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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

Theory of bending waves with applications to disk galaxies

Description: A theory of bending waves is surveyed which provides an explanation for the required amplification of the warp in the Milky Way. It also provides for self-generated warps in isolated external galaxies. The shape of observed warps and partly their existence in isolated galaxies are indicative of substantial spheroidal components. The theory also provides a plausible explanation for the bending of the inner disk (<2 kpc) of the Milky Way.
Date: January 1, 1982
Creator: Mark, J.W.K.
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

The gravitational properties of antimatter

Description: It is argued that a determination of the gravitational acceleration of antimatter towards the earth is capable of imposing powerful constraints on modern quantum gravity theories. Theoretical reasons to expect non-Newtonian non-Einsteinian effects of gravitational strength and experimental suggestions of such effects are reviewed. 41 refs. (LEW)
Date: September 1, 1986
Creator: Goldman, T.; Hughes, R.J. & Nieto, M.M.
Partner: UNT Libraries Government Documents Department

The inverse-square law and quantum gravity

Description: This paper briefly discusses a modification to central potential of gravity when antimatter is involved and the possible existence of quantum gravity and a fifth force of nature. 1 ref. (LSP)
Date: January 1, 1988
Creator: Nieto, M.M.; Goldman, T. & Hughes, R.J.
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

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

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

A measurement of the gravitational acceleration of the antiproton

Description: A fundamental experiment in gravity proposed by us, is the measurement of the gravitational force on antimatter. This measurement would constitute the first direct test of the Weak Equivalence Principle (WEP) for antimatter. The availability of low-energy antiprotons at CERN has made such an experiment feasible, and a proposal to carry out such a measurement has been accepted by the CERN Program Committee. We plan to use a time-of-flight technique similar to that pioneered by Fairbank and Witteborn in their measurement of the gravitational force on an electron. Very slow particles are launched into a vertical drift tube and the time-of-flight spectrum of these particles is recorded. This spectrum will exhibit a cut-off point directly related to the gravitational acceleration of the particles. Obtaining very slow antiprotons involves several stages of deceleration. Antiprotons from LEAR will be initially decelerated from 2 MeV to tens of kilovolts by passing them through a thin foil. After capture and cooling in a series of ion traps, the antiprotons will be in a thermal distribution with a temperature of a few degrees Kelvin. These ultra-cold antiprotons will then be released a few at a time into the drift tube. A detector will measure the arrival time of the particles at the exit of the drift tube. H{sup {minus}}-ion, which have almost identical electromagnetic properties to the antiprotons, will be used for comparison and as a calibration standard. 7 refs., 1 fig.
Date: January 1, 1990
Creator: Holzscheiter, M.H.
Partner: UNT Libraries Government Documents Department

Measurement of the gravitational acceleration of the antiproton: an experimental overview

Description: An ambitious experiment is being developed to measure the force on the antiproton due to the gravitational field of the earth. The technique consists in obtaining antiprotons of the lowest energy possible from the LEAR facility at CERN, decelerating them further in an external beam line, trapping and cooling them to ultralow energy, and measuring their gravitational acceleration by time-of-flight methods. The experiment has been granted CERN approval (PS-200). Present plans and initial development efforts are described.
Date: January 1, 1986
Creator: Jarmie, N.
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

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

Falling antimatter: An experiment to measure the gravitational acceleration of the antiproton

Description: According to some theories of gravity, antimatter will fall faster than matter in the earth's gravitational field. An experiment to measure the gravitational force on the antiproton is under construction. Antiprotons of a few MeV from the LEAR facility of CERN will be slowed down and caught in a large Penning electromagnetic trap. They will then be cooled and transferred to Penning cooling and launching traps. The gravitational acceleration will be measured by the time-of-flight in a drift tube shielding stray electronic fields, and will be compared with that measured for H/sup /minus// ions. Progress on a number of fronts is described. 9 refs., 2 figs.
Date: January 1, 1988
Creator: Dyer, P.; Camp, J.; Holzscheiter, M.H. & Graessle, S.
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