arXiv subjects

Orr Sela

Publications and source records attributed to Orr Sela.

At least 19 recordsLinked to original sources

arXiv2025

Higher structure of non-invertible symmetries from Lagrangian descriptions

The symmetry structure of a quantum field theory is determined not only by the topological defects that implement the symmetry and their fusion rules, but also by the topological networks they can form, which is referred to as the higher structure of the symmetry. In this paper, we consider theories with non-invertible symmetries that have an explicit Lagrangian description, and use it to study their higher structure. Starting with the 2d free compact boson theory and its non-invertible duality defects, we will find Lagrangian descriptions of networks of defects and use them to recover all the $F$-symbols of the familiar Tambara-Yamagami fusion category $\operatorname{TY}(\mathbb{Z}_N,+1)$. We will then use the same approach in 4d Maxwell theory to compute $F$-symbols associated with its non-invertible duality and triality defects, which are 2d topological field theories. In addition, we will also compute some of the $F$-symbols using a different (group theoretical) approach that is not based on the Lagrangian description, and find that they take the expected form.

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arXiv2024

Dimensionally Reducing Generalized Symmetries from (3+1)-Dimensions

Recently there has been an increasing interest in the study of generalized symmetries in dimensions higher than two. This has lead to the discovery of various manifestations of generalized symmetries, notably higher-group and non-invertible symmetries, in four dimensions. In this paper we shall examine what happens to this structure when the 4d theory is compactified to lower dimensions, specifically to 3d and 2d, where we shall be mainly interested in generalized symmetry structures whose origin can be linked to mixed flavor-gauge anomalies. We discuss several aspects of the compactification, and in particular argue that under certain conditions the discussed generalized symmetry structure may trivialize in the infrared. Nevertheless, we show that even when this happens the presence of the 4d generalized symmetry structure may still leave an imprint on the low-energy theory in terms of additional 't Hooft anomalies or by breaking part of the symmetry. We apply and illustrate this using known examples of compactifications from four dimensions, particularly, the reduction of 4d $\mathcal{N}=1$ $U(N_c)$ SQCD on a circle to 3d and on a sphere to 2d.

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arXiv2024

Emergent non-invertible symmetries in $\mathcal{N}=4$ Super-Yang-Mills theory

One of the simplest examples of non-invertible symmetries in higher dimensions appears in 4d Maxwell theory, where its $SL(2,\mathbb{Z})$ duality group can be combined with gauging subgroups of its electric and magnetic 1-form symmetries to yield such defects at many different values of the coupling. Even though $\mathcal{N}=4$ Super-Yang-Mills (SYM) theory also has an $SL(2,\mathbb{Z})$ duality group, it only seems to share two types of such non-invertible defects with Maxwell theory (known as duality and triality defects). Motivated by this apparent difference, we begin our investigation of the fate of these symmetries by studying the case of 4d $\mathcal{N}=4$ $U(1)$ gauge theory which contains Maxwell theory in its content. Surprisingly, we find that the non-invertible defects of Maxwell theory give rise, when combined with the standard $U(1)$ symmetry acting on the free fermions, to defects which act on local operators as elements of the $U(1)$ outer-automorphism of the $\mathcal{N}=4$ superconformal algebra, an operation that was referred to in the past as the "bonus symmetry". Turning to the nonabelian case of $\mathcal{N}=4$ SYM, the bonus symmetry is not an exact symmetry of the theory but is known to emerge at the supergravity limit. Based on this observation we study this limit and show that if it is taken in a certain way, non-invertible defects that realize different elements of the bonus symmetry emerge as approximate symmetries, in analogy to the abelian case.

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arXiv2023

Exploring Non-Invertible Symmetries in Free Theories

Symmetries corresponding to local transformations of the fundamental fields that leave the action invariant give rise to (invertible) topological defects, which obey group-like fusion rules. One can construct more general (codimension-one) topological defects by specifying a map between gauge-invariant operators from one side of the defect and such operators on the other side. In this work, we apply such construction to Maxwell theory in four dimensions and to the free compact scalar theory in two dimensions. In the case of Maxwell theory, we show that a topological defect that mixes the field strength $F$ and its Hodge dual $\star F$ can be at most an $SO(2)$ rotation. For rational values of the bulk coupling and the $θ$-angle we find an explicit defect Lagrangian that realizes values of the $SO(2)$ angle $φ$ such that $\cos φ$ is also rational. We further determine the action of such defects on Wilson and 't Hooft lines and show that they are in general non-invertible. We repeat the analysis for the free compact scalar $ϕ$ in two dimensions. In this case we find only four discrete maps: the trivial one, a $Z_2$ map $dϕ\rightarrow -dϕ$, a $\mathcal{T}$-duality-like map $dϕ\rightarrow i \star dϕ$, and the product of the last two.

