9,810 research outputs found
Dynamically forced cells of a viscoelastic fluid over an array of rollers
Our fluid dynamics video shows the response of a layer of viscoelastic fluid
to an array of four-roll mills steadily rotating underneath. When the
relaxation time of the fluid is sufficiently long, the fluid divides into
"cells" with a convex free surface above the site of each roller. This is
reminiscent of the rod-climbing effect. On this relaxation time-scale, the flow
also transitions from being initially Newtonian-like to one where the fluids'
elasticity plays a dynamical role: The fluid cells oscillate with regularity in
position and shape on a timescale much longer than the relaxation time. As the
relaxation time is further increased, the cells become less localized to the
underlying rollers, and their now irregular oscillations reflect the presence
of many frequencies
Cycle frequency in standard Rock-Paper-Scissors games: Evidence from experimental economics
The Rock-Paper-Scissors (RPS) game is a widely used model system in game
theory. Evolutionary game theory predicts the existence of persistent cycles in
the evolutionary trajectories of the RPS game, but experimental evidence has
remained to be rather weak. In this work we performed laboratory experiments on
the RPS game and analyzed the social-state evolutionary trajectories of twelve
populations of N=6 players. We found strong evidence supporting the existence
of persistent cycles. The mean cycling frequency was measured to be period per experimental round. Our experimental observations can be
quantitatively explained by a simple non-equilibrium model, namely the
discrete-time logit dynamical process with a noise parameter. Our work
therefore favors the evolutionary game theory over the classical game theory
for describing the dynamical behavior of the RPS game.Comment: 7 Page, 3 figure; Keyword: Rock-Paper-Scissors game; cycle; social
state; population dynamics; evolutionary trajector
Modified holographic dark energy in DGP brane world
In this paper, the cosmological dynamics of a modified holographic dark
energy which is derived from the UV/IR duality by considering the black hole
mass in higher dimensions as UV cutoff, is investigated in
Dvali-Gabadaze-Porrati (DGP) brane world model. We choose Hubble horizon and
future event horizon as IR cutoff respectively. And the two branches of the DGP
model are both taken into account. When Hubble horizon is considered as IR
cutoff, the modified holographic dark energy (HDE) behaves like an effect dark
energy that modification of gravity in pure DGP brane world model acts and it
can drive the expansion of the universe speed up at late time in
branch which in pure DGP model can not undergo an accelerating phase. When
future event horizon acts as IR cutoff, the equation of state parameter of the
modified HDE can cross the phantom divide.Comment: 8 pages, 4 figures, accepted for publication in PL
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