scholarly journals Solidity without inhomogeneity: perfectly homogeneous, weakly coupled, UV-complete solids

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Angelo Esposito ◽  
Rafael Krichevsky ◽  
Alberto Nicolis
Keyword(s):  
Large Scale ◽  
Spontaneous Breaking ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Speed Of Light ◽  
Weakly Coupled ◽  
Low Energies ◽  
Renormalizable Theory ◽  
The One ◽  
Isotropic Solids

Abstract Solid-like behavior at low energies and long distances is usually associated with the spontaneous breaking of spatial translations at microscopic scales, as in the case of a lattice of atoms. We exhibit three quantum field theories that are renormalizable, Poincaré invariant, and weakly coupled, and that admit states that on the one hand are perfectly homogeneous down to arbitrarily short scales, and on the other hand have the same infrared dynamics as isotropic solids. All three examples presented here lead to the same peculiar solid at low energies, featuring very constrained interactions and transverse phonons that always propagate at the speed of light. In particular, they violate the well known $$ {c}_L^2>\frac{4}{3}{c}_T^2 $$ c L 2 > 4 3 c T 2 bound, thus showing that it is possible to have a healthy renormalizable theory that at low energies exhibits a negative bulk modulus (we discuss how the associated instabilities are absent in the presence of suitable boundary conditions). We do not know whether such peculiarities are unavoidable features of large scale solid-like behavior in the absence of short scale inhomogeneities, or whether they simply reflect the limits of our imagination.

Introduction to renormalization theory and renormalization group (RG)

2021 ◽  
pp. 185-219
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Field Theory ◽  
Renormalization Group ◽  
Short Distance ◽  
Large Scale ◽  
Relativistic Quantum ◽  
Power Counting ◽  
Fine Tuning ◽  
Quantum Field ◽  
Renormalizable Theory ◽  
Renormalization Theory

A straightforward construction of a local, relativistic quantum field theory (QFT) leads to ultraviolet (UV) divergences and a QFT has to be regularized by modifying its short-distance or large energy momentum structure (momentum regularization is often used in this work). Since such a modification is somewhat arbitrary, it is necessary to verify that the resulting large-scale predictions are, at least to a large extent, short-distance insensitive. Such a verification relies on the renormalization theory and the corresponding renormalization group (RG). In this chapter, the essential steps of a proof of the perturbative renormalizability of the scalar φ4 QFT in dimension 4 are described. All the basic difficulties of renormalization theory, based on power counting, are already present in this simple example. The elegant presentation of Callan is followed, which makes it possible to prove renormalizability and RG equations (in Callan–Symanzik's (CS) form) simultaneously. The background of the discussion is effective QFT and emergent renormalizable theory. The concept of fine tuning and the issue of triviality are emphasized.

BINDING ENERGIES IN WEAKLY COUPLED (2+1)-DIMENSIONAL QUANTUM FIELD THEORIES

1991 ◽  
Vol 06 (29) ◽  
pp. 2705-2711
Author(s):  
G. GAT ◽  
B. ROSENSTEIN
Keyword(s):  
Perturbation Theory ◽  
Binding Energy ◽  
Bound State ◽  
Binding Energies ◽  
Field Theories ◽  
General Question ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Weakly Coupled ◽  
Gross Neveu Model

We calculate the binding energy of the two-particle threshold bound state in the (2+1)-dimensional Gross-Neveu model. This model was recently shown to be renormalizable within the 1/N expansion. The binding energy is found to be ΔE=4mc-8Nf where m is the mass of the elementary fermion and Nf is the number of flavors. The general question of consistency of the perturbation theory within the framework of the Bethe-Salpeter equation is discussed.

BOUND STATE ENERGIES IN THE 1/N EXPANSION

1993 ◽  
Vol 08 (09) ◽  
pp. 1613-1628
Author(s):  
T. JAROSZEWICZ ◽  
P.S. KURZEPA
Keyword(s):  
Bound States ◽  
Symmetric Tensor ◽  
Bound State ◽  
Binding Energies ◽  
Field Theories ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Leading Order ◽  
3 Dimensional ◽  
Weakly Coupled

We derive and solve — in an arbitrary number of dimensions — Omnès-type equations for bound-state energies in weakly coupled quantum field theories. We show that, for theories defined in the 1/N expansion, these equations are exact to leading order in 1/N. We derive and discuss the weak coupling and nonrelativistic limits of the Omnès equations. We then calculate the binding energies and effective bound-state couplings in (1+1), (1+2) and (1+3)-dimensional O(N)-invariant ϕ4 theory. We consider both the scalar and symmetric tensor bound states.

scholarly journals Locality and General Vacua in Quantum Field Theory

2021 ◽  
Author(s):  
Daniele Colosi ◽  
◽  
Robert Oeckl ◽  
◽  
◽  
...  
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Hilbert Space ◽  
Vacuum State ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Algebraic Quantum ◽  
Particle Pairs ◽  
The One ◽  
Gns Construction

