arXiv subjects

Robert Lacaze

Publications and source records attributed to Robert Lacaze.

4 recordsLinked to original sources

arXiv2006

Towards continuum limit of screening lengths with chiral Fermions

We investigate mesonic screening correlators at T=2T_c using the overlap Fermions in the quenched approximation, where T_c is the QCD phase transition temperature. Using lattices with temporal extent up to 8, we found that both pseudoscalar and vector correlators exhibit a nice $cosh$ behaviour, leading to a plateau behaviour in the local screening masses as a function of distance. The rho and pi masses so determined show very little variation with the lattice spacing a. This augurs well for the use of chiral Fermions, and further suggests the small deviations of these masses from the ideal gas values are genuine effects of interactions.

hep-lat↗

arXiv2003

Speed and Adaptability of Overlap Fermion Algorithms

We compare the efficiency of four different algorithms to compute the overlap Dirac operator, both for the speed, i.e., time required to reach a desired numerical accuracy, and for the adaptability, i.e., the scaling of speed with the condition number of the (square of the) Wilson Dirac operator. Although orthogonal polynomial expansions give good speeds at moderate condition number, they are highly non-adaptable. One of the rational function expansions, the Zolotarev approximation, is the fastest and is adaptable. The conjugate gradient approximation is adaptable, self-tuning, and nearly as fast as the ZA.

hep-lat↗

arXiv2000

spl(2,1) dynamical supersymmetry and suppression of ferromagnetism in flat band double-exchange models

The low energy spectrum of the ferromagnetic Kondo lattice model on a N-site complete graph extended with on-site repulsion is obtained from the underlying spl(2,1) algebra properties in the strong coupling limit. The ferromagnetic ground state is realized for 1 and N+1 electrons only. We identify the large density of states to be responsible for the suppression of the ferromagnetic state and argue that a similar situation is encountered in the Kagome, pyrochlore, and other lattices with flat bands in their one-particle density of states.

cond-mat.str-el↗

arXiv1998

Solution of quantum double exchange on the complete graph from spl(2,1) dynamical supersymmetry

The exact and analytical low energy spectrum of the ferromagnetic Kondo lattice model on a complete graph extended with on-site repulsion $U$ is obtained in terms of a dynamical spl(2,1) supersymmetry in the limit of infinitely strong Hund's coupling (double exchange). Furthermore, we show that for the particular value of $U=J_H/2$ the supersymmetry is not constrained to infinite $J_H/t$ only and we calculate the energy including the $t^2/J_H$ corrections analytically and we give numerical evidence which suggest that the Kondo Hamiltonian is itself supersymmetric for any $J_H/t$. On a $N$ site graph, the ferromagnetic ground state is realized for 1 and $N$+1 electrons only. In the leading order in the value of the core spin, the quantum and semiclassical spectra are identical.

cond-mat.str-el↗