Publications from previous years
Publications 2018

Heterotic and bosonic string amplitudes via field theory
Authors: Thales Azevedo, Marco Chiodaroli, Henrik Johansson and Oliver Schlotterer
Preprint number: UUITP07/18
Previous work has shown that massless tree amplitudes of the type I and IIA/B superstrings can be dramatically simplified by expressing them as double copies between fieldtheory amplitudes and scalar disk/sphere integrals, the latter containing all the $\alpha'$corrections. In this work, we pinpoint similar doublecopy constructions for the heterotic and bosonic string theories using an $\alpha'$dependent field theory and the same disk/sphere integrals. Surprisingly, this field theory, built out of dimensionsix operators such as $(D_\mu F^{\mu \nu})^2$, has previously appeared in the doublecopy construction of conformal supergravity. We elaborate on the $\alpha' \rightarrow \infty$ limit in this picture and derive new amplitude relations for various gaugegravity theories from those of the heterotic string.

Infinitely Many M2instanton Corrections to Mtheory on G_2 manifolds
Authors: Andreas P. Braun, Michele Del Zotto, James Halverson, Magdalena Larfors, David R. Morrison and Sakura SchäferNameki
Preprint number: UUITP06/18
We consider the nonperturbative superpotential for a class of fourdimensional N = 1 vacua obtained from Mtheory on sevenmanifolds with holonomy $G_2$. The class of $G_2$holonomy manifolds we consider are socalled twisted connected sum (TCS) constructions, which have the topology of a K3fibration over $S^3$. We show that the nonperturbative superpotential of Mtheory on a class of TCS geometries receives infinitely many inequivalent M2instanton contributions from infinitely many threespheres, which we conjecture are supersymmetric (and thus associative) cycles. The rationale for our construction is provided by the duality chain of [1], which relates Mtheory on TCS $G_2$manifolds to $E_8 \times E_8$ heterotic backgrounds on the Schoen CalabiYau threefold, as well as to Ftheory on a K3fibered CalabiYau fourfold. The latter are known to have an infinite number of instanton corrections to the superpotential and it is these contributions that we trace through the duality chain back to the $G_2$compactification.

4D Gauge Theories with Conformal Matter
Authors: Fabio Apruzzi, Jonathan J. Heckman, David R. Morrison and Luigi Tizzano
Preprint number: UUITP05/18
One of the hallmarks of 6D superconformal field theories (SCFTs) is that on a partial tensor branch, all known theories resemble quiver gauge theories with links comprised of 6D conformal matter, a generalization of weakly coupled hypermultiplets. In this paper we construct 4D quiverlike gauge theories in which the links are obtained from compactifications of 6D conformal matter on Riemann surfaces with flavor symmetry fluxes. This includes generalizations of super QCD with exceptional gauge groups and quarks replaced by 4D conformal matter. Just as in super QCD, we find evidence for a conformal window as well as confining gauge group factors depending on the total amount of matter. We also present Ftheory realizations of these field theories via elliptically fibered CalabiYau fourfolds. Gauge groups (and flavor symmetries) come from 7branes wrapped on surfaces, conformal matter localizes at the intersection of pairs of 7branes, and Yukawas between 4D conformal matter localize at points coming from triple intersections of 7branes. Quantum corrections can also modify the classical moduli space of the Ftheory model, matching expectations from effective field theory.

Fiveloop massless propagator integrals
Authors: Alessandro Georgoudis, Vasco Goncalves, Erik Panzer and Raul Pereira
Preprint number: UUITP02/18
We develop a method to obtain εexpansions of massless twopoint
integrals in position space, based on the constraints implied by symmetries of
the asymptotic expansion of conformal fourpoint integrals. Together with
parametric integration, we are able to fix the expansions of 170 genuine
fiveloop master integrals. In particular, we computed the expansions of all
planar master integrals up to transcendental weight 9. 
Matter Field Kahler Metric in Heterotic String Theory from Localisation
Authors: Stefan Blesneag, Evgeny I. Buchbinder, Andrei Constantin, Andre Lukas, Eran Palti
Preprint Number: UUITP04/18
Abstract: We propose an analytic method to calculate the matter field Kähler metric in heterotic compactifications on smooth CalabiYau threefolds with Abelian internal gauge fields. The matter field Kähler metric determines the normalisations of the N = 1 chiral superfields, which enter the computation of the physical Yukawa couplings. We first derive the general formula for this Kähler metric by a dimensional reduction of the relevant supergravity theory and find that its Tmoduli dependence can be determined in general. It turns out that, due to large internal gauge flux, the remaining integrals localise around certain points on the compactification manifold and can, hence, be calculated approximately without precise knowledge of the Ricciflat CalabiYau metric. In a final step, we show how this local result can be expressed in terms of the global moduli of the CalabiYau manifold. The method is illustrated for the family of CalabiYau hypersurfaces embedded in P1 × P3 and we obtain an explicit result for the matter field Kähler metric in this case.

Permutation in the CHYFormulation
Authors: Rijun Huang, Fei Teng and Bo Feng
Preprint Number: UUITP03/18
Abstract: The CHYintegrand of biadjoint cubic scalar theory is a product of two PTfactors. This pair of PTfactors can be interpreted as defining a permutation. We introduced the cycle representation of permutation in this paper for the understanding of cubic scalar amplitude. We showed that, given a permutation related to the pair of PTfactors, the pole and vertex information of Feynman diagrams of corresponding CHYintegrand is completely characterized by the cycle representation of permutation. Inversely, we also showed that, given a set of Feynman diagrams, the cycle representation of corresponding PTfactor can be recursively constructed from three point ones. Based on these results, we have investigated the relations among different independent pairs of PTfactors in the context of cycle representation as well as the multiplication of crossratio factors.

