Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where José María Román is active.

Publication


Featured researches published by José María Román.


Nuclear Physics | 2002

Large-N limit of the exactly solvable BCS model: analytics versus numerics

José María Román; Germán Sierra; J. Dukelsky

Abstract We have studied the numerical solutions of Richardson equations of the BCS model in the limit of large number of energy levels at half-filling, and compare them with the analytic results derived by Gaudin and Richardson, which in turn leads to the standard BCS solution. We focus on the location and density of the roots, the eigenvalues of the conserved quantities, and the scaling properties of the total energy for the equally spaced and the two-level models.


Physical Review B | 2004

Russian doll renormalization group and superconductivity

André LeClair; José María Román; Germán Sierra

We show that a simple extension of the standard BCS Hamiltonian leads to an infinite number of BCS eigenstates with different energy gaps and self-similar properties, described by a cyclic renormalization group flow of the BCS coupling constant which returns to its original value after a finite renormalization group time.


Nuclear Physics | 2003

Russian doll renormalization group and Kosterlitz–Thouless flows

André LeClair; José María Román; Germán Sierra

We investigate the previously proposed cyclic regime of the Kosterlitz-Thouless renormalization group (RG) flows. The period of one cycle is computed in terms of the RG invariant. Using bosonization, we show that the theory has


Nuclear Physics | 2004

Log-periodic behavior of finite size effects in field theories with RG limit cycles

André LeClair; José María Román; Germán Sierra

U_q (\hat{sl(2)})


Physical Review B | 2003

Elementary excitations of the BCS model in the canonical ensemble

José María Román; Germán Sierra; J. Dukelsky

quantum affine symmetry, with


Journal of Physics A | 1996

The regulated four-parameter one-dimensional point interaction

José María Román; R. Tarrach

q


Nuclear Physics | 2004

Charge and spin quantum fluids generated by many-electron interactions

J. M. P. Carmelo; José María Román; Karlo Penc

{\it real}. Based on this symmetry, we study two possible S-matrices for the theory, differing only by overall scalar factors. We argue that one S-matrix corresponds to a continuum limit of the XXZ spin chain in the anti-ferromagnetic domain


International Journal of Modern Physics B | 1999

Effective Field Theory Approach to Ferromagnets and Antiferromagnets in Crystalline Solids

José María Román; Joan Soto

\Delta<-1


Journal of Physics A | 1998

The matrix product approach to quantum spin ladders

José María Román; Germán Sierra; J. Dukelsky; M. A. Martin-Delgado

. The latter S-matrix has a periodicity in energy consistent with the cyclicity of the RG. We conjecture that this S-matrix describes the cyclic regime of the Kosterlitz-Thouless flows. The other S-matrix we investigate is an analytic continuation of the usual sine-Gordon one. It has an infinite number of resonances with masses that have a Russian doll scaling behavior that is also consistent with the period of the RG cycles computed from the beta-function. Closure of the bootstrap for this S-matrix leads to an infinite number of particles of higher spin with a mass formula suggestive of a string theory.


Physical Review B | 2002

What are the elementary excitations of the BCS model in the canonical ensemble

José María Román; Germán Sierra; J. Dukelsky

Abstract We compute the finite size effects in the ground state energy, equivalently the effective central charge c eff , based on S-matrix theories recently conjectured to describe a cyclic regime of the Kosterlitz–Thouless renormalization group flows. The effective central charge has periodic properties consistent with renormalization group predictions. Whereas c eff for the massive case has a singularity in the very deep ultra-violet, we argue that the massless version is non-singular and periodic on all length scales.

Collaboration


Dive into the José María Román's collaboration.

Top Co-Authors

Avatar

Germán Sierra

Spanish National Research Council

View shared research outputs
Top Co-Authors

Avatar

J. Dukelsky

Spanish National Research Council

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

A. Clemente

University of Valencia

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

M. A. Martin-Delgado

Complutense University of Madrid

View shared research outputs
Top Co-Authors

Avatar

R. Tarrach

University of Barcelona

View shared research outputs
Researchain Logo
Decentralizing Knowledge