We extend the framework of general boundary quantum field theory (GBQFT) to achieve a fully local description of realistic quantum field theories. This requires the quantization of non-Kähler polarizations which occur generically on timelike hypersurfaces in Lorentzian spacetimes as has been shown recently. We achieve this in two ways: On the one hand we replace Hilbert space states by observables localized on hypersurfaces, in the spirit of algebraic quantum field theory. On the other hand we apply the GNS construction to twisted star-structures to obtain Hilbert spaces, motivated by the notion of reflection positivity of the Euclidean approach to quantum field theory. As one consequence, the well-known representation of a vacuum state in terms of a sea of particle pairs in the Hilbert space of another vacuum admits a vast generalization to non-Kähler vacua, particularly relevant on timelike hypersurfaces.

scholarly journals SUBFACTORS AND 1+1-DIMENSIONAL TQFTs

2007 ◽  
Vol 18 (01) ◽  
pp. 69-112 ◽  
Author(s):  
VIJAY KODIYALAM ◽  
VISHWAMBHAR PATI ◽  
V. S. SUNDER
Keyword(s):  
The Other ◽  
Field Theories ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Planar Algebras ◽  
Topological Quantum ◽  
The One ◽  
Topological Quantum Field Theories

We construct a certain "cobordism category" [Formula: see text] whose morphisms are suitably decorated cobordism classes between similarly decorated closed oriented 1-manifolds, and show that there is essentially a bijection between (1+1-dimensional) unitary topological quantum field theories (TQFTs) defined on [Formula: see text], on the one hand, and Jones' subfactor planar algebras, on the other.

scholarly journals Global aspects of spaces of vacua

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Adar Sharon
Keyword(s):  
Closed Loop ◽  
Field Theories ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Strongly Coupled ◽  
Weakly Coupled

Abstract We study “vacuum crossing”, which occurs when the vacua of a theory are exchanged as we vary some periodic parameter θ in a closed loop. We show that vacuum crossing is a useful non-perturbative tool to study strongly-coupled quantum field theories, since finding vacuum crossing in a weakly-coupled regime of the theory can lead to nontrivial consequences in the strongly-coupled regime. We start by discussing a mechanism where vacuum crossing occurs due to an anomaly, and then discuss some applications of vacuum crossing in general. In particular, we argue that vacuum crossing can be used to check IR dualities and to look for emergent IR symmetries.

scholarly journals NONCOMMUTATIVE THERMOFIELD DYNAMICS

2010 ◽  
Vol 25 (16) ◽  
pp. 3209-3220 ◽  
Author(s):  
MARCELO L. COSTA ◽  
AMILCAR R. QUEIROZ ◽  
ADEMIR E. SANTANA
Keyword(s):  
Field Theories ◽  
Effect Of Temperature ◽  
Integral Approach ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Point Function ◽  
Operator Formalism ◽  
Noncommutative Spaces ◽  
The One ◽  
Noncommutative Parameter

The real-time operator formalism for thermal quantum field theories, thermofield dynamics, is formulated in terms of a path-integral approach in noncommutative spaces. As an application, the two-point function for a thermal noncommutative λϕ4 theory is derived at the one-loop level. The effect of temperature and the noncommutative parameter, competing with one another, is analyzed.

θ–PHYSICS: 0–vacuum versus π–vacuum

2003 ◽  
Vol 18 (33n35) ◽  
pp. 2303-2310 ◽  
Author(s):  
M. Aguado ◽  
M. Asorey ◽  
D. García-Alvarez
Keyword(s):  
Symmetry Breaking ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Nodal Structure ◽  
First Order ◽  
Schrödinger Representation ◽  
Low Energies ◽  
Cp Symmetry

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.

ANOMALIES AT FINITE TEMPERATURE AND DENSITY

1994 ◽  
Vol 09 (09) ◽  
pp. 1423-1442 ◽  
Author(s):  
A. GÓMEZ NICOLA ◽  
R. F. ALVAREZ-ESTRADA
Keyword(s):  
Analytic Continuation ◽  
Finite Temperature ◽  
Arbitrary Number ◽  
Field Theories ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Zero Temperature ◽  
Functional Methods ◽  
Abelian Case ◽  
The One

Chiral anomalies for Abelian and non-Abelian quantum field theories at finite temperature and density (FTFD) are analyzed in detail in both imaginary and real time (IT and RT) formalisms. IT and RT triangle diagrams and IT functional methods (à la Fujikawa) are used at FTFD. The vector anomaly (the one regarding the lepton and baryon numbers) in the Weinberg–Salam theory, for an arbitrary number of fermion families, is also treated using IT functional methods at FTFD. In all cases, the expressions for the FTFD anomalies (as functions of the corresponding quantities) turn out to be identical to those at zero temperature and density, thereby extending previous results by various authors for the finite temperature and zero density case. Moreover, the independence of anomalies from temperature and density is shown to be consistent, at least in the Abelian case, with the analytic continuation from the IT formulation to the RT one.

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