Superconformal indices on $S^1\times (S^5/\mathbb{Z}_p)$
Authors: Andreas Gustavsson
Preprint number: UUITP01/18
We obtain generating functions associated to the abelian superconformal indices for 6d $(1,0)$ tensor and hypermultiplets on $S^1\times (S^5/\mathbb{Z}_p)$. We extract the superconformal indices and their high and low temperature behaviors. We consider round and generically squashed $S^5$ in turn. We show that the unsquashed limit of the superconformal indices is smooth. We examine Sduality in the large $p$ limit that acts by exchanging the Hopf circle with the temporal circle.
PUBLICATIONS 2017

Syzygies for integrationbyparts reductions from Laplace expansion
Authors: Janko Böhm, Alessandro Georgoudis, Kasper J. Larsen, Mathias Schulze, Yang Zhang
Preprint number: UUITP44/17
Integrationbyparts identities between loop integrals arise from the vanishing integration of total derivatives in dimensional regularization. Generic choices of total derivatives lead to identities which involve dimension shifts. These dimension shifts can be avoided by imposing a constraint on the total deriva tives which takes the form of a specific type of polynomial equation, known in algebraic geometry as syzygy equations. We present an explicit generating set of solutions to the encountered syzygy equation, valid for any number of loops and external momenta. The generating set of solutions is obtained from the Laplace expansion of the Gram determinant formed of the loop momenta and independent external momenta. In particular, no Spolynomial computations are required in order to obtain the syzygies. We moreover show how to obtain the syzygies needed for integrationbyparts identities evaluated on a generalized unitarity cut.

Towards an explicit model of large field inflation
Authors: Juan Diaz Dorronsoro, Marjorie Schillo
Preprint number: UUITP51/17
The unwinding inflation mechanism is studied in a type IIB flux compactification where all moduli are stabilized using flux, nonperturbative effects, and the leading α′ corrections of the large volume scenario. We consider the backreaction on the geometry due to the presence of antiD3 branes as well as the backreaction of inflation on the Kähler moduli, and compute the resulting corrections to the slowroll potential. By taking large flux numbers, we are able to find inflationary epochs where backreaction effects are under control, the inflaton traverses a superPlanckian field range, and the resulting amplitude of scalar perturbations is consistent with observation.

String corrections to circular Wilson loop and anomalies
Authors: A. Cagnazzo, D. MedinaRincon and K. Zarembo
Preprint number: UUITP52/17
We study string quantum corrections to the ratio of latitude and circular Wilson loops in N=4 superYangMills theory at strong coupling. Conformal gauge for the corresponding minimal surface in AdS(5)xS(5) is singular and we show that an IR anomaly associated with the divergence in the conformal factor removes previously reported discrepancy with exact fieldtheory results. We also carefully check conformal anomaly cancellation and recalculate fluctuation determinants by directly evaluting phaseshifts for all the fluctuation modes.

Wilson loops in antisymmetric representations from localization in supersymmetric gauge theories
Authors: J. Russo and K. Zarembo
Preprint number: UUITP50/17
LargeN phase transitions occurring in massive N=2 theories can be probed by Wilson loops in large antisymmetric representations. The logarithm of the Wilson loop is effectively described by the free energy of a Fermi distribution and exhibits secondorder phase transitions (discontinuities in the second derivatives) as the size of representation varies. We illustrate the general features of antisymmetric Wilson loops on a number of examples where the phase transitions are known to occur: N=2 SQCD with various mass arrangements and N=2* theory. As a byproduct we solve planar N=2 SQCD with three independent mass parameters, m, M, Lambda. This model has two effective mass scales and undergoes two phase transitions.

Conformal Data of Fundamental GaugeYukawa Theories
Authors: Nicola Andrea Dondi, Vladimir Prochazka, Francesco Sannino
Preprint Number: UUITP49/17
We determine central charges, critical exponents and appropriate gradient flow relations for nonsupersymmetric vectorlike and chiral GaugeYukawa theories that are fundamental according to Wilson and that feature calculable UV or IR interacting fixed points. We further uncover relations and identities among the various local and global conformal data. This information is used to provide the first extensive characterisation of general classes of free and safe quantum field theories of either chiral or vectorlike nature via their conformal data. Using large Nf techniques we also provide examples in which the safe fixed point is nonperturbative but for which conformal perturbation theory can be used to determine the global variation of the a central charge.

