Particle production in matrix cosmology

Abstract

We consider cosmological particle production in 1ϩ1 dimensional string theory. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum fields in time-dependent backgrounds is resolved by the underlying matrix model. This leads to a finite energy density for the ''in'' state which cancels the effect of anomalous particle production.

Collective Field Description of Matrix Cosmologies

“…Supposedly such a complication would appear for the droplet cosmologies as well, but there is no obvious candidate for what it might be. Therefore, it seems unlikely that a spacetime analysis of tachyon scattering can be carried out as has been done in the case of the standard, static Fermi sea as well as the moving hyperbola solution (3.7) [9,10]. In addition, the leg pole transform is only known on the null boundaries of spacetime, and not in its bulk.…”

“…We also have ∂ x σ = √ g/f . Now we can use the equation of motion (2.7) to find the forms of f and g. Using (4.4), notice that 10) so the equation of motion (2.7) implies…”

Spacelike boundaries from thec=1matrix model

“…From the general formulae in [10] (equation (36)) it follows that the fluctuations are massless particles in a metric which is conformally equivalent to In this metric, t = 0 is a coordinate singularity. The transformations (13) and (17) render the metric Minkowskian…”

“…The static Fermi sea is, of course, not the only solution of the equations of motion. A class of nontrivial solutions can be obtained by acting with various W ∞ transformations on this static profile [10]. In phase space, one class of transformations is given by…”

“…The availability of such a model has inspired recent work aimed at understanding the physics of time dependent backgrounds. While classical time dependent solutions of the matrix model have been known for quite some time [5,6,7], only recently has it been suggested [8] that these backgrounds should be regarded as "matrix cosmologies" and fruitfully utilized to understand conceptual issues related to quantum cosmology such as particle production [9,10,11] and thermality [12].…”