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arXiv2023

5d to 3d compactifications and discrete anomalies

Much insight into the dynamics of quantum field theories can be gained by studying the relationship between field theories in different dimensions. An interesting observation is that when two theories are related by dimensional reduction on a compact surface, their 't Hooft anomalies corresponding to continuous symmetries are also related: the anomaly polynomial of the lower-dimensional theory can be obtained by integrating that of the higher-dimensional one on the compact surface. Naturally, this relation only holds if both theories are even dimensional. This raises the question of whether similar relations can also hold for the case of anomalies in discrete symmetries, which might be true even in odd dimensions. The natural generalization to discrete symmetries is that the anomaly theories, associated with the lower and higher dimensional theories, would be related by reduction on the compact surface. We explore this idea for compactifications of 5d superconformal field theories (SCFTs) to 3d on Riemann surfaces with global-symmetry fluxes. In this context, it can be used both as a check for these compactification constructions and for discovering new anomalies in the 5d SCFTs. This opens the way to applying the same idea of dimensional reduction of the anomaly theory to more general types of compactifications.

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arXiv2023

Trinions for the $3d$ compactification of the $5d$ rank 1 $E_{N_f+1}$ SCFTs

Many interesting phenomena in quantum field theory such as dualities and symmetry enhancements can be understood using higher dimensional constructions. In this paper, we study compactifications of the rank $1$ $5d$ Seiberg $E_{N_f+1}$ SCFTs to $3d$ on Riemann surfaces of genus $g>1$. We rely on the recent progress in the study of compactifications of $6d$ SCFTs to $4d$ and torus compactifications of $5d$ SCFTs to conjecture $3d$ $\mathcal{N}=2$ theories corresponding to the reduction of said $5d$ SCFTs on three punctured spheres. These can then be used to build $3d$ $\mathcal{N}=2$ models corresponding to compactifications on more general surfaces. The conjectured theories are tested by comparing their properties against those expected from the compactification picture.

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arXiv2022

Aspects of 4d supersymmetric dynamics and geometry

In this set of five lectures we present a basic toolbox to discuss the dynamics of four dimensional supersymmetric quantum field theories. In particular we overview the program of geometrically engineering the four dimensional supersymmetric models as compactifications of six dimensional SCFTs. We discuss how strong coupling phenomena in four dimensions, such as duality and emergence of symmetry, can be naturally imbedded in the geometric constructions. The lectures mostly review results which previously appeared in the literature but also contain some unpublished derivations.

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arXiv2021

On the 3d compactifications of 5d SCFTs associated with SU(N+1) gauge theories

We study the $3d$ $\mathcal{N}=2$ theories resulting from the compactification of a family of $5d$ SCFTs on a torus with flux in the global symmetry. The family of $5d$ SCFTs used in the analysis is the one that UV completes the $5d$ $SU(N+1)$ gauge theories with Chern--Simons level $k$ and $N_f$ fundamental hypermultiplets, generalizing the previous investigation of the torus compactifications of the rank 1 Seiberg $E_{N_f+1}$ SCFT (which is the $N=1$ member of the family). This construction systematically yields three-dimensional theories presenting highly non-trivial non-perturbative phenomena such as infra-red dualities and enhanced symmetries, which we check using various methods.

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arXiv2021

Compactifying 5d superconformal field theories to 3d

Building on recent progress in the study of compactifications of $6d$ $(1,0)$ superconformal field theories (SCFTs) on Riemann surfaces to $4d$ $\mathcal{N}=1$ theories, we initiate a systematic study of compactifications of $5d$ $\mathcal{N}=1$ SCFTs on Riemann surfaces to $3d$ $\mathcal{N}=2$ theories. Specifically, we consider the compactification of the so-called rank 1 Seiberg $E_{N_f+1}$ SCFTs on tori and tubes with flux in their global symmetry, and put the resulting $3d$ theories to various consistency checks. These include matching the (usually enhanced) IR symmetry of the $3d$ theories with the one expected from the compactification, given by the commutant of the flux in the global symmetry of the corresponding $5d$ SCFT, and identifying the spectrum of operators and conformal manifolds predicted by the $5d$ picture. As the models we examine are in three dimensions, we encounter novel elements that are not present in compactifications to four dimensions, notably Chern-Simons terms and monopole superpotentials, that play an important role in our construction. The methods used in this paper can also be used for the compactification of any other $5d$ SCFT that has a deformation leading to a $5d$ gauge theory.

