Featured Researches

High Energy Physics Theory

A new Wilson line-based action for gluodynamics

We perform a canonical transformation of fields that brings the Yang-Mills action in the light-cone gauge to a new classical action, which does not involve any triple-gluon vertices. The lowest order vertex is the four-point MHV vertex. Higher point vertices include the MHV andMHV¯¯¯¯¯¯¯¯¯¯¯¯vertices, that reduce to the corresponding amplitudes in the on-shell limit. In general, anyn-leg vertex has2?�m?�n??negative helicity legs. The canonical transformation of fields can be compactly expressed in terms of path-ordered exponentials of fields and their functional derivative. We apply the new action to compute several tree-level amplitudes, up to 8-point NNMHV amplitude, and find agreement with the standard methods. The absence of triple-gluon vertices results in fewer diagrams required to compute amplitudes, when compared to the CSW method and, obviously, considerably fewer than in the standard Yang-Mills action.

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High Energy Physics Theory

A new family ofAdS4S-folds in type IIB string theory

We construct infinite new classes ofAdS4?S1?S5solutions of type IIB string theory which have non-trivialSL(2,Z)monodromy along theS1direction. The solutions are supersymmetric and holographically dual, generically, toN=1SCFTs ind=3. The solutions are first constructed asAdS4?Rsolutions inD=5SO(6)gauged supergravity and then uplifted toD=10. Unlike the knownAdS4?RS-fold solutions, there is no continuous symmetry associated with theRdirection. The solutions all arise as limiting cases of Janus solutions ofd=4,N=4SYM theory which are supported both by a different value of the coupling constant on either side of the interface, as well as by fermion and boson mass deformations. As special cases, the construction recovers three known S-fold constructions, preservingN=1,2and 4 supersymmetry, as well as a recently constructedN=1AdS4?S1?S5solution (not S-folded). We also present some novel "one-sided Janus" solutions that are non-singular.

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High Energy Physics Theory

A novel representation of an integrated correlator inN=4SYM theory

An integrated correlator of four superconformal stress-tensor primaries ofN=4supersymmetricSU(N)Yang-Mills theory (SYM), originally obtained by localisation, is re-expressed as a two-dimensional lattice sum that is manifestly invariant underSL(2,Z)S-duality. This expression is shown to satisfy a novel Laplace equation in the complex coupling constant?that relates theSU(N)integrated correlator to those of theSU(N+1)andSU(N??)theories. The lattice sum is shown to precisely reproduce known perturbative and non-perturbative properties ofN=4SYM for any finiteN, as well as extending previously conjectured properties of the large-Nexpansion.

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High Energy Physics Theory

A roadmap for bootstrapping critical gauge theories: decoupling operators of conformal field theories ind>2dimensions

We propose a roadmap for bootstrapping conformal field theories (CFTs) described by gauge theories in dimensionsd>2. In particular, we provide a simple and workable answer to the question of how to detect the gauge group in the bootstrap calculation. Our recipe is based on the notion of \emph{decoupling operator}, which has a simple (gauge) group theoretical origin, and is reminiscent of the null operator of2dWess-Zumino-Witten CFTs in higher dimensions. Using the decoupling operator we can efficiently detect the rank (i.e. color number) of gauge groups, e.g., by imposing gap conditions in the CFT spectrum. We also discuss the physics of the equation of motion, which has interesting consequences in the CFT spectrum as well. As an application of our recipes, we study a prototypical critical gauge theory, namely the scalar QED which has aU(1)gauge field interacting with critical bosons. We show that the scalar QED can be solved by conformal bootstrap, namely we have obtained its kinks and islands in bothd=3andd=2+ϵdimensions.

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High Energy Physics Theory

A technical analog of the cosmological constant problem and a solution thereof

The near vanishing of the cosmological constant is one of the most puzzling open problems in theoretical physics. We consider a system, the so-called framid, that features a technically similar problem. Its stress-energy tensor has a Lorentz-invariant expectation value on the ground state, yet there are no standard, symmetry-based selection rules enforcing this, since the ground state spontaneously breaks boosts. We verify the Lorentz invariance of the expectation value in question with explicit one-loop computations. These, however, yield the expected result only thanks to highly nontrivial cancellations, which are quite mysterious from the low-energy effective theory viewpoint.

