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Sedigheh Deldar

Publications and source records attributed to Sedigheh Deldar.

At least 19 recordsLinked to original sources
arXiv2023

SU($2$) string tension in the continuum limit using an effective theory of center vortices

Using an effective theory for an ensemble of center vortices, we observe the area law fall-off in the continuum limit for the SU($2$) gauge group in three-dimensional Euclidean space-time. The string tension is obtained in terms of the intrinsic properties of the vortices and a parameter which describes their interactions. In addition, fitting our analytical results on lattice data, we show that the repulsive force between the vortices increases with temperature. This behavior is expected due to the reduction of vortex configuration at higher temperatures, required for the deconfinement regime.

hep-ph↗
arXiv2022

Introducing vortices in the continuum using direct and indirect methods

Inspired by direct and indirect maximal center gauge methods which confirm the existence of vortices in lattice calculations and by using the connection formalism, we show that under some appropriate gauge transformations vortices and chains appear in the QCD vacuum of the continuum limit. In the direct method, by applying center gauge transformation and \textquotedblleft center projection,\textquotedblright QCD is reduced to a gauge theory including vortices, which corresponds to the non-trivial first homotopy group $Π_1\left( \text{SO}(3)\right) =Z_2.$ On the other hand, using the indirect method, in addition to the center gauge transformation and \textquotedblleft center projection,\textquotedblright an initial step called Abelian gauge transformation and then Abelian projection are applied. Therefore, instead of single vortices, chains that contain monopoles and vortices appear in the theory.

hep-lat↗
arXiv2021

Detection of monopoles and vortices in SU(2) Yang-Mills theory

Motivated by the correlated monopoles and vortices observed in lattice QCD, using Cho decomposition method and two successive gauge transformations which lead to the observation of configurations that include both monopoles and center vortices simultaneously, we obtain a Lagrangian density that explicitly indicates these two magnetic defects and the interaction between them.

hep-th↗
arXiv2021

Influence of Fermions on Vortices in SU(2)-QCD

Gauge fields control the dynamics of fermions, also a back reaction of fermions on the gauge field is expected. This back reaction is investigated within the vortex picture of the QCD vacuum. We show that the center vortex model reproduces the string tension of the full theory also with the presence of fermionic fields.

hep-lat↗
arXiv2019

The far field limit profile functions of two overlapped dyons

We study the profile functions of two overlapped dyons at infinity. We assume that the superposition of two dyons satisfies Yang-Mills (Y-M) equation and then we find new equations of motion for individual dyons which do not satisfy the original Y-M equation, anymore. By solving these new equations, we find out that the profile functions of two overlapped dyons of the same type at infinity, looks like the profile functions of one dyon. However, the superposition of two dyons of different types gives trivial holonomy and therefore no contribution in the confinement phase is observed.

hep-th↗
arXiv2019

Cho decomposition, Abelian gauge fixing and monopoles in G(2) Yang-Mills theory

By extending the Cho decomposition method to G(2) gauge group, monopoles of this group are studied. Since SU(2) and SU(3) are subgroups of G(2), discussions are done mostly based on these subgroups of G(2). A direct relation between root vectors of G(2) and the associated magnetic charges is presented by group theoretical issues. In addition, G(2) monopoles are obtained by an Abelian gauge fixing method, and it is shown that the results agree with the ones we obtain by the Cho decomposition method.

hep-ph↗
arXiv2018

The Interaction of Two Dyons in The Near Field Limit

We study the interaction of two dyons in the region of their cores where they are non-linear and non-Abelian. We assume the superposition of two dyons as a solution of the equation of motion. The terms due to the non-linearity of the strength tensor are considered as the perturbation terms which deforms the profile function of two individual dyons. As a result, the profile function of dyons are obtained to be dependent on the polar angle and the spherical symmetry is lost.

hep-th↗
arXiv2017

Interacting dyon ensemble and confinement by particle mesh Ewald's method

The free energy of a static quark-antiquark pair is obtained in an interacting dyon ensemble near the deconfinement temperature. Comparing the results with the noninteracting case, we observe that the string tension between the quark-antiquark pair increases for the interacting ensemble. As a result, the confinement temperature decreases.

hep-ph↗
arXiv2017

Correlations between Abelian Monopoles and center vortices

We study the correlations between center vortices and Abelian monopoles for SU($3$) gauge group. Combining fractional fluxes of monopoles, center vortex fluxes are constructed in the thick center vortex model. Calculating the potentials induced by fractional fluxes constructing the center vortex flux in a thick center vortex-like model and comparing with the potential induced by center vortices, we observe an attraction between fractional fluxes of monopoles constructing the center vortex flux. We conclude that the center vortex flux is stable, as expected. In addition, we show that adding a contribution of the monopole-antimonopole pairs in the potentials induced by center vortices ruins the Casimir scaling at intermediate regime.

