Abstract We give a short introduction to discrete flat fronts in hyperbolic space and prove that any front the mixed area sense admits Weierstrass representation.

Hawking and the author have proposed a class of singular, finite action instantons for defining the initial conditions for inflation. Vilenkin has argued they are unacceptable. He exhibited an analogous class of asymptotically flat instantons which on the face of it lead to an instability of Minkowski space. However, all these instantons must be defined by introducing a constraint into the path...

Following the idea that information is the negative entropy, we propose that the information and entropy of an isolated system can convert into each other while the sum of them is an invariant for any physical process. The holographic principle is then reformulated in the way that this invariant is bounded by the Bekenstein-Hawking entropy of the system. It is found that Heisenberg’s uncertaint...

We study the near-flat space limit for strings on AdS5 × M5, where the internal manifold M5 is equipped with a generic metric with U(1)3 isometry. In the bosonic sector, the limiting sigma model is similar to the one found for AdS5 × S5, as the global symmetries are reduced in the most general case. When M5 is a SasakiEinstein space like T 1,1, Y p,q and Lp,q,r, whose dual CFT’s have N = 1 supe...