arXiv subjects

Jeffrey A. Harvey

Publications and source records attributed to Jeffrey A. Harvey.

At least 37 records · Page 2Linked to original sources

arXiv2017

Conway Subgroup Symmetric Compactifications Of Heterotic String

We investigate special compactifications of the heterotic string for which the space of half-BPS states is, in a natural way, a representation of various subgroups of the Conway group. These compactifications provide a useful framework for analyzing the action of some of the large symmetry groups appearing in discussions of Moonshine in the physics literature. We investigate toroidal compactifications of heterotic string with sixteen supersymmetries as well as asymmetric toroidal orbifolds with $N=2$ supersymmetry in four dimensions that arise as $K3 \times T^2$ compactifications. The latter Conway subgroup symmetric compactifications of the heterotic string might have some interesting implications for D-brane bound states on Calabi-Yau manifolds.

hep-th↗

arXiv2017

Weight One Jacobi Forms and Umbral Moonshine

We analyze holomorphic Jacobi forms of weight one with level. One such form plays an important role in umbral moonshine, leading to simplifications of the statements of the umbral moonshine conjectures. We prove that non-zero holomorphic Jacobi forms of weight one do not exist for many combinations of index and level, and use this to establish a characterization of the McKay--Thompson series of umbral moonshine in terms of Rademacher sums.

math.NT↗

arXiv2015

Traces of Singular Moduli and Moonshine for the Thompson Group

We describe a relationship between the representation theory of the Thompson sporadic group and a weakly holomorphic modular form of weight one-half that appears in work of Borcherds and Zagier on Borcherds products and traces of singular moduli. We conjecture the existence of an infinite dimensional graded module for the Thompson group and provide evidence for our conjecture by constructing McKay--Thompson series for each conjugacy class of the Thompson group that coincide with weight one-half modular forms of higher level. We also observe a discriminant property in this moonshine for the Thompson group that is closely related to the discriminant property conjectured to exist in Umbral Moonshine.

math.RT↗

arXiv2014

The Umbral Moonshine Module for the Unique Unimodular Niemeier Root System

We use canonically-twisted modules for a certain super vertex operator algebra to construct the umbral moonshine module for the unique Niemeier lattice that coincides with its root sublattice. In particular, we give explicit expressions for the vector-valued mock modular forms attached to automorphisms of this lattice by umbral moonshine. We also characterize the vector-valued mock modular forms arising, in which four of Ramanujan's fifth order mock theta functions appear as components.

math.RT↗

arXiv2014

ADE Double Scaled Little String Theories, Mock Modular Forms and Umbral Moonshine

We consider double scaled little string theory on $K3$. These theories are labelled by a positive integer $k \ge 2$ and an $ADE$ root lattice with Coxeter number $k$. We count BPS fundamental string states in the holographic dual of this theory using the superconformal field theory $K3 \times \left( \frac{SL(2,\mathbb{R})_k}{U(1)} \times \frac{SU(2)_k}{U(1)} \right) \big/ \mathbb{Z}_k$. We show that the BPS fundamental string states that are counted by the second helicity supertrace of this theory give rise to weight two mixed mock modular forms. We compute the helicity supertraces using two separate techniques: a path integral analysis that leads to a modular invariant but non-holomorphic answer, and a Hamiltonian analysis of the contribution from discrete states which leads to a holomorphic but not modular invariant answer. From a mathematical point of view the Hamiltonian analysis leads to a mixed mock modular form while the path integral gives the completion of this mixed mock modular form. We also compare these weight two mixed mock modular forms to those that appear in instances of Umbral Moonshine labelled by Niemeier root lattices $X$ that are powers of $ADE$ root lattices and find that they are equal up to a constant factor that we determine. In the course of the analysis we encounter an interesting generalization of Appell-Lerch sums and generalizations of the Riemann relations of Jacobi theta functions that they obey.

hep-th↗

arXiv2014

Umbral Moonshine and the Niemeier Lattices

In this paper we relate umbral moonshine to the Niemeier lattices: the 23 even unimodular positive-definite lattices of rank 24 with non-trivial root systems. To each Niemeier lattice we attach a finite group by considering a naturally defined quotient of the lattice automorphism group, and for each conjugacy class of each of these groups we identify a vector-valued mock modular form whose components coincide with mock theta functions of Ramanujan in many cases. This leads to the umbral moonshine conjecture, stating that an infinite-dimensional module is assigned to each of the Niemeier lattices in such a way that the associated graded trace functions are mock modular forms of a distinguished nature. These constructions and conjectures extend those of our earlier paper, and in particular include the Mathieu moonshine observed by Eguchi-Ooguri-Tachikawa as a special case. Our analysis also highlights a correspondence between genus zero groups and Niemeier lattices. As a part of this relation we recognise the Coxeter numbers of Niemeier root systems with a type A component as exactly those levels for which the corresponding classical modular curve has genus zero.

math.RT↗

arXiv2014

Central Production of Eta and Eta-prime via Double Pomeron Exchange in the Sakai-Sugimoto Model

