Unbroken Supersymmetry Research Articles

Supersymmetric Sachdev-Ye-Kitaev models

We discuss a supersymmetric generalization of the Sachdev-Ye-Kitaev (SYK) model. These are quantum mechanical models involving $N$ Majorana fermions. The supercharge is given by a polynomial expression in terms of the Majorana fermions with random coefficients. The Hamiltonian is the square of the supercharge. The $\mathcal{N}=1$ model with a single supercharge has unbroken supersymmetry at large $N$, but nonperturbatively spontaneously broken supersymmetry in the exact theory. We analyze the model by looking at the large $N$ equation, and also by performing numerical computations for small values of $N$. We also compute the large $N$ spectrum of ``singlet'' operators, where we find a structure qualitatively similar to the ordinary SYK model. We also discuss an $\mathcal{N}=2$ version. In this case, the model preserves supersymmetry in the exact theory and we can compute a suitably weighted Witten index to count the number of ground states, which agrees with the large $N$ computation of the entropy. In both cases, we discuss the supersymmetric generalizations of the Schwarzian action which give the dominant effects at low energies.

Deconstructing zero: resurgence, supersymmetry and complex saddles

We explain how a vanishing, or truncated, perturbative expansion, such as often arises in semi-classically tractable supersymmetric theories, can nevertheless be related to fluctuations about non-perturbative sectors via resurgence. We also demonstrate that, in the same class of theories, the vanishing of the ground state energy (unbroken supersymmetry) can be attributed to the cancellation between a real saddle and a complex saddle (with hidden topological angle pi), and positivity of the ground state energy (broken supersymmetry) can be interpreted as the dominance of complex saddles. In either case, despite the fact that the ground state energy is zero to all orders in perturbation theory, all orders of fluctuations around non-perturbative saddles are encoded in the perturbative E(N, g). We illustrate these ideas with examples from supersymmetric quantum mechanics and quantum field theory.

M-theory potential from the G 2 Hitchin functional in superspace

We embed the component fields of eleven-dimensional supergravity into a superspace of the form $X\times Y$ where $X$ is the standard 4D, $N=1$ superspace and $Y$ is a smooth 7-manifold. The eleven-dimensional 3-form gives rise to a tensor hierarchy of superfields gauged by the diffeomorphisms of $Y$. It contains a natural candidate for a $G_2$ structure on $Y$, and being a complex of superforms, defines a superspace Chern-Simons invariant. Adding to this a natural generalization of the Riemannian volume on $X\times Y$ and freezing the (superspin-$\frac32$ and 1) supergravity fields on $X$, we obtain an approximation to the eleven-dimensional supergravity action that suffices to compute the scalar potential. In this approximation the action is the sum of the superspace Chern-Simons term and a superspace generalization of the Hitchin functional for $Y$ as a $G_2$-structure manifold. Integrating out auxiliary fields, we obtain the conditions for unbroken supersymmetry and the scalar potential. The latter reproduces the Einstein-Hilbert term on $Y$ in a form due to Bryant.

Mass formulae for broken supersymmetry in curved space-time

We derive the mass formulae for ${\cal N}=1$, $D=4$ matter-coupled Supergravity for broken (and unbroken) Supersymmetry in curved space-time. These formulae are applicable to de Sitter configurations as is the case for inflation. For unbroken Supersymmetry in anti-de Sitter (AdS) one gets the mass relations modified by the AdS curvature. We compute the mass relations both for the potential and its derivative non-vanishing.

Do all BPS black hole microstates carry zero angular momentum?

From the analysis of the near horizon geometry and supersymmetry algebra it has been argued that all the microstates of single centered BPS black holes with four unbroken supersymmetries carry zero angular momentum in the region of the moduli space where the black hole description is valid. A stronger form of the conjecture would be that the result holds for any sufficiently generic point in the moduli space. In this paper we set out to test this conjecture for a class of black hole microstates in type II string theory on $T^6$, represented by four stacks of D-branes wrapped on various cycles of $T^6$. For this system the above conjecture translates to the statement that the moduli space of classical vacua must be a collection of points. Explicit analysis of systems carrying a low number of D-branes supports this conjecture.

