Publications

RSS Feed from https://arxiv.org/

  • Emitted Radiation and Geometry
    by Bianchi, Lorenzo on 16 October 2019 at 7:04

    arXiv:1910.06332by: Bianchi, LorenzoAbstract: In conformal $\mathcal{N}=2$ Super Yang-Mills theory, the energy emitted by an accelerated heavy particle is computed by the one-point function of the stress tensor operator in the presence of a Wilson line. In this paper, we consider the theory on the ellipsoid and we prove a conjectured relation between the stress tensor one-point function and the first order expansion of the Wilson loop expectation value in the squashing parameter. To do this, we analyze the behavior of the Wilson loop for a small deformation of the background geometry and, at first order in the deformation, we fix the kinematics using defect CFT constraints. In the final part of the paper, we analyze the consequences of our results for the weak coupling perturbative expansion. In particular, comparing the weakly coupled matrix model with the ordinary Feynman diagram expansion, we find a natural transcendentality driven organization for the latter. […]

  • $\mathcal{N}$-Extended $D=4$ Supergravity, Unconventional SUSY and Graphene
    by Andrianopoli, L. on 9 October 2019 at 3:08

    arXiv:1910.03508by: Andrianopoli, L.Abstract: We derive a $2+1$ dimensional model with unconventional supersymmetry at the boundary of an ${\rm AdS}_4$ $\mathcal{N}$-extended supergravity, generalizing previous results. The (unconventional) extended supersymmetry of the boundary model is instrumental in describing, within a top-down approach, the electronic properties of graphene at the two Dirac points, ${\bf K}$ and ${\bf K}'$. The two valleys correspond to the two independent sectors of the ${\rm OSp}(p|2)\times {\rm OSp}(q|2)$ boundary model in the $p=q$ case, which are related by a parity transformation. The Semenoff and Haldane-type masses entering the corresponding Dirac equations are identified with the torsion parameters of the substrate in the model. […]

  • The String Geometry Behind Topological Amplitudes
    by Angelantonj, Carlo on 9 October 2019 at 3:07

    arXiv:1910.03347by: Angelantonj, CarloAbstract: It is shown that the generating function of $\mathscr{N}=2$ topological strings, in the heterotic weak coupling limit, is identified with the partition function of a six-dimensional Melvin background. This background, which corresponds to an exact CFT, realises in string theory the six-dimensional $\varOmega$-background of Nekrasov, in the case of opposite deformation parameters $\epsilon_1=-\epsilon_2$, thus providing the known perturbative part of the Nekrasov partition function in the field theory limit. The analysis is performed on both heterotic and type I strings and for the cases of ordinary $\mathscr{N}=2$ and $\mathscr{N}=2^*$ theories. […]

  • String Field Theory Solution for Any Open String Background. II
    by Erler, Theodore on 27 September 2019 at 12:34

    arXiv:1909.11675by: Erler, Theodore (ASCR, Prague) et al.Abstract: Generalizing previous work, we give a new analytic solution in Witten's open bosonic string field theory which can describe any open string background. The central idea is to use Riemann surface degenerations as a mechanism for taming OPE singularities. This requires leaving the familiar subalgebra of wedge states with insertions, but the payoff is that the solution makes no assumptions about the reference and target D-brane systems, and is therefore truly general. For example, unlike in previous work, the solution can describe time dependent backgrounds and multiple copies of the reference D-brane within the universal sector. The construction also resolves some subtle issues resulting from associativity anomalies, giving a more complete understanding of the relation between the degrees of freedom of different D-brane systems, and a nonperturbative proof of background independence in classical open bosonic string field theory. […]

