Particle theory

Abstract:

We present a new scenario for baryogenesis in the context of heterotic brane-world models. The baryon asymmetry of the universe is generated at a small-instanton phase transition which is initiated by a moving brane colliding with the observable boundary. We demonstrate, in the context of a simple model, that reasonable values for the baryon asymmetry can be obtained. As a byproduct we find a new class of moving-brane cosmological solutions in the presence of a perfect fluid. © 2002 The American Physical Society.

Abstract:

We present results for the static interquark potential, lightest glueballs, light hadron spectrum, and topological susceptibility using a nonperturbatively improved action on a 163×32 lattice at a set of values of the bare gauge coupling and bare dynamical quark mass chosen to keep the lattice size fixed in physical units (∼1.7 fm). By comparing these measurements with a matched quenched ensemble, we study the effects due to two degenerate flavors of dynamical quarks. With the greater control over residual lattice spacing effects which these methods afford, we find some evidence of charge screening and some minor effects on the light hadron spectrum over the range of quark masses studied (MPS/Mv ≥ 0.58, where PS denotes pseudoscalar and V denotes vector). More substantial differences between quenched and unquenched simulations are observed in measurements of topological quantities. ©2002 The American Physical Society.

Abstract:

The effective action for five-dimensional heterotic M theory in the presence of five-branes is systematically derived from Hořava-Witten theory coupled to an M5-brane world-volume theory. This leads to a five-dimensional N=1 gauged supergravity theory on S1/Z2 coupled to four-dimensional N=1 theories residing on the two orbifold fixed planes and an additional bulk three-brane. We analyze the properties of this action, particularly the four-dimensional effective theory associated with the domain-wall vacuum state. The moduli Kähler potential and the gauge-kinetic functions are determined along with the explicit relations between four-dimensional superfields and five-dimensional component fields. ©2002 The American Physical Society.