We construct a string-inspired model for the central production of $η$ and $η'$ mesons in proton-proton collisions, via double Pomeron exchange. Using general symmetry considerations, we construct a low-energy differential cross section for double glueball exchange in terms of some undetermined coupling constants and form factors. We extend this model to the Regge regime, replacing the glueball propagators with Pomeron trajectories, and modifying the interaction term by a factor derived from the 5-string scattering amplitude in flat space. We then fix the couplings which remain undetermined, using the Sakai-Sugimoto framework to model low-energy QCD. Finally, we generate a simulation of the scattering process at $\sqrt{s} = 29.1 GeV$, where double Pomeron exchange should play a role (secondary to double Reggeon exchange). We focus on the dependence of the scattering cross section on the angle between the scattered protons in the transverse plane. The results exhibit a definite deviation from the angular dependence that arises as a consequence of natural parity violation alone. The amount of deviation is primarily determined by couplings that come from the Chern-Simons action of the AdS/QCD supergravity dual, which is directly related to the QCD gravitational anomaly, and thus constitutes a universal part of any five-dimensional string/gravity dual theory of QCD. We argue that this makes the high energy central production of pseudoscalar mesons an interesting probe of AdS/QCD models.

hep-ph↗

arXiv2014

Elliptic genera of ALE and ALF manifolds from gauged linear sigma models

We compute the equivariant elliptic genera of several classes of ALE and ALF manifolds using localization in gauged linear sigma models. In the sigma model computation the equivariant action corresponds to chemical potentials for U(1) currents and the elliptic genera exhibit interesting pole structure as a function of the chemical potentials. We use this to decompose the answers into polar terms that exhibit wall crossing and universal terms. We compare our results to previous results on the large radius limit of the Taub-NUT elliptic genus and also discuss applications of our results to counting of BPS world-sheet spectrum of monopole strings in the 5d N=2 super Yang-Mills theory and self-dual strings in the 6d N=(2,0) theories.

hep-th↗

arXiv2014

Comments on Quantum Higgs Vacua

We study two-dimensional N=(4,4) supersymmetric gauge theories which do not have classical Higgs branches, but are believed to have isolated quantum Higgs vacua. We provide arguments for the existence of such vacua based on brane dynamics in string theory and the supersymmetric partition sums of the gauge theories.

hep-th↗

arXiv2013

Moonshine in Fivebrane Spacetimes

We consider type II superstring theory on $K3 \times S^1 \times \mathbb{R}^{1,4}$ and study perturbative BPS states in the near-horizon background of two Neveu-Schwarz fivebranes whose world-volume wraps the $K3 \times S^1$ factor. These states are counted by the spacetime helicity supertrace $χ_2(τ)$ which we evaluate. We find a simple expression for $χ_2(τ)$ in terms of the completion of the mock modular form $H^{(2)}(τ)$ that has appeared recently in studies of the decomposition of the elliptic genus of K3 surfaces into characters of the N=4 superconformal algebra and which manifests a moonshine connection to the Mathieu group $M_{24}$.

hep-th↗

arXiv2013

Umbral Moonshine

We describe surprising relationships between automorphic forms of various kinds, imaginary quadratic number fields and a certain system of six finite groups that are parameterised naturally by the divisors of twelve. The Mathieu group correspondence recently discovered by Eguchi-Ooguri-Tachikawa is recovered as a special case. We introduce a notion of extremal Jacobi form and prove that it characterises the Jacobi forms arising by establishing a connection to critical values of Dirichlet series attached to modular forms of weight two. These extremal Jacobi forms are closely related to certain vector-valued mock modular forms studied recently by Dabholkar-Murthy-Zagier in connection with the physics of quantum black holes in string theory. In a manner similar to monstrous moonshine the automorphic forms we identify constitute evidence for the existence of infinite-dimensional graded modules for the six groups in our system. We formulate an umbral moonshine conjecture that is in direct analogy with the monstrous moonshine conjecture of Conway-Norton. Curiously, we find a number of Ramanujan's mock theta functions appearing as McKay-Thompson series. A new feature not apparent in the monstrous case is a property which allows us to predict the fields of definition of certain homogeneous submodules for the groups involved. For four of the groups in our system we find analogues of both the classical McKay correspondence and McKay's monstrous Dynkin diagram observation manifesting simultaneously and compatibly.

math.RT↗

arXiv2013

Mathieu Moonshine and N=2 String Compactifications

There is a `Mathieu moonshine' relating the elliptic genus of K3 to the sporadic group M_{24}. Here, we give evidence that this moonshine extends to part of the web of dualities connecting heterotic strings compactified on K3 \times T^2 to type IIA strings compactified on Calabi-Yau threefolds. We demonstrate that dimensions of M_{24} representations govern the new supersymmetric index of the heterotic compactifications, and appear in the Gromov--Witten invariants of the dual Calabi-Yau threefolds, which are elliptic fibrations over the Hirzebruch surfaces F_n.