  • Near-Conformal Dynamics at Large Charge
    by Orlando, Domenico on 20 September 2019 at 2:47

    arXiv:1909.08642CP3-Origins-2019-36 DNRF90by: Orlando, Domenico (INFN, Turin) et al.Abstract: We investigate four-dimensional near-conformal dynamics by means of the large-charge limit. We first introduce and justify the formalism in which near-conformal invariance is insured by adding a dilaton and then determine the large-charge spectrum of the theory. The dilaton can also be viewed as the radial mode of the EFT. We calculate the two-point functions of charged operators. We discover that the mass of the dilaton, parametrising the near-breaking of conformal invariance, induces a novel term that is logarithmic in the charge. One can therefore employ the large-charge limit to explore near-conformal dynamics and determine dilaton-related properties. […]

  • Large charge at large N
    by Alvarez-Gaume, Luis on 9 September 2019 at 4:19

    arXiv:1909.02571by: Alvarez-Gaume, Luis (Stony Brook U., New York, SCGP) et al.Abstract: We apply the large-charge expansion to O(N) vector models starting from first principles, focusing on the Wilson-Fisher point in three dimensions. We compute conformal dimensions at zero and finite temperature at fixed charge Q, concentrating on the regime $1 \ll N \ll Q$. Our approach places the earlier effective field theory treatment on firm ground and extends its predictions. […]

  • Modular Bootstrap, Elliptic Points, and Quantum Gravity
    by Gliozzi, Ferdinando on 2 August 2019 at 3:01

    arXiv:1908.00029by: Gliozzi, Ferdinando (INFN, Turin)Abstract: The modular bootstrap program for 2d CFTs could be seen as a systematic exploration of the physical consequences of consistency conditions at the elliptic points and at the cusp of their toruspartition function. The study at $\tau=i$, the elliptic point stabilized by the modular inversion $S$, was initiated by Hellerman, who found a general upper bound for the most relevant scaling dimension $\Delta$. Likewise, analyticity at $\tau=i\infty$, the cusp stabilized by the modular translation $T$, yields an upper bound on the twist gap. Here we study consistency conditions at $\tau=\exp[2i\pi/3]$, the elliptic point stabilized by $S T$. We find a much stronger upper bound in the large-c limit, namely $\Delta […]

  • Pictures from Super Chern-Simons Theory
    by Cremonini, C.A. on 17 July 2019 at 11:31

    arXiv:1907.07152ARC-19-08by: Cremonini, C.A. (Milan U.) et al.Abstract: We study super-Chern-Simons theory on a generic supermanifold. After a self-contained review of integration on supermanifolds, the complexes of forms (superforms, pseudo-forms and integral forms) and the extended Cartan calculus are discussed. We then introduce Picture Changing Operators. We provide several examples of computation of PCO's acting on different type of forms. We illustrate also the action of the $\eta$ operator, crucial ingredient to define the interactions of super Chern-Simons theory. Then, we discuss the action for super Chern-Simons theory on any supermanifold, first in the factorized form (3-form $\times$ PCO) and then, we consider the most general expression. The latter is written in term of psuedo-forms containing an infinite number of components. We show that the free equations of motion reduce to the usual Chern-Simons equations yielding the proof of the equivalence between the formulations at different pictures of the same theory. Finally, we discuss the interaction terms. They require a suitable definition in order to take into account the picture number. That implies the construction of a 2-product which is not associative that inherits an $A_\infty$ algebra structure. That shares several similarities with a recent construction of a super string field theory action by Erler, Konopka and Sachs. […]

  • $O(d,d)$ transformations preserve classical integrability
    by Orlando, Domenico on 10 July 2019 at 3:04

    arXiv:1907.03759KUNS-2767by: Orlando, Domenico (Turin U.) et al.Abstract: In this note, we study the action of $O(d,d)$ transformations on the integrable structure of two-dimensional non-linear sigma models via the doubled formalism. We construct the Lax pairs associated with the $O(d,d)$-transformed model and find that they are in general non-local because they depend on the winding modes. We conclude that every $O(d,d;\mathbb{R})$ deformation preserves integrability. As an application we compute the Lax pairs for continuous families of deformations, such as $J\bar{J}$ marginal deformations and TsT transformations of the three-sphere with $H$-flux. […]