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arXiv2021

Analysis of quantum effects inside spherical charged black holes

We numerically compute the renormalized expectation value $\langle\hatΦ^{2}\rangle_{ren}$ of a minimally-coupled massless quantum scalar field in the interior of a four-dimensional Reissner-Nordstrom black hole, in both the Hartle-Hawking and Unruh states. To this end we use a recently developed mode-sum renormalization scheme based on covariant point splitting. In both quantum states, $\langle\hatΦ^{2}\rangle_{ren}$ is found to approach a \emph{finite} value at the inner horizon (IH). The final approach to the IH asymptotic value is marked by an inverse-power tail $r_{*}^{-n}$, where $r_{*}$ is the Regge-Wheeler "tortoise coordinate", and with $n=2$ for the Hartle-Hawking state and $n=3$ for the Unruh state. We also report here the results of an analytical computation of these inverse-power tails of $\langle\hatΦ^{2}\rangle_{ren}$ near the IH. Our numerical results show very good agreement with this analytical derivation (for both the power index and the tail amplitude), in both quantum states. Finally, from this asymptotic behavior of $\langle\hatΦ^{2}\rangle_{ren}$ we analytically compute the leading-order asymptotic behavior of the trace $\langle\hat{T}_μ^μ\rangle_{ren}$ of the renormalized stress-energy tensor at the IH. In both quantum states this quantity is found to diverge like $b(r-r_{-})^{-1}r_{*}^{-n-2}$ (with $n$ specified above, and with a known parameter $b$). To the best of our knowledge, this is the first fully-quantitative derivation of the asymptotic behavior of these renormalized quantities at the inner horizon of a four-dimensional Reissner-Nordstrom black hole.

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arXiv2020

A Nilpotency Index of Conformal Manifolds

We show that exactly marginal operators of Supersymmetric Conformal Field Theories (SCFTs) with four supercharges cannot obtain a vacuum expectation value at a generic point on the conformal manifold. Exactly marginal operators are therefore nilpotent in the chiral ring. This allows us to associate an integer to the conformal manifold, which we call the nilpotency index of the conformal manifold. We discuss several examples in diverse dimensions where we demonstrate these facts and compute the nilpotency index.

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arXiv2019

Symmetry enhancement in 4d Spin(n) gauge theories and compactification from 6d

We consider a known sequence of dualities involving $4d$ ${\cal N}=1$ theories with $Spin(n)$ gauge groups and use it to construct a new sequence of models exhibiting IR symmetry enhancement. Then, motivated by the observed pattern of IR symmetries we conjecture six-dimensional theories the compactification of which on a Riemann surface yields the $4d$ sequence of models along with their symmetry enhancements, and put them to several consistency checks.

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arXiv2019

Black hole entropy function for toric theories via Bethe Ansatz

We evaluate the large-$N$ behavior of the superconformal indices of toric quiver gauge theories, and use it to find the entropy functions of the dual electrically charged rotating $\mathrm{AdS}_5$ black holes. To this end, we employ the recently proposed Bethe Ansatz method, and find a certain set of solutions to the Bethe Ansatz Equations of toric theories. This, in turn, allows us to compute the large-$N$ behavior of the index for these theories, including the infinite families $Y^{pq}$, $X^{pq}$ and $L^{pqr}$ of quiver gauge theories. Our results are in perfect agreement with the predictions made recently using the Cardy-like limit of the superconformal index. We also explore the index structure in the space of chemical potentials and describe the pattern of Stokes lines arising in the conifold theory case.