hep-ph↗
arXiv2016

Particle Mesh Ewald's Method and Non-Interacting Dyon Gas

We study the free energy of a quark-antiquark pair near the deconfinement temperature by particle mesh Ewald's method for non-interacting dyon ensemble. We show that the free energy of the quark-antiquark pair increases linearly by increasing the distance between them. The string tension decreases by increasing the temperature, as expected.

hep-lat↗
arXiv2016

Monopole-center vortex chains in $SU(2)$ gauge theory

We study the relation between center vortex fluxes and monopole fluxes for $SU(2)$ gauge group in a model. This model is the same as thick center vortex model but we use monopole-antimonopole configurations instead of center vortices in the vacuum. Monopole-antimonopole configurations are line-like similar to center vortices. The group factor and potential for the fundamental representation of these configurations are studied and compared with those of center vortices. As a result, we obtain monopole-vortex chains which appear in lattice Monte Carlo simulations, as well. If these monopole-vortex chains intersect the large Wilson loop in two points, screening is observed for the potential in the fundamental representation at large distances and confinement is observed when one leg of the chain intersects the Wilson loop.

hep-ph↗
arXiv2015

Partition Function of Interacting Calorons Ensemble

We present a method for computing the partition function of a caloron ensemble taking into account the interaction of calorons. We focus on caloron-Dirac string interaction and show that the metric that Diakonov and Petrov offered works well in the limit where this interaction occurs. We suggest computing the correlation function of two polyakov loops by applying Ewald's method.

hep-ph↗
arXiv2015

Center vortices as composites of monopole fluxes

We study the relation between the flux of a center vortex obtained from the center vortex model and the flux formed between monopoles obtained from the Abelian gauge fixing method. Motivated by the Monte Carlo simulations which have shown that almost all monopoles are sitting on the top of vortices, we construct the fluxes of center vortices for $SU(2)$ and $SU(3)$ gauge groups using fractional fluxes of monopoles. Then, we compute the potentials in the fundamental representation induced by center vortices and fractional fluxes of monopoles. We show that by combining the fractional fluxes of monopoles one can produce the center vortex fluxes for $SU(3)$ gauge group in a "center vortex model". Comparing the potentials, we conclude that the fractional fluxes of monopoles attract each other.

hep-ph↗
arXiv2015

Contributions of the center vortices and vacuum domain in potentials between static sources

In this paper, we study the role of the domain structure of the Yang Mills vacuum. The Casimir scaling and $N$-ality are investigated in the potentials between static sources in various representations for $SU(2)$ and $SU(3)$ gauge groups based on the domain structure model using square ansatz for angle $α_{C}(x)$. We also discuss about the contributions of the vacuum domain and center vortices in the static potentials. As a result, the potentials obtained from vacuum domains agree with Casimir scaling better than the ones obtained from center vortices. The reasons of these observations are investigated by studying the behavior of the potentials obtained from vacuum domains and center vortices and the properties of the group factors. Then, the vacuum domains in $SU(N)$ and $G(2)$ gauge groups are compared and we argue that the $G(2)$ vacuum is filled with center vortices of its subgroups.

hep-ph↗
arXiv2015

Appearance of vortices and monopoles in a decomposition of an SU(2) Yang-Mills field

We show how vortices can appear in the low energy limit of a pure SU(2) Yang-Mills theory as topological solitons. Motivated by Abelian dominance, we suppose that in the infrared regime of the SU(2) Yang-Mills theory, the field strength tensor can be obtained by multiplying two parts: $ G_{μν} $ and $ \textbf{n} $ such that $ \textbf{G}_{μν}=G_{μν} \textbf{n} $. The first part, $ G_{μν} $, is a space-time tensor and the second part, $ \textbf{n} $, is an isotriplet unit vector field which gives the Abelian direction at each space-time point. This leads to a decomposition for the SU(2) Yang-Mills field in the infrared regime. We show that vortices as well as monopoles can appear as a result of this decomposition where we have started with a pure Yang-Mills theory and we have ended up with a theory with an Abelian gauge field coupled to a scalar field. The effect of this scalar field on monopoles is also discussed.

hep-ph↗
arXiv2014

Abelian-Higgs model from Cho-Faddeev-Niemi decomposition

Applying Cho-Faddeev-Niemi decomposition for SU(2) Yang-Mills field, we obtain the Abelian-Higgs Lagrangian by some approximation. Abelian-Higgs Lagrangian with a spontaneous symmetry breaking potential has vortex solutions known as Nielsen-Olesen solutions. We conclude that vortices as well as magnetic monopoles can exist in Cho-Faddeev-Niemi decomposition of SU(2) Yang-Mills field.

hep-th↗
arXiv2014

Role of the SU($2$) and SU($3$) subgroups in observing confinement in the G($2$) gauge group

Applying the domain model to the G($2$) gauge group and the thick center vortex model to the SU($2$) and SU($3$) subgroups of G($2$), we calculate the potentials between static sources, as well as some parameters of the vortex profile. Comparing the results obtained from G($2$) and its subgroups, we argue that SU($2$) and SU($3$) gauge groups have important roles in observing confinement in the G($2$) gauge group.

hep-ph↗