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S. Rouhani

Publications and source records attributed to S. Rouhani.

61 records · Page 4Linked to original sources
arXiv1996

Logarithmic Correlation Functions in Two Dimensional Turbulence

We consider the correlation functions of two-dimensional turbulence in the presence and absence of a three-dimensional perturbation, by means of conformal field theory. In the persence of three dimensional perturbation, we show that in the strong coupling limit of a small scale random force, there is some logarithmic factor in the correlation functions of velocity stream functions. We show that the logarithmic conformal field theory $c_{8,1}$ describes the 2D- turbulence both in the absence and the presence of the perturbation. We obtain the following energy spectrum $E(k) \sim k^{-5.125 } \ln(k )$ for perturbed 2D - turbulence and $E(k) \sim k^{-5 } \ln(k )$ for unperturbed turbulence. Recent numerical simulation and experimental results confirm our prediction.

hep-th↗
arXiv1996

A Logarithmic Conformal Field Theory Solution For Two Dimensional Magnetohydrodynamics In Presence of The Alf'ven Effect

When Alf`ven effect is peresent in magnetohydrodynamics one is naturally lead to consider conformal field theories, which have logarithmic terms in their correlation functions. We discuss the implications of such logarithmic terms and find a unique conformal field theory with centeral charge $c=-\frac{209}{7}$, within the border of the minimal series, which satisfies all the constraints. The energy espectrum is found to be \newline $E(k)\sim k^{-\frac{13}{7}} \log{k}$.

hep-th↗
arXiv1996

Shape Phase Transition of Polyampholytes in Two Dimensions

We have studied the transition in shape of two dimensional polyampholytes using Monte Carlo simulation. We observe that polymers with randomly charged monomers get into a globular shape at lower temperatures, provided that their total charge is below a critical value $Q_c$. Collapse into globular form happens for all forms of force law, but the critical charge depends on the form of the force law, inversely dependent on the range of interaction. The value of the critical charge is proportional to $N$, the size of the polymer, in the thermodynamic limit. PACS numbers: 36.20.-r, 35.20.Bm, 64.60.-i

cond-mat↗
arXiv1996

The Alf'ven Effect and Conformal Field Theory

Noting that two-dimensional magnetohydrodynamics can be modeled by conformal field theory, we argue that when the Alf'ven effect is also taken into account one is naturally lead to consider conformal field theories, which have logarithmic terms in their correlation functions. We discuss the implications of such logarithmic terms in the context of magnetohydrodynamics, and derive a relationship between conformal dimensions of the velocity stream function, the magnetic flux function and the Reynolds number.

hep-th↗
arXiv1995

Turbulent Two Dimensional Magnetohydrodynamics and Conformal Field Theory.

We show that an infinite number of non-unitary minimal models may describe two dimensional turbulent magnetohydrodynamics (MHD), both in the presence and absence of the Alf'ven effect. We argue that the existence of a critical dynamical index results in the Alf'ven effect or equivelently the equipartition of energy. We show that there are an infinite number of conserved quantities in $2D-MHD$ turbulent systems both in the limit of vanishing the viscocities and in force free case. In the force free case, using the non-unitary minimal model $ M_{2,7} $ we derive the correlation functions for the velocity stream function and magnetic flux function. Generalising this simple model we find the exponents of the energy spectrum in the inertial range for a class of conformal field theories.

hep-th↗
arXiv1994

On Little Groups and Boosts of $κ$-deformed Poincare Group

We show how Wigner's little group approach to the representation theory of Poincaré group may be generalized to the case of $κ$-deformed Poincaré group. We also derive the deformed Lorentz transformations of energy and momentum. We find that if the $κ$-deformed Poincaré group is adopted as the fundamental symmetry of nature, it results in deviations from predictions of the Poincaré symmetry at large energies, which may be experimentally observable.

hep-th↗