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CeCu sub 4 A ell and CeCu sub 2 Zn sub 2 A ell : Very heavy fermion systems in high magnetic fields

Description: CeCu{sub 4}A{ell} and CeCu{sub 2}Zn{sub 2}A{ell} are heavy fermion systems with extremely enhanced C/T (specific heat divided by temperature) values of 2.3 and 1.8 J/K{sup 2} respectively as T {yields} 0 K. The field dependence of the low temperature specific heat is also extreme; 11 T reduces C of CeCu{sub 4}A{ell} by more than a factor of five, 12.5 T suppresses C of CeCu{sub 2}Zn{sub 2}A{ell} about seven times. Magnetic field caused changes of the specific heat of CeCu{sub 4}A{ell} are consistent with a single ion Kondo model. Magnetic correlations are at least partially responsible for the enhanced low temperature specific heat of CeCu{sub 2}Zn{sub 2}A{ell}.
Date: January 1, 1990
Creator: Andraka, B.; Kim, J.S. (Florida Univ., Gainesville, FL (United States). Dept. of Physics); Stewart, G.R. (Florida Univ., Gainesville, FL (United States). Dept. of Physics Augsburg Univ. (Germany)) & Fisk, Z. (Los Alamos National Lab., NM (United States))
Partner: UNT Libraries Government Documents Department

X-ray scattering studies of non-equilibrium ordering processes

Description: We report on the progress of the project entitled X-ray Scattering Studies of Non-Equilibrium Ordering Processes.'' The past year has seen continued progress in the study of kinetic effects in metallic binary alloys and polymers. In addition, work has begun on a low dimensional CDW system: blue bronze. A sample chamber has been constructed to perform small angle neutron scattering measurements on a model quantum system with phase separation: solid He3/He4. Work is continuing on magnetic systems. Planned future experiments include an investigation of crystallization in Rubidium.
Date: January 1, 1991
Creator: Nagler, S.E.
Partner: UNT Libraries Government Documents Department

Mass hierarchies from anomalies: A peek behind the Planck curtain

Description: The masses of quarks and leptons suggest a strong hierarchical structure. We argue that their patterns can be reproduced through the introduction of a new Abelian symmetry. The data suggest that this symmetry is anomalous. We suggest that the cancellation of its anomalies occurs through the Green-Schwarz mechanism. An important check of this idea is that it links the Weinberg angle to a mass ration of the elementary fermions. The Green-Schwarz mechanism occurs naturally in many superstring compactifications, and produces a small parameter, which we use to determine the quark mass hierarchy. We show that hierarchy and mixings among the chiral fermions is a consequence of the Green-Schwarz mechanism. We present several models where this idea is realized. 16 refs., 2 tabs.
Date: May 1, 1996
Creator: Ramond, P.
Partner: UNT Libraries Government Documents Department

Caustic rings of dark matter

Description: It is shown that the infall of collisionless dark matter onto isolated galaxies produce a series of caustic rings in the halo dark matter distribution. The properties of these caustics are investigated. It is found in particular that the density profile of the caustic behaves as the inverse distance to the ring. Bumps in the rotation curve of NGC 3198 are interpreted as due to caustic rings of dark matter.
Date: May 6, 1997
Creator: Sikivie, P.
Partner: UNT Libraries Government Documents Department

Anomalous U(1) and low-energy physics: The power of D-flatness and holomorphy

Description: In models with an anomalous abelian symmetry broken at a very large scale, we study which requirements to impose on the anomalous charges in order to prevent standard model fields from acquiring large vacuum expectation values. The use of holomorphic invariants to study D-flat directions for the anomalous symmetry, proves to be a very powerful tool. We find that in order to forbid unphysical vacuum configurations at that scale, the superpotential must contain many interaction terms, including the usual Yukawa terms. Our analysis suggests that the anomalous charge of the {mu}-term is zero. It is remarkable that, together with the seesaw mechanism, and mass hierarchies, this implies a natural conservation of R-parity.
Date: March 1, 1997
Creator: Binetruy, P.; Irges, N.; Ramond, P. & Lavignac, S.
Partner: UNT Libraries Government Documents Department