  • The $\mathcal{N}_3=3\to \mathcal{N}_3=4$ enhancement of Super Chern-Simons theories in $D=3$, Calabi HyperKähler metrics and M2-branes on the $\mathcal{C}(\mathrm{N^{0,1,0}})$ conifold
    by Fré, P. on 28 June 2019 at 8:09

    arXiv:1906.11672ARC-19-07by: Fré, P. (Turin U.) et al.Abstract: Considering matter coupled supersymmetric Chern-Simons theories in three dimensions we extend the Gaiotto-Witten mechanism of supersymmetry enhancement $\mathcal{N}_3=3\to \mathcal{N}_3=4$ from the case where the hypermultiplets span a flat HyperK\"ahler manifold to that where they live on a curved one. We derive the precise conditions of this enhancement in terms of generalized Gaiotto-Witten identities to be satisfied by the tri-holomorphic moment maps. An infinite class of HyperK\"ahler metrics compatible with the enhancement condition is provided by the Calabi metrics on $T^\star \mathbb{P}^{n}$. In this list we find, for $n=2$ the resolution of the metric cone on $\mathrm{N}^{0,1,0}$ which is the unique homogeneous Sasaki Einstein 7-manifold leading to an $\mathcal{N}_4=3$ compactification of M-theory. This leads to challenging perspectives for the discovery of new relations between the enhancement mechanism in $D=3$, the geometry of M2-brane solutions and also for the dual description of super Chern Simons theories on curved HyperK\"ahler manifolds in terms of gauged fixed supergroup Chern Simons theories. The relevant supergroup is in this case $\mathrm{SU(3|N)}$ where $\mathrm{SU(3)}$ is the flavor group and $\mathrm{U(N)}$ is the color group. […]

  • BPS wilson loops in generic conformal $ \mathcal{N} $ = 2 SU(N) SYM theories
    by Billò, M. on 18 June 2019 at 3:05

    arXiv:1906.07085JHEP 1908 (2019) 108by: Billò, M. (Turin U.) et al.Abstract: We consider the 1/2 BPS circular Wilson loop in a generic $ \mathcal{N} $ = 2 SU(N) SYM theory with conformal matter content. We study its vacuum expectation value, both at finite N and in the large-N limit, using the interacting matrix model provided by localization results. We single out some families of theories for which the Wilson loop vacuum expectation values approaches the $ \mathcal{N} $ = 4 result in the large-N limit, in agreement with the fact that they possess a simple holographic dual. At finite N and in the generic case, we explicitly compare the matrix model result with the field-theory perturbative expansion up to order g$^{8}$ for the terms proportional to the Riemann value ζ (5), finding perfect agreement. Organizing the Feynman diagrams as suggested by the structure of the matrix model turns out to be very convenient for this computation. […]

  • Modular properties of surface operators in $N=2$ SQCD
    by Ballav, Sourav on 28 May 2019 at 3:04

    arXiv:1905.10898JHEP 1907 (2019) 177by: Ballav, Sourav (HBNI, Mumbai) et al.Abstract: We study half-BPS surface operators in $ \mathcal{N} $ = 2 supersymmetric QCD in four dimensions with gauge group SU(2) and four fundamental flavours. We compute the twisted chiral superpotential that describes the effective theory on the surface operator using equivariant localization as well as the Seiberg-Witten data. We then use the constraints imposed by S-duality to resum the instanton contributions to the twisted superpotential into elliptic functions and (quasi-) modular forms. The resummed results match what one would obtain from the description of surface operators as the insertion of a degenerate operator in a spherical conformal block in Liouville CFT. […]

