Found 5 result(s)

23.01.2019 (Wednesday)

What spatial geometry does the (2+1)-d QFT vacuum prefer?

Regular Seminar Toby Wiseman (Imperial College London)

at:
13:15 KCL
room S2.49
abstract:

We consider the energy of a (2+1)-d relativistic QFT on a deformation of flat space in either the quantum or thermal vacuum state. Looking at both free scalars and fermions, with and without mass (and in the scalar case including a curvature coupling) we surprisingly find that any deformation of flat space is always energetically preferred to flat space itself. This is a UV finite effect, insensitive to any cut- off. We see the same behaviour for any (2+1)-holographic CFT which we compute via the gravity dual. We consider the physical application of this to membranes carrying relativistic degrees of freedom, the vacuum energy of which then induce a tendency for the membrane to crumple. An interesting case is monolayer graphene, which experimentally is observed to ripple, and on large scales can be understood as a membrane carrying free massless Dirac degrees of freedom.

28.01.2015 (Wednesday)

On black hole thermodynamics from super Yang-Mills

Regular Seminar Toby Wiseman (Imperial College)

at:
15:15 QMW
room G.O. Jones 610
abstract:

I will review the link between 1+p dimensional maximally supersymmetric Yang-Mills and the black hole thermodynamics of Dp-branes via the gauge/string correspondence. The finite temperature behaviour of Dp-brane supergravity black holes looks very alien from the perspective of the dual strongly coupled Yang-Mills. However, I will argue that in a natural set of Yang-Mills variables, the classical moduli (which unfortunately are still strongly coupled), certain features of these thermodynamics become quite transparent.

10.10.2007 (Wednesday)

05.03.2007 (Monday)

Ricci flow and black holes

String Theory & Geometry Seminar Toby Wiseman (Imperial College)

at:
13:30 IC
room Maths Institute seminar room
abstract:

02.06.2005 (Thursday)

Numerical Ricci flat metrics on K3

Regular Seminar Toby Wiseman (Harvard)

at:
16:00 IC
room H503
abstract:

Compact Calabi-Yau manifolds are a key ingredient for dimensional reduction in string theory. For this, one requires the Ricci-flat metric on these manifolds. Whilst Yau proved this metric exists, no explicit smooth examples are known, essentially as it is very difficult (impossible?) to find them analytically as they have no continuous isometries. Taking a new approach, I will discuss numerical methods to solve the Einstein equation on these manifolds. I will pedagogically describe the construction, and give results, for a particular one parameter family of metrics on K3 (the unique 4-dimensional Calabi-Yau manifold). I will discuss possible applications of these methods, and generalizations to geometries with matter such as those relevant for flux compactifications. There will be some nice pictures.