15,692 research outputs found
Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains
The ground state spin-wave excitations and thermodynamic properties of two
types of ferrimagnetic chains are investigated: the alternating spin-1/2
spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the
spin-5/2 site. Results for magnetic susceptibility, magnetization and specific
heat are obtained through the finite-temperature Lanczos method with the aim in
describing available experimental data, as well as comparison with theoretical
results from the semiclassical approximation and the low-temperature
susceptibility expansion derived from Takahashi's modified spin-wave theory. In
particular, we study in detail the temperature vs. magnetic field phase diagram
of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases
are identified: the Luttinger Liquid phase, the ferrimagnetic plateau and the
fully polarized one, and the respective quantum critical points and crossover
lines
Vector meson quasinormal modes in a finite-temperature AdS/QCD model
We study the spectrum of vector mesons in a finite temperature plasma. The
plasma is holographically described by a black hole AdS/QCD model. We compute
the boundary retarded Green's function using AdS/CFT prescriptions. The
corresponding thermal spectral functions show quasiparticle peaks at low
temperatures. Then we calculate the quasinormal modes of vector mesons in the
soft-wall black hole geometry and analyse their temperature and momentum
dependences.Comment: 27 pages, 9 figure
Majority-Vote Model on a Random Lattice
The stationary critical properties of the isotropic majority vote model on
random lattices with quenched connectivity disorder are calculated by using
Monte Carlo simulations and finite size analysis. The critical exponents
and are found to be different from those of the Ising and
majority vote on the square lattice model and the critical noise parameter is
found to be .Comment: 4 pages, 6 figure
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