arXiv subjects

Neda Sadooghi

Publications and source records attributed to Neda Sadooghi.

10 recordsLinked to original sources

arXiv2009

Chiral MHD description of a perfect magnetized QGP using the effective NJL model in a strong magnetic field

To study the effect of a strong magnetic field $B$ on the sound velocity $v_{s}$ of plane waves propagating in a strongly magnetized quark-gluon plasma (QGP), a chiral magnetohydrodynamical (MHD) description of a perfect (non-dissipative) QGP exhibiting dynamical chiral symmetry breaking (D$χ$SB) is developed using the effective action of the Nambu-Jona-Lasinio (NJL) model of QCD at finite temperature, finite baryon chemical potential and in the presence of a strong magnetic field. Here, the D$χ$SB arises due to the phenomenon of magnetic catalysis. Apart from an interesting frequency dependence, for plane waves propagating in the transverse or longitudinal direction with respect to the $B$ field, the sound velocity is anisotropic and depends on the angle between the corresponding wave vectors and the direction of the $B$ field. Moreover, for plane waves propagating in the transverse (longitudinal) direction to the external $B$ field, the sound velocity has a maximum (minimum) at $T<T_{c}$, reaches a local minimum (maximum) at $T\sim T_{c}$ and remains constant at $T\gtrsim T_{c}$. Here, $T_{c}$ is the critical temperature of the chiral phase transition. Thus, the constant value $v_{s}\sim 1.5 c_{s}$ at $T \gtrsim T_{c}$ turns out to be a lower (upper) bound for waves propagating in the transverse (longitudinal) direction with respect to the external $B$ field. Here, $c_{s}=1/\sqrt{3}$ is the sound velocity in an ideal gas.

hep-ph↗

arXiv2006

Dynamics of O(N) Model in a Strong Magnetic Background Field as a Modified Noncommutative Field Theory

In the presence of a strong magnetic field, the effective action of a composite scalar field in an scalar O(N) model is derived using two different methods. First, in the framework of worldline formalism, the 1PI n-point vertex function for the composites is determined in the limit of strong magnetic field. Then, the n-point effective action of the composites is calculated in the regime of lowest Landau level dominance. It is shown that in the limit of strong magnetic field, the results coincide and an effective field theory arises which is comparable with the conventional noncommutative field theory. In contrast to the ordinary case, however, the UV/IR mixing is absent in this modified noncommutative field theory.

hep-th↗

arXiv2005

Planar and Nonplanar Konishi Anomalies and Effective Superpotential for Noncommutative N=1 Supersymmetric U(1)

The Konishi anomalies for noncommutative N=1 supersymmetric U(1) gauge theory arising from planar and nonplanar diagrams are calculated. Whereas planar Konishi anomaly is the expected \star-deformation of the commutative anomaly, nonplanar anomaly reflects the important features of nonplanar diagrams of noncommutative gauge theories, such as UV/IR mixing and the appearance of nonlocal open Wilson lines. We use the planar and nonplanar Konishi anomalies to calculate the effective superpotential of the theory. In the limit of vanishing |Θp|, with Θthe noncommutativity parameter, the noncommutative effective superpotential depends on a gauge invariant superfield, which includes supersymmetric Wilson lines, and has nontrivial dependence on the gauge field supermultiplet.

hep-th↗

arXiv2003

One-Loop Perturbative Corrections to non(anti)commutativity Parameter of N=1/2 Supersymmetric U(N) Gauge Theory

Perturbative corrections to N=1/2 supersymmetric U(N) gauge theory at one-loop order are studied. It is shown that whereas the quantum corrections to N=1 sector of the theory are not affected by the C-deformation, the non(anti)commutativity parameter C receives one-loop perturbative corrections. These perturbative corrections are computed by performing an explicit one-loop calculation of the three and four-point functions of the theory. The running of the non(anti)commutativity parameter C is also studied using an appropriate Callan-Symanzik equation.

hep-th↗

arXiv2002

On the $β$-Function and Conformal Anomaly of Noncommutative QED with Adjoint Matter Fields

In the first part of this work, a perturbative analysis up to one-loop order is carried out to determine the one-loop $β$-function of noncommutative U(1) gauge theory with matter fields in the adjoint representation. In the second part, the conformal anomaly of the same theory is calculated using the Fujikawa's path integral method. The value of the one-loop $β$-function calculated in both methods coincides. As it turns out, noncommutative QED with matter fields in the adjoint representation is asymptotically free for the number of flavor degrees of freedom $N_{f}<3$.

hep-th↗

arXiv2002

Noncommutative Dipole QED

The noncommutative dipole QED is studied in detail for the matter fields in the adjoint representation. The axial anomaly of this theory is calculated in two and four dimensions using various regularization methods. The Ward-Takahashi identity is proved by making use of a non-perturbative path integral method. The one-loop $β$-function of the theory is calculated explicitly. It turns out that the value of the $β$-function depends on the direction of the dipole length $\vec{L}$, which defines the noncommutativity. Finally using a semi-classical approximation a non-perturbative definition of the form factors is presented and the anomalous magnetic moment of this theory at one-loop order is computed.

hep-th↗

arXiv2001

Anomaly and Nonplanar Diagrams in Noncommutative Gauge Theories

Anomalies arising from nonplanar triangle diagrams of noncommutative gauge theory are studied. Local chiral gauge anomalies for both noncommutative U(1) and U(N) gauge theories with adjoint matter fields are shown to vanish. For noncommutative QED with fundamental matters, due to UV/IR mixing a finite anomaly emerges from the nonplanar contributions. It involves a generalized $\star$-product of gauge fields.

hep-th↗

arXiv2001

Axial Anomaly in Noncommutative QED on R^4

The axial anomaly of the noncommutative U(1) gauge theory is calculated by a number of methods and compared with the commutative one. It is found to be given by the corresponding Chern class.

hep-th↗

arXiv1998

A New Look at the Axial Anomaly in Lattice QED with Wilson Fermions

By carrying out a systematic expansion of Feynman integrals in the lattice spacing, we show that the axial anomaly in the U(1) lattice gauge theory with Wilson fermions, as determined in one-loop order from an irrelevant lattice operator in the Ward identity, must necessarily be identical to that computed from the dimensionally regulated continuum Feynman integrals for the triangle diagrams.

hep-lat↗

arXiv1996

Continuum Behaviour of Lattice QED, Discretized with One-Sided Lattice Differences, in One-Loop Order

A lattice action for QED is considered, where the derivatives in the Dirac operator are replaced by one-sided lattice differences. A systematic expansion in the lattice spacing of the one-loop contribution to the fermion self energy, vacuum polarization tensor and vertex function is carried out for an arbitrary choice of one-sided lattice differences. It is shown that only the vacuum polarization tensor possesses the correct continuum limit, while the fermion self energy and vertex function receive non-covariant contributions. A lattice action, discretized with a fixed choice of one-sided lattice differences therefore does not define a renormalizable field theory. The non-covariant contributions can however be eliminated by averaging the expressions over all possible choices of one-sided lattice differences.

hep-lat↗