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Joseph Ben Geloun

Publications and source records attributed to Joseph Ben Geloun.

At least 55 records · Page 3Linked to original sources
arXiv2013

Counting Tensor Model Observables and Branched Covers of the 2-Sphere

Lattice gauge theories of permutation groups with a simple topological action (henceforth permutation-TFTs) have recently found several applications in the combinatorics of quantum field theories (QFTs). They have been used to solve counting problems of Feynman graphs in QFTs and ribbon graphs of large $N$, often revealing inter-relations between different counting problems. In another recent development, tensor theories generalizing matrix theories have been actively developed as models of random geometry in three or more dimensions. Here, we apply permutation-TFT methods to count gauge invariants for tensor models (colored as well as non-colored), exhibiting a relationship with counting problems of branched covers of the 2-sphere, where the rank $d$ of the tensor gets related to a number of branch points. We give explicit generating functions for the relevant counting and describe algorithms for the enumeration of the invariants. As well as the classic count of Hurwitz equivalence classes of branched covers with fixed branch points, collecting these under an equivalence of permuting the branch points is relevant to the color-symmetrized tensor invariant counting. We also apply the permutation-TFT methods to obtain some formulae for correlators of the tensor model invariants.

hep-th↗
arXiv2013

The finite and large-$N$ behaviors of independent-value matrix models

We investigate the finite and large $N$ behaviors of independent-value O(N)-invariant matrix models. These are models defined with matrix-type fields and with no gradient term in their action. They are generically nonrenormalizable but can be handled by nonperturbative techniques. We find that the functional of any O(N) matrix trace invariant may be expressed in terms of an O(N)-invariant measure. Based on this result, we prove that, in the limit that all interaction coupling constants go to zero, any interacting theory is continuously connected to a pseudo-free theory. This theory differs radically from the familiar free theory consisting in putting the coupling constants to zero in the initial action. The proof is given for generic finite-size matrix models, whereas, in the limiting case $N\rightarrow\infty$, we succeed in showing this behavior for restricted types of actions using a particular scaling of the parameters.

hep-th↗
arXiv2013

Renormalizable Models in Rank $d\geq 2$ Tensorial Group Field Theory

Classes of renormalizable models in the Tensorial Group Field Theory framework are investigated. The rank $d$ tensor fields are defined over $d$ copies of a group manifold $G_D=U(1)^D$ or $G_D= SU(2)^D$ with no symmetry and no gauge invariance assumed on the fields. In particular, we explore the space of renormalizable models endowed with a kinetic term corresponding to a sum of momenta of the form $p^{2a}$, $a\in ]0,1]$. This study is tailored for models equipped with Laplacian dynamics on $G_D$ (case $a=1$) but also for more exotic nonlocal models in quantum topology (case $0<a<1$). A generic model can be written $(_{\dim G_D}Φ^{k}_{d}, a)$, where $k$ is the maximal valence of its interactions. Using a multi-scale analysis for the generic situation, we identify several classes of renormalizable actions including matrix model actions. In this specific instance, we find a tower of renormalizable matrix models parametrized by $k\geq 4$. In a second part of this work, we focus on the UV behavior of the models up to maximal valence of interaction $k =6$. All rank $d\geq 3$ tensor models proved renormalizable are asymptotically free in the UV. All matrix models with $k=4$ have a vanishing $β$-function at one-loop and, very likely, reproduce the same feature of the Grosse-Wulkenhaar model [Commun. Math. Phys. {\bf 256}, 305 (2004)].

hep-th↗
arXiv2013

Some classes of renormalizable tensor models

We identify new families of renormalizable of tensor models from anterior renormalizable tensor models via a mapping capable of reducing or increasing the rank of the theory without having an effect on the renormalizability property. Mainly, a version of the rank 3 tensor model as defined in [arXiv:1201.0176 [hep-th]], the Grosse-Wulkenhaar model in 4D and 2D generate three different classes of renormalizable models. The proof of the renormalizability is fully performed for the first reduced model. The same procedure can be applied for the remaining cases. Interestingly, we find that, due to the peculiar behavior of anisotropic wave function renormalizations, the rank 3 tensor model reduced to a matrix model generates a simple super-renormalizable vector model.

hep-th↗
arXiv2013

Topos Analogues of the KMS State

We identify the analogues of KMS state in topos theory. Topos KMS states can be viewed as classes of truth objects associated with a measure μ^ρ(in one-to-one correspondence with an original KMS state ρ) which satisfies topos condition analogues to the ordinary KMS conditions. Topos KMS states can be defined both externally or internally according to whether the automorphism group of geometric morphisms acts externally on the topos structure, or the automorphism group is an object in the topos itself, in which case, it acts internally. We illustrate the formalism by a simple example on the Hilbert space $\Cl^3$.

math-ph↗
arXiv2012

On terminal forms for topological polynomials for ribbon graphs: The $N$-petal flower

The Bollobas-Riordan polynomial [Math. Ann. 323, 81 (2002)] extends the Tutte polynomial and its contraction/deletion rule for ordinary graphs to ribbon graphs. Given a ribbon graph $\cG$, the related polynomial should be computable from the knowledge of the terminal forms of $\cG$ namely specific induced graphs for which the contraction/deletion procedure becomes more involved. We consider some classes of terminal forms as rosette ribbon graphs with $N\ge 1$ petals and solve their associate Bollobas-Riordan polynomial. This work therefore enlarges the list of terminal forms for ribbon graphs for which the Bollobas-Riordan polynomial could be directly deduced.