The size of a polymer of string-bits: a numerical investigation

Description: In string bit models, string is described as a polymer of point-like constituents. We attempt to use string-bit ideas to investigate how the size of string is affected by string interactions in a non-perturbative context. Lacking adequate methods to deal with the full complications of bit rearrangement interactions, we study instead a simplified analog model with only ``direct`` potential interactions among the bits. We use the variational principle in an approximate calculation of the mean-square size of a polymer as a function of the number of constituents/bits for various interaction strengths {ital g} in three specific models. 14 refs., 2 figs.
Date: April 1, 1997
Creator: Bergman, O. & Thorn, C.B.
Partner: UNT Libraries Government Documents Department

Calculating fermion masses in superstring derived standard-like models

Description: One of the intriguing achievements of the superstring derived standard-like models in the free fermionic formulation is the possible explanation of the top quark mass hierarchy and the successful prediction of the top quark mass. An important property of the superstring derived standard-like models, which enhances their predictive power, is the existence of three and only three generations in the massless spectrum. Up to some motivated assumptions with regard to the light Higgs spectrum, it is then possible to calculate the fermion masses in terms of string tree level amplitudes and some VEVs that parameterize the string vacuum. I discuss the calculation of the heavy generation masses in the superstring derived standard-like models. The top quark Yukawa coupling is obtained from a cubic level mass term while the bottom quark and tau lepton mass terms are obtained from nonrenormalizable terms. The calculation of the heavy fermion Yukawa couplings is outlined in detail in a specific toy model. The dependence of the effective bottom quark and tau lepton Yukawa couplings on the flat directions at the string scale is examined. The gauge and Yukawa couplings are extrapolated from the string unification scale to low energies. Agreement with {alpha}{sub strong}, sin{sup 2} {theta}{sub W} and {alpha}{sub em} at M{sub Z} is imposed, which necessitates the existence of intermediate matter thresholds. The needed intermediate matter thresholds exist in the specific toy model. The effect of the intermediate matter thresholds on the extrapolated Yukawa couplings is studied. It is observed that the intermediate matter thresholds help to maintain the correct b/{tau} mass relation. It is found that for a large portion of the parameter space, the LEP precision data for {alpha}{sub strong}, sin{sup 2} {theta}{sub W} and {alpha}{sub em}, as well as the top quark mass and the b/{tau} mass relation can all simultaneously ...
Date: April 1, 1996
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Cosmological and phenomenological implications of Wilsonian matter in realistic superstring derived models

Description: Superstring phenomenology aims at achieving two goals. The first is to reproduce the observed physics of the Standard Model. The second is to identify experimental signatures of superstring unification which, if observed, will provide further evidence for the validity of superstring theory. I discuss such potential signatures of superstring unification. I propose that proton lifetime constraints imply that the Standard Model gauge group must be obtained directly at the string level. In this case the unifying gauge group, for example SO(10), is broken to the Standard Model gauge group by ``Wilson lines``. The symmetry breaking by ``Wilson line`` has important implications. It gives rise to exotic massless states which cannot fit into multiplets of the original unifying gauge group. This is an important feature because it results in conservation laws which forbid the interaction of the exotic ``Wilsonian`` states with the Standard Model states. The ``Wilsonian`` matter states then have important phenomenological implications. I discuss two such implications: exotic ``Wilsonian`` states as dark matter candidates and ``Wilsonian`` matter as the messenger sector in gauge mediated dynamical SUSY breaking scenarios.
Date: August 1, 1996
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Meeting the constraint of neutrino-Higgsino mixing in gravity unified theories

Description: In Gravity Unified Theories all operators that are consistent with the local gauge and discrete symmetries are expected to arise in the effective low-energy theory. given the absence of multiplets like 126 of S0(10) in string models, and assuming that B - L is violated spontaneously to generate light neutrino masses via a seesaw mechanism, it is observed that string theory solutions genetically face the problem of producing an excessive {nu}{sub L} - {tilde H} mixing mass at the GUT scale, which is some nineteen orders of magnitude larger than the experimental bound of 1 MeV. The suppression of {nu}{sub L} - {tilde H} mixing, like proton longevity, thus provides one of the most severe restraints on the validity of any string theory solution. We examine this problem in a class of superstring derived models. We find a family of solutions within this class for which the symmetries of the models and an allowed pattern of VEVs, surprisingly, succeed in adequately suppressing the neutrino-Higgsino mixing terms. At the same time they produce the terms required to generate small neutrino masses via seesaw mechanism.
Date: February 1, 1997
Creator: Faraggi, A.E. & Pati, J.C.
Partner: UNT Libraries Government Documents Department

