Search results for "Models"
showing 10 items of 8211 documents
Finite Entanglement Entropy in Asymptotically Safe Quantum Gravity
2018
Entanglement entropies calculated in the framework of quantum field theory on classical, flat or curved, spacetimes are known to show an intriguing area law in four dimensions, but they are also notorious for their quadratic ultraviolet divergences. In this paper we demonstrate that the analogous entanglement entropies when computed within the Asymptotic Safety approach to background independent quantum gravity are perfectly free from such divergences. We argue that the divergences are an artifact due to the over-idealization of a rigid, classical spacetime geometry which is insensitive to the quantum dynamics.
Conformal and non-conformal symmetries in 2D dilaton gravity
1996
We introduce new extra symmetry transformations for generic 2D dilaton-gravity models. These symmetries are non-conformal but special linear combinations of them turn out to be the extra (conformal) symmetries of the CGHS model and the model with an exponential potential. We show that one of the non-conformal extra symmetries can be converted into a conformal one by means of adequate field redefinitions involving the metric and the derivatives of the dilaton. Finally, by expressing the Polyakov-Liouville effective action in terms of an auxiliary invariant metric, we construct one-loop models which maintain the extra symmetry of the classical action. © 1997 Elsevier Science B.V.
WMAPing the Universe: Supersymmetry, Dark Matter, Dark Energy, Proton Decay and Collider Physics
2003
In this review we discuss constraints on minimal supersymmetric models of particle physics implied by the recent astrophysical observations of WMAP. Although the prospects of detecting supersymmetry increase and 90 percent of the available MSSM parameter space can safely be reached by the sensitivity of future colliders, nevertheless we pay particular emphasis on discussing regions of the appropriate phase diagrams, which -if realized - would imply that detection of supersymmetry, at least in the context of minimal models, could be out of colliders reach. We also discuss the importance of a precise determination of the radiative corrections to the muon anomalous magnetic moment, both theore…
First-order flows and stabilisation equations for non-BPS extremal black holes
2011
28 páginas.-- This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.
Testing Hawking particle creation by black holes through correlation measurements
2010
Hawking's prediction of thermal radiation by black holes has been shown by Unruh to be expected also in condensed matter systems. We show here that in a black hole-like configuration realized in a BEC this particle-creation does indeed take place and can be unambiguously identified via a characteristic pattern in the density-density correlations. This opens the concrete possibility of the experimental verification of this effect.
High Energy Emission from Shocks Due to Jets and Accretion in Young Stars with Disks: Combining Observations, Numerical Models, and Laboratory Experi…
2018
High energy emission from young stars with disks, with all their components due to accretion and outflow activity, can have a deep impact on the evolution of their disks and on the formation of exo-planetary systems. An inter-disciplinary approach, which combines multi-wavelength observations, magnetohydrodynamical models, and laboratory experiments, allows us to get a more complete description of the accretion/ejection phenomena characterizing young stars. We discuss the case of the HH 154 jet, its X-ray emission localized at the base of the jet and its complex morphology, comparing observations, models, and laser experiments. We present the comparison between magnetohydrodynamical models …
X(5) critical-point symmetries in 138Gd
2011
International audience; The lifetimes of low-lying transitions in 138Gd have been measured using the recoil-distance Doppler-shift technique. The resultant reduced transition probabilities have been compared to X(5) critical-point calculations to assess the potential 'phase-transitional' behaviour of 138Gd. The X(5) symmetry describes the first order 'phase transition' between sphericity, U(5) and an axially deformed nuclear shape, SU(3). Although a high degree of correspondence is observed between the experimental and theoretical excitation energies, the large uncertainties of the experimental B(E2) values cannot preclude contributions from either vibrational or rotational modes of excitat…
Emission of fragments in Ca+Ca reaction at 25 MeV/nucleon
2013
We discuss experimental data concerning 40,48Ca+ 40,48Ca reactions at 25 MeV/nucleon; the 4π multi-detector Chimera has been used as detection device. Effects that can be attributed to the neutron to proton ratios (N/Z) degree of freedom have been investigated. From the analysis of experimental data it seems that the neutron richness of the interacting system plays an important role on the evolution of fusion-like sources formed in semi-central collisions. In particular, it is observed that the larger is the neutron content and the larger is the emission of heavy residues. Experimental data have been compared with CoMD-II model calculations; a moderately stiff symmetry energy should be used…
The discovery of an expanding X-ray source in the HH 154 protostellar jet
2006
We have performed, in October 2005, a deep Chandra X-ray observation of HH 154. Comparison with the previous (2001) Chandra observation allows to detect proper motion down to the level predicted by models of X-ray emitting shocks in the jet. The 2005 Chandra observation of HH 154 shows unexpected morphological changes of the X-ray emission in comparison with the 2001 data. Two components are present: a stronger, point-like component with no detectable motion and a weaker component which has expanded in size by approximately 300 AU over the 4 years time base of the two observations. This expansion corresponds to approximately 500 km/s, very close to the velocity of the X-ray emitting shock i…
Microscopic approach to the kinetics of pattern formation of charged molecules on surfaces.
2010
A microscopic formalism based on computing many-particle densities is applied to the analysis of the diffusion-controlled kinetics of pattern formation in oppositely charged molecules on surfaces or adsorbed at interfaces with competing long-range Coulomb and short-range Lennard-Jones interactions. Particular attention is paid to the proper molecular treatment of energetic interactions driving pattern formation in inhomogeneous systems. The reverse Monte Carlo method is used to visualize the spatial molecular distribution based on the calculated radial distribution functions (joint correlation functions). We show the formation of charge domains for certain combinations of temperature and dy…