math.CO↗
arXiv2012

Enhanced Quantization: The particle on the circle

Enhanced quantization is an improved program for overcoming difficulties which may arise during an ordinary canonical quantization procedure. We review here how this program applies for a particle on circle.

math-ph↗
arXiv2012

Two and four-loop $β$-functions of rank 4 renormalizable tensor field theories

A recent rank 4 tensor field model generating 4D simplicial manifolds has been proved to be renormalizable at all orders of perturbation theory [arXiv:1111.4997 [hep-th]]. The model is built out of $ϕ^6$ ($ϕ^6_{(1/2)}$), $ϕ^4$ ($ϕ^4_{(1)}$) interactions and an anomalous term ($ϕ^4_{(2)}$). The $β$-functions of this model are evaluated at two and four loops. We find that the model is asymptotically free in the UV for both the main $ϕ^6_{(1/2)}$ interactions whereas it is safe in the $ϕ^4_{(1)}$ sector. The remaining anomalous term turns out to possess a Landau ghost.

hep-th↗
arXiv2012

3D Tensor Field Theory: Renormalization and One-loop $β$-functions

We prove that the rank 3 analogue of the tensor model defined in [arXiv:1111.4997 [hep-th]] is renormalizable at all orders of perturbation. The proof is given in the momentum space. The one-loop $γ$- and $β$-functions of the model are also determined. We find that the model with a unique coupling constant for all interactions and a unique wave function renormalization is asymptotically free in the UV.

hep-th↗
arXiv2012

Enhanced quantization on the circle

We apply the quantization scheme introduced in [arXiv:1204.2870] to a particle on a circle. We find that the quantum action functional restricted to appropriate coherent states can be expressed as the classical action plus $\hbar$-corrections. This result extends the examples presented in the cited paper.

math-ph↗
arXiv2012

A Renormalizable 4-Dimensional Tensor Field Theory

We prove that an integrated version of the Gurau colored tensor model supplemented with the usual Bosonic propagator on $U(1)^4$ is renormalizable to all orders in perturbation theory. The model is of the type expected for quantization of space-time in 4D Euclidean gravity and is the first example of a renormalizable model of this kind. Its vertex and propagator are four-stranded like in 4D group field theories, but without gauge averaging on the strands. Surprisingly perhaps, the model is of the $ϕ^6$ rather than of the $ϕ^4$ type, since two different $ϕ^6$-type interactions are log-divergent, i.e. marginal in the renormalization group sense. The renormalization proof relies on a multiscale analysis. It identifies all divergent graphs through a power counting theorem. These divergent graphs have internal and external structure of a particular kind called melonic. Melonic graphs dominate the 1/N expansion of colored tensor models and generalize the planar ribbon graphs of matrix models. A new locality principle is established for this category of graphs which allows to renormalize their divergences through counterterms of the form of the bare Lagrangian interactions. The model also has an unexpected anomalous log-divergent $(\int ϕ^2)^2$ term, which can be interpreted as the generation of a scalar matter field out of pure gravity.

hep-th↗
arXiv2012

Coherent states for continuous spectrum operators with non-normalizable fiducial states

The problem of building coherent states from non-normalizable fiducial states is considered. We propose a way of constructing such coherent states by regularizing the divergence of the fiducial state norm. Then, we successfully apply the formalism to particular cases involving systems with a continuous spectrum: coherent states for the free particle and for the inverted oscillator $(p^2 - x^2)$ are explicitly provided. Similar ideas can be used for other systems having non-normalizable fiducial states.

math-ph↗
arXiv2011

Classical Group Field Theory

The ordinary formalism for classical field theory is applied to dynamical group field theories. Focusing first on a local group field theory over one copy of SU(2) and, then, on more involved nonlocal theories (colored and non colored) defined over a tensor product of the same group, we address the issue of translation and dilatation symmetries and the corresponding Noether theorem. The energy momentum tensor and dilatation current are derived and their properties identified for each case.

hep-th↗
arXiv2011

Ward-Takahashi identities for the colored Boulatov model

Ward-Takahashi identities of the colored Boulatov model are derived using a generic unitary field transformation. In a specific instance, this generic transformation turns out to be a symmetry of the interaction so that particular classes of reduced Ward-Takahashi identities for that symmetry are consequently identified and interpreted.

hep-th↗
arXiv2011

Radiative corrections in the Boulatov-Ooguri tensor model: The 2-point function

The Boulatov-Ooguri tensor model generates a sum over spacetime topologies for the $D$-dimensional BF theory. We study here the quantum corrections to the propagator of the theory. In particular, we find that the radiative corrections at the second order in the coupling constant yield a mass renormalization. They also exhibit a divergence which cannot be balanced with a counter-term in the initial action, and which usually corresponds to the wave-function renormalization.

hep-th↗
arXiv2010

Asymptotes in SU(2) Recoupling Theory: Wigner Matrices, $3j$ Symbols, and Character Localization

In this paper we employ a novel technique combining the Euler Maclaurin formula with the saddle point approximation method to obtain the asymptotic behavior (in the limit of large representation index $J$) of generic Wigner matrix elements $D^{J}_{MM'}(g)$. We use this result to derive asymptotic formulae for the character $χ^J(g)$ of an SU(2) group element and for Wigner's $3j$ symbol. Surprisingly, given that we perform five successive layers of approximations, the asymptotic formula we obtain for $χ^J(g)$ is in fact exact. This result provides a non trivial example of a Duistermaat-Heckman like localization property for discrete sums.

math-ph↗
arXiv2010

EPRL/FK Group Field Theory

The purpose of this short note is to clarify the Group Field Theory vertex and propagators corresponding to the EPRL/FK spin foam models and to detail the subtraction of leading divergences of the model.

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