scholarly journals Temperature profile in a liquid–vapour interface near the critical point

2017 ◽  
Vol 473 (2204) ◽  
pp. 20170229 ◽  
Author(s):  
Henri Gouin ◽  
Pierre Seppecher
Keyword(s):  
Critical Point ◽  
Temperature Profile ◽  
Density Gradient ◽  
Mass Density ◽  
Entropy Density ◽  
State Law ◽  
Inhomogeneous Fluids ◽  
Realistic Potentials ◽  
Density Expansion

Thanks to an expansion with respect to densities of energy, mass and entropy, we discuss the concept of thermocapillary fluid for inhomogeneous fluids. The non-convex state law valid for homogeneous fluids is modified by adding terms taking account of the gradients of these densities. This seems more realistic than Cahn and Hilliard’s model which uses a density expansion in mass-density gradient only. Indeed, through liquid–vapour interfaces, realistic potentials in molecular theories show that entropy density and temperature do not vary with the mass density as it would do in bulk phases. In this paper, we prove using a rescaling process near the critical point, that liquid–vapour interfaces behave essentially in the same way as in Cahn and Hilliard’s model.

HOLOGRAPHIC SPHERICALLY SYMMETRIC METRICS

2007 ◽  
Vol 16 (06) ◽  
pp. 1603-1641 ◽  
Author(s):  
MICHAEL PETRI
Keyword(s):  
Energy Density ◽  
Degrees Of Freedom ◽  
Mass Density ◽  
Entropy Density ◽  
Constant Factor ◽  
Spherically Symmetric ◽  
Scale Invariant ◽  
Total Energy Density ◽  
Boundary Area ◽  
Symmetric Metrics

The holographic principle (HP) conjectures, that the maximum number of degrees of freedom of any realistic physical system is proportional to the system's boundary area. The HP has its roots in the study of black holes. It has recently been applied to cosmological solutions. In this article we apply the HP to spherically symmetric static space-times. We find that any regular spherically symmetric object saturating the HP is subject to tight constraints on the (interior) metric, energy-density, temperature and entropy-density. Whenever gravity can be described by a metric theory, gravity is macroscopically scale invariant and the laws of thermodynamics hold locally and globally, the (interior) metric of a regular holographic object is uniquely determined up to a constant factor and the interior matter-state must follow well defined scaling relations. When the metric theory of gravity is general relativity, the interior matter has an overall string equation of state (EOS) and a unique total energy-density. Thus the holographic metric derived in this article can serve as simple interior 4D realization of Mathur's string fuzzball proposal. Some properties of the holographic metric and its possible experimental verification are discussed. The geodesics of the holographic metric describe an isotropically expanding (or contracting) universe with a nearly homogeneous matter-distribution within the local Hubble volume. Due to the overall string EOS the active gravitational mass-density is zero, resulting in a coasting expansion with Ht = 1, which is compatible with the recent GRB-data.

Mass Density Gradient

2016 ◽  
Author(s):  
H. P. Lehmann ◽  
X. Fuentes-Arderiu ◽  
L. F. Bertello
Keyword(s):  
Density Gradient ◽  
Mass Density

BARYOGENESIS WITHOUT BARYON NUMBER VIOLATION

1990 ◽  
Vol 05 (21) ◽  
pp. 1623-1628 ◽  
Author(s):  
SCOTT DODELSON ◽  
LAWRENCE M. WIDROW
Keyword(s):  
High Temperatures ◽  
Mass Density ◽  
Scalar Particle ◽  
Baryon Number ◽  
Entropy Density ◽  
New Paradigm ◽  
Weakly Interacting ◽  
Baryon Number Violation ◽  
Number Violation ◽  
The Universe

We review a new paradigm for baryogenesis in which the fundamental Lagrangian is baryon conserving [invariant under U (1) B ]. At high temperatures, U (1)B is spontaneously broken and an excess of quarks over antiquarks of 10−10s (s≡entropy density) is produced. Today, U(1)B is restored. A fundamental consequence of our assumptions is that the baryon number of the Universe is constant. If initially zero, it will be zero today. The excess baryon number produced in the quark fields is exactly compensated by antibaryon number in a weakly interacting scalar particle. We suggest that this scalar provides the mass density necessary to close the Universe.

scholarly journals Structures and Instabilities in Reaction Fronts Separating Fluids of Different Densities

2019 ◽  
Vol 24 (2) ◽  
pp. 51
Author(s):  
Johan Llamoza ◽  
Desiderio A. Vasquez
Keyword(s):  
Porous Media ◽  
Density Gradient ◽  
Stokes Flow ◽  
Numerical Solutions ◽  
Mass Density ◽  
Fluid Velocity ◽  
Two Dimensional ◽  
Narrow Gap ◽  
Reaction Fronts ◽  
Brinkman’S Equation

Density gradients across reaction fronts propagating vertically can lead to Rayleigh–Taylor instabilities. Reaction fronts can also become unstable due to diffusive instabilities, regardless the presence of a mass density gradient. In this paper, we study the interaction between density driven convection and fronts with diffusive instabilities. We focus in fluids confined in Hele–Shaw cells or porous media, with the hydrodynamics modeled by Brinkman’s equation. The time evolution of the front is described with a Kuramoto–Sivashinsky (KS) equation coupled to the fluid velocity. A linear stability analysis shows a transition to convection that depends on the density differences between reacted and unreacted fluids. A stabilizing density gradient can surpress the effects of diffusive instabilities. The two-dimensional numerical solutions of the nonlinear equations show an increase of speed due to convection. Brinkman’s equation lead to the same results as Darcy’s laws for narrow gap Hele–Shaw cells. For large gaps, modeling the hydrodynamics using Stokes’ flow lead to the same results.

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