  • Localization of effective actions in open superstring field theory: small Hilbert space
    by Maccaferri, Carlo on 14 May 2019 at 8:55

    arXiv:1905.04958JHEP 1906 (2019) 101by: Maccaferri, Carlo (Turin U.) et al.Abstract: We consider the algebraic effective couplings for open superstring massless modes in the framework of the $A_\infty$ theory in the small Hilbert space. Focusing on quartic algebraic couplings, we reduce the effective action of the $A_\infty$ theory to the Berkovits one where we have already shown that such couplings are fully computed from contributions at the boundary of moduli space, when the massless fields under consideration are appropriately charged under an ${\cal N}\!=\!2$ $R$-symmetry. Here we offer a proof of localization which is in the small Hilbert space. We also discuss the flat directions of the obtained quartic potentials and give evidence for the existence of exactly marginal deformations in the $D3/D(-1)$ system in the framework of string field theory. […]

  • A safe CFT at large charge
    by Orlando, Domenico on 2 May 2019 at 2:46

    arXiv:1905.00026JHEP 1908 (2019) 164by: Orlando, Domenico (INFN, Turin) et al.Abstract: We apply the large-charge limit to the first known example of a four-dimensional gauge-Yukawa theory featuring an ultraviolet interacting fixed point in all couplings. We determine the energy of the ground state in presence of large fixed global charges and deduce the global symmetry breaking pattern. We show that the fermions decouple at low energy leaving behind a confining Yang-Mills theory and a characteristic spectrum of type I (relativistic) and type II (non-relativistic) Goldstone bosons. Armed with the knowledge acquired above we finally arrive at establishing the conformal dimensions of the theory as a triple expansion in the large-charge, the number of flavors and the controllably small inverse gauge coupling constant at the UV fixed point. Our results unveil a number of noteworthy properties of the low-energy spectrum, vacuum energy and conformal properties of the theory. They also allow us to derive a new consistency condition for the relative sizes of the couplings at the fixed point. […]

  • The Quantum Theory of Chern-Simons Supergravity
    by Andrianopoli, L. on 12 March 2019 at 3:22

    arXiv:1903.04431ARC-18-18JHEP 1906 (2019) 036by: Andrianopoli, L. (Turin Polytechnic) et al.Abstract: We consider AdS$_{3}$N-extended Chern-Simons supergravity (à la Achucarro-Townsend) and we study its gauge symmetries. We promote those gauge symmetries to a BRST symmetry and we perform its quantization by choosing suitable gauge-fixings. The resulting quantum theories have different features which we discuss in the present work. In particular, we show that a special choice of the gauge-fixing correctly reproduces the Ansatz by Alvarez, Valenzuela and Zanelli for the graphene fermion. […]

  • Conformal dimensions in the large charge sectors at the O(4) Wilson-Fisher fixed point
    by Banerjee, Debasish on 27 February 2019 at 2:45

    arXiv:1902.09542Phys.Rev.Lett. 123 (2019) 051603by: Banerjee, Debasish (Humboldt U., Berlin) et al.Abstract: We study the O(4) Wilson-Fisher fixed point in 2+1 dimensions in fixed large-charge sectors identified by products of two spin-j representations (jL,jR). Using effective field theory we derive a formula for the conformal dimensions D(jL,jR) of the leading operator in terms of two constants, c3/2 and c1/2, when the sum jL+jR is much larger than the difference |jL-jR|. We compute D(jL,jR) when jL=jR with Monte Carlo calculations in a discrete formulation of the O(4) lattice field theory, and show excellent agreement with the predicted formula and estimate c3/2=1.068(4) and c1/2=0.083(3). […]

