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Gravitational Gauge Mediation

Description: It is often the case that naive introduction of the messenger sector to supersymmetry breaking models causes the supersymmetry restoration. We discuss a possibility of stabilizing the supersymmetry broken vacuum by the gravitational interaction.
Date: August 11, 2006
Creator: Kitano, Ryuichiro
Partner: UNT Libraries Government Documents Department

Negative energy modes and gravitational instability of interpenetrating fluids

Description: The authors study the longitudinal instabilities of two interpenetrating fluids interacting only through gravity. When one of the constituents is of relatively low density, it is possible to have a band of unstable wave numbers well separated from those involved in the usual Jeans instability. If the initial streaming is large enough, and there is no linear instability, the indefinite sign of the free energy has the possible consequence of explosive interactions between positive and negative energy modes in the nonlinear regime. The effect of dissipation on the negative energy modes is also examined.
Date: September 1, 1998
Creator: Casti, A.R.R.; Spiegel, E.A. & Morrison, P.J.
Partner: UNT Libraries Government Documents Department

SN1987A Constraints on Large Compact Dimensions

Description: Recently there has been a lot of interest in models in which gravity becomes strong at the TeV scale. The observed weakness of gravitational interactions is then explained by the existence of extra compact dimensions of space, which are accessible to gravity but not to Standard Model particles. In this letter we consider graviton emission into these extra dimensions from a hot supernova core. The phenomenology of SN1987A places strong constraints on this energy loss mechanism, allowing us to derive a bound on the fundamental Planck scale. For the case of two extra dimensions we obtain a very strong bound of M {ge} 50 TeV, which corresponds to a radius R {le} 0.3 {micro}m. While there are a lot of sources of uncertainty associated with this bound, we find that pushing it down to the few-TeV range, which could in principle be probed by ground-based experiments, is disfavored. For three or more extra dimensions the SN1987A constraints do not exclude a TeV gravitational scale.
Date: March 23, 1999
Creator: Perelstein, Maxim
Partner: UNT Libraries Government Documents Department

The generic world-sheet action of irrational conformal field theory

Description: We review developments in the world-sheet action formulation of the generic irrational conformal field theory, including the non-linear and the linearized forms of the action. These systems form a large class of spin-two gauged WZW actions which exhibit exotic gravitational couplings. Integrating out the gravitational field, we also speculate on a connection with sigma models.
Date: May 1, 1995
Creator: Clubok, K. & Halpern, M.B.
Partner: UNT Libraries Government Documents Department

Gravitational Baryogenesis

Description: We show that a gravitational interaction between the derivative of the Ricci scalar curvature and the baryon-number current dynamically breaks CPT in an expanding universe and, combined with baryon-number-violating interactions, can drive the universe towards an equilibrium baryon asymmetry that is observationally acceptable.
Date: March 2, 2004
Creator: Davoudias, Hooman; Kitano, Ryuichiro; Kribs, Graham D.; Murayama, Hitoshi & Steinhardt, Paul J.
Partner: UNT Libraries Government Documents Department

Five Kepler target stars that show multiple transiting exoplanet candidates

Description: We present and discuss five candidate exoplanetary systems identified with the Kepler spacecraft. These five systems show transits from multiple exoplanet candidates. Should these objects prove to be planetary in nature, then these five systems open new opportunities for the field of exoplanets and provide new insights into the formation and dynamical evolution of planetary systems. We discuss the methods used to identify multiple transiting objects from the Kepler photometry as well as the false-positive rejection methods that have been applied to these data. One system shows transits from three distinct objects while the remaining four systems show transits from two objects. Three systems have planet candidates that are near mean motion commensurabilities - two near 2:1 and one just outside 5:2. We discuss the implications that multitransiting systems have on the distribution of orbital inclinations in planetary systems, and hence their dynamical histories; as well as their likely masses and chemical compositions. A Monte Carlo study indicates that, with additional data, most of these systems should exhibit detectable transit timing variations (TTV) due to gravitational interactions - though none are apparent in these data. We also discuss new challenges that arise in TTV analyses due to the presence of more than two planets in a system.
Date: June 1, 2010
Creator: Steffen, Jason H.; /Fermilab; Batalha, Natalie M.; U., /San Jose State; Borucki, William J.; /NASA, Ames et al.
Partner: UNT Libraries Government Documents Department

