3,694 research outputs found
The A-theoretic Farrell–Jones conjecture for virtually solvable groups
We prove the A -theoretic Farrell–Jones conjecture for virtually solvable groups. As a corollary, we obtain that the conjecture holds for S -arithmetic groups and lattices in almost connected Lie groups
Anderson-Mott Transition in a Magnetic Field: Corrections to Scaling
It is shown that the Anderson-Mott metal-insulator transition of
paramagnetic, interacting disordered electrons in an external magnetic field is
in the same universality class as the transition from a ferromagnetic metal to
a ferromagnetic insulator discussed recently. As a consequence, large
corrections to scaling exist in the magnetic-field universality class, which
have been neglected in previous theoretical descriptions. The nature and
consequences of these corrections to scaling are discussed.Comment: 5pp., REVTeX, no figs, final version as publishe
Limit cycles of effective theories
A simple example is used to show that renormalization group limit cycles of
effective quantum theories can be studied in a new way. The method is based on
the similarity renormalization group procedure for Hamiltonians. The example
contains a logarithmic ultraviolet divergence that is generated by both real
and imaginary parts of the Hamiltonian matrix elements. Discussion of the
example includes a connection between asymptotic freedom with one scale of
bound states and the limit cycle with an entire hierarchy of bound states.Comment: 8 pages, 3 figures, revtex
The WARPS survey - IV: The X-ray luminosity-temperature relation of high redshift galaxy clusters
We present a measurement of the cluster X-ray luminosity-temperature relation
out to high redshift (z~0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters
detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fit
in redshift and luminosity bins. The resulting temperature and luminosity
measurements of these bins, which occupy a region of the high redshift L-T
relation not previously sampled, are compared to existing measurements at low
redshift in order to constrain the evolution of the L-T relation. We find a
best fit to low redshift (z1 keV, to be L proportional
to T^(3.15\pm0.06). Our data are consistent with no evolution in the
normalisation of the L-T relation up to z~0.8. Combining our results with ASCA
measurements taken from the literature, we find eta=0.19\pm0.38 (for Omega_0=1,
with 1 sigma errors) where L_Bol is proportional to (1 + z)^eta T^3.15, or
eta=0.60\pm0.38 for Omega_0=0.3. This lack of evolution is considered in terms
of the entropy-driven evolution of clusters. Further implications for
cosmological constraints are also discussed.Comment: 11 pages, 7 figures, accepted for publication in MNRA
Electrons in an annealed environment: A special case of the interacting electron problem
The problem of noninteracting electrons in the presence of annealed magnetic
disorder, in addition to nonmagnetic quenched disorder, is considered. It is
shown that the proper physical interpretation of this model is one of electrons
interacting via a potential that is long-ranged in time, and that its technical
analysis by means of renormalization group techniques must also be done in
analogy to the interacting problem. As a result, and contrary to previous
claims, the model does not simply describe a metal-insulator transition in
() dimensions. Rather, it describes a transition
to a ferromagnetic state that, as a function of the disorder, precedes the
metal-insulator transition close to . In , a transition from a
paramagnetic metal to a paramagnetic insulator is possible.Comment: 13 pp., LaTeX, 2 eps figs; final version as publishe
Spontaneous symmetry breaking in the colored Hubbard model
The Hubbard model is reformulated in terms of different ``colored'' fermion
species for the electrons or holes at different lattice sites.
Antiferromagnetic ordering or d-wave superconductivity can then be described in
terms of translationally invariant expectation values for colored composite
scalar fields. A suitable mean field approximation for the two dimensional
colored Hubbard model shows indeed phases with antiferromagnetic ordering or
d-wave superconductivity at low temperature. At low enough temperature the
transition to the antiferromagnetic phase is of first order. The present
formulation also allows an easy extension to more complicated microscopic
interactions.Comment: 19 pages, 5 figure
Mesons in (2+1) Dimensional Light Front QCD. II. Similarity Renormalization Approach
Recently we have studied the Bloch effective Hamiltonian approach to bound
states in 2+1 dimensional gauge theories. Numerical calculations were carried
out to investigate the vanishing energy denominator problem. In this work we
study similarity renormalization approach to the same problem. By performing
analytical calculations with a step function form for the similarity factor, we
show that in addition to curing the vanishing energy denominator problem,
similarity approach generates linear confining interaction for large transverse
separations. However, for large longitudinal separations, the generated
interaction grows only as the square root of the longitudinal separation and
hence produces violations of rotational symmetry in the spectrum. We carry out
numerical studies in the G{\l}azek-Wilson and Wegner formalisms and present low
lying eigenvalues and wavefunctions. We investigate the sensitivity of the
spectra to various parameterizations of the similarity factor and other
parameters of the effective Hamiltonian, especially the scale . Our
results illustrate the need for higher order calculations of the effective
Hamiltonian in the similarity renormalization scheme.Comment: 31 pages, 4 figures, to be published in Physical Review
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