(2003, NS 127)

Ulf Danielsson, Ariel Goobar, Bengt Nilsson

August 14-19

Sigtuna, Sweden and The Royal Swedish Academy of Sciences, Stockholm, Sweden

Proceedings: published in Physica Scripta, The Royal
Swedish Academy of Sciences in 2004.

One of the most important goals of the Nobel symposium was to gather the most distinguished and active scientists of the world in string theory and cosmology, theoreticians as well as experimentalists, and give them the opportunity to discuss the present status of their subjects. Throughout the symposium special attention was given to the connections between the fields. Can cosmology be used to test string theory? Can string theory answer deep questions about cosmology?

The conference venue, Sigtuna stiftelsen, was chosen for its relaxed environment suitable for informal interactions and discussions. Each day of the symposium consisted of one or two sessions devoted to a specific subject. The specific contents of the sessions were organized in advance by a chairman/chairwoman who also lead the discussions following the talks. In the schedule we allowed for equal time to lectures and discussions, an extremely successful arrangement. The lively discussions continued until very late hours.

The two scientific areas, cosmology and string theory, have witnessed enormous progress during the last few years. This is especially true for the observational side of cosmology where many new measurements, of ever higher precision, have increased our understanding of the universe. One dramatic example is the experimental evidence for a cosmological constant. The cosmological constant was first introduced by Einstein almost a century ago but ignored for many years and, until now, assumed to be irrelevant and vanishing. Another example is the new measurements of the acoustic peaks in the CMBR performed by the WMAP-satellite.

A key piece of theoretical work developed by cosmologists to describe observed properties of the universe, is inflation. Inflation has solved several difficult problems of the Big Bang model, but there are many questions about inflation that remain to be understood. Another important aspect of the history of the early universe is the question of an initial moment. Did time have a beginning? A reason for us not being able to answer this question, is the lack of an accepted theory that can be used for extreme energies and small distances, i.e. a theory of quantum gravity. The general hope is that string theory will develop into such a theory and soon be able to answer this and many other deep questions.

The various sessions of the symposium showed how string theory and cosmology have grown closer to each other during the past several years. The first few sessions presented the current observational status and how the accuracy with which the various parameters describing the universe are expected to improve in the years to come. The later sessions discussed string theory and its importance for cosmology. Our understanding of string theory is now good enough for us to be able to start discussing rather specific models of inflation and to investigating their consequences.

It is our hope that the Nobel symposium in 2003 on String Theory and Cosmology, will be remembered as a meeting where a new era began in our understanding of the very small and the very large.

Efstathiou, G.: Large Scale Structure

Tonry, J.: Studying the Dark Sector
with Supernovae and Lensing

Perlmutter, S.: Studying Dark
Energy with Supernovae: From Now to a Future Space Based
Mission

Spergel, D.: What Have We Learned
from the CMB?

Kamionkowski, M.: CMB and Polarization, Expectations

Steinhardt, P.: Quintessence:
Models and Predictions

Guth, A.: Birth of Inflationary Ideas

Linde, A.: Prospects of Inflation

Hawking, S.: A Non Singular
Universe

Starobinsky, A.: De Sitter
Space-Time Foam

Veneziano, G.: Unconventional
Scenarios and Perturbations Therein

Greene, B.: Aspects of String
Cosmology

Susskind, L.: The Landscape of String Theory

Banks, T.: Holographic Cosmology

Polchinski, J.: Can the
Universe Bounce?

Sen, A.: Dynamics of D-brane
Decay

Turok, N.: Beyond Inflation: A
Cyclic Universe Scenario

Horowitz, G.: Naked
Singularities and Negative Energy Density

Dvali, G.: Filtering
Gravity

Kutasov, D.: Cosmological
Singularities in String Theory

Turner, M.: Where do We Stand in
Cosmology?

Gross, D.: Where do We Stand in
Fundamental Theory?

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