An upper bound on Q-star masses

Description: Q-stars (the gravitational generalization of Q-balls, strongly bound bulk matter that an appear in field theories of strongly interacting hadrons) are the only known impact objects consistent with the known bulk structure of nuclei and chiral symmetry that evade the Rhoades-Ruffini upper bound of 3.2M{sub {circle_dot}}. Generic bounds are quite weak: M{sub Q-star} < 400M{sub {circle_dot}}. If, however, we assume that the 1.558 ms pulsar is a Q-star, equilibrium. A stability criteria of rotating fluids place a much stronger upper bound of M{sub c} {le} 5.3M{sub {circle_dot}} on such models under certain special assumptions. This has important implications for heavy compact objects such as Cygnus X-1.
Date: June 1, 1992
Creator: Hochron, D.R.; Lynn, B.W. & Selipsky, S.B.
Partner: UNT Libraries Government Documents Department

Tidal disruption of a star by a supermassive black hole

Description: The analysis of stars in galactic nuclei that are captured and tidally disrupted by a black hole of mass > 10{sup 6} M{sub {circle dot}} requires the inclusion of general relativistic effects. We present the first numerical study of tidal breakup of a 1M{sub {circle dot}} main sequence star by a 10{sup 7} M{sub {circle dot}} black hole. We use a smoothed particle code to solve the hydrodynamic equations for a relativistic fluid in a static curved spacetime geometry to analyze, among other things, the fraction of the debris captured by the hole and the velocity of fragments escaping the hole.
Date: January 1, 1991
Creator: Laguna, P.; Miller, W.A. & Zurek, W.H.
Partner: UNT Libraries Government Documents Department

Higher Curvature Effects in the ADD and RS Models

Description: Over the last few years several extra-dimensional models have been introduced in attempt to deal with the hierarchy problem. These models can lead to rather unique and spectacular signatures at Terascale colliders such as the LHC and ILC. The ADD and RS models, though quite distinct, have many common feature including a constant curvature bulk, localized Standard Model(SM) fields and the assumption of the validity of the EH action as a description of gravitational interactions.
Date: July 5, 2006
Creator: Rizzo, Thomas G.
Partner: UNT Libraries Government Documents Department

String driven inflation

Description: It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig.
Date: November 1, 1987
Creator: Turok, N.
Partner: UNT Libraries Government Documents Department

Star-disk collisions in active galactic nuclei and the origin of the broad line region

Description: Stars of a cluster surrounding the central black hole in an AGN will collide with the accretion disk. For a central black hole of 10{sup 8} M{circle dot} and a cluster with 10{sup 7} {minus} 10{sup 8} stars within a parsec, one estimates that {approximately}10{sup 4} such collisions will occur per year. Collisions are hypersonic (Mach number M {much gt} 1). Some of the wake of the star -- the disk material shocked by its passage -- will follow it out of the disk. Such star tails'' with the estimated masses {delta}m {approximately} 10{sup 25} {minus} 10{sup 27} g subsequently expand, cool and begin to recombine. We propose that -- when illuminated by the ionizing flux from the central source -- they are likely to be the origin of the observed broad emission lines.
Date: December 5, 1991
Creator: Zurek, W.H.; Colgate, S.A. (Los Alamos National Lab., NM (United States)) & Siemiginowska, A. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States))
Partner: UNT Libraries Government Documents Department

Experiment to measure the gravitational force on the antiproton

Description: A collaboration has been formed to measure the acceleration of antiprotons in the earth's gravitational field. The technique is to produce, decelerate, and trap quantities of antiprotons, to cool them to untralow energy, and to measure their acceleration in a time-of-flight experiment. Present plans and the results of initial efforts toward this end are presented.
Date: January 1, 1985
Creator: Brown, R.E.
Partner: UNT Libraries Government Documents Department

