20,359 research outputs found
Thermodynamic quantum critical behavior of the Kondo necklace model
We obtain the phase diagram and thermodynamic behavior of the Kondo necklace
model for arbitrary dimensions using a representation for the localized and
conduction electrons in terms of local Kondo singlet and triplet operators. A
decoupling scheme on the double time Green's functions yields the dispersion
relation for the excitations of the system. We show that in there is
an antiferromagnetically ordered state at finite temperatures terminating at a
quantum critical point (QCP). In 2-d, long range magnetic order occurs only at
T=0. The line of Neel transitions for varies with the distance to the
quantum critical point QCP as, where the shift
exponent . In the paramagnetic side of the phase diagram, the
spin gap behaves as for consistent with
the value found for the dynamical critical exponent. We also find in this
region a power law temperature dependence in the specific heat for
and along the non-Fermi liquid trajectory. For , in the so-called Kondo spin liquid phase, the thermodynamic
behavior is dominated by an exponential temperature dependence.Comment: Submitted to PR
A Gaussian Weave for Kinematical Loop Quantum Gravity
Remarkable efforts in the study of the semi-classical regime of kinematical
loop quantum gravity are currently underway. In this note, we construct a
``quasi-coherent'' weave state using Gaussian factors. In a similar fashion to
some other proposals, this state is peaked in both the connection and the spin
network basis. However, the state constructed here has the novel feature that,
in the spin network basis, the main contribution for this state is given by the
fundamental representation, independently of the value of the parameter that
regulates the Gaussian width.Comment: 15 pages, 3 figures, Revtex file. Comments added and references
updated. Final version to appear in IJMP-
Renormalization in a Lorentz-violating model and higher-order operators
The renormalization in a Lorentz-breaking scalar-spinor higher-derivative
model involving self-interaction and the Yukawa-like coupling is
studied. We explicitly de- monstrate that the convergence is improved in
comparison with the usual scalar-spinor model, so, the theory is
super-renormalizable, with no divergences beyond four loops. We compute the
one-loop corrections to the propagators for the scalar and fermionic fields and
show that in the presence of higher-order Lorentz invariance violation, the
poles that dominate the physical theory, are driven away from the standard
on-shell pole mass due to radiatively induced lower dimensional operators. The
new operators change the standard gamma-matrix structure of the two-point
functions, introduce large Lorentz-breaking corrections and lead to
modifications in the renormalization conditions of the theory. We found the
physical pole mass in each sector of our model.Comment: 20 pages, 5 figures. New version with modifications in the
renormalized Lagrangian. To be published in EPJ
Combined Relativistic and static analysis for all Delta B=2 operators
We analyse matrix elements of Delta B=2 operators by combining QCD results
with the ones obtained in the static limit of HQET. The matching of all the QCD
operators to HQET is made at NLO order. To do that we have to include the
anomalous dimension matrix up to two loops, both in QCD and HQET, and the one
loop matching for all the Delta B=2 operators. The matrix elements of these
operators are relevant for the prediction of the B-\bar B mixing, B_s meson
width difference and supersymmetric effects in Delta B=2 transitions.Comment: 3 pages, 1 figure. Lattice2001(heavyquark
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