  The robotic 2m Liverpool Telescope, based on the Canary island of La Palma,
has a diverse instrument suite and a strong track record in time domain
science, with highlights including early time photometry and spectra of
supernovae, measurements of the polarization of gamma-ray burst afterglows, and
high cadence light curves of transiting extrasolar planets. In the next decade
the time domain will become an increasingly prominent part of the astronomical
agenda with new facilities such as LSST, SKA, CTA and Gaia, and promised
detections of astrophysical gravitational wave and neutrino sources opening new
windows on the transient universe. To capitalise on this exciting new era we
intend to build Liverpool Telescope 2: a new robotic facility on La Palma
dedicated to time domain science. The next generation of survey facilities will
discover large numbers of new transient sources, but there will be a pressing
need for follow-up observations for scientific exploitation, in particular
spectroscopic follow-up. Liverpool Telescope 2 will have a 4-metre aperture,
enabling optical/infrared spectroscopy of faint objects. Robotic telescopes are
capable of rapid reaction to unpredictable phenomena, and for fast-fading
transients like gamma-ray burst afterglows. This rapid reaction enables
observations which would be impossible on less agile telescopes of much larger
aperture. We intend Liverpool Telescope 2 to have a world-leading response
time, with the aim that we will be taking data with a few tens of seconds of
receipt of a trigger from a ground- or space-based transient detection
facility. We outline here our scientific goals and present the results of our
preliminary optical design studies.
