2,484 research outputs found
Supersymmetric Approach to Heavy-Fermion Systems
We present a new supersymmetric approach to the Kondo lattice model in order
to describe simultaneously the quasiparticle excitations and the low-energy
magnetic fluctuations in heavy-Fermion systems. This approach mixes the
fermionic and the bosonic representation of the spin following the standard
rules of superalgebra. Our results show the formation of a bosonic band within
the hybridization gap reflecting the spin collective modes. The density of
states at the Fermi level is strongly renormalized while the Fermi surface sum
rule includes states. The dynamical susceptibility is made of a Fermi
liquid superimposed on a localized magnetism contribution.Comment: 5 pages, 2 figure
Multiquark Systems in a Constituent Quark Model with Chiral Dynamics
We discuss the stability of multiquark systems within the recent model of
Glozman et al. where the chromomagnetic hyperfine interaction is replaced by
pseudoscalar-meson exchange. We find that such an interaction binds a heavy
tetraquark system ( and by GeV.
This is at variance with results of previous models where is
unstable.Comment: 6 pages, Plain Latex, Contribution to the Workshop''Quark Confinement
and the Hadron Spectrum II'', Como, Italy, June 26--29, 1996, to appear in
the Proceedings, ed. Nora Brambilla, World Scientifi
Heavy-Flavour Pentaquarks in a Chiral Constituent Quark Model
Within the chiral constituent quark model of Glozman and Riska, we discuss
the stability of heavy pentaquarks, i.e. hadrons containing four light quarks
and a heavy antiquark. The spin-dependent part of the Hamiltonian is dominated
by the short-range part of the Goldstone-boson-exchange interaction. We find
that these systems are not bound, having an energy above the lowest
dissociation threshold into a baryon and a meson.Comment: 10 pages + table
Quantum Phase Transitions
We give a general introduction to quantum phase transitions in
strongly-correlated electron systems. These transitions which occur at zero
temperature when a non-thermal parameter like pressure, chemical
composition or magnetic field is tuned to a critical value are characterized by
a dynamic exponent related to the energy and length scales and
. Simple arguments based on an expansion to first order in the effective
interaction allow to define an upper-critical dimension (where
and is the spatial dimension) below which mean-field description is
no longer valid. We emphasize the role of pertubative renormalization group
(RG) approaches and self-consistent renormalized spin fluctuation (SCR-SF)
theories to understand the quantum-classical crossover in the vicinity of the
quantum critical point with generalization to the Kondo effect in heavy-fermion
systems. Finally we quote some recent inelastic neutron scattering experiments
performed on heavy-fermions which lead to unusual scaling law in
for the dynamical spin susceptibility revealing critical local modes beyond the
itinerant magnetism scheme and mention new attempts to describe this local
quantum critical point.Comment: 13 pages, 4 figure
Thermodynamics of Fateev's models in the Presence of External Fields
We study the Thermodynamic Bethe Ansatz equations for a one-parameter quantum
field theory recently introduced by V.A.Fateev. The presence of chemical
potentials produces a kink condensate that modifies the excitation spectrum.
For some combinations of the chemical potentials an additional gapless mode
appears. Various energy scales emerge in the problem. An effective field
theory, describing the low energy excitations, is also introduced.Comment: To appear in Nucl.Phys.
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