Cyclic Mario Worlds – ColorDecomposition for OneLoop QCD
Authors: Gregor Kälin
Preprint number: UUITP48/17
We present a new color decomposition for QCD amplitudes at one
loop level as a generalization of the Del DucaDixonMaltoni and JohanssonOchirov
decomposition at tree level. Starting from a minimal basis of planar primitive ampli
tudes we write down a color decomposition that is free of linear dependencies among
appearing primitive amplitudes or color factors. The decomposition applies to any
number of quark flavors and is independent of the choice of gauge group and matter
representation. The results also hold for higherdimensional or supersymmetric ex
tensions of QCD. We provide expressions for any number of external quarkantiquark
pairs and gluons. 
ScalarFermion Analytic Bootstrap in 4D
Authors: Emtinan Elkhidir and Denis Karateev
PrePrint: UUITP47/17
In this work we discuss an analytic bootstrap approach [1,2] in the context of spinning 4D conformal blocks [3,4]. As an example we study the simplest spinning case, the scalarfermion correlator $\langle \phi \psi \phi \overline\psi \rangle$. We find that to every pair of primary scalar $\phi$ and fermion $\psi$ correspond two infinite towers of fermionic large spin primary operators. We compute their twists and products of OPE coefficients using both st and ut bootstrap equations to the leading and subleading orders. We find that the leading order is represented by the scalarfermion generalized free theory and the subleading order is governed by the minimal twist bosonic (light scalars, currents and the energymomentum tensor) and fermionic (light fermions and the suppersymmetric current) operators present in the spectrum.

Observational signatures from horizonless black shells imitating rotating black holes
Authors: Ulf Danielsson and Suvendu Giri
Preprint number: UUITP46/17
In arXiv:1705.10172 it was proposed that string theory replaces Schwarzschild black holes with horizonless thin shells with an AdS interior. In this paper we extend the analysis to slowly rotating black holes, solving the IsraelLanczosSen junction conditions for a rotating shell composed of stringy matter to determine the metric. Outside of the shell we find a vacuum solution that differs from Kerr with a 39% larger quadrupole moment. We discuss the observational consequences and explore the possibility to distinguish between a black shell and a black hole. Promising methods include imaging of the black hole at the center of the Milky Way using the Event Horizon Telescope, precision measurements of stars in close orbits around the central black hole, and future observations of colliding super massive black holes using the space based gravitational wave observatory LISA.

An integrable Lorentzbreaking deformation of twodimensional CFTs
Authors: Monica Guica
Preprint number: UUITP45/17
It has been recently shown that the deformation of an arbitrary twodimensional conformal field theory by the composite irrelevant operator $T \bar T$, built from the components of the stress tensor, is solvable; in particular, the finitesize spectrum of the deformed theory can be obtained from that of the original CFT through a universal formula. We study a similarly universal, Lorentzbreaking deformation of twodimensional CFTs that possess a conserved $U(1)$ current, $J$. The deformation takes the schematic form $J \bar T$ and is interesting because it preserves an $SL(2,\mathbb{R}) \times U(1)$ subgroup of the original global conformal symmetries. For the case of a purely (anti)chiral current, we find the finitesize spectrum of the deformed theory and study its thermodynamic properties. We test our predictions in a simple example involving deformed free fermions.

S duality and Framed BPS States via BPS Graphs
Authors: D. Gang, P. Longhi and M. Yamazaki
Preprint number: UUITP42/17
We study a realization of S dualities of fourdimensional N=2 class S theories based on BPS graphs. S duality transformations of the UV curve are explicitly expressed as a sequence of topological transitions of the graph, and translated into cluster transformations of the algebra associated to the dual BPS quiver. Our construction applies to generic class S theories, including those with nonmaximal flavor symmetry, generalizing previous results based on higher triangulations. We study the the action of S duality on UV line operators, and show that it matches precisely with the mapping class group, by a careful analysis of framed wallcrossing. We comment on the implications of our results for the computation of threemanifold invariants via cluster partition functions.

3d Expansions of 5d Instanton Partition Functions
Authors: Fabrizio Nieri, Yiwen Pan, Maxim Zabzine.
Preprint Number: UUITP43/17
We propose a set of novel expansions of Nekrasov’s instanton partition functions. Focusing on 5d N = 1 U(N) pure YangMills theory on C(2)xS(1), we show that the instanton partition functions admit expansions in terms of partition functions of unitary gauge theories living on the 3d subspaces (C(1)xS(1))\cup(C(1)xS(1)) and their intersection along S(1). These new expansions are natural from the BPS/CFT viewpoint, as they can be matched with W(q,t) correlators involving an arbitrary number of screening charges of two kinds. Our constructions generalize and interpolate existing results in the literature.

Analytic continuation of dimensions in supersymmetric localization
Author: Anastasios Gorantis, Joseph A. Minahan and Usman Naseer
Preprint Number: UUITP41/17
We compute the oneloop determinants for vector and hypermultiplets on spheres with d≤5 for supersymmetric gauge theories with 8 supersymmetries, showing that they are consistent with a recent conjectured form. This construction is valid for noninteger d. We then apply similar methods to gauge theories with 4 supersymmetries on spheres with d≤3, and find the oneloop determinants for vector and chiral multiplets, again valid for noninteger d. We then propose an analytic continuation from d = 3 to d = 4 that gives the perturbative partition function for an N = 1 gauge theory. We find that the results are consistent for free multiplets and with the oneloop βfunctions for general N = 1 gauge theories. We also consider the analytic continuation of a mass deformation of the maximally supersymmetric gauge theory that preserves four supersymmetries and compare to recent supergravity results of Bobev et. al. for N = 1* super YangMills. We find that to the extent where we can compare results, they are consistent at strong coupling, at least for the real part of the free energy.

