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Non-Relativistic Superstring Theories

Description: We construct a supersymmetric version of the 'critical' non-relativistic bosonic string theory [1] with its manifest global symmetry. We introduce the anticommuting bc CFT which is the super partner of the {beta}{gamma} CFT. The conformal weights of the b and c fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider 'noncritical' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.
Date: December 14, 2007
Creator: Kim, Bom Soo
Partner: UNT Libraries Government Documents Department

Dynamical (super) symmetry breaking

Description: Dynamical Symmetry Breaking (DSB) is a concept theoristsrely on very often in the discussions of strong dynamics, model building,and hierarchy problems. In this talk, I will discuss why this is such apermeating concept among theorists and how they are used in understandingphysics. I also briefly review recent progress in using dynamicalsymmetry breaking to construct models of supersymmetry breaking andfermion masses.
Date: October 3, 2000
Creator: Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

Final Technical Report, Grant DE-FG02-91ER45443: Heavy fermions and other highly correlated electron systems

Description: Properties of highly correlated electrons, such as heavy fermion compounds, metal-insulator transitions, one-dimensional conductors and systems of restricted dimensionality are studied theoretically. The main focus is on Kondo insulators and impurity bands due to Kondo holes, the low-temperature magnetoresistivity of heavy fermion alloys, the n-channel Kondo problem, mesoscopic systems and one-dimensional conductors.
Date: October 12, 1998
Creator: Schlottmann, P.
Partner: UNT Libraries Government Documents Department

Minimal Doubling and Point Splitting

Description: Minimally-doubled chiral fermions have the unusual property of a single local field creating two fermionic species. Spreading the field over hypercubes allows construction of combinations that isolate specific modes. Combining these fields into bilinears produces meson fields of specific quantum numbers. Minimally-doubled fermion actions present the possibility of fast simulations while maintaining one exact chiral symmetry. They do, however, introduce some peculiar aspects. An explicit breaking of hyper-cubic symmetry allows additional counter-terms to appear in the renormalization. While a single field creates two different species, spreading this field over nearby sites allows isolation of specific states and the construction of physical meson operators. Finally, lattice artifacts break isospin and give two of the three pseudoscalar mesons an additional contribution to their mass. Depending on the sign of this mass splitting, one can either have a traditional Goldstone pseudoscalar meson or a parity breaking Aoki-like phase.
Date: June 14, 2010
Creator: Creutz, M.
Partner: UNT Libraries Government Documents Department

Excitations of the nucleon with dynamical fermions

Description: We measure the spectrum of low-lying nucleon resonances using Bayesian fitting methods. We compare the masses obtained in the quenched approximation to those obtained with two flavours of dynamical fermions at a matched lattice spacing. At the pion masses employed in our simulations, we find that the mass of the first positive-parity nucleon excitation is always greater than that of the parity partner of the nucleon.
Date: June 1, 2002
Creator: Maynard, C.M. & Richards, D.G.
Partner: UNT Libraries Government Documents Department

Fermion Monte Carlo

Description: We review the fundamental challenge of fermion Monte Carlo for continuous systems, the "sign problem". We seek that eigenfunction of the many-body Schriodinger equation that is antisymmetric under interchange of the coordinates of pairs of particles. We describe methods that depend upon the use of correlated dynamics for pairs of correlated walkers that carry opposite signs. There is an algorithmic symmetry between such walkers that must be broken to create a method that is both exact and as effective as for symmetric functions, In our new method, it is broken by using different "guiding" functions for walkers of opposite signs, and a geometric correlation between steps of their walks, With a specific process of cancellation of the walkers, overlaps with antisymmetric test functions are preserved. Finally, we describe the progress in treating free-fermion systems and a fermion fluid with 14 <sup>3</sup>He atoms.
Date: December 1, 1998
Creator: Kalos, M. H. & Pederiva, F.
Partner: UNT Libraries Government Documents Department

Many-body effects in heavy fermion compounds [sic]. Final technical report for period September 1984 - January 2001

