The thirty-ninth meeting of the North British Mathematical
Physics Seminar was held on **Wednesday 6 November
2013** in Durham, in the Collier Room at
St Hild & St Bede College.
These
people attended the meeting.

11:00-11:30

Coffee

11:30-12:30

David Fairlie
(Durham/Manchester)

Galileons satisfy equations of motion with terms containing only second order derivatives of the fields.
They have many intriguing properties, derivation from Lagrangian hierarchies, implicit solutions,
dualities etc, and have become new players in cosmological models.

12:30-13:30

Lunch

13:30-14:30

Tristan McLoughlin
(Trinity College Dublin)

The study of the worldsheet S-matrix for AdS_5 x S^5 strings
was a key step in the complete determination of the spectrum
of anomalous dimensions for planar N=4 super-Yang-Mills gauge
theory. To go beyond the spectral problem it is important to consider
higher-point worldsheet correlation functions and one approach is
the study of form factors. We will discuss the calculation of form
factors in the two-dimensional light-cone gauge-fixed string theory
and their connection to four-dimensional gauge theory three-point
functions.

14:30-15:00

Helen Baron
(Durham)

We present the collective coordinate approximation to model the dynamics of two interacting nonlinear Schrodinger (NLS) solitons; and discuss the accuracy of this approximation by comparing our results to those of the full numerical simulations.

15:00-15:30

Tea

15:30-16:30

Jonathan Pearson
(Durham)

We consider a class of phenomenological modified gravity models where the terms added to the standard Einstein-Hilbert Lagrangian are just a function of the metric only. For linearized perturbations around an isotropic space-time, this class of models is entirely specified by a rank 4 tensor that encodes possibly time-dependent masses for the gravitons. This tensor has the same symmetries as an elasticity tensor, suggesting an interpretation of massive gravity as an effective rigidity of space-time. If we choose a form for this tensor which is compatible with the symmetries of FRW and enforce full reparameterization invariance, then the only theory possible is a cosmological constant. However, in the case where the theory is only time translation invariant, the ghost-free massive gravity theory is equivalent to the elastic dark energy scenario with the extra Lorentz violating vector giving rise to 2 transverse and 1 longitudinal degrees of freedom, whereas when one demands spatial translation invariance one is left with a theory where the entropy perturbation is not gauge invariant.

16:30-17:00

Nick Behr
(Heriot-Watt)

Reporting on work in progress with A. Konechny, I will talk about the
important role redundant operators play in the renormalization of 2d QFTs.
The analysis is performed both via the study of the local renormalization
anomaly equation as well as in explicit conformal perturbation theory. Our
results reveal the existence of a symmetry on coupling space due to the
redundant operators, indicating that physical quantities such as the
c-function and the beta-functions should depend only on equivalence classes
of couplings under this symmetry. Partial progress towards the study of the
geometry of coupling space as well as illustrating examples will be
presented.

Train information can be obtained here.

For this meeting, do **not** go to the Department of Mathematical
Sciences. We will be in the College of St Hild & St Bede
which is building number 30 on this
map.

Lunch, as well as morning and afternoon tea, coffee and biscuits will be provided free of charge. However, we need to know numbers in advance so please
make sure you email Douglas Smith if you are coming to the meeting, **by Monday 28th October** if possible.

Limited funds are available to help with travel expenses of participants with no other source of funding. We hope that this will encourage postgraduate students and postdocs to attend the meeting. Please email Douglas Smith in advance if you would like to apply for support and please book early to take advantage of the cheaper fares.

Douglas Smith
Last modified: 7 November 2013