Yangian Symmetry of String Theory on AdS(3)xS(3)xS(3)xS(1) with Mixed 3form Flux
Author: Antonio Pittelli
Preprint Number: UUITP40/17
We find the Yangian symmetry underlying the integrability of type IIB superstrings on AdS(3)xS(3)xS(3)xS(1) with mixed RamondRamond and NeveuSchwarzNeveuSchwarz flux. The abstract commutation relations of the Yangian are formulated via RTT realisation, while its matrix realisation is in evaluation representation and depends on the quantised coefficient of the WessZumino term. The construction naturally encodes a secret symmetry of the worldsheet scattering matrix whose generators map different Yangian levels to each other. We show that in the large effective string tension limit the Yangian becomes a deformation of a unitary loop algebra and derive its universal, representation independent classical rmatrix.

Rigid limit for hypermultiplets and fivedimensional gauge theories
Authors: Sergei Alexandrov, Sibasish Banerjee and Pietro Longhi
Preprint Number: UUITP39/17
We study the rigid limit of a class of hypermultiplet moduli spaces appearing in CalabiYau compactifications of type IIB string theory, which is induced by a local limit on the CalabiYau. We show that the resulting hyperkahler manifold is obtained by performing a hyperkahler quotient of the Swann bundle over the moduli space, along the isometries arising in the limit. Physically, this manifold appears as the target space of the nonlinear sigma model obtained by compactification of a fivedimensional gauge theory on a torus. This allows to compute dyonic and stringy instantons of the gauge theory from the known results on Dinstantons in string theory. Besides, we formulate a simple condition on the existence of a nontrivial local limit in terms of intersection numbers of the CalabiYau, and find an explicit form for the hypermultiplet metric including corrections from all mutually nonlocal Dinstantons, which can be of independent interest.

qVirasoro modular triple
Authors: Fabrizio Nieri, Yiwen Pan, Maxim Zabzine
Preprint Number: UUITP38/17
Inspired by 5d supersymmetric YangMills theories placed on the compact space S5, we propose an intriguing algebraic construction for the qVirasoro algebra. We show that, when multiple qVirasoro “chiral” sectors have to be fused together, a natural SL(3, Z) structure arises. This construction, which we call the modular triple, is consistent with the observed triple factorization properties of supersymmetric partition functions derived from localization arguments. We also give a 2d CFTlike construction of the modular triple, and conjecture for the first time a (nonlocal) Lagrangian formulation for a qVirasoro model, resembling ordinary Liouville theory.

Gauged supergravities and spontaneous SUSY breaking from the double copy
Authors: Marco Chiodaroli, Murat Gunaydin, Henrik Johansson and Radu Roiban
Preprint Number: UUITP37/17
Supergravities with gauged Rsymmetry and Minkowski vacua allow for spontaneous supersymmetry breaking and, as such, provide a framework for building supergravity models of phenomenogical relevance. In this letter we initiate the study of doublecopy constructions for these supergravities. On general grounds we expect that their scattering amplitudes are described by a double copy of the type: (Higgsed gauge theory) ⊗ (gauge theory with broken SUSY). We present a simple realization in which the resulting supergravity has U(1)_R gauge symmetry, spontaneouslybroken N = 2 supersymmetry, and massive gravitini. This is the first instance of a doublecopy construction for a gauged supergravity and for a theory with spontaneouslybroken supersymmetry. The construction extends in a straightforward manner to a large family of gauged YangMillsEinstein supergravity theories with or without spontaneous gauge symmetry breaking.

7D supersymmetric YangMills on curved manifolds
Authors: Konstantina Polydorou, Andreas Rocén and Maxim Zabzine
Preprint Number: UUITP36/17.
We study 7D maximally supersymmetric YangMills theory on curved manifolds that
admit Killing spinors. If the manifold admits at least two Killing spinors (Sasaki
Einstein manifolds) we are able to rewrite the supersymmetric theory in terms of
a cohomological complex. In principle this cohomological complex makes sense for
any Kcontact manifold. For the case of toric SasakiEinstein manifolds we derive
explicitly the perturbative part of the partition function and speculate about the non
perturbative part. We also discuss briefly the case of 3Sasaki manifolds and suggest
the plausible form of the full nonperturbative answer. 
Konishi OPE coefficient at the five loop order
Authors: Alessandro Georgoudis, Vasco Gonçalves and Raul Pereira
Preprint Number: UUITP35/17.
We study the OPE limit of a four point function in N = 4 SYM at the five loop
order and we extract the OPE coefficient at that order. 
Chiral Algebras, Localization and Surface Defects
Authors: Yiwen Pan and Wolfger Peelaers.
Preprint Number: UUITP34/17.
Abstract: Fourdimensional N = 2 superconformal quantum field theories contain a subsector carrying the structure of a chiral algebra. Using localization techniques, we show for the free hypermultiplet that this structure can be obtained directly from the path integral on the foursphere. We extend the localization computation to include supersymmetric surface defects described by a generic 4d/2d coupled system. The presence of a defect corresponds to considering a module of the chiral algebra: our results provide a calculational window into its structure constants.

