The SQCD vacuum coupled to supergravity and string theory moduli

We calculate the scalar potential of supersymmetric QCD (in the regime N_f < N_c) coupled to N=1 supergravity with moduli-dependent gauge kinetic function and masses. The gauge dynamics are described by the Taylor-Veneziano-Yankielowicz superpotential for composite effective fields. The potential can be expanded about the ``truncated'' point in the gaugino and matter condensate directions in order to find corrections to the globally supersymmetric minimum. The results are relevant to the phenomenology of supersymmetry-breaking in string-inspired supergravity models, and also to recent work on domain walls in SQCD.Comment: 13 pages, 3 eps figures. Minor typos and layout change

Fundamental constants and their variability in theories of High Energy Physics

The Standard Model of particle physics and the theory of General Relativity (GR) currently provide a good description of almost all phenomena of particle physics and gravitation that have received controlled experimental tests. However, the Standard Model contains many a priori variable parameters whose values, and whose apparent (near-)constancy, have yet to receive a convincing theoretical explanation. At the same time, GR may now require to be extended or altered at the largest length scales, to account for the recent apparent accelerated cosmological expansion. In this introductory review I present theoretical aspects of the search for explanations of the values and possible variations of fundamental ``constants'', focusing on the possibility of unification of interactions. I also relate cosmological variations to modifications of gravity both locally and cosmologically.Comment: 17 pages pdflatex, proceedings of introductory lecture for ACFC Seminar, Bad Honnef 2007, to be published in EPJ Special Topic

On the modular invariance of mass eigenstates and CP violation

We investigate the modular transformation properties of observable (light) fields in heterotic orbifolds, in the light of recent calculations of CP-violating quantities. Measurable quantities must be modular invariant functions of string moduli, even if the light fields are noninvariant. We show that physical invariance may arise by patching smooth functions that are separately noninvariant. CP violation for on the unit circle, which requires light and heavy states to mix under transformation, is allowed in principle, although the Jarlskog parameter J_CP(T) must be amended relative to previous results. However, a toy model of modular invariant mass terms indicates that the assumption underlying these results is unrealistic. In general the mass eigenstate basis is manifestly modular invariant and coupling constants are smooth invariant functions of T, thus CP is unbroken on the unit circle. We also discuss the status of CP-odd quantities when CP is a discrete gauge symmetry, and point out a link with baryogenesis.Comment: 18 pages JHEP style, 1 fig., amssymb, amsmath, graphicx. As publishe

Modular symmetry, twisted sectors and flavour

We investigate the implications for fermion mass models in heterotic orbifolds of the modular symmetry mixing twisted states localized at different fixed points. We show that, unlike in the case of continuous gauge symmetries, the mass eigenstates do not mix under the symmetry; thus coupling constants in the low-energy theory are invariant functions of the moduli.Comment: 4 pages, ws-procs9x6.cls included. Contribution to conference proceedings, String Phenomenology '02, Oxfor

Baryogenesis with four-fermion operators in low-scale models

We describe a nonstandard proposal for baryogenesis in models with a low (O(10-100)TeV) fundamental scale. The scenario has Standard Model field content and enhanced baryon number violating operators deriving from time-dependent fermion localization in an extra dimension. The CKM matrix provides sufficient CP violation. The major constraints are the low reheating temperature and rate of perturbative B-violating reactions compared to the total entropy created. A sufficient baryon fraction may arise, but the cosmological evolution required is likely to be somewhat contrived. Based on work in collaboration with D.J.H. Chung.Comment: 10 pages latex, graphicx + amssymb, 2 figures. Talk presented at M-Theory Cosmology conference, August 2001, Cambridge (UK), also contributed to Erice ISSP '01 Proceedings, "New Fields and Strings in Subnuclear Physics". v3: references adde