摘要:

We discuss two different themes in non‐supersymmetric strings. First we analyze the backreaction of dilaton tadpoles on the background in a prototype example with 8‐branes. Our analysis of the solutions for the warped metric and the dilaton profile confirms a process of spontaneous compactification in non‐supersymmetric strings. Secondly we consider the construction of non‐supersymmetric closed strings in various dimensions using orbifolds. We partially classify tachyon‐free heterotic models and compute the spectrum of several tachyonic type II and heterotic examples. We also discuss the relation to compactification on K3 and Calabi‐Yau manifolds. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594341

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We examine the extent to which the action for the membrane of M‐theory (the eleven‐dimensional construct which underlies and unifies all of the known string theories) simplifies in the so‐called Open Membrane (OM) limit, a limit which lies at the root of the various manifestations of noncommutativity in the string context. In order for the discussion to be relatively self‐contained, we start out by reviewing why the strings of ten‐dimensional string theory are in fact membranes (M2‐branes) living in eleven dimensions. After that, we recall the definition of OM theory, as well as the arguments showing that it is part of a larger, eleven‐dimensional structure known as Galilean or Wrapped M2‐brane (WM2) theory. WM2 theory is a rich theoretical construct which is interesting for several reasons, in particular because it is essentially a toy model of M‐theory. We then proceed to deduce a membrane action for OM/WM2 theory, and spell out its implications for the four different types of M2‐branes one can consider in this setting. For two of these types, the action in question can be simplified by gauge‐fixing to a form which implies adiscretemembrane spectrum. The boundary conditions for the remaining two cases do not allow this same gauge choice, and so their dynamics remain to be unraveled. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594342

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We present a short review of the essential ingredients for baryogenesis. We discuss two popular mechanisms for the production of the baryon asymmetry of the Universe: electroweak baryogenesis and leptogenesis. We also summarize the relevant constraints on some low scale extended (supersymmetric) baryogenesis models. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594343

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We study the possibility that the quintessence field responsible for the dark energy and the present day acceleration of the universe is given by a condensate field generated at a late phase transition scale determined by the condensation scale. We show that the quintessence field can be described naturally by the condensates of a non‐abelian gauge group. The non‐perturbative effects generated by a strong gauge coupling constant can de determined and a scalar potential for the dark meson fields is generated parameterizing the dark energy. On the other hand it is the massive particles, e.g. dark baryons, of the dark gauge group that give the corresponding dark matter. This gauge group is unified with the standard model gauge groups. The model hasno freeparameters. Even the initial energy density at the unification scale and at the condensation scale are fixed by the number of degrees of freedom of the gauge group. The cosmological observations are pushing the condensation scale to an epoch close to radiation and matter equality and this late time phase transition is the reason why the universe is accelerating at present time. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594344

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Starting from the Plebanski‐Ashtekar complex formulation of gravitation, we formulate a topological and a dynamical noncommutative theory of gravitation. In both cases the gauge approach based on the Seiberg‐Witten map is followed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594345

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The construction of effective Hamiltonians arising from Loop Quantum Gravity and incorporating Planck scale corrections to the dynamics of photons and spin 1/2 particles is summarized. The imposition of strict bounds upon some parameters of the model using already existing experimental data is also reviewed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594346

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Time variation of fundamental constants, a strong signal of new physics, is analyzed comparing extant data with two phenomenological models. Results are discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594347

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We consider a plausible scenario in the Minimal Supersymmetric Standard Model (MSSM) where all the genuine supersymmetric (SUSY) particles are heavier than the electroweak scale. In this situation, indirect searches via their radiative corrections to low energy observables are complementary to direct searches, and they can be crucial if the SUSY masses are at the TeV energy range. We summarize the most relevant heavy SUSY radiative effects in Higgs boson physics and emphasize those that manifest a non‐decoupling behaviour. We focus, in particular, on the SUSY‐QCD non‐decoupling effects in fermionic Higgs decays, flavour changing Higgs decays and Yukawa couplings. Some of their phenomenological implications at future colliders are also studied. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594348

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The renormalization group approach to the SUSY flavor problem is elucidated. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594349

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We calculate the tree‐level mass matrices for the neutral and charged lepton sectors, and for the Up and Down quark sectors, in a particular model based on the local gauge groupSU(3)c⊗SU(3)L⊗U(1)Xwhich does not contain particles with exotic electric charges. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1594350

出版商:AIP    

年代:1903

数据来源: AIP