SU(N)→Z(N){\rm SU}(N) \to {\rm Z}(N) dual superconductor models: the magnetic loop ensemble point of view

In this work, we initially discuss some physical properties of effective ${\rm SU}(N) \to {\rm Z}(N)$ YMH models, emphasizing the important role of valence gluons. Next, we review how adjoint fields are naturally generated as an effective description of "adjoint" loops in $4D$. Finally, we discuss the consequences that can be learnt from this point of view, and briefly comment on some improvements.Comment: 14 pages, 7 figures, proceedings of the XII Quark Confinement conference, Thessaloniki, Greece, from 28th August to 4rd September 201

Universal Landauer conductance in chiral symmetric 2d systems

We study transport properties of an arbitrarily shaped ultraclean graphene sheet, adiabatically connected to leads,composed by the same material. If the localized interactions do not destroy chiral symmetry, we show that the conductance is quantized, since it is dominated by the quasi one-dimensional leads. As an example, we show that smooth structural deformations of the graphene plane do not modify the conductance quantization.Comment: 6 pages, no figure

Métodos cuánticos para teorías de campo de orden superior

En este trabajo estudiaremos las teorias de campo de orden superior, haciendo énfasisen el tratamiento de los modos complejos (grados de libertad asociados a parámetroscomplejos de masa). En el primer capítulo mostramos la relación de los modos complejos y las teoríasde métrica indefinida; también veremos que estos modos aparecen de manera naturalcuando se extiende el modelo supersimétrico de Wess-Zumino a un espacio dedimensión mayor a cuatro. I En el segundo capítulo presentaremos los métodos lagrangianos para campos queobedecen ecuaciones de orden superior. Usando el teorema de Nöether construiremoslos tensores canónicos, en particular obtendremos el hamiltoniano (magnitudconservada por la simetría ante traslaciones temporales). Para estudiar las caracteristicas escenciales del tratamiento de los modos complejos,consideraremos en el tercer capítulo un modelo de orden superior en el cualintervienen un modo de masa real y un par de modos complejos conjugados. Elrequerimiento de que a nivel cuántico el hamiltoniano genere las traslaciones temporalesdel sistema nos llevará al algebra de conmutadores para los coeficientes en eldesarrollo de Fourier de los campos. La representación para los operadores correspondientesa los modos complejos, a diferencia del caso habitual de masa real (donde larepresentación es holomorfa), se asemeja a la de los operadores canónicos de posicióne impulso, actuando sobre funciones de z y z¯. Obtendremos entonces una representaciónpara el operador de energía-momento lo cual nos permitirá representar alvacío y calcular los valores de expectación de los distintos productos de operadoresde campo. En particular, el propagador para los modos complejos resultará mitadavanzado y mitad retardado. En el cuarto capítulo calcularemos la auto-energia a segundo orden para el modeloanteriormente descrito (con una auto-interacción ʎϕ3). Para ello representaremos a losdistintos propagadores por medio de funcionales analíticas y obtendremos la expresiónpara la convolución de dos funcionales analíticas definidas por caminos de integracióngenerales. Mostraremos entonces que el diagrama de auto-energía es compatible conunitariedad y la eliminación de los modos complejos del espacio asintótico. Finalmente, en el quinto capitulo estudiaremos algunas propiedades de la autoenergia.a segundo orden. Siendo la teoría relativista y el vacío invariante de Lorentz,las amplitudes de probabilidad para los distintos procesos deben ser invariantes de Lorentz; verificaremos entonces que la auto-energía calculada es invariante de Lorentz. Además, veremos que los modos complejos actúan como reguladores pues mejoran elcomportamiento ultravioleta de la auto-energia debida sólo al modo real.Fil: Oxman, Luis E.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Prospecting effective Yang-Mills-Higgs models for the asymptotic confining flux tube

In this work, we analyze a large class of effective Yang-Mills-Higgs models constructed in terms of adjoint scalars. In particular, we reproduce asymptotic properties of the confining string, suggested by lattice simulations of $SU(N)$ pure Yang-Mills theory, in models that are stable in the whole range of Higgs-field mass parameters. These properties include $N$-ality, Abelian-like flux-tube profiles, independence of the profiles with the $N$-ality of the quark representation, and Casimir scaling. We find that although these models are formulated in terms of many fields and possible Higgs potentials, a collective behavior can be established in a large region of parameter space, where the desired asymptotic behavior is realized.Comment: 24 pages, 1 figur