Fivedimensional fermionic ChernSimons theory
Authors: Dongsu Bak and Andreas Gustavsson
Preprint Number: UUITP33/17
Abstract: We study 5d fermionic CS theory with a fermionic 2form gauge potential. This theory can be obtained from 5d MSYM theory by performing the maximal topological twist. We put the theory on a fivemanifold and compute the partition function. We find that it is a topological quantity, which involves the RaySinger torsion of the fivemanifold. For abelian gauge group we consider the uplift to the 6d theory and find a mismatch between the 5d partition function and the 6d index, due to the nontrivial dimensional reduction of a selfdual twoform gauge field on a circle. We also discuss an application of the 5d theory to generalized knots made of 2d sheets embedded in 5d. 
N = 2 supersymmetric AdS(4) solutions of type IIB supergravity
Authors: Achilleas Passias, Gautier Solard, Alessandro Tomasiello
Preprint number: UUITP32/17We analyze general N=2 supersymmetric AdS(4) solutions of type IIB supergravity.
Utilizing a set of pure spinor equations directly adapted to N=2, the necessary and sufficient conditions for supersymmetry are reduced to a concise system of partial differential equations for two functions which determine the solutions. We show that using this system analytic solutions can be generated, thus potentially expanding the rather limited set of known AdS(4) solutions in type IIB supergravity. 
Restrictions of Heterotic G2 Structures and Instanton Connections
Authors: Xenia de la Ossa, Magdalena Larfors and Eirik E. Svanes
Preprint number: UUITP31/17
Abstract: This note revisits recent results regarding the geometry and moduli of solutions of the heterotic string on manifolds Y with a G2 structure. In particular, such heterotic G2 systems can be rephrased in terms of a differential Dˇ acting on a complex Ωˇ∗(Y,Q), where Q=T∗Y⊕End(TY)⊕End(V) and Dˇ is an appropriate projection of an exterior covariant derivative D which satisfies an instanton condition. The infinitesimal moduli are further parametrised by the first cohomology H1ˇ(Y,Q). We proceed to restrict this system to manifolds X with an SU(3) structure corresponding to supersymmetric compactifications to four dimensional Minkowski space, often referred to as StromingerHull solutions. In doing so, we derive a new result: the StromingerHull system is equivalent to a particular holomorphic YangMills covariant derivative on QX=T∗X⊕End(TX)⊕End(V).

On the Prospects for Detecting a Net Photon Circular Polarization Produced by Decaying Dark Matter
Authors: Andrey Elagin, Jason Kumar, Pearl Sandick, Fei Teng
Preprint Number: UUITP30/17
If dark matter interactions with Standard Model particles are CPviolating, then dark matter annihilation/decay can produce photons with a net circular polarization. We consider the prospects for experimentally detecting evidence for such a circular polarization. We identify optimal models for dark matter interactions with the Standard Model, from the point of view of detectability of the net polarization, for the case of either symmetric or asymmetric dark matter. We find that, for symmetric dark matter, evidence for net polarization could be found by a search of the Galactic Center by an instrument sensitive to circular polarization with an efficiencyweighted exposure of at least 50000 cm^2 yr, provided the systematic detector uncertainties are constrained at the 1% level. Much better sensitivity can be obtained in the case of asymmetric dark matter. We discuss the prospects for achieving the needed level of performance using possible detector technologies.

The FiveLoop FourPoint Integrand of N = 8 Supergravity as a Generalized Double Copy
Authors: Zvi Bern, John Joseph Carrasco, WeiMing Chen, Henrik Johansson, Radu Roiban, Mao Zeng
Preprint Number: UUITP29/17
We use the recently developed generalized doublecopy procedure to construct an integrand for the fiveloop fourpoint amplitude of N = 8 supergravity. [...] The fiveloop fourpoint integrand is a crucial ingredient towards future determinations of ultraviolet properties of N = 8 supergravity at five loops and beyond. We also present a nontrivial check of the consistency of the integrand, based on modern approaches for loop integration in the ultraviolet region.

A swamp of nonSUSY vacua
Authors: U. H. Danielsson, G. Dibitetto, and S. C. Vargas
Preprint Number: UUITP28/17
We consider known examples of nonsupersymmetric AdS7 and AdS4 solutions arising from compactifications of massive type IIA supergravity and study their stability, taking into account the coupling between closed and openstring sector excitations. Generically, open strings are found to develop modes with masses below the BreitenlohnerFreedman (BF) bound. We comment on the relation with the Weak Gravity Conjecture, and how this analysis may play an important role in examining the validity of nonsupersymmetric constructions in string theory.

6D Fractional Quantum Hall Effect
Authors: Jonathan J. Heckman and Luigi Tizzano
Preprint Number: UUITP27/17
Abstract:
We present a 6D generalization of the fractional quantum Hall effect involving membranes coupled to a threeform potential in the presence of a large background fourform flux. The low energy physics is governed by a bulk 7D topological field theory of abelian three form potentials with a single derivative ChernSimonslike action coupled to a 6D antichiral theory of Euclidean effective strings. We derive the fractional conductivity, and explain how continued fractions which figure prominently in the classification of 6D superconformal field theories correspond to a hierarchy of excited states. Using methods from conformal field theory we also compute the analog of the Laughlin wavefunction. Compactification of the 7D theory provides a uniform perspective on various lowerdimensional gapped systems coupled to boundary degrees of freedom. We also show that a supersymmetric version of the 7D theory embeds in Mtheory, and can be decoupled from gravity. Encouraged by this, we present a conjecture in which IIB string theory is an edge mode of a 10 + 2dimensional bulk topological theory, thus placing all twelve dimensions of Ftheory on a physical footing.

