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Orbits of exceptional groups, duality and BPS states in string theory
 J. MOD. PHYS. A
, 1998
"... We give an invariant classification of orbits of the fundamental representations of exceptional groups E 7(7) and E 6(6) which classify BPS states in string and M theories toroidally compactified to d = 4 and 5. The exceptional Jordan algebra and the exceptional Freudenthal triple system and their c ..."
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Cited by 110 (46 self)
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We give an invariant classification of orbits of the fundamental representations of exceptional groups E 7(7) and E 6(6) which classify BPS states in string and M theories toroidally compactified to d = 4 and 5. The exceptional Jordan algebra and the exceptional Freudenthal triple system and their cubic and quartic invariants play a major role in this classification. The cubic and quartic invariants correspond to the black hole entropy in d = 5 and d = 4, respectively. The classification of BPS states preserving different numbers of supersymmetries is in close parallel to the classification of the little groups and the orbits of timelike, lightlike and spacelike vectors in Minkowski space.
Supersymmetry
, 1997
"... Introduction I.2. Structure of the MSSM I.3. Parameters of the MSSM I.4. The Higgs sector of the MSSM I.5. The supersymmetricparticle sector I.6. Reducing the MSSM parameter freedom I.7. The constrained MSSMs: mSUGRA, GMSB, and SGUTs I.8. The MSSM and precision of electroweak data I.9. Beyond the M ..."
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Cited by 69 (0 self)
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Introduction I.2. Structure of the MSSM I.3. Parameters of the MSSM I.4. The Higgs sector of the MSSM I.5. The supersymmetricparticle sector I.6. Reducing the MSSM parameter freedom I.7. The constrained MSSMs: mSUGRA, GMSB, and SGUTs I.8. The MSSM and precision of electroweak data I.9. Beyond the MSSM Supersymmetry, Part II (Experiment) II.1. Introduction II.2. Common supersymmetry scenarios II.3. Experimental issues II.4. Supersymmetry searches in e + e \Gamma colliders II.5. Supersymmetry searches at proton machines II.6. Supersymmetry searches at HERA and fixedtarget experiments II.7. Conclusions SUPERSYMMETRY, PART I (THEORY) (by H.E. Haber) I.1. Introduction: Supersymmetry (SUSY) is a generalization of the spacetime symmetries of quantum field theory that transforms fermions into bosons and vice versa. It also provides a framework for the unification of particle physics and gravity [13], which is g
Fronts, pulses, sources and sinks in generalized complex GinzburgLandau equations
, 1992
"... An important clement in the longtime dynamics of pattern forming systems is a class of solutions we will call "coherent structures". These are states that are either themselves localized, or that consist of domains of regular patterns connected by localized defects or interfaces. ..."
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Cited by 66 (2 self)
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An important clement in the longtime dynamics of pattern forming systems is a class of solutions we will call &quot;coherent structures&quot;. These are states that are either themselves localized, or that consist of domains of regular patterns connected by localized defects or interfaces. This paper summarizes and extends recent work on such coherent structures in the onedimensional complex GinzburgLandau equation and its generalizations, for which rather complete information can be obtained on the existence and competition of fronts, pulses, sources and sinks. For the special subclass of uniformly translating structures, the solutions are derived from a set of ordinary differential equations that can be interpreted as a flow in a threedimensional phase space. Fixed points of the flow correspond to the two basic building blocks of coherent structures, uniform amplitude states and evanescent waves whose amplitude decreases smoothly to zero. A study of the stability of the fixed points under the flow leads to results on the existence and multiplicity of the different coherent structures. The dynamical analysis of the original partial differential equation focusses on the competition between pulses and fronts, and is expressed in terms of a set of conjectures for front propagation that generalize the &quot;marginal stability&quot; and &quot;pinchpoint &quot; approaches of earlier authors. These rules, together with an exact front solution whose dynamics plays an important role in the selection of patterns, yield an analytic expression for the upper limit of the range of existence of pulse solutions, as well as a determination of the regions of parameter space where uniformly translating fron t solutions can exist. Extensive numerical simulations show consistency with these rules and conjectures for the existence of fronts and pulses. In
Precision corrections in the minimal supersymmetric standard model
, 1997
"... In this paper we compute oneloop corrections to masses and couplings in the minimal supersymmetric standard model. We present explicit formulae for the complete corrections and a set of compact approximations which hold over the unified parameter space associated with radiative electroweak symmetry ..."
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Cited by 56 (0 self)
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In this paper we compute oneloop corrections to masses and couplings in the minimal supersymmetric standard model. We present explicit formulae for the complete corrections and a set of compact approximations which hold over the unified parameter space associated with radiative electroweak symmetry breaking. We illustrate the importance of the corrections and the accuracy of our approximations by scanning over the parameter space. We calculate the supersymmetric oneloop corrections to the Wboson mass, the effective weak mixing angle, and the quark and lepton masses, and discuss implications for gauge and Yukawa coupling unification. We also compute the oneloop corrections to the entire superpartner and Higgsboson mass spectrum. We find significant corrections over much of the parameter space, and illustrate that our approximations are good to O(1%) for many of the superparticle masses.