Description: A theoretical investigation of many-body effects in Cerium and Uranium Heavy Fermion and Mixed Valent Compounds and their experimental manifestations in thermodynamic, transport, and spectroscopic properties is discussed in this report.
Date: May 1, 2002
Creator: Riseborough, Peter S.
Partner: UNT Libraries Government Documents Department

Toward the M(F)-theory embedding of realistic free-fermion models

Description: We construct a Landau-Ginzburg model with the same data and symmetries as a Z{sub 2} x Z{sub 2} orbifold that corresponds to a class of realistic free-fermion models. Within the class of interest, we show that this orbifolding connects between different Z{sub 2} x Z{sub 2} orbifold models and connects with the mirror symmetry. Our work suggests that duality symmetries previously discussed in the context of specific M and F theory compactifications may be extended to the special Z{sub 2} x Z{sub 2} orbifold that characterizes realistic free-fermion models.
Date: March 1, 1998
Creator: Berglund, P.; Ellis, J. & Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Renormalization of currents for massive fermions

Description: The renormalization of vector and axial-vector currents for massive fermions (in the ''Fermilab formalism'') is discussed. We give results for non-degenerate masses, which are needed for semi-leptonic form factors.
Date: December 1, 1998
Creator: Hashimoto, Andreas S. Kronfeld and Shoji
Partner: UNT Libraries Government Documents Department

Questions of Identity

Description: As an introduction to {nu}Fact '99, the ICFA/ECFA Workshop on Neutrino Factories Based on Muon Storage Rings, I place the issues of neutrino properties and neutrino oscillations in the broader context of fermion flavor.
Date: August 25, 1999
Creator: Quigg, Chris
Partner: UNT Libraries Government Documents Department

Dirac charge dynamics in graphene by infrared spectroscopy

Description: A remarkable manifestation of the quantum character of electrons in matter is offered by graphene, a single atomic layer of graphite. Unlike conventional solids where electrons are described with the Schr&#246;dinger equation, electronic excitations in graphene are governed by the Dirac hamiltonian. Some of the intriguing electronic properties of graphene, such as massless Dirac quasiparticles with linear energy-momentum dispersion, have been confirmed by recent observations. Here, we report an infrared spectromicroscopy study of charge dynamics in graphene integrated in gated devices. Our measurements verify the expected characteristics of graphene and, owing to the previously unattainable accuracy of infrared experiments, also uncover significant departures of the quasiparticle dynamics from predictions made for Dirac fermions in idealized, free-standing graphene. Several observations reported here indicate the relevance of many-body interactions to the electromagnetic response of graphene.
Date: April 29, 2008
Creator: Martin, Michael C.; Li, Z. Q.; Henriksen, E. A.; Jiang, Z.; Hao, Z.; Martin, Michael C et al.
Partner: UNT Libraries Government Documents Department

Anarchy and hierarchy

Description: We advocate a new approach to study models of fermion massesand mixings, namely anarchy proposed in hep-ph/9911341. In this approach,we scan the O(1) coefficients randomly. We argue that this is the correctapproach when the fundamental theory is sufficiently complicated.Assuming there is no physical distinction among three generations ofneutrinos, the probability distributions in MNS mixing angles can bepredicted independent of the choice of the measure. This is because themixing angles are distributed according to the Haar measure of the Liegroups whose elements diagonalize the mass matrices. The near-maximalmixings, as observed in the atmospheric neutrino data and as required inthe LMA solution to the solar neutrino problem, are highly probable. Asmall hierarchy between the Delta m2 for the atmospheric and the solarneutrinos is obtained very easily; the complex seesaw case gives ahierarchy of a factor of 20 as the most probable one, even though thisconclusion is more measure-dependent. U_e3 has to be just below thecurrent limit from the CHOOZ experiment. The CP-violating parameter sindelta is preferred to be maximal. We present a simple SU(5)-likeextension of anarchy to the charged-lepton and quark sectors which workswell phenomenologically.
Date: September 14, 2000
Creator: Haba, Naoyuki & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