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arXiv2019

Curing the Self-Force Runaway Problem in Finite-Difference Integration

The electromagnetic self-force equation of motion is known to be afflicted by the so-called runaway problem. A similar problem arises in the semiclassical Einstein's field equation and plagues the self-consistent semiclassical evolution of spacetime. Motivated to overcome the latter challenge, we first address the former (which is conceptually simpler), and present a pragmatic finite-difference method designed to numerically integrate the self-force equation of motion while curing the runaway problem. We restrict our attention here to a charged point-like mass in a one-dimensional motion, under a prescribed time-dependent external force $F_{ext}(t)$. We demonstrate the implementation of our method using two different examples of external force: a Gaussian and a Sin^4 function. In each of these examples we compare our numerical results with those obtained by two other methods (a Dirac-type solution and a reduction-of-order solution). Both external-force examples demonstrate a complete suppression of the undesired runaway mode, along with an accurate account of the radiation-reaction effect at the physically relevant time scale, thereby illustrating the effectiveness of our method in curing the self-force runaway problem.

gr-qc↗

arXiv2018

Chiral 3d SU(3) SQCD and N=2 mirror duality

Recently a very interesting three-dimensional $\mathcal{N}=2$ supersymmetric theory with $SU(3)$ global symmetry was discussed by several authors. We denote this model by $T_x$. This was conjectured to have two dual descriptions, one with explicit supersymmetry and emergent flavor symmetry and the other with explicit flavor symmetry and emergent supersymmetry. We discuss a third description of the model which has both flavor symmetry and supersymmetry manifest. We then investigate models which can be constructed by using $T_x$ as a building block gauging the global symmetry and paying special attention to the global structure of the gauge group. We conjecture several cases of $\mathcal{N}=2$ mirror dualities involving such constructions with the dual being either a simple $\mathcal{N}=2$ Wess-Zumino model or a discrete gauging thereof.

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arXiv2018

Curious patterns of IR symmetry enhancement

We study several cases of IR enhancements of global symmetry in four dimensions. In particular, we consider a sequence of $Spin(n+4)$ supersymmetric gauge theories ($8\geq n\geq 1$) with $n$ vectors and spinor matter with $32$ components. We show that the subgroup of the flavor symmetry of these theories rotating the matter in the spinor representations in the UV, when proper gauge singlet fields are added, enhances to the commutant of $SU(2)$ in $E_{9-n}$. We discuss several other interesting cases of enhanced symmetries and the interplay between symmetry enhancement and self-duality. We also make some observations about possible interconnections between chiral ring relations and symmetry enhancement. Finally, we conjecture relations of the discussed models to compactifications of certain conformal matter models in six dimensions on tori. The conjecture is based on deriving a relation between five dimensional models with $Spin$ gauge groups and conformal theories in six dimensions. As a by product of our considerations we discover a new instance of a simple self-duality of a theory with an $SU(6)$ gauge group.

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arXiv2018

Quantum effects near the Cauchy horizon of a Reissner-Nordstrom black hole

We consider a massless, minimally-coupled quantum scalar field on a Reissner-Nordstrom black hole background, and we study the leading asymptotic behavior of the expectation value of the stress energy tensor operator $\langle\hat{T}_{μν}\rangle_{ren}$ and of $\langle\hatΦ^{2}\rangle_{ren}$ near the inner horizon, in both the Unruh and the Hartle-Hawking quantum states. We find that the coefficients of the expected leading-order divergences of these expectation values vanish, indicating that the modifications of the classical geometry due to quantum vacuum effects might be weaker than expected. In addition, we calculate the leading-order divergences of $\langle\hat{T}_{μν}\rangle_{ren}$ and of $\langle\hatΦ^{2}\rangle_{ren}$ in the Boulware state near the outer (event) horizon, and we obtain analytical expressions that correspond to previous numerical results.

gr-qc↗

arXiv2018

Two-point function of a quantum scalar field in the interior region of a Reissner-Nordstrom black hole

We derive explicit expressions for the two-point function of a massless scalar field in the interior region of a Reissner-Nordstrom black hole, in both the Unruh and Hartle-Hawking quantum states. The two-point function is expressed in terms of the standard $lmω$ modes of the scalar field (those associated with a spherical harmonic $Y_{lm}$ and a temporal mode $e^{-iωt}$), which can be conveniently obtained by solving an ordinary differential equation, the radial equation. These explicit expressions are the internal analogs of the well known results in the external region (originally derived by Christensen and Fulling), in which the two-point function outside the black hole is written in terms of the external $lmω$ modes of the field. They allow the computation of $<Φ^{2}>_{ren}$ and the renormalized stress-energy tensor inside the black hole, after the radial equation has been solved (usually numerically). In the second part of the paper, we provide an explicit expression for the trace of the renormalized stress-energy tensor of a minimally-coupled massless scalar field (which is non-conformal), relating it to the d'Alembertian of $<Φ^{2}>_{ren}$. This expression proves itself useful in various calculations of the renormalized stress-energy tensor.

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