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Missouri University of Science and Technology

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Full-Text Articles in Physics

Relic Gravitons On Kasner-Like Branes, Marco Cavaglia, G. De Risi, M. Gasperini Mar 2005

Relic Gravitons On Kasner-Like Branes, Marco Cavaglia, G. De Risi, M. Gasperini

Physics Faculty Research & Creative Works

We discuss the cosmological amplification of tensor perturbations in a simple example of brane-world scenario, in which massless gravitons are localized on a higher-dimensional Kasner-like brane embedded in a bulk AdS background. Particular attention is paid to the canonical normalization of the quadratic action describing the massless and massive vacuum quantum fluctuations, and to the exact mass-dependence of the amplitude of massive fluctuations on the brane. The perturbation equations can be separated. In contrast to de Sitter models of brane inflation, we find no mass gap in the spectrum and no enhancement for massless modes at high curvature. The massive ...


Approximately Self-Similar Critical Collapse In 2+1 Dimensions, Marco Cavaglia, Gerard Clement, Alessandro Fabbri Aug 2004

Approximately Self-Similar Critical Collapse In 2+1 Dimensions, Marco Cavaglia, Gerard Clement, Alessandro Fabbri

Physics Faculty Research & Creative Works

Critical collapse of a self-gravitating scalar field in a (2+1)-dimensional spacetime with negative cosmological constant seems to be dominated by a continuously self-similar solution of the field equations without cosmological constant. However, previous studies of linear perturbations in this background were inconclusive. We extend the continuously self-similar solutions to solutions of the field equations with negative cosmological constant, and analyze their linear perturbations. The extended solutions are characterized by a continuous parameter. A suitable choice of this parameter seems to improve the agreement with the numerical results. We also study the dynamics of the apparent horizon in the ...


Order-Parameter Symmetry And Mode-Coupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan Jan 2004

Order-Parameter Symmetry And Mode-Coupling Effects At Dirty Superconducting Quantum Phase Transitions, Rastko Sknepnek, Thomas Vojta, Rajesh Narayanan

Physics Faculty Research & Creative Works

We derive an order-parameter field theory for a quantum phase transition between a disordered metal and an exotic (non- s -wave) superconductor. Mode coupling effects between the order parameter and other fermionic soft modes lead to an effective long-range interaction between the anomalous density fluctuations which is reflected in singularities in the free energy functional. However, this long-range interaction is not strong enough to suppress disorder fluctuations. The asymptotic critical region is characterized by run-away flow to large disorder. For weak coupling, this asymptotic region is very narrow. It is preempted by a wide crossover regime with mean-field critical behavior ...


Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia Sep 2003

Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia

Physics Faculty Research & Creative Works

If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeV-gravity theories. We show that the bulk-to-brane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at trans-Planckian energies is not known, it is premature to claim that the black hole emits mainly on ...


Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto Aug 2003

Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, Eun-Joo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto

Physics Faculty Research & Creative Works

In models with large extra dimensions, particle collisions with a center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 108 TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large ...


Brane Factories, Eun-Joo Ahn, Marco Cavaglia, Angela V. Olinto Jan 2003

Brane Factories, Eun-Joo Ahn, Marco Cavaglia, Angela V. Olinto

Physics Faculty Research & Creative Works

We propose that higher-dimensional extended objects (p-branes) are created by super-Planckian scattering processes in theories with TeV scale gravity. As an example, we compute the cross section for p-brane creation in a (n + 4)-dimensional spacetime with asymmetric compactification. We find that the cross section for the formation of a brane which is wounded on a compact submanifold of size of the fundamental gravitational scale is larger than the cross section for the creation of a spherically symmetric black hole. Therefore, we predict that branes are more likely to be created than black holes in super-Planckian scattering processes ...


Two-Dimensional Ds/Cft Correspondence, Mariano Cadoni, P. Carta, Marco Cavaglia, S. Mignemi Sep 2002

Two-Dimensional Ds/Cft Correspondence, Mariano Cadoni, P. Carta, Marco Cavaglia, S. Mignemi

Physics Faculty Research & Creative Works

We investigate de Sitter/conformal field theory (dS/CFT) correspondence in two dimensions. We define the conserved mass of de Sitter spacetime and formulate the correspondence along the lines of the anti–de Sitter/conformal field theory duality. The asymptotic symmetry group, mass, and central charge of de Sitter spacetime are equal to those of anti–de Sitter spacetime. The entropy of two-dimensional de Sitter spacetime is evaluated by applying the Cardy formula. We calculate the boundary correlators induced by the propagation of the dilaton in two-dimensional de Sitter space. Although the dilaton is a tachyonic perturbation in the bulk ...


Open Strings, 2d Gravity, And Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia Mar 2001

Open Strings, 2d Gravity, And Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a detailed discussion of the duality between dilaton gravity on AdS2 and open strings. The correspondence between the two theories is established using their symmetries and field theoretical, thermodynamic, and statistical arguments. We use the dual conformai field theory to describe two-dimensional black holes. In particular, all the semiclassical features of the black holes, including the entropy, have a natural interpretation in terms of the dual microscopic conformai dynamics. The previous results are discussed in the general framework of the anti-de Sitter/conformal field theory dualities.


Two-Dimensional Black Holes As Open Strings: A New Realization Of The Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia Feb 2001

Two-Dimensional Black Holes As Open Strings: A New Realization Of The Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We show that weak-coupled two-dimensional dilation gravity on anti-de Sitter space can be described by the dynamics of an open string. Neumann and Dirichlet boundary conditions for the string lead two different realizations of the anti-de Sitter/Conformal Field Theory correspondence. In particular, in the Dirichlet case the thermodynamical entropy of two-dimensional black holes can be exactly reproduced by counting the string states.


Doppler Shift Anisotropy In Small Angle Neutron Scattering, Barbara Ellen Wyslouzil, Gerald Wilemski, Janice L. Cheung, Reinhard Strey, John G. Barker Oct 1999

Doppler Shift Anisotropy In Small Angle Neutron Scattering, Barbara Ellen Wyslouzil, Gerald Wilemski, Janice L. Cheung, Reinhard Strey, John G. Barker

Physics Faculty Research & Creative Works

The two-dimensional patterns in our small angle neutron scattering (SANS) experiments from rapidly moving aerosols are anisotropic. To test the kinematic theory of two-body scattering that describes the anisotropy, we conducted SANS experiments using a constant source of D2O aerosol with droplets moving at ~440 m/s, and varied the neutron velocity from 267 to 800 m/s. The theoretically predicted anisotropy of the laboratory scattering intensities agrees well with the experimental results. Based on an analysis of the scattering intensity in the Guinier region, we also determined the particle velocity. The results are in very good agreement ...