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Pressure and Compressibility of Conformal Field Theories from the AdS/CFT Correspondence
Get PDFThe equation of state associated with N = 4 supersymmetric Yang-Mills in 4 dimensions, for SU(N) in the large N limit, is investigated using the AdS/CFT correspondence. An asymptotically AdS black-hole on the grav-ity side provides a thermal background for the Yang-Mills theory on the boundary in which the cosmological constant is equivalent to a volume. The thermodynamic variable conjugate to the cosmological constant is a pressure and the P − V diagram is studied. It is known that there is a critical point where the heat capacity diverges and this is reflected in the isothermal com-pressibility. Critical exponents are derived and found to be mean field in the large N limit. The same analysis applied to 3 and 6 dimensional con-formal field theories again yields mean field exponents associated with the compressibility at the critical point. [1
Non-Abelian clouds around Reissner-Nordström black holes: The existence line
Get PDFA known feature of electrically charged Reissner-Nordström-anti-de Sitter planar black holes is that they can become unstable when considered as solutions of Einstein–Yang-Mills theory. The mechanism for this is that the linearized Yang-Mills equations in the background of the Reissner-Nordström (RN) black holes possess a normalizable zero mode, resulting in non-Abelian (nA) magnetic clouds near the horizon. In this work we show that the same pattern may occur also for asymptotically flat RN black holes. Different from the anti-de Sitter case, in the Minkowskian background the prerequisite for the existence of the nA clouds is i) a large enough gauge group and ii) the presence of some extra interaction terms in the matter Lagrangian. To illustrate this mechanism we present two specific examples, one in four and the other in five dimensional asymptotically flat spacetime. In the first case, we augment the usual SU (3) Yang-Mills Lagrangian with higher order (quartic) curvature term, while for the second one we add the Chern-Simons density to the SO(6) Yang-Mills system. In both cases, an Abelian gauge symmetry is spontaneously broken near a RN black hole horizon with the appearance of a condensate of nA gauge fields. In addition to these two examples, we review the corresponding picture for anti-de Sitter black holes. All these solutions are studied both analytically and numerically, existence proofs being provided for nA clouds in the background of RN black holes. The proofs use shooting techniques which are suggested by and in turn offer insights for our numerical methods. They indicate that, for a black hole of given mass, appropriate electric charge values are required to ensure the existence of solutions interpolating desired boundary behavior at the horizons and spatial infinity
Magnetic monopoles in noncommutative quantum mechanics
Get PDFWe discuss certain generalization of the Hilbert space of states in noncommutaive quantum mechanics that, as we show, introduces magnetic monopoles into the theory. Such generalization arises very naturally in the considered model, but can be easily reproduced in ordinary quantum mechanics as well. This approach offers a different viewpoint on the Dirac quantization condition and other important relations for magnetic monopoles. We focus mostly on the kinematic structure of the theory, but investigate also a dynamical problem (with the Coulomb potential)
Towards an Improved Catalog of Irish Seismicity in the years 2010-2015
Get PDFIreland has traditionally been categorised as a region of very low seismicity. However, the low number of permanent seismic stations across Ireland may have contributed to this viewpoint. Since 2010, seismic station coverage across Ireland has dramatically improved with the establishment of the Irish National Seismic Network (INSN), and the deployment of the Ireland Array (IA) and UCD temporary seismic networks. The INSN has produced a catalog of seismic events from 2010 to 2015, of which the vast majority are suspected to be quarry/mine blasts. Discrimination between natural and man-made seismic events represents a major challenge for seismological observatories, particularly in regions of low seismicity. Previously, the factors used by the INSN to discriminate between naturally occurring earthquakes and quarry/mine blasts were location and origin time. With the inclusion of the IA and UCD data, it now becomes possible to precisely relocate these events, compare their location with known quarry/mine sites and thus identify groups of events having occurred in the same quarry/mine. In this work, we attempt to develop a new tool for discrimination based on waveform cross-correlation to identify repeating quarry blasts. Once man-made seismic events have been excluded, we are left with a more accurate view of the natural Irish seismicity rate for the period 2010-2015
Melnikov’s method in String Theory
Get PDFMelnikov’s method is an analytical way to show the existence of classical chaos generated by a Smale horseshoe. It is a powerful technique, though its applicability is somewhat limited. In this paper, we present a solution of type IIB supergravity to which Melnikov’s method is applicable. This is a brane-wave type deformation of the AdS_5 × S^5 background. By employing two reduction ansätze, we study two types of coupled pendulum-oscillator systems. Then the Melnikov function is computed for each of the systems by following the standard way of Holmes and Marsden and the existence of chaos is shown analytically
Review of Alan Macquarrie, Legends of Scottish Saints.
Get PDFA book review of Alan Macquarrie et al., Legends of Scottish Saints: Readings, Hymns and Prayers for the Commemoration of Scottish Saints in the Aberdeen Breviary (Dublin, 2012)
Supernova blast waves in wind-blown bubbles, turbulent, and power-law ambient media
Get PDFSupernova (SN) blast waves inject energy and momentum into the interstellar medium (ISM), control its turbulent multiphase structure and the launching of galactic outflows. Accurate modelling of the blast wave evolution is therefore essential for ISM and galaxy formation simulations. We present an efficient method to compute the input of momentum, thermal energy, and the velocity distribution of the shock-accelerated gas for ambient media (densities of 0.1 >= n_{0} [cm^{−3}] >= 100) with uniform (and with stellar wind blown bubbles), power-law, and turbulent (Mach numbers M from 1-100) density distributions. Assuming solar metallicity cooling, the blast wave evolution is followed to the beginning of the momentum conserving snowplough phase. The model recovers previous results for uniform ambient media. The momentum injection in wind-blown bubbles depend on the swept-up mass and the efficiency of cooling, when the blast wave hits the wind shell. For power-law density distributions with n(r) ~ r^{−2} (for n(r) > n_{floor}) the amount of momentum injection is solely regulated by the background density n_{floor} and compares to n_{uni} = n_{floor}. However, in turbulent ambient media with lognormal density distributions the momentum input can increase by a factor of 2 (compared to the homogeneous case) for high Mach numbers. The average momentum boost can be approximated: [Equation]. The velocity distributions are broad as gas can be accelerated to high velocities in low-density channels. The model values agree with results from recent, computationally expensive, three-dimensional simulations of SN explosions in turbulent media