The light bound states of supersymmetric SU(2) Yang-Mills theory

Supersymmetry provides a well-established theoretical framework for extensions of the standard model of particle physics and the general understanding of quantum field theories. We summarise here our investigations of N=1 supersymmetric Yang-Mills theory with SU(2) gauge symmetry using the non-perturbative first-principles method of numerical lattice simulations. The strong interactions of gluons and their superpartners, the gluinos, lead to confinement, and a spectrum of bound states including glueballs, mesons, and gluino-glueballs emerges at low energies. For unbroken supersymmetry these particles have to be arranged in supermultiplets of equal masses. In lattice simulations supersymmetry can only be recovered in the continuum limit since it is explicitly broken by the discretisation. We present the first continuum extrapolation of the mass spectrum of supersymmetric Yang-Mills theory. The results are consistent with the formation of supermultiplets and the absence of non-perturbative sources of supersymmetry breaking. Our investigations also indicate that numerical lattice simulations can be applied to non-trivial supersymmetric theories.

Supersymmetry restoration in superstring perturbation theory

Superstring perturbation theory based on the 1PI effective theory approach has been useful for addressing the problem of mass renormalization and vacuum shift. We derive Ward identities associated with space-time supersymmetry transformation in this approach. This leads to a proof of the equality of renormalized masses of bosons and fermions and identities relating fermionic amplitudes to bosonic amplitudes after taking into account the effect of mass renormalization. This also relates unbroken supersymmetry to a given order in perturbation theory to absence of tadpoles of massless scalars to higher order. The results are valid at the perturbative vacuum as well as in the shifted vacuum when the latter describes the correct ground state of the theory. We apply this to SO(32) heterotic string theory on Calabi-Yau 3-folds where a one loop Fayet-Iliopoulos term apparently breaks supersymmetry at one loop, but analysis of the low energy effective field theory indicates that there is a nearby vacuum where supersymmetry is restored. We explicitly prove that the perturbative amplitudes of this theory around the shifted vacuum indeed satisfy the Ward identities associated with unbroken supersymmetry. We also test the general arguments by explicitly verifying the equality of bosonic and fermionic masses at one loop order in the shifted vacuum, and the appearance of two loop dilaton tadpole in the perturbative vacuum where supersymmetry is expected to be broken.

Superfield description of [formula omitted]-dimensional SYM theories and their mixtures on magnetized tori

We provide a systematic way of dimensional reduction for (4+2n)-dimensional U(N) supersymmetric Yang–Mills (SYM) theories (n=0,1,2,3) and their mixtures compactified on two-dimensional tori with background magnetic fluxes, which preserve a partial N=1 supersymmetry out of full N=2,3 or 4 in the original SYM theories. It is formulated in an N=1 superspace respecting the unbroken supersymmetry, and the four-dimensional effective action is written in terms of superfields representing N=1 vector and chiral multiplets, those arise from the higher-dimensional SYM theories. We also identify the dilaton and geometric moduli dependence of matter Kähler metrics and superpotential couplings as well as of gauge kinetic functions in the effective action. The results would be useful for various phenomenological/cosmological model buildings with SYM theories or D-branes wrapping magnetized tori, especially, with mixture configurations of them with different dimensionalities from each other.

Generalised universality of gauge thresholds in heterotic vacua with and without supersymmetry

We study one-loop quantum corrections to gauge couplings in heterotic vacua with spontaneous supersymmetry breaking. Although in non-supersymmetric constructions these corrections are not protected and are typically model dependent, we show how a universal behaviour of threshold differences, typical of supersymmetric vacua, may still persist. We formulate specific conditions on the way supersymmetry should be broken for this to occur. Our analysis implies a generalised notion of threshold universality even in the case of unbroken supersymmetry, whenever extra charged massless states appear at enhancement points in the bulk of moduli space. Several examples with universality, including non-supersymmetric chiral models in four dimensions, are presented.

