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S. Teber

Publications and source records attributed to S. Teber.

At least 19 recordsLinked to original sources
arXiv2023

Critical properties of three-dimensional many-flavour QEDs

We review several variants of three-dimensional quantum electrodynamics (QED$_3$) with $N_f$ fermion (or boson) flavors including fermionic (or spinorial) QED$_3$, bosonic (or scalar) QED$_3$, $\mathcal{N}=1$ supersymmetric QED and also models of reduced QED (supersymmetric or not). We begin with an introduction to these models and their flow to a stable infra-red fixed point in the large-$N_f$ limit. We then present detailed state-of-the-art computations of the critical exponents of these models within the dimensional regularization (and reduction) scheme(s), at the next-to-leading order in the $1/N_f$ expansion and in an arbitrary covariant gauge. We finally discuss dynamical (matter) mass generation and the current status of our understanding of the phase structure of these models.

hep-th↗
arXiv2022

Electron mass anomalous dimension at $O(1/N_f^2)$ in three-dimensional $\mathcal{N}=1$ supersymmetric QED

We consider massless three-dimensional $\mathcal{N}=1$ supersymmetric quantum electrodynamics (QED) with $N_f$ flavours of electrons. Within the dimensional reduction scheme, we compute the critical exponents corresponding to both the electron and selectron field and (parity-even) mass anomalous dimensions at the next-to-leading order in the $1/N_f$ expansion and in an arbitrary covariant gauge. The equality of the gauge-invariant mass anomalous dimensions of the electron and the selectron is found to result from a subtle role played by the epsilon-scalars. Our general framework also allows us to compute the critical exponents of pure scalar QED and to recover known results in the case of spinor QED. An application of our results to dynamical (s)electron mass generation is considered. We find evidence that, while dynamical flavor symmetry breaking occurs in spinor QED, both pure scalar QED and supersymmetric QED remain in an interacting conformal phase.

hep-th↗
arXiv2022

Flat polymerized membranes at three-loop order

In this conference report, we present a recent field theoretic renormalization group analysis of flat polymerized membranes at three-loop order by the present authors [Phys. Rev. E 105, L012603 (2022)].

cond-mat.stat-mech↗
arXiv2021

Three-loop order approach to flat polymerized membranes

We derive the three-loop order renormalization group equations that describe the flat phase of polymerized membranes within the modified minimal subtraction scheme, following the pioneering one-loop order computation of Aronovitz and Lubensky [Phys. Rev. Lett. 60, 2634 (1988)] and the recent two-loop order one of Coquand, Mouhanna and Teber [Phys. Rev. E 101, 062104 (2020)]. We analyze the fixed points of these equations and compute the associated field anomalous dimension $\eta$ at three-loop order. Our results display a marked proximity with those obtained using nonperturbative techniques and reexpanded in powers of $\epsilon=4-D$. Moreover, the three-loop order value that we get for $\eta$ at the stable fixed point, $\eta=0.8872$, in $D=2$, is compatible with known theoretical results and within the range of accepted numerical values.

cond-mat.stat-mech↗
arXiv2021

Two-loop mass anomalous dimension in reduced quantum electrodynamics and application to dynamical fermion mass generation

We consider reduced quantum electrodynamics (RQED$_{d_\gamma,d_e}$) a model describing fermions in a $d_e$-dimensional space-time and interacting via the exchange of massless bosons in $d_\gamma$-dimensions ($d_e \leq d_\gamma$). We compute the two-loop mass anomalous dimension, $\gamma_m$, in general RQED$_{4,d_e}$ with applications to RQED$_{4,3}$ and QED$_4$. We then proceed on studying dynamical (parity-even) fermion mass generation in RQED$_{4,d_e}$ by constructing a fully gauge-invariant gap equation for RQED$_{4,d_e}$ with $\gamma_m$ as the only input. This equation allows for a straightforward analytic computation of the gauge-invariant critical coupling constant, $\alpha_c$, which is such that a dynamical mass is generated for $\alpha_r > \alpha_c$, where $\alpha_r$ is the renormalized coupling constant, as well as the gauge-invariant critical number of fermion flavours, $N_c$, which is such that $\alpha_c \rightarrow \infty$ and a dynamical mass is generated for $N < N_c$. For RQED$_{4,3}$, our results are in perfect agreement with the more elaborate analysis based on the resolution of truncated Schwinger-Dyson equations at two-loop order. In the case of QED$_4$, our analytical results (that use state of the art five-loop expression for $\gamma_m$) are in good quantitative agreement with those obtained from numerical approaches.

