We use effective string theory to study mesons with large spin $\textit{J}$ in large $\textit{N}$ QCD as rotating open strings. In the first part of this work, we formulate a consistent effective field theory (EFT) for open spinning strings with light quarks. Our EFT provides a consistent treatment of the endpoints’ singularities that arise in the massless limit. We obtain results, in a systematic 1/$\textit{J}$ expansion, for the spectrum of the leading and daughter Regge trajectories. Interestingly, we find that the redshift factor associated with the quarks’ acceleration implies that the applicability regime of the EFT is narrower compared to that of static flux tubes. In the second part of this work, we discuss several extensions of phenomenological interests, including mesons with heavy quarks, the quarks’ spin and the daughter Regge trajectories associated with the worldsheet axion, a massive string mode identified in lattice simulations of 4$\textit{d}$ flux tubes. We compare our predictions with 4$\textit{d}$ QCD spectroscopy data, and suggest potential $\textit{stringy}$ interpretations of the observed mesons. We finally comment on the relation between the EFT spectrum and the Axionic String Ansatz, a recently proposed characterization of the spectrum of Yang-Mills glueballs.

United States

Gabriel Cuomo

Sergei Dubovsky

Uruguay

Guzmán Hernández-Chifflet

Alexander Monin

Shahrzad Zare

The EFT of large spin mesons

Recent lattice results strongly support the Axionic String Ansatz (ASA) for quantum numbers of glueballs in 3D Yang-Mills theory. The ASA treats glueballs as closed bosonic strings. The corresponding worldsheet theory is a deformation of the minimal Nambu-Goto theory. In order to understand better the ASA strings and as a first step towards a perturbative calculation of the glueball mass splittings we compare the ASA spectrum to the closed effective string theory. Namely, we model glueballs as excitations around the folded rotating rod solution with a large angular momentum J. The resulting spectrum agrees with the ASA in the regime of validity of the effective theory, i.e., in the vicinity of the leading Regge trajectory. In particular, closed effective string theory correctly predicts that only glueballs of even spin J show up at the leading Regge trajectory. Interestingly though, the closed effective string theory overestimates the number of glueball states far above the leading Regge trajectory.

3D Yang-Mills glueballs vs closed effective strings

We consider the most general set of integrable deformations extending the <math><mrow><mi>T</mi><mover><mrow><mi>T</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> deformation of two-dimensional relativistic QFTs. They are CDD deformations of the theory’s factorized <math><mrow><mi>S</mi></mrow></math> matrix related to the higher-spin conserved charges. Using a mirror version of the generalized Gibbs ensemble, we write down the finite-volume expectation value of the higher-spin charges, and derive a generalized flow equation that every charge must obey under a generalized <math><mrow><mi>T</mi><mover><mrow><mi>T</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> deformation. This also reproduces the known flow equations on the nose.

Stefano Negro

Switzerland

Italy

Alessandro Sfondrini

Flow Equations for Generalized <math><mrow><mi>T</mi><mover><mrow><mi>T</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> Deformations

According to the Axionic String Ansatz (ASA) confining flux tubes in pure gluodynamics are in the same equivalence class as a new family of integrable non-critical strings, called axionic strings. In addition to translational modes, axionic strings carry a set of worldsheet axions transforming as an antisymmetric tensor under the group of transverse rotations. We initiate a study of integrable axionic strings at general number of space-time dimensions D. We show that in the infinite tension limit worldsheet axions should be described by a peculiar “pseudofree” theory — their S-matrix is trivial, but the corresponding action cannot be brought into a free form by a local field redefinition. This requirement fixes the axionic action to take a form of the O(D − 2) Wess-Zumino-Witten (WZW) model.

John Donahue

Sergey Monin

From QCD Strings to WZW

Lattice QCD simulations provide crucial information about the world sheet dynamics of confining strings (flux tubes). An accurate extraction of the world sheet <math><mi>S</mi></math>-matrix from lattice spectra requires accounting for polarization effects. Approximate integrability of the low energy world sheet theory makes it possible to apply the thermodynamic Bethe ansatz to incorporate polarization effects at all orders in the number of windings and at the leading order in the derivative expansion. However, a systematic application of this technique in the presence of nonintegrable effects and for multiparticle states becomes increasingly challenging. We point out that a recently understood equivalence between gravitational dressing and <math><mi>T</mi><mover><mi>T</mi><mo>¯</mo></mover></math> deformation provides a fully systematic and straightforward recipe to incorporate the leading polarization effects in the presence of an arbitrary inelasticity and for any number of particles. We illustrate this technique with several examples.

Chang Chen

Peter Conkey

Undressing confining flux tubes with <math><mi>T</mi><mover><mi>T</mi><mo>¯</mo></mover></math>

The  <math><mi>T</mi><mover><mi>T</mi><mo>¯</mo></mover></math> $$ T\overline{T} $$ deformation of a relativistic two-dimensional theory results in a solvable gravitational theory. Deformed scattering amplitudes can be obtained from coupling the undeformed theory to the flat space Jackiw-Teitelboim (JT) gravity. We show that the JT description is applicable and useful also in finite volume. Namely, we calculate the torus partition function of an arbitrary matter theory coupled to the JT gravity, formulated in the first order (vielbein) formalism. The first order description provides a natural set of dynamical clocks and rods for this theory, analogous to the target space coordinates in string theory. These dynamical coordinates play the role of relational observables allowing to define a torus path integral for the JT gravity. The resulting partition function is one-loop exact and reproduces the  <math><mi>T</mi><mover><mi>T</mi><mo>¯</mo></mover></math> $$ T\overline{T} $$ deformed finite volume spectrum.

Victor Gorbenko

<math><mi>T</mi><mover><mi>T</mi><mo>¯</mo></mover></math> $$ T\overline{T} $$ partition function from topological gravity

We put forward the Axionic String Ansatz (ASA), which provides a unified description for the worldsheet dynamics of confining strings in pure Yang-Mills theory both in D = 3 and D = 4 space-time dimensions. The ASA is motivated by the excitation spectrum of long confining strings, as measured on a lattice, and by recently constructed integrable axionic non-critical string models. According to the ASA, pure gluodynamics in 3D is described by a non-critical bosonic string theory without any extra local worldsheet degrees of freedom. We argue that this assumption fixes the set of quantum numbers (spins, P -and C -parities) of almost all glueball states. We confront the resulting predictions with the properties of approximately 1 2 + 2 2 + 3 2 + 5 2 = 39 lightest glueball states measured on a lattice and find a good agreement. On the other hand, the spectrum of low lying glueballs in 4D gluodynamics suggests the presence of a massive pseudoscalar mode on the string worldsheet, in agreement with the ASA and lattice data for long strings.

Canada

Yang-Mills glueballs as closed bosonic strings

We elaborate on the dynamics of ionized interstellar medium in the presence of hidden photon dark matter. Our main focus is the ultra-light regime, where the hidden photon mass is smaller than the plasma frequency in the Milky Way. We point out that as a result of the Galactic plasma shielding direct detection of ultra-light photons in this mass range is especially challenging. However, we demonstrate that ultra-light hidden photon dark matter provides a powerful heating source for the ionized interstellar medium. This results in a strong bound on the kinetic mixing between hidden and regular photons all the way down to the hidden photon masses of order 10−20 eV.