In this paper we study a massless, minimally coupled scalar field in a FLRW spacetime with periods of different constant deceleration parameter. We assume the Bunch-Davies vacuum during inflation and then use a sudden matching approximation to match it onto radiation era and subsequently onto matter era. We then proceed to calculate the one-loop energy-momentum tensor from the inflationary quantum vacuum fluctuations in different eras. The energy-momentum tensor has the form of an ideal (quantum) fluid, characterized by an equation of state. When compared with the background, far away from the matching the quantum energy density in radiation era exhibits a contribution that grows logarithmically with the scale factor. In matter era the ratio of the quantum to classical fluid settles eventually to a tiny constant, ρ q /ρ ≃ ( H 0 ) 2 /(4πm 2 P c 4 ) ∼ 10 −13 for a grand unified scale inflation. Curiously, the late time scaling of quantum fluctuations suggests that they contribute a little to the dark matter of the Universe, provided that it clusters as cold dark matter, which needs to be checked. *

We study a three-dimensional system of self-propelled Brownian particles interacting via the LennardJones potential. Using Brownian dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential components of the pressure tensor and show that the surface tension as a function of strength of particle attractions is well fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature. Published by AIP Publishing. [http://dx

We study a three-dimensional system of self-propelled Lennard-Jones particles using Brownian Dynamics simulations. Using recent theoretical results for active matter, we calculate the pressure and report equations of state for the system. Additionally, we chart the vapour-liquid coexistence and show that the coexistence densities can be well described using simple power laws. Lastly, we demonstrate that our out-of-equilibrium system shows deviations from both the law of rectilinear diameters and the law of corresponding states.

We study the self-assembly of a system of self-propelled, Lennard-Jones particles using Brownian dynamics simulations. We examine the state diagrams of the system for different rotational diffusion coefficients of the self-propelled motion of the particles. For fast rotational diffusion, the state diagram exhibits a strong similarity to that of the equilibrium Lennard-Jones fluid. As we decrease the rotational diffusion coefficient, the state diagram is slowly transformed. Specifically, the liquid-gas coexistence region is gradually replaced by a highly dynamic percolating network state. We find significant local alignment of the particles in the percolating network state despite the absence of aligning interactions, and propose a simple mechanism to justify the formation of this novel state.