Supersymmetric laser arrays

We introduce the concept of supersymmetric laser arrays that consist of a main optical lattice and its superpartner structure, and we investigate the onset of their lasing oscillations. Due to the coupling of the two constituent lattices, their degenerate optical modes form doublets, while the extra mode associated with unbroken supersymmetry forms a singlet state. Singlet lasing can be achieved for a wide range of design parameters, either by introducing stronger loss in the partner lattice or by pumping only the main array. Our findings suggest the possibility of building single-mode, high-power laser arrays and are also important for understanding light transport dynamics in multimode parity-time symmetric photonic structures.

Twisted compactification of N = 2 5D SCFTs to three and two dimensions from F(4) gauged supergravity

We study supersymmetric $AdS_4\times \Sigma_2$ and $AdS_3\times \Sigma_3$ solutions in half-maximal gauged supergravity in six dimensions with $SU(2)_R\times SU(2)$ gauge group. The gauged supergravity is obtained by coupling three vector multiplets to the pure $F(4)$ gauged supergravity. The $SU(2)_R$ R-symmetry together with the $SO(3)\sim SU(2)$ symmetry of the vector multiplets are gauged. The resulting gauged supergravity admits supersymmetric $AdS_6$ critical points with $SO(4)\sim SU(2)\times SU(2)$ and $SO(3)\sim SU(2)_{\textrm{diag}}$ symmetries. The former corresponds to five-dimensional $N=2$ superconformal field theories (SCFTs) with $E_1\sim SU(2)$ symmetry. We find new classes of supersymmetric $AdS_4\times \Sigma_2$ and $AdS_3\times \Sigma_3$ solutions with $\Sigma_{2,3}$ being $S^{2,3}$ and $H^{2,3}$. These solutions describe SCFTs in three and two dimensions obtained from twisted compactifications of the aforementioned five-dimensional SCFTs with different numbers of unbroken supersymmetry and various types of global symmetries.

Supersymmetric gauged double field theory: systematic derivation by virtue of twist

In a completely systematic and geometric way, we derive maximal and half-maximal supersymmetric gauged double field theories in lower than ten dimensions. To this end, we apply a simple twisting ansatz to the $D=10$ ungauged maximal and half-maximal supersymmetric double field theories constructed previously within the so-called semi-covariant formalism. The twisting ansatz may not satisfy the section condition. Nonetheless, all the features of the semi-covariant formalism, including its complete covariantizability, are still valid after the twist under alternative consistency conditions. The twist allows gaugings as supersymmetry preserving deformations of the $D=10$ untwisted theories after Scherk-Schwarz-type dimensional reductions. The maximal supersymmetric twist requires an extra condition to ensure both the Ramond-Ramond gauge symmetry and the $32$ supersymmetries unbroken.

Component on-shell actions of supersymmetric 3-branes: II. 3-brane in D = 8

In the present paper we explicitly construct the on-shell supersymmetric component action for a 3-brane moving in D = 8 within the nonlinear realizations framework. Similarly to the previously considered case of the super 3-brane in D = 6, all ingredients entering the component action follow from the nonlinear realizations approach. The component action of the 3-brane possesses supersymmetry partially broken to the one. The basic Goldstone superfield is the generalized version of the hypermultiplet. The action has a structure such that all terms of higher orders in the fermions are hidden inside the covariant derivatives and vielbeins. The main part of the component action mimics its bosonic cousin in which the ordinary space–time derivatives and the bosonic worldvolume are replaced by their covariant (with respect to broken supersymmetry) supersymmetric analogs. The spontaneously broken supersymmetry fixes the Ansatz for the component action up to two constant parameters. The role of the unbroken supersymmetry is just to fix these parameters.

