  We present a new method of incorporating radiative transfer into Smoothed
Particle Hydrodynamics (SPH). There have been many recent attempts at radiative
transfer in SPH (Stamatellos et al 2005, 2005, Mayer et al 2007, Whitehouse and
Bate 2006), however these are becoming increasingly complex, with some methods
requiring the photosphere to be mapped (which is often of non-trivial geometric
shape), and extra conditions to be applied there (matching atmospheres as in
Cai et al (2008), or specifying cooling at the photosphere as in Mayer et al
(2007)). The method of identifying the photosphere is usually a significant
addition to the total simulation runtime, and often requires extra free
parameters, the changing of which will affect the final results. Our method is
not affected by such concerns, as the photosphere is constructed implicitly by
the algorithm without the need for extra free parameters. The algorithm used is
a synergy of two current formalisms for radiative effects: a) the polytropic
cooling formalism proposed by Stamatellos et al (2007), and b) flux-limited
diffusion, used by many authors to simulate radiation transport in the
optically thick regime (e.g. Mayer et al 2007). We present several tests of
this method: (1) The evolution of a 0.07 solar mass protoplanetary disc around
a 0.5 solarmass star (Pickett et al 2003, Mejia et al 2005, Boley et al 2006,
Cai et al 2008); (2) The collapse of a non-rotating 1 solar mass molecular
cloud (Masunaga & Inutsuka 2000, Stamatellos et al 2007); (3) The thermal
relaxation of temperature fluctuations in an static homogeneous sphere
(Masunaga et al 1998, Spiegel 1957, Stamatellos et al 2007)
