Warm inflation in small field models:

a stringy realisation

Juan Carlos Bueno Sánchez

Lancaster University

Work in progress with: M. Bastero-Gil (University of Granada), A. Berera (University of Edinburgh) and K. Dimopoulos (Lancaster University)

Radiation production after inflation

Inflaton may lose energy non-perturbatively (preheating: non-linear effects )

Weak dissipation:

Strong dissipation:

Inflaton EOM

Cold inflation

Introduction

InflatondecayRadiation density

(production of radiation during inflation)Warm inflation

Equilibrium approach Radiation is close to thermal equilibrium

Moss and Xiong ‘07

Warm inflation is very difficult

Inflaton may lose energy as well

High T:

Low T:

Yokoyama and Linde ‘99

Chaotic and Hybrid models Bastero-Gil and Berera ‘06

Warm inflation supported for ~ 50-60 e-folds

X and Y may belong to large rep. of GUT group

with

Introduction

Dissipation mechanism:

Allowed decays

with

Take inverted potential

A small field model

Take inflation gives way to radiation domination

before

Weak dissipation

Strong dissipation (with )

Dissipation coefficient

Warm inflation Radiation domination

Inflation after horizon exit

Spectrum curvature perturbations

Spectral index

Matching the spectrum

Warm inflation in string theory

ESP

Fixed point of symmetries

Trapping mechanism (particle production)

Moduli trapping

Why an enhanced symmetry point?

mP

Strong interaction between and

Naturalness of the trapping

prefers points with higher number of fields

Trapping operates at distances

Inflaton is a string modulus passing close to an enhanced symmetry point

Environmental selection of larger

ESPs typically at Planckian distance

Warm inflation in string theory

ESP

Fixed point of symmetries

Trapping mechanism (particle production)

Moduli trapping

Why an enhanced symmetry point?

Strong interaction between and

Naturalness of the trapping

prefers points with higher number of fields

Trapping operates at distances

Environmental selection of larger

ESPs typically at Planckian distance

Environmental selection makes easier to fit the spectrum

Inflaton is a string modulus passing close to an enhanced symmetry point

gives its oscillation density no overshoot

Decay of before inflation

Decay of during inflation no overshoot

Warm inflation in string theory

Decay of before inflation

and

may overshoot the ESP

h is larger but far from its maximum value

Warm inflation in string theory

Decay of before inflation

and

may overshoot the ESP

h is larger but far from its maximum value

Warm inflation in string theory

Decay of before inflation

and

may overshoot the ESP

h is larger but far from its maximum value

Warm inflation in string theory

Decay of before inflation

and

may overshoot the ESP

h is larger but far from its maximum value

Warm inflation in string theory

Conclusions

Full analytical description of inflation in the low-temperature regime.

Inflation may finish in weak dissipation, retaining a constant radiation density which may reheat the Universe.

Inflation may give way to radiation dominated Universe.

Spectral index may be fitted to the observational values by tunning H

The observed spectrum may be matched for a wide range of curvatures In particular for

String theory (modulus + ESP) may fix initial conditions for warm inflation

Initial radiation bath from decay products

Strong interaction between fields

Trapping provides environmental selection mechanism making easier fit spectrum