On supersymmetric Dirac-delta interactions

In this paper we construct \(\mathcal{N} = 2\) supersymmetric (SUSY) quantum mechanics over several configurations of Dirac-δ potentials from one single delta to a Dirac “comb”. We show in detail how the building of supersymmetry on potentials with delta interactions placed in two or more points on the real line requires the inclusion of quasi-square wells. Therefore, the basic ingredient of a supersymmetric Hamiltonian containing two or more Dirac-δ’s is the singular potential formed by a Dirac-δ plus a step (θ) at the same point. In this δ/θ SUSY Hamiltonian there is only one singlet ground state of zero energy annihilated by the two supercharges or a doublet of ground states paired by supersymmetry of positive energy depending on the relation between the Dirac well strength and the height of the step potential. We find a scenario of either unbroken supersymmetry with Witten index one or supersymmetry breaking when there is one “bosonic” and one “fermionic” ground state such that the Witten index is zero. We explain next the different structure of the scattering waves produced by three δ/θ potentials with respect to the eigenfunctions arising in the non-SUSY case. In particular, many more bound states paired by supersymmetry exist within the supersymmetric framework compared with the non-SUSY problem. An infinite array of equally spaced δ-interactions of the same strength but alternatively attractive and repulsive are susceptible of being promoted to a \(\mathcal{N} = 2\) supersymmetric system. The Bloch’s theorem for wave functions in periodic potentials prompts a band spectrum also paired by supersymmetry. Self-isospectrality between the two partner Hamiltonians is thus found. Zero energy ground states are the non-propagating band lower edges, which exist in the spectra of both the two diagonal operators forming the SUSY Hamiltonian. We find that for the SUSY Dirac “comb” the naif Witten index is zero but supersymmetry is unbroken.

Component on-shell actions of supersymmetric 3-branes: I. 3-brane in D = 6

In the present and accompanying papers we explicitly construct the on-shell supersymmetric component actions for 3-branes moving in D = 6 and D = 8 within the nonlinear realizations framework. In the first paper we apply our scheme to construct the action of supersymmetric 3-brane in D = 6. It turns out that all ingredients entering the component action can be obtained almost algorithmically by using the nonlinear realizations approach. Within this approach, properly adapted to the construction of the on-shell component actions, we pay much attention to broken supersymmetry. Doing so, we were able to write the action in terms of purely geometric objects (vielbeins and covariant derivatives of the physical bosonic components), covariant with respect to broken supersymmetry. It turns out that all terms of the higher orders in the fermions are hidden inside these covariant derivatives and vielbeins. Moreover, the main part of the component action just mimics its bosonic cousin in which the ordinary space–time derivatives and the bosonic worldvolume are replaced by their covariant supersymmetric analogs. The Wess–Zumino term in the action, which does not exist in the bosonic case, can be also easily constructed in terms of reduced Cartan forms. Keeping the broken supersymmetry almost explicit, one may write the ansatz for the component action, fully defined up to two constant parameters. The role of the unbroken supersymmetry is just to fix these parameters.

Transmutations of supersymmetry through soliton scattering and self-consistent condensates

We consider the two most general families of the (1+1)D Dirac systems with transparent scalar potentials, and two related families of the paired reflectionless Schrodinger operators. The ordinary N=2 supersymmetry for such Schrodinger pairs is enlarged up to an exotic N=4 nonlinear centrally extended supersymmetric structure, which involves two bosonic integrals composed from the Lax-Novikov operators for the stationary Korteweg-de Vries hierarchy. Each associated single Dirac system displays a proper N=2 nonlinear supersymmetry with a non-standard grading operator. One of the two families of the first and second order systems exhibits the unbroken supersymmetry, while another is described by the broken exotic supersymmetry. The two families are shown to be mutually transmuted by applying a certain limit procedure to the soliton scattering data. We relate the topologically trivial and nontrivial transparent potentials with self-consistent inhomogeneous condensates in Bogoliubov-de Gennes and Gross-Neveu models, and indicate the exotic N=4 nonlinear supersymmetry of the paired reflectionless Dirac systems.

