Centro Universitario de Investigación en Ciencias Básicas



Seminario
Febrero - Julio 2007

El seminario se lleva a cabo en el Auditorio de la Facultad de Ciencias.

24 de mayo
4:00 pm

Estabilizacin del radin en dimensiones extras planas

El Santos
Universidad Autnoma de Chiapas

Abstract:

16 de mayo
4:00 pm

Flavour changing currents and CP violation in supersymmetric models at LHC era : From top to tau decays

David Delepine
IFUG - Universidad de Guanajuato

Abstract: The supersymmetric extensions of the electroweak standard model (SM) contains new sources for flavour changing currents and for CP violation. We shall focus our interest on two way to look for physics beyond SM at LHC: top flavour changing processes and CP asymmetry in tau semi-leptonic CP asymmetry. First, in SM, flavour changing currents are usually suppressed and SUSY models could strongly enhanced top flavour changing processes where the expected branching ratio for these processes (as t-> g c) should be close to LHC sensitivity. We shall review the predictions of SUSY models on flavour changing top decays with light right-stop scalar. Secondly, CP violation in semi-leptonic tau decay is very sensitive to new physics as SM predictions are very suppressed. We shall focus the second part of this talk on how to generate a CP asymmetry in semi-leptonic tau decays and how sensitive it is to SUSY extensions of the SM. The "known" CP asymmetry expected in tau semi-leptonic Kaon decays and the resulting paradox of apparent CPT violation will be discussed.

16 de mayo
1:00 pm

Noncommutative spin geometry of the standard Podles 2-sphere

Elmar Wagner
Universidad de Varsovia

Abstract: Currently, there is an increasing interest in studying quantum spaces arising in Quantum Group Theory from the Noncommutative Differential Geometry point of view. One of the physical motivations has its origin in the nature of space time at small distances, where the concept of differentiable manifolds seems to fail. The idea is to describe "noncommutative spaces" by noncommutative algebras without referring to "points of a manifold" and to use Quantum Groups as generalized symmetry transformations. The talk will give a short overview how one translates geometrical concepts into the framework of noncommutative algebras.
The aim is to show that Alain Connes' Noncommutative Geometry can be applied successfully to the standard Podles 2-sphere. Using the description of quantum line bundles given by the Hopf fibration of quantum SU(2) over the standard Podles 2-sphere, the Dirac operator can be described exactly as in the classical case. An explicit description of an equivariant real even spectral triple on the standard Podles 2-sphere is given by applying the representation theory of quantum SU(2). This approach provides simple proofs of the axioms defining the noncommutative spin geometry.
Taking commutators with the Dirac operator gives the distinguished 2-dimensional covariant differential calculus found by Podles. The spectral triple is 0-summable which reflects the dimension drop of the Hochschild dimension. Replacing Hochschild and cyclic (co)homology by a twisted version, the correct dimension can be recovered. For instance, there exists a twisted Hochschild 2-cycle representing the volume form of the distinguished covariant differential calculus, and a non-trivial twisted cyclic 2-cocycle associated with volume form. As a Hilbert space operator, the volume form is a multiple of a q-deformed grading operator and so it defines an orientation. The twisted cyclic 2-cocycle pairs with equivariant K0-classes computing the q-winding number of the quantum line bundles which coincides with the q-index of the Dirac operator. Moreover, Poincare duality holds for this example.

4 de mayo
4:00 pm

Two-particle bound states in an antiferromagnet

Florian Kmpfer
Institut fuer theoretische Physik, Universidad de Bern

Abstract: First of all, I will give a motivation why antiferromagnets are interesting condensed matter systems. We will see that these systems can be doped with electrons or holes. The physics of only two doped electrons or two holes is already highly non-trivial and is best explored by a low-energy effective field theory. Using such a low- energy effective theory for lightly doped antiferromagnets, we will work out the magnon mediated forces between electrons or holes. We will see that the doped electrons or holes build pairs and we will investigate the ground state properties of these pairs.
Since the derivation of the low-energy effective field theory is quite technical and since it has already been discussed in an earlier seminar given by Christoph Brgger, I will not present all the details of the construction at length. I will rather give an overview of the ideas that we have used to perform the construction. I will try to keep things as simple as possible, such that the talk will also be suited for students.