  • Crepant resolutions of $\mathbb{C}^3/\mathbb{Z}_4$ and the generalized Kronheimer construction (in view of the gauge/gravity correspondence)
    by Bruzzo, Ugo on 5 February 2019 at 3:15

    arXiv:1902.01060J.Geom.Phys. 145 (2019) 103467by: Bruzzo, Ugo (INFN, Trieste) et al.Abstract: As a continuation of a general program started in two previous publications, in the present paper we study the K\"ahler quotient resolution of the orbifold $\mathbb{C}^3/\mathbb{Z}_4$, comparing with the results of a toric description of the same. In this way we determine the algebraic structure of the exceptional divisor, whose compact component is the second Hirzebruch surface $\mathbb F_2$. We determine the explicit K\"ahler geometry of the smooth resolved manifold $Y$, which is the total space of the canonical bundle of $\mathbb F_2$. We study in detail the chamber structure of the space of stability parameters (corresponding in gauge theory to the Fayet-Iliopoulos parameters) that are involved in the construction of the desingularizations either by generalized Kronheimer quotient, or as algebro-geometric quotients. The walls of the chambers correspond to two degenerations; one is a partial desingularization of the quotient, which is the total space of the canonical bundle of the weighted projective space $\mathbb P[1,1,2]$, while the other is the product of the ALE space $A_1$ by a line, and is related to the full resolution in a subtler way. These geometrical results will be used to look for exact supergravity brane solutions and dual superconformal gauge theories. […]

  • Two-point correlators in non-conformal $ \mathcal{N} $ = 2 gauge theories
    by Billo, M. on 29 January 2019 at 5:41

    arXiv:1901.09693ROM2F/2019/02JHEP 1905 (2019) 199by: Billo, M. (Turin U.) et al.Abstract: We study the two-point correlation functions of chiral/anti-chiral operators in $ \mathcal{N} $ = 2 supersymmetric Yang-Mills theories on $ \mathbb{R}^{4}$ with gauge group SU(N) and N$_{f}$ massless hypermultiplets in the fundamental representation. We compute them in perturbation theory, using dimensional regularization up to two loops, and show that field-theory observables built out of dimensionless ratios of two-point renormalized correlators on $ \mathbb{R}^{4}$ are in perfect agreement with the same quantities computed using localization on the four-sphere, even in the non-conformal case N$_{f}$ ≠ 2N. […]

  • Surface operators in $N=$ 2 SQCD and Seiberg Duality
    by Ashok, Sujay K. on 29 January 2019 at 3:11

    arXiv:1901.09630Eur.Phys.J. C79 (2019) 372by: Ashok, Sujay K. (HBNI, Mumbai) et al.Abstract: We study half-BPS surface operators in $\mathcal {N}=2$ supersymmetric asymptotically conformal gauge theories in four dimensions with SU(N) gauge group and 2N fundamental flavours using localization methods and coupled 2d/4d quiver gauge theories. We show that contours specified by a particular Jeffrey–Kirwan residue prescription in the localization analysis map to particular realizations of the surface operator as flavour defects. Seiberg duality of the 2d/4d quivers is mapped to contour deformations of the localization integral which in this case involves a residue at infinity. This is reflected as a modified Seiberg duality rule that shifts the Lagrangian of the purported dual theory by non-perturbative terms. The new rules, that depend on the 4d gauge coupling, lead to a match between the low energy effective twisted chiral superpotentials for any pair of dual 2d/4d quivers. […]

  • Taming boundary condition changing operator anomalies with the tachyon vacuum
    by Erler, Theodore on 24 January 2019 at 3:49

    arXiv:1901.08038JHEP 1906 (2019) 027by: Erler, Theodore (Prague, Inst. Phys.) et al.Abstract: Motivated by the appearance of associativity anomalies in the context of superstring field theory, we give a generalized solution built from boundary condition changing operators which can be associated to a generic tachyon vacuum in the KBc subalgebra of the Okawa form. We articulate sufficient conditions on the choice of tachyon vacuum to ensure that ambiguous products do not appear in the equations of motion. […]

  • $A_\infty$-Algebra from Supermanifolds
    by Catenacci, Roberto on 4 January 2019 at 4:11

    arXiv:1901.00818ARC-18-14by: Catenacci, Roberto (Piemonte Orientale U., Alessandria) et al.Abstract: Inspired by the analogy between different types of differential forms on supermanifolds and string fields in superstring theory, we construct new multilinear non-associative products of forms which yield an $A_\infty$-algebra. […]

