Christoph Mayrhofer
(Heidelberg University)
25/09/2013, 14:00
Strings & Mathematical Physics
In this talk we will describe the construction of F-Theory GUT models for elliptically fibred Calabi-Yau fourfolds admitting a non-trivial Mordell-Weil group. We work out the matter spectrum and Yukawa couplings, including singlets, for these geometries and present the fluxes corresponding to the U(1) symmetries.
Dr
Noppadol Mekareeya
(Max Planck Institute for Physics)
25/09/2013, 14:30
Strings & Mathematical Physics
In this talk, I will present a method for a systematic study of the moduli spaces of Yang-Mills instantons in a simple gauge group. For a classical group, the moduli space can be studied via the ADHM construction, which can be realised from the Lagrangian of a certain quiver gauge theory with 8 supercharges. Such a construction is, however, not available for instantons in exceptional gauge...
Mr
Jie Gu
(Universität Bonn)
25/09/2013, 15:00
Strings & Mathematical Physics
It's been conjectured that the Chern-Simons theory with SU(N) group on S3 in the large N limit can be described by closed topological string. When a Wilson line operator along some knot is inserted in the Chern-Simons theory, some brane appears in the topological string. We give support to the second half of the conjecture by computing the instanton numbers in B-model, using the topological...
Mr
Martin Sprenger
(DESY)
25/09/2013, 15:50
Strings & Mathematical Physics
In this talk, I will present results for the 6- and 7-point amplitude in strongly coupled N=4 super Yang-Mills theory in the multi-Regge regime. I will review the calculation of scattering amplitudes in strongly coupled N=4 SYM, where calculating the amplitude corresponds to calculating a specific minimal surface embedded into AdS5.
The leading order solution of this problem is determined...
Dr
Ben Hoare
(Humboldt-Universität zu Berlin)
25/09/2013, 16:10
Strings & Mathematical Physics
In this talk we will discuss recent developments in the application of unitarity techniques to 2-d integrable field theories. After outlining the general construction (mainly focussing on one loop, but with some comments on two), we will apply the method to various integrable theories, finding evidence that the one-loop S-matrix is cut-constructible. The final part of the talk will focus on...
Mr
Tobias Hansen
(Universitaet Hamburg)
25/09/2013, 16:30
Strings & Mathematical Physics
Tree level unitarity relates the residues of N-point amplitudes of scalars to lower point amplitudes of all particles in the spectrum of a theory. I will explain in the case of open bosonic string theory how to exploit this relation, in which one has to sum over all particles that are on-shell at the residue in question and all its possible polarizations. In contrast to Yang-Mills theory, here...
Mr
Ilmar Gahramanov
(Humboldt-University Berlin)
25/09/2013, 16:50
Strings & Mathematical Physics
By reduction of a single letter index a natural connection is found between superconformal indices of even-dimensional supersymmetric theories. We find that the superconformal index of the 4d N=2, 4 theory reduces to the superconformal index of the N=(2,2), (4,4) theory in the certain limit of the superconformal fugacities. The proposed reduction procedure could also help to extract...
Daniele Dorigoni
(DAMPT Cambridge)
25/09/2013, 17:10
Strings & Mathematical Physics
Also in theories without instantons non-perturbative saddle points play a crucial role. Using the example of the 2d principal chiral model we show how resurgence theory, which unifies perturbative and non-perturbative physics, predicts the existence of several types of non-perturbative saddles: the fractons. With these new saddles is possible to understand the quantum interpretation of...
Martin Ammon
(Friedrich-Schiller University Jena)
26/09/2013, 14:00
Strings & Mathematical Physics
Holographic entanglement entropy provides a direct connection between classical geometry and quantum entanglement; however the usual prescription does not apply to theories of higher spin gravity, where standard notions of geometry are no longer gauge invariant. We present a proposal for the holographic computation of entanglement entropy in field theories dual to higher spin theories of...