hep-th↗

arXiv2012

Successes and Failures of a More Comprehensive Hard Wall AdS/QCD

We explore corrections to the "hard wall" gravity dual of QCD with two-form tensor fields. These fields correspond to a dimension three quark bilinear in QCD, which generates states with 1(--) and 1(+-) quantum numbers, or omega/rho-like and h1/b1-like mesons, respectively. We include new interaction terms, which render the model complete up to dimension six. We find that breaking chiral symmetry induces modifications to the spectrum, by mixing the vector current and the new two-tensor operator. This breaks the degeneracy of the 1(--) and 1(+-) spectra. We also compute the (b1->omega + pi) decay rate and D/S ratio, and the couplings of excited rho states to two pions. We then perform a comprehensive new fit to QCD data. We obtain a value for the magnetic susceptibility of the QCD quark condensate which is consistent with phenomenological estimates. These results allow us to evaluate the success of dimension counting and UV matching in this model.

hep-th↗

arXiv2011

Completing the framework of AdS/QCD: h_1/b_1 mesons and excited omega/rho's

We extend the "hard wall" gravity dual of QCD by including tensor fields b_{MN} that correspond to the QCD quark bilinear operators qbar sigma^{mu nu} q. These fields give rise to a spectrum of states which include the h_1 and b_1 mesons, as well as a tower of excited omega/rho meson states. We also identify the lowest-dimension term which leads to mixing between the new rho states and the usual tower of rho mesons when chiral symmetry is broken.

hep-th↗

arXiv2010

The Pomeron contribution to p p and p bar p scattering in AdS/QCD

We consider the differential and total cross sections for proton-proton and proton-antiproton scattering in the Regge regime from the point of view of string dual models of QCD. We argue that the form factor which appears in the differential cross section is related to the matrix element of the stress tensor between proton states and give a procedure for computing the strength of the coupling of the Pomeron trajectory to the proton. We compute this coupling in the Sakai-Sugimoto model and find excellent agreement with the data at large $s$ and small $t$. The form factor can be estimated in the Skyrme model or in AdS/QCD models and gives a stiffer form factor than the commonly used electromagnetic form factor, in agreement with our fits to data. Our model is also in good agreement with the measured ratio of real to imaginary parts of the forward scattering amplitude at large $s$.

hep-ph↗

arXiv2010

Setting the scale of the p p and p bar p total cross sections using AdS/QCD

This paper is an addendum to our earlier paper \cite{pom} where we computed the Pomeron contribution to $p ~ p$ and $p ~ \bar p$ scattering in AdS/QCD. The model of \cite{pom} depends on four parameters: the slope and intercept of the Pomeron trajectory $α'_c, α_c(0)$, a mass scale $M_d$ which determines a form factor entering into matrix elements of the energy-momentum tensor, and a coupling $λ_{\cal P}$ between the lightest spin $2$ glueball and the proton which sets the overall scale of the total cross section. Here we perform a more detailed computation of $λ_{\cal P}$ in the Sakai-Sugimoto model using the construction of nucleons as instantons of the dual 5d gauge theory and an effective 5d fermion description of these nucleons which has been successfully used to compute a variety of nucleon-meson couplings. We find $λ_{\cal P,{\rm SS}} \simeq 6.38 ~ {\rm GeV}^{-1}$ which is in reasonable agreement with the value $λ_{{\cal P},{\rm fit}} = 8.28 ~ {\rm GeV}^{-1}$ determined by fitting single Pomeron exchange to data.

hep-th↗

arXiv2008

Gauge/gravity duality with a chiral N=(0,8) string defect

We study the defect AdS/CFT correspondence for a system of N_c D3-branes intersecting certain configurations of D7-branes and O7-planes in 1+1-dimensions. The intersection is chiral, preserving N=(0,8) supersymmetry. The geometry produced by the 7-branes does not decouple in the low energy limit on the D3-branes; consequently the field theory must be considered in the curved background of the 7-branes, and the supergravity background is the fully backreacted solution accounting for both sets of branes. Although we can not work in the probe-brane limit, we still find a consistent defect mode-operator map. In our previous study of the field theory we found chiral D3-brane zero-modes that localized to the intersection. Here we obtain a dual supergravity description of the localized R-symmetry anomaly that these zero-modes produce.

hep-th↗

arXiv2008

Localized modes at a D-brane--O-plane intersection and heterotic Alice strings

We study a system of $N_c$ $D3$-branes intersecting $D7$-branes and $O7$-planes in 1+1-dimensions. We use anomaly cancellation and string dualities to argue that there must be chiral fermion zero-modes on the $D3$-branes which are localized near the $O7$-planes. Away from the orientifold limit we verify this by using index theory as well as explicit construction of the zero-modes. This system is related to F-theory on K3 and heterotic matrix string theory, and the heterotic strings are related to Alice string defects in $\mathcal{N}=4$ Super-Yang-Mills. In the limit of large $N_c$ we find an $AdS_3$ dual of the heterotic matrix string CFT.

hep-th↗