Connecting the ambitwistor and the sectorized heterotic strings
Authors: Thales Azevedo and Renann Lipinski Jusinskas
Preprint number UUITP26/17
The sectorized description of the (chiral) heterotic string using pure spinors has been misleadingly viewed as an infinite tension string. One evidence for this fact comes from the tree level 3point graviton amplitude, which we show to contain the usual Einstein term plus a higher curvature
contribution. After reintroducing a dimensionful parameter $\ell$ in the theory, we demonstrate that the heterotic model is in fact twofold, depending on the choice of the supersymmetric sector, and that the spectrum also contains one massive (open string like) multiplet. By taking the $\ell\to\infty$ limit, we finally show that the ambitwistor string is recovered, reproducing the unexpected heterotic state in Mason and Skinner's RNS description. 
Holographic microstate counting for AdS(4) black holes in massive IIA supergravity
Authors: Seyed Morteza Hosseini, Kiril Hristov, Achilleas Passias
Preprint number: UUITP25/17We derive the BekensteinHawking entropy for a class of BPS black holes in the massive type IIA supergravity background AdS(4) x S^6 from a microscopic counting of supersymmetric ground states in a holographically dual field theory. The counting is performed by evaluating the topologically twisted index of threedimensional N=2 ChernSimonsmatter gauge theories in the large N limit. The Iextremization principle is shown to match the attractor mechanism for the nearhorizon geometries constructed in the fourdimensional dyonic N=2 gauged supergravity, that arises as a consistent truncation of massive type IIA supergravity on S^6. In particular, our results prove that the imaginary part of the threedimensional partition functions plays a crucial role in holography.

Ambitwistor formulations of R^2 gravity and (DF)^2 gauge theories
Authors: Thales Azevedo, Oluf Tang Engelund
Preprint number UUITP24/17
We consider Ddimensional amplitudes in R^2 gravities (conformal gravity in D=4) and in the recently introduced (DF)^2 gauge theory, from the perspective of the CHY formulae and ambitwistor string theory. These theories are related through the BCJ doublecopy construction, and the (DF)^2 gauge theory obeys colorkinematics duality. We work out the worldsheet details of these theories and show that they admit a formulation as integrals on the support of the scattering equations, or alternatively, as ambitwistor string theories. For gravity, this generalizes the work done by Berkovits and Witten on conformal gravity to D dimensions. The ambitwistor is also interpreted as a Ddimensional generalization of Witten's twistor string (SYM + conformal supergravity). As part of our ambitwistor investigation, we discover another (DF)^2 gauge theory containing a photon that couples to Einstein gravity. This theory can provide an alternative KLT description of Einstein gravity compared to the usual YangMills squared.

6d surface defects from massive type IIA
Authors: Giuseppe Dibitetto and Nicolò Petri
Preprint Number: UUITP23/17
We present a new BPS flow within minimal N=1 supergravity in seven dimensions describing a warped AdS_3 background supported by a ``dyonic'' profile of the threeform. Furthermore, we discuss the holographic interpretation of the above solution in terms of a defect CFT_2 inside the 6d (1,0) theory dual to the AdS in the asymptotic region. Finally we provide the brane picture of the aforementioned defect CFT as D2 and wrapped D4branes ending on a D6  NS5  D8 funnel in massive type IIA string theory.

BPS objects in D=7 supergravity and their Mtheory origin
Authors: Giuseppe Dibitetto and Nicolò Petri
Preprint Number: UUITP22/17
We study several different types of BPS flows within minimal N=1, D=7 supergravity with SU(2) gauge group and nonvanishing topological mass. After reviewing some known domain wall solutions involving only the metric and the R^+ scalar field, we move to considering more general flows involving a ``dyonic'' profile for the 3form gauge potential. In this context, we consider flows featuring a Mkw_3 as well as an AdS_3 slicing, write down the corresponding flow equations, and integrate them analytically to obtain many examples of asymptotically AdS_7 solutions in presence of a running 3form. Furthermore, we move to adding the possibility of nonvanishing vector fields, find the new corresponding flows and integrate them numerically. Finally, we discuss the elevendimensional interpretation of the aforementioned solutions as effective descriptions of M2  M5 bound states.

Conformal Gravity from Gauge Theory
Authors: Henrik Johansson and Josh Nohle
Preprint number UUITP21/17
We use the duality between color and kinematics to obtain scattering amplitudes in nonminimal conformal N = 0, 1, 2, 4 (super)gravity theories. Generic tree amplitudes can be constructed from a double copy between (super)YangMills theory and a new gauge theory built entirely out of dimensionsix operators. The latter theory is marginal in six dimensions and contains modes with a wrongsign propagator, echoing the behavior of conformal gravity. The dimensionsix Lagrangian is uniquely determined by demanding that its scattering amplitudes obey the colorkinematics duality. The conformal gravity amplitudes obtained from the double copy are compared with the BerkovitsWitten twistor string and shown to agree up to at least eight points in the MHV sector.

All (4,0): Sigma Models with (4,0) OffShell Supersymmetry
Authors: Chris Hull and Ulf Lindström
Preprint number UUITP20/17
Offshell $(4,0)$ supermultiplets in 2dimensions are constructed. These are used to construct sigma models whose target spaces are vector bundles over manifolds that are hyperk\"ahler with torsion. The offshell supersymmetry implies the complex structures are simultaneously integrable and allows us to construct actions using extended superspace and projective superspace, giving an explicit construction of the target space geometries.