hep-th↗
arXiv2021

$\mathcal{N}=1$ supersymmetric three-dimensional QED in the large-$N_f$ limit and applications to super-graphene

We study $\mathcal{N}=1$ supersymmetric three-dimensional Quantum Electrodynamics with $N_f$ two-component fermions. Due to the infra-red (IR) softening of the photon, $\ep$-scalar and photino propagators, the theory flows to an interacting fixed point deep in the IR, $p_E \ll e^2 N_f/8$, where $p_E$ is the euclidean momentum and $e$ the electric charge. At next-to-leading order in the $1/N_f$-expansion, we find that the flow of the dimensionless effective coupling constant $\overline{\al}$ is such that: $\overline{\al} \ra 8/\big(N_f \,(1+C/N_f)\big) \approx (8/N_f)(1-0.4317/N_f)$ where $C= 2\,(12-\pi^2)/\pi^2$. Hence, the non-trivial IR fixed point is stable with respect to quantum corrections. Various properties of the theory are explored and related via a mapping to the ones of a $\mathcal{N}=1$ model of super-graphene. In particular, we derive the interaction correction coefficient to the optical conductivity of super-graphene, $C_{\rm sg} = (12-\pi^2)/(2\pi) = 0.3391$, which is six times larger than in the non-supersymmetric case, $C_{\rm g} = (92-9\pi^2)/(18\pi) = 0.0561$.

hep-th↗
arXiv2020

Four-loop singularities of the massless fermion propagator in quenched three-dimensional QED

We calculate the three- and four-loop corrections to the massless fermion propagator in three-dimensional quenched Quantum Electrodynamics with four-component fermions. The three-loop correction is finite and gauge invariant but the four-loop one has singularities except in the Feynman gauge where it is also finite. Our results explicitly show that, up to four loops, gauge-dependent terms are completely determined by lower order ones in agreement with the Landau-Khalatnikov-Fradkin transformation.

hep-th↗
arXiv2020

Landau-Khalatnikov-Fradkin transformation in three-dimensional quenched QED

We study the gauge-covariance of the massless fermion propagator in three-dimensional quenched Quantum Electrodynamics in the framework of dimensional regularization in d=3-2\ep. Assuming the finiteness of the quenched perturbative expansion, that is the existence of the limit \ep \to 0, we state that, exactly in d=3, all odd perturbative coefficients, starting with the third order one, should be zero in any gauge.

hep-th↗
arXiv2020

The flat phase of polymerized membranes at two-loop order

We investigate two complementary field-theoretical models describing the flat phase of polymerized - phantom - membranes by means of a two-loop, weak-coupling, perturbative approach performed near the upper critical dimension $D_{uc}=4$, extending the one-loop computation of Aronovitz and Lubensky [Phys. Rev. Lett. 60, 2634 (1988)]. We derive the renormalization group equations within the modified minimal substraction scheme, then analyze the corrections coming from two-loop with a particular attention paid to the anomalous dimension and the asymptotic infrared properties of the renormalization group flow. We finally compare our results to those provided by nonperturbative techniques used to investigate these two models.

cond-mat.stat-mech↗
arXiv2019

Landau-Khalatnikov-Fradkin transformation and hatted zeta-values

We show an exact formula obtained in [1], which relates hatted and standard zeta-values to all orders of perturbation theory. The formula is based on the Landau-Khalatnikov-Fradkin (LKF) transformation between the massless propagators of charged particles interacting with gauge fields, in two different gauges.

hep-th↗
arXiv2019

Landau-Khalatnikov-Fradkin transformation of the fermion propagator in massless reduced QED

We study the gauge-covariance of the massless fermion propagator in reduced Quantum Electrodynamics (QED). Starting from its value in some gauge, we evaluate an all order expression for it in another gauge by means of the Landau-Khalatnikov-Fradkin transformation. We find that the weak coupling expansions thus derived are in perfect agreement with the exact calculations. We also prove that the fermion anomalous dimension of reduced QED is gauge invariant to all orders of perturbation theory except for the first one.

hep-th↗
arXiv2019

Landau-Khalatnikov-Fradkin transformation and the mystery of even $\zeta$-values in Euclidean massless correlators

The Landau-Khalatnikov-Fradkin (LKF) transformation is a powerful and elegant transformation allowing to study the gauge dependence of the propagator of charged particles interacting with gauge fields. With the help of this transformation, we derive a non-perturbative identity between massless propagators in two different gauges. From this identity, we find that the corresponding perturbative series can be exactly expressed in terms of a hatted transcendental basis that eliminates all even Euler $\zeta$-functions. This explains the mystery of even $\zeta$-values observed in multi-loop calculations of Euclidean massless correlators for almost three decades now. Our construction further allows us to derive an exact formula relating hatted and standard $\zeta$-functions to all orders of perturbation theory.

