arXiv subjects

Palash Das

Publications and source records attributed to Palash Das.

4 recordsLinked to original sources

arXiv2004

Shear Thinning of a Critical Viscoelastic Fluid

The frequency and shear dependent critical viscosity at a correlation length $ξ=κ^{-1}$, has the form $η=η_{0}κ^{-x_η}G(z_{1},z_{2})$, where $z_{1}$ and $z_{2}$ are the independent dimensionless numbers in the problem defined as $z_{1}=\frac{-iω}{2Γ_{0}κ^{3}}$ and $z_{2}=\frac{-iω}{2Γ_{0}κ_{c}^{3}}$. The decay rate of critical fluctuations of correlation length $κ^{-1}$ is $Γ_{0}κ^{3}$ and $k_{c}$ is the effective wave number for which $Γ_{0}k_{c}^{3}=S$, the shear rate. The function $G(z_{1},z_{2})$ is calculated in a one loop self-consistent theory.

cond-mat.stat-mech↗

arXiv2003

Scaling Function for the Diffusion Coefficient of a Critical Fluid in a Finite Geometry

The long wavelength diffusion coefficient of a critical fluid confined between two parallel plates separated by a distance L is strongly affected by the finite size. Finite size scaling leads us to expect that the vanishing of the diffusion coefficient as ξ^{-1} for ξ< >L. We show that this is not strictlytrue. There is a logarthmic scaling violation. We construct a Kawasaki like scaling function that connects the thermodynamic regime to the extreme critical (ξ>>L) regime.

cond-mat.stat-mech↗

arXiv2002

Critical Viscosity Exponent for Fluids: What Happend to the Higher Loops

We arrange the loopwise perturbation theory for the critical viscosity exponent $x_η$, which happens to be very small, as a power series in $x_η$ itself and argue that the effect of loops beyond two is negligible. We claim that the critical viscosity exponent should be very closely approximated by $x_η=\frac{8}{15 π^2}(1+\frac{8}{3 π^2})\simeq 0.0685$.

cond-mat.stat-mech↗

arXiv2000

Frequency Dependent Viscosity Near the Critical Point: The Scale to Two Loop Order

The recent accurate measurements of Berg, Moldover and Zimmerli of the viscoelastic effect near the critical point of xenon has shown that the scale factor involved in the frequency scaling is about twice the scale factor obtained theoretically. We show that this discrepancy is a consequence of using first order perturbation theory. Including two loop contribution goes a long way towards removing the discrepancy.

cond-mat↗