Gauge boson mass without a Higgs field: a simple model

Description: A simple, anomaly-free chiral gauge theory can be perturbatively quantized and renormalized in such a way as to generate fermion and gauge boson masses. This development exploits certain freedoms inherent in choosing the unperturbed Lagrangian and in the renormalization procedure. Apart from its intrinsic interest, such a mechanism might be employed in electroweak gauge theory to generate fermion and gauge boson masses without a Higgs sector. 38 refs.
Date: February 1, 1997
Creator: Nicholson, A.F. & Kennedy, D.C.
Partner: UNT Libraries Government Documents Department

Relativistic charged particle in the dipole-sphere configuration I. Classical and semiclassical surface orbits

Description: The classical and semiclassical orbits of a relativistic charged particle on a rotating sphere threaded by a magnetic dipole field are examined. The rotational and dipole axes are in general not aligned. Several physically distinct regimes emerge, depending on the relative sizes of the total energy, canonical azimuthal angular momentum, and magnetic field strength. Magnetic flux enclosed by orbits is quantised very close to the poles. Application of this system to neutron star magnetic fields and questions for future research are outlined.
Date: January 1, 1997
Creator: Gopinath, K.S.; Kennedy, D.C. & Gelb, J.M.
Partner: UNT Libraries Government Documents Department

Dark matter axions `96

Description: This report discusses why axions have been postulated to exist, what cosmology implies about their presence as cold dark matter in the galactic halo, how axions might be detected in cavities wherein strong magnetic fields stimulate their conversion into photons, and relations between axions` energy spectra and galactic halos` properties.
Date: December 31, 1996
Creator: Sikivie, P.
Partner: UNT Libraries Government Documents Department

Superstring phenomenology present-and-future perspective

Description: The objective of superstring phenomenology is to develop the models and methodology needed to connect quantitatively between Planck scale and electroweak scale experimental data. I review the present status of this endeavor with a focus on the three generation free fermionic models.
Date: July 1, 1997
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Relativistic charged particle in magnetic dipole-spherical geometry. III. Local three-dimensional states

Description: Following two previous papers, we examine single- and many-body states of relativistic charged particles in an intense, rotating magnetic dipole field. Single-body orbits are derived classically and semiclassically, and then applied to the many-body orbits are derived classically and semiclassically, and then applied to the many-body case via the Thomas-Fermi approximation. Examples of electrons in a realistic neutron star crust are considered with both fixed density profiles and constant Fermi energy. In the first case, the varying magnetic field and Coriolis correction lead to a varying Fermi energy and macroscopic currents; in the second, the electron density is redistributed by the magnetic field. Further questions are outlined. 16 refs., 10 figs.
Date: July 1, 1997
Creator: Gopinath, K.S.; Kennedy, D.C. & Gelb, J.M.
Partner: UNT Libraries Government Documents Department

The pooltable analogy to axion physics

Description: An imaginary character named TSP finds himself in a playroom whose floor is tilted to one side. However, the pooltable in the playroom is horizontal. TSP wonders how this can be. In doing so, he embarks upon an intellectual journey which parallels that which has been travelled during the past two decades by physicists interested in the Strong CP Problem and axion physics.
Date: January 1, 1996
Creator: Sikivie, P.
Partner: UNT Libraries Government Documents Department

Quantum gravity slows inflation

Description: We consider the quantum gravitational back-reaction on an initially inflating, homogeneous and isotropic universe whose topology is T{sup 3} {times} {Re}. Although there is no secular effect at one loop, an explicit calculation shows that two-loop processes act to slow the rate of expansion by an amount which becomes non-pertubatively large at late times. By exploiting Feynman`s tree theorem we show that all higher loops act in the same sense. 18 refs., 1 fig.
Date: February 1, 1996
Creator: Tsamis, N.C. & Woodard, R.P.
Partner: UNT Libraries Government Documents Department

The velocity peaks in the cold dark matter spectrum on earth

Description: The cold dark matter spectrum on earth is expected to have peaks in velocity space. We obtain estimates for the sizes and locations of these peaks. To this end we have generalized the secondary infall model of galactic halo formation to include angular momentum of the dark matter particles. This new model is still spherically symmetric and it has self-similar solutions. Our results are relevant to direct dark matter search experiments.
Date: April 13, 1995
Creator: Sikivie, P.; Tkachev, I.I. & Wang, Y.
Partner: UNT Libraries Government Documents Department

