2001: A Spacetime Odyssey

FOREWORD.

PREFACE.

CONTENTS.

No abstract received.

I summarize the first four decades of solar neutrino research and suggest what may be possible to learn with extragalactic neutrinos and with solar neutrinos in the next decade.

The adiabatic invariant nature of black hole horizon area in classical gravity suggests that in quantum theory the corresponding operator has a discrete spectrum. I here develop further an algebraic approach to black hole quantization which starts from very elementary assumptions, and proceeds by exploiting symmetry. It predicts a uniformly spaced area spectrum for all charges and angular momenta. Area eigenvalues are degenerate; correspondence with black hole entropy then dictates a precise value for the interval between eigenvalues.

This lecture consists of two parts. The first is a (totally unsystematic) survey of some of the high points in the evolution of gravity and its successors, primarily in the course of the past century. The second summarizes some new work on surprising properties of higher (>1) spin fields in cosmological backgrounds: the presence of Λ gives rise to discrete sets of massive models endowed with gauge invariances, that divide the (m², Λ) plane into unitary and non-unitary phases. The unitary region common to fermions and bosons shrinks to flat space (Λ → 0) as their spins increase.

We propose a model of soft CP violation that evades the strong CP problem and can describe observed CP violation in the neutral kaon sector, both direct and indirect. Our model requires two "duark" mesons carrying quark number two that have complex (CP-violating) bare masses and are coupled to quark pairs. Aside from the existence of these potentially observable new particles with masses of several hundred GeV, we predict a flat unitarity triangle (i.e., no observable direct CP violation in the B-meson sector) and a possibly anomalous branching ratio for the decay mode .

New, large, ground and space telescopes are contributing to an exciting and rapid period of growth in observational cosmology. The subject is now far from its earlier days of being data-starved and unconstrained, and new data are fueling a healthy interplay between observations and experiment and theory. I report here on the status of measurements of a number of quantities of interest in cosmology: the expansion rate or Hubble constant, the total mass-energy density, the matter density, the cosmological constant or dark energy component, and the total optical background light.

The weakly coupled vacuum of E₈ ⊗ E₈ heterotic string theory remains an attractive scenario for particle physics. The particle spectrum and the issue of dilaton stabilization are reviewed. A specific model for hidden sector condensation and supersymmetry breaking, that respects known constraints from string theory, is described, and its phenomenological and cosmological implications are discussed.

No abstract received.

No abstract received.

I will give a brief review of the various versions of inflationary theory, from Starobinsky model to chaotic inflation, and of recent observational data supporting inflationary theory. In the second part of the talk I will discuss the recently proposed ekpyrotic scenario and argue that in its present form it does not provide a viable alternative to inflation.

No abstract received.

In this article I attempt to collect some ideas, opinions and formulae which may be useful in solving the problem of gauge/string/space-time correspondence. This includes the validity of D-brane representation, counting of gauge-invariant words, relations between the null states and the Yang-Mills equations and the discussion of the strong coupling limit of the string sigma model. The article is based on the talk given at the "Odyssey 2001" conference.

This talk reviews the history of ideas on antimatter, the symmetry of physical laws for matter and antimatter, and the breaking of that symmetry, in these laws and in the evolution of the Universe.

The mechanism by which gauge and gravitational anomalies cancel in certain string theories is reviewed. The presentation is aimed at theorists who do not necessarily specialize in string theory.

Most of the matter in the universe is invisible. I review the status of dark matter and describe how both the theory of galaxy formation and novel types of experimental searches are revitalizing attempts to find non-baryonic dark matter.

Over the past three years we have determined the basic features of the Universe — spatially flat; accelerating; comprised of 1/3 a new form of matter, 2/3 a new form of energy, with some ordinary matter and a dash of massive neutrinos; and apparently born from a burst of rapid expansion during which quantum noise was stretched to astrophysical size seeding cosmic structure. The New Cosmology greatly extends the highly successful hot big-bang model. Now we have to make sense of all this: What is the dark matter particle? What is the nature of the dark energy? Why this mixture? How did the matter — antimatter asymmetry arise? What is the underlying cause of inflation (if it indeed occurred)?

The geometry of spacetime has a deep influence on our physical world. Hence any significant understanding of our physical world gives rise to important insights into geometry. The exchange of ideas between geometry and fundamental physics have been extensive in the past twenty years. Ideas from string theory have been vital in unifying several disciplines in mathematics.

In this talk, I shall discuss a few examples in geometry that are related to physics.

In this paper, we describe a method for obtaining the nonabelian Seiberg-Witten map for any gauge group and to any order in θ. The equations defining the Seiberg-Witten map are expressed using a coboundary operator, so that they can be solved by constructing a corresponding homotopy operator. The ambiguities, of both the gauge and covariant type, which arise in this map are manifest in our formalism.