Physics with ultra-low energy antiprotons

Description: The experimental observation that all forms of matter experience the same gravitational acceleration is embodied in the weak equivalence principle of gravitational physics. However no experiment has tested this principle for particles of antimatter such as the antiproton or the antihydrogen atom. Clearly the question of whether antimatter is in compliance with weak equivalence is a fundamental experimental issue, which can best be addressed at an ultra-low energy antiproton facility. This paper addresses the issue. 20 refs.
Date: January 1, 1989
Creator: Holtkamp, D.B.; Holzscheiter, M.H. & Hughes, R.J. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

WINDII atmospheric wave airglow imaging

Description: Preliminary WINDII nighttime airglow wave-imaging data in the UARS rolldown attitude has been analyzed with the goal to survey gravity waves near the upper boundary of the middle atmosphere. Wave analysis is performed on O[sub 2](0,0) emissions from a selected 1[sup 0] x 1[sup 0] oblique view of the airglow layer at approximately 95 km altitude, which has no direct earth background and only an atmospheric background which is optically thick for the 0[sub 2](0,0) emission. From a small data set, orbital imaging of atmospheric wave structures is demonstrated, with indication of large variations in wave activity across land and sea. Comparison ground-based imagery is discussed with respect to similarity of wave variations across land/sea boundaries and future orbital mosaic image construction.
Date: December 31, 1996
Creator: Armstrong, W.T.; Hoppe, U.-P.; Solheim, B.H. & Shepherd, G.G.
Partner: UNT Libraries Government Documents Department

Gravity theories in more than four dimensions

Description: String theories suggest particular forms for gravity interactions in higher dimensions. We consider an interesting class of gravity theories in more than four dimensions, clarify their geometric meaning and discuss their special properties. 9 refs.
Date: March 1, 1985
Creator: Zumino, B.
Partner: UNT Libraries Government Documents Department

Antiprotons are another matter

Description: Theories of gravity abound, whereas experiments in gravity are few in number. An important experiment in gravity that has not been performed is the measurement of the gravitational acceleration of antimatter. Although there have been attempts to infer these properties from those of normal matter, none of these theoretical arguments are compelling. Modern theories of gravity that attempt to unify gravity with the other forces of nature predict that in principle antimatter can fall differently than normal matter in the Earth's field. Some of these supergravity theories predict that antimatter will fall faster, and that normal matter will fall with a small Baryon-number dependance in the earth's field. All of these predictions violate the Weak Equivalence Principle, a cornerstone of General Relativity, but are consistent with CPT conservation. In our approved experiment at LEAR (PS-200) we will test the Weak Equivalence Principle for antimatter by measuring the gravitational acceleration of the antiproton. Through a series of deceleration stages, antiprotons from LEAR will be lowered in energy to approx.4 Kelvin at which energy the gravitational effect will be measureable. The measurement will employ the time-of-flight technique wherein the antiprotons are released vertically in a drift tube. The spectrum of time-of-flight measurements can be used to extract the gravitational acceleration experienced by the particles. The system will be calibrated using H/sup -/ ions which simulates the electromagnetic behavior of the antiproton, yet is a baryon to approx.0.1%. To extract the gravitational acceleration of the antiproton relative to the H/sup -/ ion with a statistical precision of 1% will require the release of approx.10/sup 6/ to 10/sup 7/ particles.
Date: January 1, 1987
Creator: Hynes, M.V.
Partner: UNT Libraries Government Documents Department