Single Superfield Representation for Mixed Retarded and Advanced Correlators in Disordered Systems

We propose a new single superfield representation for mixed retarded and advanced correlators for noninteracting disordered systems. The method is tested in the simpler context of Random Matrix theory, by comparing with well known universal behavior for level spacing correlations. Our method is general and could be especially interesting to study localization properties encoded in the mixed correlators of Quantum Hall systems.Comment: 13 pages including two figures, RevTex4. Improved version. Figures changed. To appear in Journal of Physics

Canonical quantization of non-local field equations

We consistently quantize a class of relativistic nonlocal field equations characterized by a nonlocal kinetic term in the Lagrangian. We solve the classical nonlocal equations of motion for a scalar field and evaluate the on-shell Hamiltonian. The quantization is realized by imposing Heisenberg’s equation, which leads to the commutator algebra obeyed by the Fourier components of the field. We show that the field operator carries, in general, a reducible representation of the Poincare group. We also consider the Gupta-Bleuler quantization of a nonlocal gauge theory and analyze the propagators and the physical modes of the gauge field.Facultad de Ciencias Exacta

A Family of Unitary Higher Order Equations

A scalar field obeying a Lorentz invariant higher order wave equation, is minimally coupled to the electromagnetic field. The propagator and vertex factors for the Feynman diagrams, are determined. As an example we write down the matrix element for the Compton effect. This matrix element is algebraically reduced to the usual one for a charged Klein–Gordon particle. It is proven that the nth order theory is equivalent to n independent second order theories. It is also shown that the higher order theory is both renormalizable and unitary for arbitrary n.Facultad de Ciencias Exacta

Non-perturbative behavior of the quantum phase transition to a nematic Fermi fluid

We discuss shape (Pomeranchuk) instabilities of the Fermi surface of a two-dimensional Fermi system using bosonization. We consider in detail the quantum critical behavior of the transition of a two dimensional Fermi fluid to a nematic state which breaks spontaneously the rotational invariance of the Fermi liquid. We show that higher dimensional bosonization reproduces the quantum critical behavior expected from the Hertz-Millis analysis, and verify that this theory has dynamic critical exponent $z=3$. Going beyond this framework, we study the behavior of the fermion degrees of freedom directly, and show that at quantum criticality as well as in the the quantum nematic phase (except along a set of measure zero of symmetry-dictated directions) the quasi-particles of the normal Fermi liquid are generally wiped out. Instead, they exhibit short ranged spatial correlations that decay faster than any power-law, with the law $|x|^{-1} \exp(-\textrm{const.} |x|^{1/3})$ and we verify explicitely the vanishing of the fermion residue utilizing this expression. In contrast, the fermion auto-correlation function has the behavior $|t|^{-1} \exp(-{\rm const}. |t|^{-2/3})$. In this regime we also find that, at low frequency, the single-particle fermion density-of-states behaves as $N^*(\omega)=N^*(0)+ B \omega^{2/3} \log\omega +...$, where $N^*(0)$ is larger than the free Fermi value, N(0), and $B$ is a constant. These results confirm the non-Fermi liquid nature of both the quantum critical theory and of the nematic phase.Comment: 20 pages, 2 figures, 1 table; new version with minor changes; new subsection 3C2 added with an explicit calculation of the quasiparticle residue at the nematic transition; minor typos corrected, new references; general beautification of the text and figure

Competition between Pomeranchuk instabilities in the nematic and hexatic channels in a two-dimensional spinless Fermi fluid

We study the competition between the nematic and the hexatic phases of a two-dimensional spinless Fermi fluid near Pomeranchuk instabilities. We show that the general phase diagram of this theory contains a bicritical point where two second-order lines and a first-order nematic/hexatic phase transition meet together. We found that at criticality and deep inside the associated symmetry broken phases, the low energy theory is governed by a dissipative cubic mode, even near the bicritical point where nematic and hexatic fluctuations cannot be distinguished due to very strong dynamical couplings.Facultad de Ciencias ExactasInstituto de Física La Plat