Electromagnetic nucleon form factors from QCD sum rules

The electromagnetic form factors of the nucleon, in the space-like region, are determined from three-point function Finite Energy QCD Sum Rules. The QCD calculation is performed to leading order in perturbation theory in the chiral limit, and to leading order in the non-perturbative power corrections. The results for the Dirac form factor, $F_1(q^2)$, are in very good agreement with data for both the proton and the neutron, in the currently accessible experimental region of momentum transfers. This is not the case, though, for the Pauli form factor $F_2(q^2)$, which has a soft $q^2$-dependence proportional to the quark condensate $$.Comment: Replaced Version. An error has been corrected in the numerical evaluation of the Pauli form factor. This changes the results for F_2(q^2), as well as the conclusion

Energy Extraction and Particle Acceleration Around Rotating Black Hole in Horava-Lifshitz Gravity

Penrose process on rotational energy extraction of the black hole (BH) in the original non-projectable Ho\v{r}ava-Lifshitz gravity is studied. The strong dependence of the extracted energy from the special range of parameters of the Ho\v{r}ava-Lifshitz gravity, such as parameter $\Lambda_W$ and specific angular momentum $a$ has been found. Particle acceleration near the rotating BH in Ho\v{r}ava-Lifshitz gravity has been studied. It is shown that the fundamental parameter of the Ho\v{r}ava-Lifshitz gravity can impose limitation on the the energy of the accelerating particles preventing them from the infinite value.Comment: 6 pages, 3 figures, accepted for publication in Physical Review

Local continuity laws on the phase space of Einstein equations with sources

Local continuity equations involving background fields and variantions of the fields, are obtained for a restricted class of solutions of the Einstein-Maxwell and Einstein-Weyl theories using a new approach based on the concept of the adjoint of a differential operator. Such covariant conservation laws are generated by means of decoupled equations and their adjoints in such a way that the corresponding covariantly conserved currents possess some gauge-invariant properties and are expressed in terms of Debye potentials. These continuity laws lead to both a covariant description of bilinear forms on the phase space and the existence of conserved quantities. Differences and similarities with other approaches and extensions of our results are discussed.Comment: LaTeX, 13 page

Extraperitoneal laparoscopic retroperitoneal lymph node dissection in non-seminomatous testicular cancer

Indexación: Web of Science; ScieloObjective: The aim is to describe the technique of extraperitoneal laparoscopic access for retroperitoneal lymph node dissection in a series of patients with testis cancer stage A. Material and Methods: The extraperitoneal approach was performed in 5 patients with stage A testicular cancer. The technique includes the creation of a totally extraperitoneal space, full exposition of the retroperitoneum and classic retroperito-neal lymph node dissection. We analyzed demographic data, histology, access and surgical complications, estimated blood loss and follow up. Results: The average age was 29.4 years old (22-41). The mean operative time was 144 minutes, with an estimated blood loss of 42.4 ml. There were no surgical complications. The average hospital stay was 33.6 hr, and mean number of lymph nodes was 27.4 (24 -32). In long-term follow up there was no recurrence. Discussion: The extraperitoneal approach is an alternative access for retroperitoneal lymph node dissection in testis cancer patients. It allows avoiding potential intestinal lesions and there is no contraindication in patients with prior abdominal surgery.Objetivo: Mostrar la experiencia en la técnica de disección lumboaórtica por vía totalmente extra-peritoneal, en un grupo de pacientes con cáncer testicular en estadio A. Material y Métodos: La serie está formada por 5 pacientes, portadores de un tumor testicular no seminoma, en estadio A. En ellos se planteó como alternativa la linfadenectomía retroperitoneal lumboaórtica laparoscópica. La técnica quirúrgica consistió en la formación de un espacio extraperitoneal, con rechazo de peritoneo, exposición del retroperitoneo y disección linfática clásica. Se analizaron los datos demográficos, histología, complicaciones del acceso y la técnica quirúrgica, tiempo operatorio, sangrado estimado y seguimiento a largo plazo. Resultados: El tiempo operatorio medio fue de 144 min, con un sangrado medio estimado en 42,5 ml (20-150 ml). No hubo complicaciones intra ni postoperatorias. El tiempo medio de hospitalización fue de 33,6 h. El número medio de nodos linfáticos resecados fue de 27,4 (24 a 32). Con un promedio de seguimiento de 134 meses, no ha habido recurrencia retroperitoneal ni diseminación a distancia. Discusión: La vía extraperitoneal es una alternativa de acceso para la disección linfática retroperitoneal en pacientes con cáncer testicular. Permite evitar potenciales lesiones intestinales y es factible de realizar en pacientes con cirugía abdominal previa.extraperitoneal.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-40262013000100003&nrm=is

Dissecting the Power Sources of Low-Luminosity Emission-Line Galaxy Nuclei via Comparison of HST-STIS and Ground-Based Spectra

Using a sample of ~100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of H_alpha and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which Transition Objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at <10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in the line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The Transition Objects show a threefold increase in the incidence of broad H_alpha emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z~0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude.Comment: 27 pages, 13 figures, 4 tables, accepted for publication in Ap

Time reparametrization invariance in arbitrary range p-spin models: symmetric versus non-symmetric dynamics

We explore the existence of time reparametrization symmetry in p-spin models. Using the Martin-Siggia-Rose generating functional, we analytically probe the long-time dynamics. We perform a renormalization group analysis where we systematically integrate over short timescale fluctuations. We find three families of stable fixed points and study the symmetry of those fixed points with respect to time reparametrizations. One of those families is composed entirely of symmetric fixed points, which are associated with the low temperature dynamics. The other two families are composed entirely of non-symmetric fixed points. One of these two non-symmetric families corresponds to the high temperature dynamics. Time reparametrization symmetry is a continuous symmetry that is spontaneously broken in the glass state and we argue that this gives rise to the presence of Goldstone modes. We expect the Goldstone modes to determine the properties of fluctuations in the glass state, in particular predicting the presence of dynamical heterogeneity.Comment: v2: Extensively modified to discuss both high temperature (non-symmetric) and low temperature (symmetric) renormalization group fixed points. Now 16 pages with 1 figure. v1: 13 page