CORRELATION EFFECTS IN MANY FERMION SYSTEMS: MULTIPLE PARTICLE EXCITATION EXPANSION

Description: The ground-state wave function and energy of a finite system of interacting fermions are expanded in terms of multiple-particle excitations on an uncorrelated zero-order state. The resulting set of coupled equations constitutes a systematic variational generalization of Hartree-Fock theory. Comparison is made with many-body perturbation theory and it is shown that to any order the theory incorporates an infinite number of perturbation theory terms. Solutions of the equations for ground-state atomic systems are discussed and related to previous work using many-body perturbation theory. It is shown that the sums of perturbation terms necessary for convergence are automatically included in the equations for two-particle excitations. Application of the equations to open-shell atoms is described.
Date: July 1, 1963
Creator: Kelly, Hugh P. & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

Perturbative Corrections for Staggered Fermion Bilinears

Description: We calculate the perturbative corrections to fermion bilinears that are used in numerical simulations when extracting weak matric elements using staggered fermions.This extends previous calculations of Golterman and Smit, and Daniel and Sheard.In particular, we calculate the corrections for non-local bilinears defined in Landau gauge with gauge links excluded.We do this for the simplest operators, i.e. those defined on a 2^4 hypercube, and for tree level improved operators which live on 4^4 hypercubes.We also consider gauge invariant operators in which the "tadpole" contributions are suppressed by projecting the sums of products of gauge links back in to the gauge group.In all cases, we find that the variation in the size of the perturbative corrections is smaller than those with the gauge invariant unimproved operators.This is most strikingly true for the smeared operators.We investigate the efficacy of the mean-field method of Lepage and Mackenzie at summing up tadpole
Date: January 1, 1992
Creator: Patel, Apoorva & Sharpe, Stephen
Partner: UNT Libraries Government Documents Department

The f-spin physics of rare-earth iron pnictides: influence of d-electron antiferromagnetic order on heavy fermion phase diagram

Description: Some of the high {Tc} iron pnictides contain rare-earth elements, raising the question of how the existence and tunability of a d-electron antiferromagnetic order influences the heavy fermion behavior of the f-moments. With CeOFeP and CeOFeAs in mind as prototypes, we derive an extended Anderson lattice model appropriate for these quaternary systems. We show that the Kondo screening of the f-moments are efficiently suppressed by the d-electron ordering. We also argue that, inside the d-electron ordered state (as in CeOFeAs), the f-moments provide a rare realization of a quantum frustrated magnet with competing J{sub 1}-J{sub 2}-J{sub 3} interactions in an effective square lattice. Implications ofr the heavy fermion physics in broader contexts are also discussed.
Date: January 1, 2009
Creator: Zhu, Jian-xin; Dai, Jianhui & Si, Qimiao
Partner: UNT Libraries Government Documents Department

News about NHMFL user program.

Description: For the past decade, ultrasound measurements have proven to be of great importance in the investigation of systems close to magnetic instabilities. Many interesting results can be found in thc literature (at reasonably high DC fields) dealing with systems presenting metamagnetic transitions where ultrasound measurenients provided important information regarding the electron-lattice coupling. The group Ketterson, Suslov, and Sarma has been the first in the United States to extend this technique to be used in pulsed magnets. Their report that follows describes experimental details of the technique and presents results regarding the lattice behavior around the 35 T metamagnetic transition of the heavy fermion compound URu,Si,. I am sure that many of you will find the article very interesting. We are working hard to make this technique available to the user community soon.
Date: January 1, 2001
Creator: Lacerda, A. H. (Alex H.)
Partner: UNT Libraries Government Documents Department

Effects of lattice disorder in the UCu(5-x)Pd(x) system

Description: The UCu5-x Pdx system exhibits non-Fermi liquid (NFL) behavior in thermodynamic and transport properties at low temperatures for Pd concentrations 0.9 less than or approximately x less than or approximately 1.5. The local structure around the U, Cu, and Pd atoms has been measured for
Date: February 19, 2002
Creator: Bauer, E.D.; Booth, C.H.; Kwei, G.H.; Chau, R. & Maple, M.B.
Partner: UNT Libraries Government Documents Department