hep-th↗
arXiv2019

Addendum to "Critical behaviour of ($2+1$)-dimensional QED: $1/N_f$-corrections in an arbitrary non-local gauge"

Dynamical chiral symmetry breaking (D$\chi$SB) is studied within ($2+1$)-dimensional QED with $N$ four-component fermions. The leading and next-to-leading orders of the $N$ expansion were computed exactly in Refs.~[\onlinecite{Gusynin:2016som,Kotikov:2016prf}] in an arbitrary non-local gauge. In this addendum to [\onlinecite{Kotikov:2016prf}], we show that the resummation of the wave-function renormalization constant at the level of the gap equation yields a {\it complete} cancellation of the gauge dependence of the critical fermion flavour number resulting in: $N_c= 2.8469$, which is such that D$\chi$SB takes place for $N<N_c$. The result is in full agreement with one of Ref.~[\onlinecite{Gusynin:2016som}].

hep-th↗
arXiv2018

Field theoretic study of electron-electron interaction effects in Dirac liquids

The aim of this habilitation thesis is to present recent results, obtained during the period 2012-2017, related to interaction effects in condensed matter physics systems such as planar Dirac liquids, e.g., graphene and graphene-like systems, the surface states of some topological insulators and possibly half-filled fractional quantum Hall systems (for their Dirac composite fermions). These liquids are characterized by gapless bands, strong electron-electron interactions and emergent Lorentz invariance deep in the infra-red. We address a number of important issues raised by experiments on these systems covering subjects of wide current interest in low-energy (condensed matter) as well as high-energy (particle) physics. We shall consider in particular the subtle influence of interactions on transport properties and their supposedly crucial influence on a potential dynamical mass generation. The resolution of these problems will guide us from the thorough examination of the perturbative structure of gauge field theories to the development and application of non-perturbative approaches known from quantum electro/chromo-dynamics to address strong coupling issues.

cond-mat.mes-hall↗
arXiv2018

Multi-loop techniques for massless Feynman diagram calculations

We review several multi-loop techniques for analytical massless Feynman diagram calculations in relativistic quantum field theories: integration by parts, the method of uniqueness, functional equations and the Gegenbauer polynomial technique. A brief, historically oriented, overview of some of the results obtained over the decades for the massless 2-loop propagator-type diagram is given. Concrete examples of up to $5$-loop diagram calculations are also provided.

hep-th↗
arXiv2018

Field theoretic renormalization study of interaction corrections to the universal ac conductivity of graphene

The two-loop interaction correction coefficient to the universal ac conductivity of disorder-free intrinsic graphene is computed with the help of a field theoretic renormalization study using the BPHZ prescription. Non-standard Ward identities imply that divergent subgraphs (related to Fermi velocity renormalization) contribute to the renormalized optical conductivity. Proceeding either via density-density or via current-current correlation functions, a single well-defined value is obtained: $\mathcal{C}= (19-6\pi)/12) = 0.01$ in agreement with the result first obtained by Mishchenko and which is compatible with experimental uncertainties.

cond-mat.mes-hall↗
arXiv2018

Field theoretic renormalization study of reduced quantum electrodynamics and applications to the ultra-relativistic limit of Dirac liquids

The field theoretic renormalization study of reduced quantum electrodynamics (QED) is performed up to two loops. In the condensed matter context, reduced QED constitutes a very natural effective relativistic field theory describing (planar) Dirac liquids, e.g., graphene and graphene-like materials, the surface states of some topological insulators and possibly half-filled fractional quantum Hall systems. From the field theory point of view, the model involves an effective (reduced) gauge field propagating with a fractional power of the d'Alembertian in marked contrast with usual QEDs. The use of the BPHZ prescription allows for a simple and clear understanding of the structure of the model. In particular, in relation with the ultra-relativistic limit of graphene, we straightforwardly recover the results for both the interaction correction to the optical conductivity: $\mathcal{C}^*=(92-9\pi^2)/(18\pi)$ and the anomalous dimension of the fermion field: $\gamma_{\psi}(\bar{\alpha},\xi) = 2 \bar{\alpha}\,(1-3\xi)/3 -16\,\left( \zeta_2 N_F + 4/27 \right)\, \bar{\alpha}^2 + O(\bar{\alpha}^3)$, where $\bar{\alpha} = e^2/(4\pi)^2$ and $\xi$ is the gauge-fixing parameter.

hep-th↗