Interatomic Potentials from FirstPrinciples Calculations – The ForceMatching Method
 Europhysics Letters
, 1994
"... We present a new scheme to extract numerically “optimal ” interatomic potentials from large amounts of data produced by firstprinciples calculations. The method is based on fitting the potential to ab initio atomic forces of many atomic configurations, including surfaces, clusters, liquids and crys ..."
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Cited by 46 (0 self)
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We present a new scheme to extract numerically “optimal ” interatomic potentials from large amounts of data produced by firstprinciples calculations. The method is based on fitting the potential to ab initio atomic forces of many atomic configurations, including surfaces, clusters, liquids and crystals at finite temperature. The extensive data set overcomes the difficulties encountered by traditional fitting approaches when using rich and complex analytic forms, allowing to construct potentials with a degree of accuracy comparable to that obtained by ab initio methods. A glue potential for aluminum obtained with this method is presented and discussed.
OffShell Bethe Ansatz Equation for Gaudin Magnets and Solutions of KnizhnikZamolodchikov Equations
, 1993
"... We generalize the previously established connection between the offshell Bethe ansatz equation for inhomogeneous SU(2) lattice vertex models in the quasiclassical limit and the solutions of the SU(2) KnizhnikZamolodchikov equations to the case of arbitrary simple Lie algebras. ..."
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Cited by 40 (2 self)
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We generalize the previously established connection between the offshell Bethe ansatz equation for inhomogeneous SU(2) lattice vertex models in the quasiclassical limit and the solutions of the SU(2) KnizhnikZamolodchikov equations to the case of arbitrary simple Lie algebras.
Noncommutative geometry on a discrete periodic lattice and gauge theory,” Phys
 Rev. D
, 2000
"... We discuss the quantum mechanics of a particle in a magnetic field when its position x µ is restricted to a periodic lattice, while its momentum p µ is restricted to a periodic dual lattice. Through these considerations we define noncommutative geometry on the lattice. This leads to a deformation o ..."
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Cited by 37 (0 self)
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We discuss the quantum mechanics of a particle in a magnetic field when its position x µ is restricted to a periodic lattice, while its momentum p µ is restricted to a periodic dual lattice. Through these considerations we define noncommutative geometry on the lattice. This leads to a deformation of the algebra of functions on the lattice, such that their product involves a “diamond ” product, which becomes the star product in the continuum limit. We apply these results to construct noncommutative U(1) and U(M) gauge theories, and show that they are equivalent to a pure U(NM) matrix theory, where N 2 is the number of lattice points.
NonUnitary Conformal Field Theory and Logarithmic Operators for Disordered Systems
, 1997
"... We consider the supersymmetric approach to gaussian disordered systems like the random bond Ising model and Dirac model with random mass and random potential. These models appeared in particular in the study of the integer quantum Hall transition. The supersymmetric approach reveals an osp(2/2)1 aff ..."
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Cited by 37 (0 self)
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We consider the supersymmetric approach to gaussian disordered systems like the random bond Ising model and Dirac model with random mass and random potential. These models appeared in particular in the study of the integer quantum Hall transition. The supersymmetric approach reveals an osp(2/2)1 affine symmetry at the pure critical point. A similar symmetry should hold at other fixed points. We apply methods of conformal field theory to determine the conformal weights at all levels. These weights can generically be negative because of nonunitarity. Constraints such as locality allow us to quantize the level k and the conformal dimensions. This provides a class of (possibly disordered) critical points in two spatial dimensions. Solving the KnizhnikZamolodchikov equations we obtain a set of fourpoint functions which exhibit a logarithmic dependence. These functions are related to logarithmic operators. We show how all such features have a natural setting in the superalgebra approach as long as gaussian disorder is concerned.
Hysteresis and hierarchies: Dynamics of disorderdriven firstorder phase transformations
 Physical Review Letters
, 1993
"... ABSTRACT: We use the zero–temperature random–field Ising model to study hysteretic behavior at first–order phase transitions. Sweeping the external field through zero, the model exhibits hysteresis, the return–point memory effect, and avalanche fluctuations. There is a critical value of disorder at ..."
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Cited by 33 (3 self)
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ABSTRACT: We use the zero–temperature random–field Ising model to study hysteretic behavior at first–order phase transitions. Sweeping the external field through zero, the model exhibits hysteresis, the return–point memory effect, and avalanche fluctuations. There is a critical value of disorder at which a jump in the magnetization (corresponding to an infinite avalanche) first occurs. We study the universal behavior at this critical point using mean–field theory, and also present preliminary results of numerical simulations in three dimensions.
Cosmological solutions of type II string theory, Phys. Lett. B 393
 Phys. B
, 1997
"... We study cosmological solutions of type II string theory with a metric of the Kaluza–Klein type and nontrivial Ramond–Ramond forms. It is shown that models with only one form excited can be integrated in general. Moreover, some interesting cases with two nontrivial forms can be solved completely sin ..."
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Cited by 33 (2 self)
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We study cosmological solutions of type II string theory with a metric of the Kaluza–Klein type and nontrivial Ramond–Ramond forms. It is shown that models with only one form excited can be integrated in general. Moreover, some interesting cases with two nontrivial forms can be solved completely since they correspond to Toda models. We find two types of solutions corresponding to a negative time superinflating phase and a positive time subluminal expanding phase. The two branches are separated by a curvature singularity. Within each branch the effect of the forms is to interpolate between different solutions of pure Kaluza–Klein theory.