Long-Range Critical Exponents near the Short-Range Crossover.

The d-dimensional long-range Ising model, defined by spin-spin interactions decaying with the distance as the power 1/r^{d+s}, admits a second-order phase transition with continuously varying critical exponents. At s=s_{*}, the phase transition crosses over to the usual short-range universality class. The standard field-theoretic description of this family of models is strongly coupled at the crossover. We find a new description, which is instead weakly coupled near the crossover, and use it to compute critical exponents. The existence of two complementary UV descriptions of the same long-range fixed point provides a novel example of infrared duality.

Mellin Amplitudes for Supergravity on AdS_{5}×S

We revisit the calculation of holographic correlation functions in type-IIB supergravity on AdS_{5}×S^{5}. Results for four-point functions simplify drastically when expressed in Mellin space. We conjecture a compact formula for the four-point functions of one-half Bogomol'nyi-Prasad-Sommerfield single-trace operators of arbitrary weight. Our methods rely on general consistency conditions and eschew detailed knowledge of the supergravity effective action.

N=4 superconformal bootstrap.

We implement the conformal bootstrap for N=4 superconformal field theories in four dimensions. The consistency of the four-point function of the stress-energy tensor multiplet imposes significant upper bounds for the scaling dimensions of unprotected local operators as functions of the central charge of the theory. At the threshold of exclusion, a particular operator spectrum appears to be singled out by the bootstrap constraints. We conjecture that this extremal spectrum is that of N=4 supersymmetric Yang-Mills theory at an S-duality invariant value of the complexified gauge coupling.

Four dimensional superconformal index from q-deformed two dimensional Yang-Mills theory.

We show that the superconformal index (the partition function on the three-sphere times a circle) of a certain class of 4D supersymmetric field theories is exactly equal to a partition function of q-deformed nonsupersymmetric 2D Yang-Mills theory.

Patología biliar en ancianos / Biliary disease in ancient

Se analizaron 101 pacientes con patología biliar mayores de 60 años de edad, admitidos al Servicio de Cirugía IV del Hospital "Miguel Pérez Carreño", en el lapso comprendido entre enero de 1993 y septiembre de 1996. La edad promedio fue de 68,33 años y predominó el sexo femenino. Se constata la presencia de un gran número de enfermedades concomitantes en ese grupo etáreo. Llama la atención el predominio de patología biliar litiásica complicada (más del 50 por ciento) y la mayor incidencia de patología neoplásica, así como el porcentaje de intervenciones de emergencia. También se registra un mayor número de complicaciones posoperatorias, mayor mortalidad y estancia hospitalaria más prolongada