The quantum gravitational back-reaction on inflation

Description: We describe our recent calculation of the dominant late time behavior of the expectation value of the metric at two loops in a locally de Sitter background on the manifold T{sup 3} {times} {Re}. If correct, our result proves that quantum gravitational effects slow the rate of inflation by an amount which becomes non-perturbatively large at late times. 11 refs., 9 figs., 11 tabs.
Date: February 1, 1995
Creator: Tsamis, N.C. & Woodard, R.P.
Partner: UNT Libraries Government Documents Department

One loop graviton self-energy in a locally de Sitter background

Description: The graviton tadpole has recently been computed at two loops in a locally de Sitter background. We apply intermediate results of this work to exhibit the graviton self-energy at one loop. This quantity is interesting both to check the accuracy of the first calculation and to understand the relaxation effect it reveals. In the former context we show that the self-energy obeys the appropriate Ward identity. We also show that its flat space limit agrees with the flat space result obtained by Capper in what should be the same gauge. 15 refs., 4 figs., 10 tabs.
Date: February 1996
Creator: Tsamis, N. C. & Woodard, R.P.
Partner: UNT Libraries Government Documents Department

Symplectic structure of isospin particles in Yang-Mills fields

Description: Using Dirac's constraint analysis, we explore the Hamiltonian formalism of isospin particles in external Yang-Mills fields without kinetic and potential energy term. We consider an example of isospin particle in 't Hooft-Polyakov magnetic monopole field and discuss possible quantization condition of magnetic charge in terms of geometric quantization.
Date: January 1, 1992
Creator: Oh, P.
Partner: UNT Libraries Government Documents Department

Quark-antiquark Regge trajectories in large N sub c QCD

Description: We apply methods developed by Lovelace, Lipatov, and Kirschner to evaluate the leading Regge trajectories {alpha}(t) with the quantum numbers of nonexotic quark-antiquark mesons at N{sub e} = {infinity} in the limit t {yields} {minus}{infinity} where renormalization group improved perturbation theory should be valid. We discuss the compatibility of nonlinear trajectories with narrow resonance approximations.
Date: January 1, 1992
Creator: McGuigan, M. & Thorn, C.B.
Partner: UNT Libraries Government Documents Department

Wiggly relativistic strings

Description: We derive the equations of motion for general strings, i.e. strings with arbitrary relation between tension {tau} and energy per unit length {epsilon}. The renormalization of {tau} and {epsilon} results from averaging out small scale wiggles on the string is obtained in the general case to lowest order in the amount of wiggliness. For Nambu-Goto strings we find deviations from the equation of state {epsilon}{tau} = constant in higher orders. Finally we show that under plausible assumptions wiggliness radically modifies the cosmic gauge string scenario.
Date: January 1, 1992
Creator: Hong, Jooyoo; Kim, Jaewan & Sikivie, P.
Partner: UNT Libraries Government Documents Department

A tumbling top-quark condensate model

Description: We propose a renormalizable model with no fundamental scalars which breaks itself in the manner of a tumbling'' gauge theory down to the standard model with a top-quark condensate. Because of anomaly cancellation requirements, this model contains two color sextet fermions (quixes), which are vector-like with respect to the standard model gauge group. The model also has a large number of pseudo-Nambu-Goldstone bosons, some of which can be light. The top-quark condensate is responsible for breaking the electroweak gauge symmetry and gives the top quark a large mass. We discuss the qualitative features and instructive shortcomings of the model in its present form. We also show that this model can be naturally embedded into an aesthetically pleasing model in which the standard model fermion appear symmetrically.
Date: January 1, 1992
Creator: Martin, S.P.
Partner: UNT Libraries Government Documents Department

Mode analysis and Ward identities for perturbative quantum gravity in de Sitter space

Description: We study linearized gravitons on the D-dimensional open submanifold spanned by de Sitter conformal coordinates. The physical modes are found in the same way as for flat space by imposing exact gauge conditions on the invariant field equations and then exploiting the residual gauge freedom of solutions. The resulting polarization tensors have vanishing zero components and are transverse and traceless, just as in flat space. We also show that vacua exist such that the ghost and graviton propagators obey the Ward identity relating them.
Date: June 1, 1992
Creator: Tsamis, N.C. (Crete Univ., Iraklion (Greece). Dept. of Physics) & Woodard, R.P. (Florida Univ., Gainesville, FL (United States). Dept. of Physics)
Partner: UNT Libraries Government Documents Department