Constraints on the R-charges of free bound states from the Römelsberger index

The Romelsberger index on S 3 × $$ \mathbb{R} $$ serves as a powerful test for conjectured dualities, relying on the claim that this object is an RG-invariant. In this work we support this claim by showing that the singularities suggested by Witten of “states moving in from infinity” are excluded on S 3 × $$ \mathbb{R} $$ . In addition, we provide an application of the Romelsberger index, in the form of a constraint on the RG flow of supersymmetric theories. The constraint, which applies for asymptotically free theories with unbroken supersymmetry and non-anomalous R-symmetry, is the following: if the R-charges of the chiral multiplets in the UV theory are q i ∈ (0, 2) and the IR theory can be described as a free theory of chiral bound states, then the R-charges of these bound states, $$ {\tilde{q}}_j $$ , are constrained such that $$ {\tilde{q}}_j\in \left(0,2\right) $$ . We thus provide a proof of a weak version of a conjecture proposed by Intriligator. We mention some applications of this result.

Distributed SUSY breaking: dark energy, Newton’s law and the LHC

We identify the underlying symmetry mechanism that suppresses the low-energy effective 4D cosmological constant within 6D supergravity models, leading to results suppressed by powers of the KK scale relative to the much larger masses associated with particles localized on codimension-2 branes. In these models the conditions for unbroken supersymmetry can be satisfied locally everywhere within the extra dimensions, but are obstructed by global conditions like flux quantization or the mutual inconsistency of boundary conditions at the various branes. Consequently quantities forbidden by supersymmetry cannot be nonzero until wavelengths of order the KK scale are integrated out, since only such long wavelength modes see the entire space and so know that supersymmetry breaks. We verify these arguments by extending earlier rugby-ball calculations of one-loop vacuum energies to more general pairs of branes within two warped extra dimensions. The predicted effective 4D vacuum energy density can be of order C (m Mg/4 pi Mp)^4, where Mg (Mp) is the rationalized 6D (4D) Planck scale and m is the heaviest brane-localized particle. Numerically this is C (5.6 x 10^{-5} eV)^4 if we take m = 173 GeV and take Mg as small as possible (10 TeV corresponding to KK size r < 1 micron), consistent with supernova bounds. C is a constant depending on details of the bulk spectrum, which could be ~ 500 for each of hundreds of fields. The value C ~ 6 x 10^6 gives the observed Dark Energy density.

Generalized geometry of two-dimensional vacua

We derive the conditions for unbroken supersymmetry for a Mink2, (2, 0) vacuum, arising from Type II supergravity on a compact eight-dimensional manifold ℳ8. When specialized to internal manifolds enjoying SU(4) × SU(4) structure the resulting system is elegantly rewritten in terms of generalized complex geometry. This particular class of vacua violates the correspondence between supersymmetry conditions and calibrations conditions of D branes (supersymmetry-calibrations correspondence). Our analysis includes and extends previous results about the failure of the supersymmetry-calibrations correspondence, and confirms the existence of a precise relation between such a failure and a subset of the supersymmetry conditions.

A search for an \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$ \mathcal{N} =2 $\end{document} inflaton potential

AbstractWe consider \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$ \mathcal{N} =2 $\end{document} supergravity theories that have the same spectrum as the R + R2 supergravity, as predicted from the off‐shell counting of degrees of freedom. These theories describe standard \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$ \mathcal{N} =2 $\end{document} supergravity coupled to one or two long massive vector multiplets. The central charge is not gauged in these models and they have a Minkowski vacuum with \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$ \mathcal{N} =2 $\end{document} unbroken supersymmetry. The gauge symmetry, being non‐compact, is always broken. α‐deformed inflaton potentials are obtained, in the case of a single massive vector multiplet, with α = 1/3 and 2/3. The α = 1 potential (i.e. the Starobinsky potential) is also obtained, but only at the prize of having a single massive vector and a residual unbroken gauge symmetry. The inflaton corresponds to one of the Cartan fields of the non‐compact quaternionic‐Kähler cosets.