Twoloop supersymmetric QCD and halfmaximal supergravity amplitudes
Author: Henrik Johansson, Gregor Kälin and Gustav Mogull
Preprint Number: UUITP19/17
Using the duality between color and kinematics, we construct twoloop fourpoint scattering amplitudes in N=2 superYangMills (SYM) theory coupled to N_f fundamental hypermultiplets. Our results are valid in D<=6 dimensions, where the upper bound corresponds to sixdimensional chiral N=(1,0) SYM theory. By exploiting a close connection with N=4 SYM theory  and, equivalently, sixdimensional N=(1,1) SYM theory  we find compact integrands with fourdimensional external vectors in both the maximallyhelicityviolating (MHV) and allchiralvector sectors. Via the doublecopy construction corresponding Ddimensional halfmaximal supergravity amplitudes with external graviton multiplets are obtained in the MHV and allchiral sectors. Appropriately tuning N_f enables us to consider both pure and mattercoupled supergravity, with arbitrary numbers of vector multiplets in D=4. As a bonus, we obtain the integrands of the genuinely sixdimensional supergravities with N=(1,1) and N=(2,0) supersymmetry. Finally, we extract the potential ultraviolet divergence of halfmaximal supergravity in D=52e and show that it nontrivially cancels out as expected.

Integrability in dipoledeformed N=4 super YangMills
Authors: M. Guica, F. LevkovichMaslyuk and K. Zarembo
Preprint number: UUITP18/17
We study the null dipole deformation of N=4 super YangMills theory, which is an example of a potentially solvable ``dipole CFT'': a theory that is nonlocal along a null direction, has nonrelativistic conformal invariance along the remaining ones, and is holographically dual
to a Schrödinger spacetime. We initiate the fieldtheoretical study of the spectrum in this model by
using integrability inherited from the parent theory.
The dipole deformation corresponds to a nondiagonal DrinfeldReshetikhin twist in the spin chain picture, which
renders the traditional Bethe ansatz inapplicable from the very beginning.
We use instead the Baxter equation supplemented
with nontrivial asymptotics,
which gives the full 1loop spectrum in the sl(2) sector. We show that
anomalous dimensions of long gauge theory operators perfectly
match the string theory prediction,
providing a quantitative test of Schrödinger holography. 
Machine Learning of CalabiYau Volumes
Authors: Daniel Krefl, RakKyeong Seong
Preprint Number: UUITP17/17
We employ machine learning techniques to investigate the volume minimum of SasakiEinstein base manifolds of noncompact toric CalabiYau 3folds. We find that the minimum volume can be approximated via a second order multiple linear regression on standard topological quantities obtained from the corresponding toric diagram. The approximation improves further after invoking a convolutional neural network with the full toric diagram of the CalabiYau 3folds as the input. We are thereby able to circumvent any minimization procedure that was previously necessary and find an explicit mapping between the minimum volume and the topological quantities of the toric diagram. Under the AdS/CFT correspondence, the minimum volumes of SasakiEinstein manifolds correspond to central charges of a class of 4d N=1 superconformal field theories. We therefore find empirical evidence for a function that gives values of central charges without the usual extremization procedure.

Anomalous Dimensions in the WF O(N) Model with a Monodromy Line Defect
Author: Alexander Söderberg
Preprint: UUITP16/17
Implications of inserting a monodromy line defect in three dimensional O(N) models are studied. We consider then the WF O(N) model, and study the twopoint Green's function for bulklocal fields found from both the bulkdefect expansion and Feynman diagrams, to find the anomalous dimensions for bulk and defectlocal primaries as well as one of the OPE coefficients as ϵexpansions to the first loop order. As a check on our results, we study the (ϕ^k)^2ϕ^j operator both using the bulkdefect expansion as well as the equations of motion.

Black holes as bubbles of AdS
Authors: Ulf Danielsson, Giuseppe Dibitetto, Suvendu Giri
Preprint number: UUITP15/17
In this paper we propose that bubbles of AdS within Minkowski spacetime, stablized at a finite radius by stiff matter and an electromagnetic gas, can be an alternative endpoint of gravitational collapse. The bubbles are horizonless with a size up to 12.5% larger than their Schwarzschild radius depending on their charge. We argue that they are stable against small perturbations, and have thermodynamical properties similar to those of real black holes. We provide a realization of the bubbles within string theory that relies on a specific brane intersection giving rise to a shell carrying dissolved charges from lower dimensional Dbranes as well as a gas of open strings. We also note that our construction proivdes a new way of understanding the entropy of ReissnerNordström black holes in the extremal limit.

Twopoint functions of SU(2)subsector and lengthtwo operators in dCFT
Authors: Erik Widen
Preprint number: UUITP14/17
We consider a particular set of twopoint functions in the setting of N = 4 SYM with a defect, dual to the fuzzyfunnel solution for the probe D5D3brane system. The twopoint functions in focus involve a single trace operator in the SU(2)subsector of arbitrary length and a lengthtwo operator built out of any scalars. By interpreting the contractions as a spinchain operator, simple expressions were found for the leading contribution to the twopoint functions, mapping them to earlier known formulas for the onepoint functions in this setting.

The infinitesimal moduli space of heterotic G_2 systems
Authors: Xenia de la Ossa, Magdalena Larfors, Eirik E. Svanes
Preprint number: UUITP13/17

AdS(5) compactifications with punctures in massive IIA supergravity
Authors: Ibrahima Bah, Achilleas Passias, Alessandro Tomasiello
Preprint number: UUITP12/17We find AdS(5) solutions holographically dual to compactifications of sixdimensional N=(1,0) supersymmetric field theories on Riemann surfaces with punctures. We simplify a previous analysis of supersymmetric AdS(5) IIA solutions, and with a suitable Ansatz we find explicit solutions organized in three classes, where an O8D8 stack, D6 and D4branes are simultaneously present, localized and partially localized. The D4branes are smeared over the Riemann surface and this is interpreted as the presence of a uniform distribution of punctures. For the first class we identify the corresponding sixdimensional theory as an Estring theory coupled to a quiver gauge theory. The second class of solutions lacks D6branes and its central charge scales as n^{5/2}, suggesting a fivedimensional origin for the dual field theory. The last class has elements of the previous two.

