuAu and conclude that the QPT in this system is dominated by
the LQC scenario.Comment: Inveted paper, International Conference on Magnetism, ICM 2009,
Karlsruhe. Published version, added discussions of the relevance of
Fermi-surface fluctuations and of a structural transition near the QC
Fractal extra dimension in Kaluza-Klein theory
Kaluza-Klein theory in which the geometry of an additional dimension is
fractal has been considered. In such a theory the mass of an elementary
electric charge appears to be many orders of magnitude smaller than the Planck
mass, and the "tower" of masses which correspond to higher integer charges
becomes aperiodic.Comment: 3 pages, accepted for publication in Phys.Rev.D (submitted on
3.28.2001
First Order Calculation of the Inclusive Cross Section pp to ZZ by Graviton Exchange in Large Extra Dimensions
We calculate the inclusive cross section of double Z-boson production within
large extra dimensions at the Large Hadron Collider (LHC). Using perturbatively
quantized gravity in the ADD model we perform a first order calculation of the
graviton mediated contribution to the pp to ZZ cross section. At low energies
(e.g. Tevatron) this additional contribution is very small, making it virtually
unobservable, for a fundamental mass scale above 2500 GeV. At LHC energies
however, the calculation indicates that the ZZ-production rate within the ADD
model should differ significantly from the Standard Model if the new
fundamental mass scale would be below 15000 GeV. A comparison with the observed
production rate at the LHC might therefore provide direct hints on the number
and structure of the extra dimensions.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
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