  • GUT Scale Unification in Heterotic Strings
    by Angelantonj, Carlo on 18 December 2018 at 3:20

    arXiv:1812.06915ARC-18-20Phys.Lett. B789 (2019) 496-501by: Angelantonj, Carlo (Turin U.) et al.Abstract: We present a class of heterotic compactifications where it is possible to lower the string unification scale down to the GUT scale, while preserving the validity of the perturbative analysis. We illustrate this approach with an explicit example of a four-dimensional chiral heterotic vacuum with N=1 supersymmetry. […]

  • The Classical Solution for the Bosonic String in the Presence of Three D-branes Rotated by Arbitrary SO(4) Elements
    by Finotello, Riccardo on 13 December 2018 at 3:44

    arXiv:1812.04643Nucl.Phys. B941 (2019) 158-194by: Finotello, Riccardo (INFN, Turin) et al.Abstract: We consider the classical instantonic contribution to the open string configuration associated with three D-branes with relative rotation matrices in SO(4) which corresponds to the computation of the classical part of the correlator of three non Abelian twist fields. We write the classical solution as a sum of a product of two hypergeometric functions. Differently from all the previous cases with three D-branes, the solution is not holomorphic and suggests that the classical bosonic string knows when the configuration may be supersymmetric. We show how this configuration reduces to the standard Abelian twist field computation. From the phenomenological point of view, the Yukawa couplings between chiral matter at the intersection in this configuration are more suppressed with respect to the factorized case in the literature. […]

  • SUSY and the bi-vector
    by Orlando, Domenico on 30 November 2018 at 3:25

    arXiv:1811.11764Phys.Scripta 94 (2019) 095001by: Orlando, Domenico (Turin U.) et al.Abstract: In this note we give an explicit formula for the preserved Killing spinors in deformed string theory backgrounds corresponding to integrable Yang–Baxter deformations realized via (sequences of) TsT transformations. The Killing spinors can be expressed only in terms of the bi-vector Θ which encodes the deformation. This formula is applicable to deformed backgrounds related to r-matrices of various ranks, including those that do not satisfy the unimodularity condition and give rise to backgrounds in generalized supergravity. We conjecture that our formula also remains valid for integrable deformations which are not realized via TsT transformations and motivate this conjecture by explicit examples. […]

  • History operators in quantum mechanics
    by Castellani, Leonardo on 12 October 2018 at 2:08

    arXiv:1810.03624ARC-18-06by: Castellani, LeonardoAbstract: It is convenient to describe a quantum system at all times by means of a "history operator" $C$, encoding measurements and unitary time evolution between measurements. These operators naturally arise when computing the probability of measurement sequences, and generalize the "sum over position histories " of the Feynman path-integral. As we argue in the present note, this description has some computational advantages over the usual state vector description, and may help to clarify some issues regarding nonlocality of quantum correlations and collapse. A measurement on a system described by $C$ modifies the history operator, $C \rightarrow PC$, where $P$ is the projector corresponding to the measurement. We refer to this modification as "history operator collapse". Thus $C$ keeps track of the succession of measurements on a system, and contains all histories compatible with the results of these measurements. The collapse modifies the history content of $C$, and therefore modifies also the past (relative to the measurement), but never in a way to violate causality. Probabilities of outcomes are obtained as $Tr(C^\dagger P C)/Tr(C^\dagger C)$. A similar formula yields probabilities for intermediate measurements, and reproduces the result of the two-vector formalism in the case of given initial and final states. We apply the history operator formalism to a few examples: entangler circuit, Mach-Zehnder interferometer, teleportation circuit, three-box experiment. Not surprisingly, the propagation of coordinate eigenstates $|q\rangle$ is described by a history operator $C$ containing the Feynman path-integral. […]