Gravitational properties of antimatter

Description: Quantum gravity is at the forefront of modern particle physics, yet there are no direct tests, for antimatter, of even the principle of equivalence. We note that modern descriptions of gravity, such as fibre bundles and higher dimensional spacetimes, allow violations of the commonly stated form of the principle of equivalence, and of CPT. We review both indirect arguments and experimental tests of the expected gravitational properties of CPT-conjugate states. We conclude that a direct experimental test of the gravitational properties of antimatter, at the 1% (or better) level, would be of great value. We identify some experimental reasons which make the antiproton a prime candidate for this test, and we strongly urge that such an experiment be done at LEAR. 21 references.
Date: January 1, 1985
Creator: Goldman, T. & Nieto, M.M.
Partner: UNT Libraries Government Documents Department

A measurement of the gravitational acceleration of the antiproton

Description: An experiment is being developed which will compare the acceleration, g, of the antiproton in the earth's gravitational field with that of H{sup minus} ions. This measurement will constitute the first direct test of the Weak Equivalence Principle (WEP) for antimatter. Low energy antiprotons from the LEAR facility at CERN will be decelerated, cooled and launched into a field free region, and the time of flight to a detector will determine g. The technical aspects of the experiment and our progress in the different areas are presented. 4 refs., 1 fig.
Date: January 1, 1991
Creator: Schecker, J.A.
Partner: UNT Libraries Government Documents Department

Low gravity fluid-thermal experiments

Description: Pacific Northwest Laboratory (PNL) is the lead laboratory for the thermal-hydraulic research in the US Department of Energy Multimegawatt Space Nuclear Power Program. PNL must provide the tools necessary to analyze proposed space reactor concepts, which include single- and two-phase alkali metal and gas-cooled designs. PNL has divided its activities for this task into three basic areas: computer code development, thermal-hydraulic modeling, and experimentation. The subject of this paper is the low-gravity experimental program currently underway at PNL in support of the MMW Program.
Date: June 1, 1987
Creator: Krotiuk, W.J. & Cuta, J.M.
Partner: UNT Libraries Government Documents Department

Experiments beyond the standard model

Description: This paper is based upon lectures in which I have described and explored the ways in which experimenters can try to find answers, or at least clues toward answers, to some of the fundamental questions of elementary particle physics. All of these experimental techniques and directions have been discussed fully in other papers, for example: searches for heavy charged leptons, tests of quantum chromodynamics, searches for Higgs particles, searches for particles predicted by supersymmetric theories, searches for particles predicted by technicolor theories, searches for proton decay, searches for neutrino oscillations, monopole searches, studies of low transfer momentum hadron physics at very high energies, and elementary particle studies using cosmic rays. Each of these subjects requires several lectures by itself to do justice to the large amount of experimental work and theoretical thought which has been devoted to these subjects. My approach in these tutorial lectures is to describe general ways to experiment beyond the standard model. I will use some of the topics listed to illustrate these general ways. Also, in these lectures I present some dreams and challenges about new techniques in experimental particle physics and accelerator technology, I call these Experimental Needs. 92 references.
Date: September 1, 1984
Creator: Perl, M.L.
Partner: UNT Libraries Government Documents Department

Neutron star accretion and the neutrino fireball

Description: The mixing necessary to explain the Fe'' line widths and possibly the observed red shifts of 1987A is explained in terms of large scale, entropy conserving, up and down flows (calculated with a smooth particle 2-D code) taking place between the neutron star and the explosion shock wave due to the gravity and neutrino deposition. Depending upon conditions of entropy and mass flux further accretion takes place in single events, similar to relaxation oscillator, fed by the downward flows of low entropy matter. The shock, in turn, is driven by the upflow of the buoyant high entropy bubbles. Some accretion events will reach a temperature high enough to create a neutrino fireball,'' a region hot enough, 11 Mev, so as to be partially opaque to its own (neutrino) radiation. The continuing neutrino deposition drives the explosion shock until the entropy of matter flowing downwards onto the neutron star is high enough to prevent further accretion. This process should result in a robust supernova explosion.
Date: November 26, 1991
Creator: Colgate, S.A. (Los Alamos National Lab., NM (United States)); Herant, M.E. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)) & Benz, W. (Steward Observatory, Tucson, AZ (United States))
Partner: UNT Libraries Government Documents Department