BPS Graphs: From Spectral Networks to BPS Quivers
Authors: Maxime Gabella, Pietro Longhi, Chan Y. Park and Masahito Yamazaki
Preprint number: UUITP11/17
We define “BPS graphs” on punctured Riemann surfaces associated with A_{N−1} theories of class S. BPS graphs provide a bridge between two powerful frameworks for studying the spectrum of BPS states: spectral networks and BPS quivers. They arise from degenerate spectral networks at maximal intersections of walls of marginal stability on the Coulomb branch. While the BPS spectrum is illdefined at such intersections, a BPS graph captures a useful basis of elementary BPS states. The topology of a BPS graph encodes a BPS quiver, even for higherrank theories and for theories with certain partial punctures. BPS graphs lead to a geometric realization of the combinatorics of FockGoncharov Ntriangulations and generalize them in several ways.

Elliptic modular double and 4d partition functions
Authors: Rebecca Lodin, Fabrizio Nieri, Maxim Zabzine
Preprint number: UUITP09/17
We consider 4d supersymmetric (special) unitary G quiver gauge theories on compact manifolds which are T2 fibrations over S2. We show that their partition functions are correlators of vertex operators and screening charges of the modular double version of elliptic W(G) algebras. We also consider a generating function of BPS surface defects supported on T2 and show that it can be identified with a particular coherent state in the Fock module over the elliptic Heisenberg algebra.

Oneloop tests of supersymmetric gauge theories on spheres
Authors: Joseph A. Minahan and Usman Naseer
Preprint number: UUITP08/17
We show that a recently conjectured form for perturbative supersymmetric partition functions on spheres of general dimension d is consistent with the flat space limit of 6dimensional N = 1 super YangMills. We also show that the partition functions for N = 1 8 and 9dimensional theories are consistent with their known flat space limits.

Explicit Formulae for YangMillsEinstein Amplitudes from the Double Copy
Authors: Marco Chiodaroli, Murat Gunaydin, Henrik Johansson and Radu Roiban
Preprint number: UUITP07/17
Using the doublecopy construction of YangMillsEinstein theories formulated
in our earlier work, we obtain compact presentations for singletrace
YangMillsEinstein tree amplitudes with up to five external gravitons and an
arbitrary number of gluons. These are written as linear combinations of
colororderd YangMills trees, where the coefficients are given by
color/kinematicssatisfying numerators in a YangMills+\phi^3 theory. 
Quantum String Test of Nonconformal Holography
Authors: Xinyi ChenLin, Daniel MedinaRincon and Konstantin Zarembo
Preprint number: UUITP06/17
We compute Luscher corrections to the effective string tension in the
PilchWarner background, holographically dual to N = 2* supersymmetric
YangMills theory. The same quantity can be calculated directly
from field theory by solving the localization matrix model at largeN.
We find complete agreement between the fieldtheory predictions and
explicit stringtheory calculation at strong coupling. 
Elliptic Genera of 2d (0,2) Gauge Theories from Brane Brick Models
Authors: Sebastian Franco, Dongwook Ghim, Sangmin Lee, RakKyeong Seong
Preprint Number: UUITP05/17
We compute the elliptic genus of abelian 2d (0,2) gauge theories corresponding to brane brick models. These theories are worldvolume theories on a single D1brane probing a toric CalabiYau 4fold singularity. We identify a match with the elliptic genus of the nonlinear sigma model on the same CalabiYau background, which is computed using a new localization formula. The matching implies that the quantum effects do not drastically alter the correspondence between the geometry and the 2d (0,2) gauge theory. In theories whose matter sector suffers from abelian gauge anomaly, we propose an ansatz for an anomaly cancelling term in the integral formula for the elliptic genus. We provide an example in which two brane brick models related to each other by GaddeGukovPutrov triality give the same elliptic genus.

Integrability in SigmaModels
Author: K. Zarembo
Preprint Number: UUITP04/17
Abstract: These lecture notes cover the following topics: (1) Homogeneous spaces, (2) Classical integrability of principal chiral field and semisymmetric cosets, (3) Topological terms in sigmamodels, (4) Backroundfield method and betafunction, (5) Smatrix bootstrap in the $O(N)$ model, (6) Supersymmetric cosets.

Connecting Fisher information to bulk entanglement in holography
Authors: Souvik Banerjee, Johanna Erdmenger, Debajyoti Sarkar
Preprint: UUITP03/17
Abstract: In the context of relating AdS/CFT to quantum information theory, we propose a holographic dual of Fisher information metric for mixed states in the boundary field theory. This amounts to a holographic measure for the distance between two mixed quantum states. For a spherical subregion in the boundary we show that this is related to a particularly regularized volume enclosed by the RyuTakayanagi surface. We further argue that the quantum correction to the proposed Fisher information metric is related to the quantum correction to the boundary entanglement entropy. We discuss consequences of this connection.