DSpace-CRIS @ UCAhttps://repositorio.uca.edu.arDSpace es el repositorio institucional que tiene por objeto recoger ,organizar y preservar material digital de investigación. Tue, 18 Jun 2024 22:17:54 GMT2024-06-18T22:17:54Z5061Mott transition and integrable lattice models in two dimensionshttps://repositorio.uca.edu.ar/handle/123456789/5494Título : Mott transition and integrable lattice models in two dimensions
Autor : Bottesi, Federico L.; Zemba, Guillermo Raúl
Resumen : Abstract: We describe the two-dimensional Mott transition in a Hubbard-like model with nearest neighbors interactions based on a recent solution to the Zamolodchikov tetrahedron equation, which extends the notion of integrability to two-dimensional lattice systems. At the Mott transition, we find that the system is in a d-density wave or staggered flux phase that can be described by a double Chern Simons effective theory with symmetry su(2)1 xsu(2)1. The Mott transition is of topological nature, characterized by the emergence of vortices in antiferromagnetic arrays interacting strongly with the electric charges and an electric-magnetic duality. We also consider the effect of small doping on this theory and show that it leads to a quantum gas-liquid coexistence phase, which belongs to the Ising universality class and which is consistent with several experimental observations.
Tue, 01 Jan 2008 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54942008-01-01T00:00:00ZThermodynamics of a model for RNA foldinghttps://repositorio.uca.edu.ar/handle/123456789/5492Título : Thermodynamics of a model for RNA folding
Autor : Dell'Erba, Matías G.; Zemba, Guillermo Raúl
Resumen : Abstract: We analyze the thermodynamic properties of a simplified model for folded RNA molecules recently studied by G. Vernizzi, H. Orland, A. Zee (in Phys. Rev. Lett. 94 (2005) 168103). The model consists of a chain of one-flavor base molecules with a flexible backbone and all possible pairing interactions equally allowed. The spatial pseudoknot structure of the model can be effi- ciently studied by introducing a N × N hermitian random matrix model at each chain site, and associating Feynman diagrams of these models to spatial configurations of the molecules. We obtain an exact expression for the topo- logical expansion of the partition function of the system. We calculate exact and asymptotic expressions for the free energy, specific heat, entanglement and chemical potential and study their behavior as a function of temperature. Our results are consistent with the interpretation of 1/N as being a measure of the concentration of Mg++ in solution.
Tue, 01 Jan 2008 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54922008-01-01T00:00:00ZEffective field theory and integrability in two-dimensional Mott transitionhttps://repositorio.uca.edu.ar/handle/123456789/5475Título : Effective field theory and integrability in two-dimensional Mott transition
Autor : Bottesi, Federico L.; Zemba, Guillermo Raúl
Resumen : Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a Quantum Group symmetry as a consequence of a recently found solution of the Zamolodchikov Tetrahedron Equation. A projection (from three to two space-time dimen- sions) property of the solution is used to identify the symmetry of the model at the Mott critical point as Uq([sl(2)) ⊗ Uq([sl(2)), with deformation param- eter q = −1. Based on this result, the low-energy Effective Field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the Effective Filed Theory methods, we show that the Mott transi- tion that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.
Fri, 01 Jan 2010 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54752010-01-01T00:00:00ZChiral partition functions of quantum Hall dropletshttps://repositorio.uca.edu.ar/handle/123456789/5424Título : Chiral partition functions of quantum Hall droplets
Autor : Cappelli, Andrea; Viola, Giovanni; Zemba, Guillermo Raúl
Resumen : Abstract: Chiral partition functions of conformal eld theory describe the edge exci- tations of isolated Hall droplets. They are characterized by an index specifying the quasiparticle sector and transform among themselves by a nite-dimensional representation of the modular group. The partition functions are derived and used to describe electron transitions leading to Coulomb blockade conductance peaks. We nd the peak patterns for Abelian hierarchical states and non- Abelian Read-Rezayi states, and compare them. Experimental observation of these features can check the qualitative properties of the conformal eld the- ory description, such as the decomposition of the Hilbert space into sectors, involving charged and neutral parts, and the fusion rules.
Thu, 01 Jan 2009 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54242009-01-01T00:00:00ZCoulomb blockade in hierarchical quantum Hall dropletshttps://repositorio.uca.edu.ar/handle/123456789/5473Título : Coulomb blockade in hierarchical quantum Hall droplets
Autor : Cappelli, Andrea; Georgiev, Lachezar S.; Zemba, Guillermo Raúl
Resumen : Abstract: The degeneracy of energy levels in a quantum dot of Hall fluid, leading to conductance peaks, can be readily derived from the partition functions of conformal field theory. Their complete expressions can be found for Hall states with both Abelian and non-Abelian statistics, upon adapting known results for the annulus geometry. We analyze the Abelian states with hierarchical filling fractions, = m/(mp±1), and find a non trivial pattern of conductance peaks. In particular, each one of them occurs with a characteristic multiplicity, that is due to the extended symmetry of the m-folded edge. Experimental tests of the multiplicity can shed more light on the dynamics of this composite edge.
Thu, 01 Jan 2009 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54732009-01-01T00:00:00ZTopological phase transition in a RNA model in the de Gennes regimehttps://repositorio.uca.edu.ar/handle/123456789/5465Título : Topological phase transition in a RNA model in the de Gennes regime
Autor : Dell'Erba, Matías G.; Zemba, Guillermo Raúl
Resumen : Abstract: We study a simplified model of the RNA molecule proposed by G. Vernizzi, H. Orland and A. Zee in the regime of strong concentration of positive ions in solution. The model considers a flexible chain of equal bases that can pairwise interact with any other one along the chain, while preserving the property of saturation of the interactions. In the regime considered, we observe the emergence of a critical temperature Tc separating two phases that can be characterized by the topology of the predominant configurations: in the large temperature regime, the dominant configurations of the molecule have very large genera (of the order of the size of the molecule), corresponding to a complex topology, whereas in the opposite regime of low temperatures, the dominant configurations are simple and have the topology of a sphere. We determine that this topological phase transition is of first order and provide an analytic expression for Tc. The regime studied for this model exhibits analogies with that for the dense polymer systems studied by de Gennes.
Thu, 01 Jan 2009 00:00:00 GMThttps://repositorio.uca.edu.ar/handle/123456789/54652009-01-01T00:00:00Z