Abstract
Misner space, also known as the Lorentzian orbifold 
, is one of the simplest examples of a cosmological singularity in string theory. In this
work, the study of weakly coupled closed strings on this space is pursued in several
directions. (i) Physical states in the twisted sectors are found to come in two kinds: short
strings, which wind along the compact space-like direction in the cosmological (Milne)
regions, and long strings, which wind along the compact time-like direction in the (Rindler)
whiskers. The latter can be viewed as infinitely long static open strings, stretching from
Rindler infinity to a finite radius and folding back onto themselves. (ii) As in the Schwinger
effect, tunnelling between these states corresponds to local pair production of
winding strings. The tunnelling rate approaches unity as the winding number
w
gets large, as a consequence of the singular geometry. (iii) The one-loop string amplitude
has singularities on the moduli space, associated to periodic closed string trajectories in
Euclidean time. In the untwisted sector, they can be traced to the combined
existence of CTCs and Regge trajectories in the spectrum. In the twisted sectors,
they indicate pair production of winding strings. (iv) At a classical level and
in sufficiently low dimension, the condensation of winding strings can indeed
lead to a bounce, although the required initial conditions are not compatible
with Misner geometry at early times. (v) The semi-classical analysis of winding
string pair creation can be generalized to more general (off-shell) geometries. We
show that a regular geometry regularizes the divergence at large winding number.