Families Of Quantum Field Theories Research Articles

Dipole symmetry breaking and fractonic Nambu-Goldstone mode

We introduce a family of quantum field theories for fields carrying monopole and dipole charges. In contrast to previous realizations, fields have quadratic two-derivative kinetic terms. The dipole symmetry algebra is realized in a discretized internal space and connected to the physical space through a background gauge field. We study spontaneous symmetry breaking of dipole symmetry in 1+1 dimensions in a large-NN limit. The trivial classical vacuum is lifted by quantum corrections into a vacuum which breaks dipole symmetry while preserving monopole charge. By means of a Hubbard-Stratonovich transformation, heat-kernel and large-NN techniques, we compute the effective action for the low-energy modes. We encounter a fractonic immobile Nambu-Goldstone mode whose dispersion characteristics avoid Coleman-Hohenberg-Mermin-Wagner theorem independently of the large-NN limit.

Modular invariance and uniqueness of Toverline{T} deformed CFT

Any two dimensional quantum field theory that can be consistently defined on a torus is invariant under modular transformations. In this paper we study families of quantum field theories labeled by a dimensionful parameter t, that have the additional property that the energy of a state at finite t is a function only of t and of the energy and momentum of the corresponding state at t = 0, where the theory becomes conformal. We show that under this requirement, the partition sum of the theory at t = 0 uniquely determines the partition sum (and thus the spectrum) of the perturbed theory, to all orders in t, to be that of a Toverline{T} deformed CFT. Non-perturbatively, we find that for one sign of t (for which the energies are real) the partition sum is uniquely determined, while for the other sign we find non-perturbative ambiguities. We characterize these ambiguities and comment on their possible relations to holography.

Finite cutoff AdS5 holography and the generalized gradient flow

Recently proposed double trace deformations of large N holographic CFTs in four dimensions define a one parameter family of quantum field theories, which are interpreted in the bulk dual as living on successive finite radius hypersurfaces. The transformation of variables that turns the equation defining the deformation of a four dimensional large N CFT by such operators into the expression for the radial ADM Hamiltonian in the bulk is found.This prescription clarifies the role of various functions of background fields that appear in the flow equation defining the deformed holographic CFT, and also their relationship to the holographic anomaly.The effect of these deformations can also be seen as triggering a generalized gradient flow for the fields of the induced gravity theory obtained from integrating out the fundamental fields of the holographic CFT. The potential for this gradient flow is found to resemble the two derivative effective action previously derived using holographic renormalization.

θ–PHYSICS: 0–vacuum versus π–vacuum

The behaviour of 0–vacuum and π–vacuum under CP symmetry is analyzed in two different families of quantum field theories: gauge theories in 4D and [Formula: see text] sigma models in 2D. In particular, the possibility of spontaneous CP symmetry breaking is analyzed by new continuum non-perturbative techniques. In the case of θ = 0–vacuum we find that the dependence of the vacuum energy density on θ around θ = 0 has not a first order cusp singularity, a missing requirement of the proof of the Vafa-Witten theorem. The result is based on the absence of Lee-Yang singularities for pure imaginary values of the θ–parameter. In the case of θ = π the result follows from the analysis of the nodal structure of the vacuum functional in the Schrödinger representation. The dynamics of both theories favors the localization of vacuum nodes at sphalerons instead of classical vacua as corresponds to parity even states. The existence of a dynamical level repulsion between parity even and parity odd states at low energies is the mechanism behind the absence of CP symmetry breaking in π–vacuum.

Free Bosons and Tau-Functions for Compact Riemann Surfaces and Closed Smooth Jordan Curves. Current Correlation Functions

We study families of quantum field theories of free bosons on a compact Riemann surface of genus g. For the case g > 0, these theories are parameterized by holomorphic line bundles of degree g − 1, and for the case g = 0 — by smooth closed Jordan curves on the complex plane. In both cases we define a notion of τ-function as a partition function of the theory and evaluate it explicitly. For the case g > 0 the τ-function is an analytic torsion, and for the case g = 0, the regularized energy of a certain natural pseudo-measure on the interior domain of a closed curve. For these cases we rigorously prove the Ward identities for the current correlation functions and determine them explicitly. For the case g > 0, these functions coincide with those obtained by using bosonization. For the case g = 0, the τ-function we have defined coincides with the τ-function introduced as a dispersionless limit of the Sato's τ-function for the two-dimensional Toda hierarchy. As a corollary of the Ward identities, we note some recent results on relations between conformal maps of exterior domains and τ-functions. For this case, we also define a Hermitian metric on the space of all contours of given area. As another corollary of the Ward identities, we prove that the introduced metric is Kahler and the logarithm of the τ-function is its Kahler potential.

DUAL GENERALIZATIONS OF SINE–GORDON FIELD THEORY AND INTEGRABILITY SUBMANIFOLDS IN PARAMETER SPACE

The dual relationship between two n-1 parameter families of quantum field theories based on extended complex numbers is investigated in two dimensions. The nonlocal conserved charges approach is used. The lowest rank affine Toda field theories are generated and identified as integrability submanifolds in parameter space. A truncation of the model leads to a conformal field theory in extended complex space. Depending on the projection over the usual complex space chosen, a parametrized central charge is calculated.

Dual generalizations of sine-Gordon field theory and integrability submanifolds in parameter space

The dual relationship between two n-1 parameter families of quantum field theories based on extended complex numbers is investigated in two dimensions. The non-local conserved charges approach is used. The lowest rank affine Toda field theories are generated and identified as integrability submanifolds in parameter space. A truncation of the model leads to a conformal field theory in extended complex space. Depending on the projection over usual complex space chosen, a parametrized central charge is calculated.

HIDDEN SYMMETRIES IN QUANTUM FIELD THEORIES FROM EXTENDED COMPLEX NUMBERS

The two-dimensional space–time sine–Gordon field theory is extended algebraically within the n-dimensional space of extended complex numbers. This field theory is constructed in terms of an adapted extension of standard vertex operators. A whole set of nonlocal conserved charges is constructed and studied in this framework. Thereby, an algebraic nonperturbative description is possible for this n-1 parameters family of quantum field theories. Known results are obtained for specific values of the parameters, especially in relation to affine Toda field theories. Different (dual)-models can then be described in this formalism.