Andrei Linde

A new inflationary universe scenario: A possible solution of the horizon, flatness, homogeneity, isotropy and primordial monopole problems

In order to map the power distribution of a nuclear fuel element, a passive detector is laid along the fuel element in situ to record the residual radiation of the fuel element. The detector spatially records the residual radiation as an image in a radioactive reaction product. In the preferred embodiment, the detector comprises a cylindrical casing or wand enshrouding a material which converts incident gamma radiation having an energy level exceeding a preselected threshold to a correspondingly distributed neutron radiation field. The sheath encases a neutron field-sensitive activant, such as gold in the form of a filament longitudinally disposed in the casing. The image of the low-level radiation field can thereafter be analyzed according to relatively risk-free techniques to map the power distribution of the fuel element.

De Sitter vacua in string theory

We outline the construction of metastable de Sitter vacua of type IIB string theory. Our starting point is highly warped IIB compactifications with nontrivial NS and RR three-form fluxes. By incorporating known corrections to the superpotential from Euclidean D-brane instantons or gaugino condensation, one can make models with all moduli fixed, yielding a supersymmetric AdS vacuum. Inclusion of a small number of {ovr D3} branes in the resulting warped geometry allows one to uplift the AdS minimum and make it a metastable de Sitter ground state. The lifetime of our metastable de Sitter vacua is much greater than the cosmological timescale of 10{sup 10} years. We also prove, under certain conditions, that the lifetime of dS space in string theory will always be shorter than the recurrence time.

Particle Physics and Inflationary Cosmology

With the invention of unified theories of strong, weak, electromagnetic and gravitational interactions, elementaryparticle physics has entered a very interesting and unusual stage of its development. The end of the 1960s saw the introduction of the Glashow‐Weinberg‐Salam unification of the weak and electromagnetic interactions. In 1974 came the grand unified theories of the strong, weak and electromagnetic interactions. Two years later we had supergravity, giving us the first hope of unifying all fundamental interactions, including gravitation. The beginning of the 1980s witnessed a renewal of interest in the Kaluza‐Klein theories and supergravity in higher‐dimensional space‐time. Nowadays superstring theory is the leading candidate for the role of “theory of everything.”

Towards Inflation in String Theory

We investigate the embedding of brane inflation into stable compactifications of string theory. At first sight a warped compactification geometry seems to produce a naturally flat inflaton potential, evading one well known difficulty of brane?antibrane scenarios. Careful consideration of the closed string moduli reveals a further obstacle: superpotential stabilization of the compactification volume typically modifies the inflaton potential and renders it too steep for inflation. We discuss the non-generic conditions under which this problem does not arise. We conclude that brane inflation models can only work if restrictive assumptions about the method of volume stabilization, the warping of the internal space, and the source of inflationary energy are satisfied. We argue that this may not be a real problem, given the large range of available fluxes and background geometries in string theory.

Towards the theory of reheating after inflation

Reheating after inflation occurs due to particle production by the oscillating inflaton field. In this paper we describe the perturbative approach to reheating, and then concentrate on effects beyond the perturbation theory. They are related to the stage of parametric resonance called preheating. It may occur in an expanding universe if the initial amplitude of oscillations of the inflaton field is large enough. We investigate a simple model of a massive inflaton field coupled to another scalar field X. Parametric resonance in this model is very broad. It occurs in a very unusual stochastic manner, which is different from the parametric resonance in the case when the expansion of the universe is neglected. Quantum fields interacting with the oscillating inflaton field experience a series of kicks which occur with phases uncorrelated to each other. We call this process stochastic resonance. We develop the theory of preheating taking into account the expansion of the universe and backreaction of produced particles, including the effects of rescattering. The process of preheating can be divided into several distinct stages. At the first stage the backreaction of created particles is not important. At the second stage backreaction increases the frequency of oscillations of the inflaton field, which makes the process even more efficient than before. Then the effects related to scattering of X-particles terminate the resonance. We calculate the density of X-particles and their quantum fluctuations with all backreaction effects taken into account. This allows us to find the range of masses and coupling constants for which one has efficient preheating. In particular, under certain conditions this process may produce particles with a mass much greater than the mass of the inflaton field.

Reheating after inflation.

The theory of reheating of the Universe after inflation is developed. We have found that typically at the first stage of reheating the classical inflation field

The Inflationary Universe

\ensuremath{\varphi}

Is it easy to save the gravitino

rapidly decays into

Macroscopic consequences of the Weinberg model

\ensuremath{\varphi}

Infrared problem in the thermodynamics of the Yang-Mills gas

particles or into other bosons due to a broad parametric resonance. Then these bosons decay into other particles, which eventually become thermalized. Complete reheating is possible only in those theories where a single particle