3 de mayo
10:00 am

On Basic Rational Surfaces

Mustapha Lahyane
CIMAT

Abstract: In 1960, Masayoshi Nagata showed that the monoid of effective divisor classes of a smooth projective rational surface may fail to be finitely generated. This phenomenon began to be studied in detail in the 80s, beginning with work by Rosoff in 1980 and Harbourne in 1985. The aim of this seminar is to discuss some complementary work regarding this problem.

2 de mayo
12:00 pm

On the distribution of primes and the Lang-Trotter conjecture about elliptic curves

Stephan Baier
Universidad Jacobs, Bremen

Abstract: In the first part of my talk, I will give some survey about general results regarding the distribution of primes and their relation to the Riemann zeta function. In the second part, I will discuss some problems and results on primes represented by polynomials. In particular, I will talk about the relation between the Lang-Trotter conjecture on elliptic curves and primes represented by quadratic polynomials.

27 de abril
12:00 pm

Ruteo local en el toro

Maia Fraser
Universidad de Colima

Resumen: Se hablar del ruteo local en grficas encajadas en superficies. El nico algoritmo conocido de este tipo, "el ruteo por caras" ("Face Routing" en ingls), se aplica en el plano. Se demostrar que nicamente puede ser aplicada en el plano y no en superficies de gnero positivo (refutando una conjetura al contrario). Luego se propondr una generalizacin del ruteo por caras y se demostrar que s funciona en el toro.

26 de abril
12:00 pm

Confrontando las teoras finitas de Gran Unificacin con la Fenomenologa de bajas energas

Myriam Mondragn
IFUNAM

Resumen:

20 de abril
12:00 pm

Sobre la sucesin de Fibonacci

Santos Hernndez
Univ. Aut. Zacatecas

Resumen: Se hablar de dos problemas elementales concernientes a la sucesin de Fibonacci: El primero de ellos es sobre el mximo comn divisor de FM + a y Fn + b, donde Fn, Fm son nmeros de Fibonacci y a, b son nmeros enteros arbitrarios; el segundo problema concierne a la relacin entre el problema anterior y el clculo de la cerradura de la sucesin de Fibonacci en la topologa plena de Z.

2 de marzo
5:00 pm

Decaimientos semileptnicos de hiperones: algunos aspectos tericos

Rubn Flores Mendieta
Instituto de Fsica, UASLP

Resumen: Presentamos un esquema general acerca de la situacin terica actual de los decaimientos semileptnicos de bariones. En particular discutimos los dos tipos de incertidumbres tericas que los afectan: i) determinacin de los factores de forma, incluyendo su dependencia en el momento transferido, y ii) correcciones radiativas a observables integrados. Presentamos tambin, entre otras aplicaciones, cmo extraer el elemento Vus de la matriz CKM.

7 de febrero
5:00 pm

Low-energy effective theory for doped fermions in an antiferromagnet

Christoph Bruegger,
Institut fuer theoretische Physik, Bern

Abstract: I review the construction of an effective Lagrangian for magnons and holes/electrons - the condensed matter analog of baryon chiral perturbation theory for pions and nucleons in QCD. Then I will show that doping a finite density of fermions into the system with constant background field, the antiferromagnet energetically favors various phases, depending on the low-energy parameters of the theory.

Semestres anteriores

Agosto 2011 - Enero 2012

Febrero - Julio 2011

Agosto 2010 - Enero 2011

Febrero - Julio 2010

Agosto 2009 - Enero 2010

Febrero - Julio 2009

Agosto 2008 - Enero 2009

Febrero - Julio 2008

Agosto 2007 - Enero 2008

Febrero - Julio 2007