High Energy Physics Theory

We derive general covariant coupled equations of QCD describing the tetraquark in terms of a mix of four-quark states2q2q¯, and two-quark statesqq¯. The coupling of2q2q¯toqq¯states is achieved by a simple contraction of a four-quarkqq¯-irreducible Green function down to a two-quarkqq¯Bethe-Salpeter kernel. The resulting tetraquark equations are expressed in an exact field theoretic form, and are in agreement with those obtained previously by consideration of disconnected interactions; however, despite being more general, they have been derived here in a much simpler and more transparent way.

We construct purely non-perturbative anti-de Sitter vacua in string theory which, on uplifting to a de Sitter (dS) one, have a decay time many orders of magnitude smaller than those of standard constructions, such as the KKLT and LVS scenarios. By virtue of being constructed purely from non-perturbative terms, these vacua avoids certain obstructions plaguing other constructions of dS in string theory. This results in a new class of phenomenological dS vacua in string theory with novel distinctive characteristics such as having two maxima. After examining whether these uplifted dS vacua obey the TCC, we revisit some old problems of realization of dS space as a vacuum. We find that not only is it phenomenologically hard to construct TCC-compatible vacua, but also inherent temporal dependences of the degrees of freedom generically arise in such constructions, amongst other issues. This reinforces the idea that dS, if it exists in string theory, should be a Glauber-Sudarshan state and not a vacuum.

We investigate the time-dependent perturbations of strongly coupledN=4SYM theory at finite temperature and finite chemical potential with a second order phase transition. This theory is modelled by a top-down Einstein-Maxwell-dilaton description which is a consistent truncation of the dimensional reduction of type IIB string theory on AdS5?S5. We focus on spin-1 and spin-2 sectors of perturbations and compute the linearized hydrodynamic transport coefficients up to the third order in gradient expansion. We also determine the radius of convergence of the hydrodynamic mode in spin-1 sector and the lowest non-hydrodynamic modes in spin-2 sector. Analytically, we find that all the hydrodynamic quantities have the same critical exponent near the critical pointθ=1/2. Moreover, we establish a relation between symmetry enhancement of the underlying theory and vanishing the only third order hydrodynamic transport coefficientθ1, which appears in the shear dispersion relation of a conformal theory on a flat background.

We present five-loop results for the renormalization of various models with a cubic interaction (ind=6??εdimensions). For the scalar model and itsO(n)-symmetric extension we provide renormalization constants, anomalous dimensions and critical exponents. We discuss in detail the method of calculation, and provide all counterterms up to five loops. This allows one to consider generalizations of the?3theory to other symmetries.

We compute theO(1/N3)correction to the critical exponentηin the chiral XY or chiral Gross-Neveu model ind-dimensions. As the leading order vertex anomalous dimension vanishes, the direct application of the largeNconformal bootstrap formalism is not immediately possible. To circumvent this we consider the more general Nambu-Jona-Lasinio model for a general non-abelian Lie group. Taking the abelian limit of the exponents of this model produces those of the chiral XY model. Subsequently we provide improved estimates forηin the three dimensional chiral XY model for various values ofN.

We consider manifestly crossing symmetric dispersion relations for Mellin amplitudes of scalar four point correlators in conformal field theories (CFTs). This allows us to set up the non-perturbative Polyakov bootstrap for CFTs in Mellin space on a firm foundation, thereby fixing the contact term ambiguities in the crossing symmetric blocks. Our new approach employs certain "locality" constraints replacing the requirement of crossing symmetry in the usual fixed-tdispersion relation. Using these constraints we show that the sum rules based on the two channel dispersion relations and the present dispersion relations are identical. Our framework allows us to connect with the conceptually rich picture of the Polyakov blocks being Witten diagrams in anti-de Sitter (AdS) space. We also give two sided bounds for Wilson coefficients for effective field theories in AdS space.

We consider the genus-one curves which arise in the cuts of the sunrise and in the elliptic double-box Feynman integrals. We compute and compare invariants of these curves in a number of ways, including Feynman parametrization, lightcone and Baikov (in full and loop-by-loop variants). We find that the same geometry for the genus-one curves arises in all cases, which lends support to the idea that there exists an invariant notion of genus-one geometry, independent on the way it is computed. We further indicate how to interpret some previous results which found that these curves are related by isogenies instead.

In this paper we study shells of matter and black holes on the expanding bubbles realizing de Sitter space, that were proposed in arXiv:1807.01570. The explicit solutions that we find for the black holes, can also be used to construct Randall-Sundrum braneworld black holes in four dimensions.

We continue unfolding the dynamics associated with the nonrelativistic string sigma models over a class ofU(1)Galilean geometries. We start by exploring further on the generalisation of spinning string solutions in theSU(1,2|3)Spin-Matrix theory (SMT) limit of type IIB (super)strings inAdS5?S5. In particular, we explore nonrelativistic string solutions in various subsectors ofSU(1,2|3)SMT strings that correspond to different spin groups (Gs) and satisfy the respective BPS bounds. In the second part of the paper, we carry out an explicit analysis on rotating string solutions in the light of recently proposed SMT limits \cite{Harmark:2020vll}. We explore newly constructedSU(2|3),SU(1,1)andSU(1,2|3)SMT limits of strings and estimate the leading order stringy (strong coupling) corrections near the respective BPS bounds.

We study topological defect lines in two character rational conformal field theories. Among them one set of two character theories are commutant pairs inE8,1conformal field theory. Using these defect lines we construct defect partition function in theE8theory. We find that the defects preserve only a part of theE8current algebra symmetry. We also determine the defect partition function inc=24CFT using these defects lines of 2 character theories and we find that these defects preserve all current algebra symmetries ofc=24CFT.