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High Energy Physics Theory

A unitary renormalizable model of composite gravitons

A four-dimensionalSU(4)confining Yang-Mills field, coupled to a fundamental fermion field and a bi-fundamental scalar field, has excitations with spin-2, but no other quantum numbers. These spin-2 excitations can be light or can condense, depending upon the scalar coupling. If condensation occurs, there is a massless spin-2 Goldstone boson with (possibly weakly) broken Lorentz invariance in the effective theory. The low-lying spectrum contains additional spin-0 and spin-1 particles. We discuss how to couple these new fields to other matter fields. To our knowledge, this is the only explicit proposal for a unitary and perturbatively-renormalizable local field theory of gravity.

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High Energy Physics Theory

ATT¯-like deformation of the Skyrme model and the Heisenberg model of nucleon-nucleon scattering

The Skyrme model, though it admits correctly a wide range of static properties of the nucleon, does not seem to reproduce properly the scattering behavior of nucleons at high energies. In this paper we present aTT¯-like deformation of it, inspired by a 1+1 dimensional model, in which boosted nucleons behave like shock waves. The scattering of the latter saturates the Froissart bound. We start by showing that 1+1 dimensionalTT¯deformations of the free abelian pion action are in fact generalizations of the old Heisenberg model for nucleon-nucleon scattering, yielding the same saturation of the Froissart bound. We then deform the strong coupling limit of the bosonized action of multi-flavor QCD in two dimensions using theTT¯deformation of the WZW action with a mass term. We derive the classical soliton solution that corresponds to the nucleon, determine its mass and discuss its transformation into a shock-wave upon boosting. We uplift this action into a 3+1 dimensionalTT¯-like deformation of the Skyrme action. We compare this deformed action to that of chiral perturbation theory.A possible holographic gravity dual interpretation is explored.

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High Energy Physics Theory

AdS Euclidean wormholes

We explore the construction and stability of asymptotically anti-de Sitter Euclidean wormholes in a variety of models. In simple ad hoc low-energy models, it is not hard to construct two-boundary Euclidean wormholes that dominate over disconnected solutions and which are stable (lacking negative modes) in the usual sense of Euclidean quantum gravity. Indeed, the structure of such solutions turns out to strongly resemble that of the Hawking-Page phase transition for AdS-Schwarzschild black holes, in that for boundary sources above some threshold we find both a `large' and a `small' branch of wormhole solutions with the latter being stable and dominating over the disconnected solution for large enough sources. We are also able to construct two-boundary Euclidean wormholes in a variety of string compactifications that dominate over the disconnected solutions we find and that are stable with respect to field-theoretic perturbations. However, as in classic examples investigated by Maldacena and Maoz, the wormholes in these UV-complete settings always suffer from brane-nucleation instabilities (even when sources that one might hope would stabilize such instabilities are tuned to large values). This indicates the existence of additional disconnected solutions with lower action. We discuss the significance of such results for the factorization problem of AdS/CFT.

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High Energy Physics Theory

AdS superprojectors

Within the framework ofN=1anti-de Sitter (AdS) supersymmetry in four dimensions, we derive superspin projection operators (or superprojectors). For a tensor superfieldVα(m)α?(n):=V(α1...αm)(α?1...α?n)on AdS superspace, withmandnnon-negative integers, the corresponding superprojector turnsVα(m)α?(n)into a multiplet with the properties of a conserved conformal supercurrent. It is demonstrated that the poles of such superprojectors correspond to (partially) massless multiplets, and the associated gauge transformations are derived. We give a systematic discussion of how to realise the unitary and the partially massless representations of theN=1AdS4superalgebraosp(1|4)in terms of on-shell superfields. As an example, we present an off-shell model for the massive gravitino multiplet in AdS4. We also prove that the gauge-invariant actions for superconformal higher-spin multiplets factorise into products of minimal second-order differential operators.

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High Energy Physics Theory

AdS2?S2?CY2solutions in Type IIB with 8 supersymmetries

We present a new infinite family of Type IIB supergravity solutions preserving eight supercharges. The structure of the space isAdS2?S2?CY2?S1fibered over an interval. These solutions can be related through double analytical continuations with those recently constructed in \cite{Lozano:2020txg}. Both types of solutions are however dual to very different superconformal quantum mechanics. We show that our solutions fit locally in the class ofAdS2?S2?CY2solutions fibered over a 2d Riemann surfaceΣconstructed by Chiodaroli, Gutperle and Krym, in the absence of D3 and D7 brane sources. We compare our solutions to the global solutions constructed by Chiodaroli, D'Hoker and Gutperle forΣan annulus. We also construct a cohomogeneity-two family of solutions using non-Abelian T-duality. Finally, we relate the holographic central charge of our one dimensional system to a combination of electric and magnetic fluxes. We propose an extremisation principle for the central charge from a functional constructed out of the RR fluxes.

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