Dr
Aleksey Cherman
(FTPI, University of Minnesota)
26/09/2013, 14:30
Strings & Mathematical Physics
Large-N volume independence in circle-compactified QCD with Nf ≥ 1 adjoint Weyl fermions implies the absence of any phase transitions as the radius is dialed to arbitrarily small values. This class of theories are believed to possess a Hagedorn density of hadronic states. These properties are in apparent tension with each other, because a Hagedorn density of states typically implies a phase...
Dr
Oliver Schlotterer
(AEI Potsdam)
26/09/2013, 15:00
Strings & Mathematical Physics
We discuss tree level scattering of massless open superstring states on a worldsheet of disk topology -- for any number of external legs. The entire state dependence of these disk amplitudes can be expressed in terms of gauge theory subamplitudes from the point particle limit. The string corrections entering through momentum dependent integrals over the disk boundary can be disentangled from...
Mr
Maximilian Poretschkin
(Bethe Center for Theoretical Physics)
26/09/2013, 15:50
Strings & Mathematical Physics
The most detailed information about rigid $\mathcal{N}=2$ supersymmetric theories in $\mathbb{R}^4 \times S^1$ is contained in a supersymmetric index counting refined BPS states. They fall into representations of SU(2)$_L$ $\times$ SU(2)$_R$, the little group in 5$d$, which has an induced action on the cohomology of the moduli space of stable pairs.
I will present the computation of...
Mr
Daniel Plencner
(LMU Munich)
26/09/2013, 16:10
Strings & Mathematical Physics
Orbifolding a 2-dimensional quantum field theory by a symmetry group admits an elegant description in terms of defect lines and their junction fields. This perspective offers a natural generalization of the concept of an orbifold, in which the role of the symmetry group is replaced by a defect with the structure of a (symmetric) separable Frobenius algebra. In this talk I will focus on the...
Mr
Václav Tlapák
(DESY)
26/09/2013, 16:30
Strings & Mathematical Physics
Replacing the regular Lie groups in the coset construction of Goddard-Kent-Olive (GKO) with Lie supergroups yields conformal but non-unitary 2-dimensional QFTs. We extend previous studies of exactly marginal deformations in such superspace coset models to hermitian symmetric superspaces. In this case we obtain several families of N=2 superconformal field theories with continuously varying exponents.
Dr
Cagnazzo Alessandra
(DESY)
26/09/2013, 16:50
Strings & Mathematical Physics
The study of Superstring Theories on AdS backgrounds is important in the context of Gauge/Gravity correspondence. These theories can be reduced, under certain assumptions, to Sigma Models on semi-symmetric super-cosets. For a peculiar class of these cosets one can also introduce a WZ term. This correspond to study a Superstring Theory on a background supported by a mixture of RR and NSNS...
Mr
Federico Bonetti
(MPI Munich)
26/09/2013, 17:10
Strings & Mathematical Physics
A five-dimensional approach to six-dimensional tensor theories is discussed, which makes use of towers of massive five-dimensional tensors in a Kaluza-Klein inspired fashion. The relation to Chern-Simons theories in five dimensions is considered at the quantum level. A five-dimensional supersymmetric Lagrangian with tensor towers is proposed to furnish a description of non-Abelian (2,0) theories.
Dr
Christoph Horst
(University of Hamburg)
26/09/2013, 17:30
Strings & Mathematical Physics
We study N=2 vacua in gauged N=4 supergravity theories in four-dimensional spacetime. Using the embedding tensor formalism that describes general consistent magnetic gaugings of an ungauged N=4 matter-coupled supergravity theory in a symplectic frame with SO(1,1) x SO(6,n) off-shell symmetry we formulate necessary conditions for partial supersymmetry breaking and find that the Killing spinor...
Ioannis Florakis
(MPI Physik)
26/09/2013, 17:50
I will present a new class of N=2 amplitudes in string theory, generalizing the well-known F-terms which compute the topological string theory partition function. These generalized F-terms involve, in addition to the standard anti-self-dual graviphoton background, additional insertions of self-dual vertices. The latter can be identified, using the non-trivial constraint that the correct N = 2...