A lattice formulation of chiral gauge theories

Description: We present a method for implementing gauge theories of chiral fermions on the lattice. Discussed topics include: the lattice as a UV regulator, a chiral QED model, modification of the fermion determinant, large gauge-field momenta, and a non-perturbative problem.
Date: August 1, 1996
Creator: Bodwin, G.T.
Partner: UNT Libraries Government Documents Department

Conference summary: Experimnetal

Description: The conference is the 1995 International Conference on Strongly Correlated Electron Systems. The summary highlights research on the ``extended`` Doniach model, Kondo insulators, borocarbide superconductors, oxides (including cuprates), other phase transitions, and new materials.
Date: December 31, 1995
Creator: Thommpson, J.D.
Partner: UNT Libraries Government Documents Department

The electronic structure of heavy fermions: Narrow temperature independent bands

Description: The electronic structure of both Ce and U heavy fermions appears to consist of extremely narrow temperature independent bands. There is no evidence from photoemission for a collective phenomenon normally referred to as the Kondo resonance. In uranium compounds a small dispersion of the bands is easily measurable.
Date: August 1, 1996
Creator: Arko, A.J.; Joyce, J.J.; Smith, J.L. & Andrews, A.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

Physics of the 1 Teraflop RIKEN-BNL-Columbia QCD project. Proceedings of RIKEN BNL Research Center workshop: Volume 13

Description: A workshop was held at the RIKEN-BNL Research Center on October 16, 1998, as part of the first anniversary celebration for the center. This meeting brought together the physicists from RIKEN-BNL, BNL and Columbia who are using the QCDSP (Quantum Chromodynamics on Digital Signal Processors) computer at the RIKEN-BNL Research Center for studies of QCD. Many of the talks in the workshop were devoted to domain wall fermions, a discretization of the continuum description of fermions which preserves the global symmetries of the continuum, even at finite lattice spacing. This formulation has been the subject of analytic investigation for some time and has reached the stage where large-scale simulations in QCD seem very promising. With the computational power available from the QCDSP computers, scientists are looking forward to an exciting time for numerical simulations of QCD.
Date: October 16, 1998
Partner: UNT Libraries Government Documents Department

Toward the classification of the realistic free fermionic models

Description: The realistic free fermionic models have had remarkable success in providing plausible explanations for various properties of the Standard Model which include the natural appearance of three generations, the explanation of the heavy top quark mass and the qualitative structure of the fermion mass spectrum in general, the stability of the proton and more. These intriguing achievements makes evident the need to understand the general space of these models. While the number of possibilities is large, general patterns can be extracted. In this paper the author presents a detailed discussion on the construction of the realistic free fermionic models with the aim of providing some insight into the basic structures and building blocks that enter the construction. The role of free phases in the determination of the phenomenology of the models is discussed in detail. The author discusses the connection between the free phases and mirror symmetry in (2,2) models and the corresponding symmetries in the case of (2,0) models. The importance of the free phases in determining the effective low energy phenomenology is illustrated in several examples. The classification of the models in terms of boundary condition selection rules, real world-sheet fermion pairings, exotic matter states and the hidden sector is discussed.
Date: August 1, 1997
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

A lattice formulation of chiral gauge theories

Description: The authors present a method for formulating gauge theories of chiral fermions in lattice field theory. The method makes use of a Wilson mass to remove doublers. Gauge invariance is then restored by modifying the theory in two ways: the magnitude of the fermion determinant is replaced with the square root of the determinant for a fermion with vector-like couplings to the gauge field; a double limit is taken in which the lattice spacing associated with the fermion field is taken to zero before the lattice spacing associated with the gauge field. The method applies only to theories whose fermions are in an anomaly-free representation of the gauge group. They also present a related technique for computing matrix elements of operators involving fermion fields. Although the analyses of these methods are couched in weak-coupling perturbation theory, it is argued that computational prescriptions are gauge invariant in the presence of a nonperturbative gauge-field configuration.
Date: December 1, 1995
Creator: Bodwin, G.T.
Partner: UNT Libraries Government Documents Department