The Solar Course, the Chemic Force, and the Speeding Change of Water
from
Monday, 17 October 2011 (08:00)
to
Friday, 21 October 2011 (18:00)
Monday, 17 October 2011
09:30
Turbulent convection in three, two and one dimensions.
-
G Boffetta
Turbulent convection in three, two and one dimensions.
G Boffetta
09:30 - 10:00
Room: Nordita lecture room
10:00
Energy and enstrophy cascades in large scale atmospheric turbulence
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E. Lindborg
Energy and enstrophy cascades in large scale atmospheric turbulence
E. Lindborg
10:00 - 10:30
Room: Nordita lecture room
11:00
Asymptotic stability of heteroclinic cycles
-
O. Podvigina
Asymptotic stability of heteroclinic cycles
O. Podvigina
11:00 - 11:30
Room: Nordita lecture room
Dynamical systems, equivariant under the action of a non-trivial symmetry group, can possess structurally stable heteroclinic cycles. We consider stability properties of a class of structurally stable heteroclinic cycles in $\R^n$, which we call heteroclinic cycles of type Z. It is well-known that a heteroclinic cycle, that is not asymptotically stable, can attract nevertheless a positive measure set from its neighbourhood. We call such cycles fragmentarily asymptotically stable. Necessary and sufficient conditions for fragmentary asymptotic stability are expressed in terms of eigenvalues and eigenvectors of transition matrices. If all transverse eigenvalues of linearisations near steady states that are involved in the cycle are negative, then the condition for asymptotic stability is that the transition matrices have an eigenvalue larger than one in absolute value. Finally, we discuss bifurcations occurring when the conditions for asymptotic stability or for fragmentary asymptotic stability are broken
11:30
Computing non-equilibrium stationary states by message-passing?
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E. Aurell
Computing non-equilibrium stationary states by message-passing?
E. Aurell
11:30 - 12:00
Room: Nordita lecture room
12:00
Rotating Turbulence and return to isotropy.
-
A. Pouquet
Rotating Turbulence and return to isotropy.
A. Pouquet
12:00 - 12:30
Room: Nordita lecture room
14:30
Dynamics of the glassy state of matter
-
I. Procaccia
Dynamics of the glassy state of matter
I. Procaccia
14:30 - 15:15
Room: Nordita lecture room
15:45
Pirouette effect in turbulence
-
A. Pumir
Pirouette effect in turbulence
A. Pumir
15:45 - 16:15
Room: Nordita lecture room
16:15
Scaling and Intermittency in fluctuating Alpha-Shear dynamos
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D. Mitra
(
NORDITA
)
Scaling and Intermittency in fluctuating Alpha-Shear dynamos
D. Mitra
(
NORDITA
)
16:15 - 16:45
Room: Nordita lecture room
We consider mean-field dynamo models with fluctuating \alpha effect, both with and without shear. The \alpha effect is chosen to be Gaussian white noise with zero mean and given covariance. We show analytically that the mean magnetic field does not grow, but, in an infinitely large domain, the mean-squared magnetic field shows exponential growth of the fastest growing mode at a rate proportional to the shear rate, which agrees with earlier numerical results of Yousef et al (2008) and recent analytical treatment by Heinemann et al (2011) who use a method different from ours. In the absence of shear, an incoherent \alpha^2 dynamo may also be possible. We further show by explicit calculation of the growth rate of third and fourth order moments of the magnetic field that the probability density function of the mean magnetic field generated by this dynamo is non-Gaussian.
Tuesday, 18 October 2011
09:00
Optimization in astrophysics
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R. Mohayee
(
AIP, Paris
)
Optimization in astrophysics
R. Mohayee
(
AIP, Paris
)
09:00 - 09:45
Room: Nordita lecture room
09:45
Negative effective magnetic pressure instability
-
A. Brandenburg
Negative effective magnetic pressure instability
A. Brandenburg
09:45 - 10:15
Room: Nordita lecture room
We present the first demonstration of the negative effective magnetic pressure instability in direct numerical simulations of stably stratified, externally forced, isothermal hydromagnetic turbulence in the regime of large plasma beta. By the action of this instability, an initially uniform horizontal magnetic field forms flux concentrations whose scale is large compared to the turbulent scale. We further show that the magnetic energy of these large-scale structures is only weakly dependent on the magnetic Reynolds number, provided its value is large enough for the instability to be excited. Our results support earlier mean-field calculations and analytic work which identified this instability. Applications to the formation of active regions in the Sun are discussed. [Astrophys. J. Lett. 740, L50 (2011) ]
11:00
Nelkin scaling for ¨burgulence¨
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S. Chakraborty
(
NBI, Copenhagen
)
Nelkin scaling for ¨burgulence¨
S. Chakraborty
(
NBI, Copenhagen
)
11:00 - 11:30
Room: Nordita lecture room
11:30
Relaxation of Galerkin-Truncated Gyrokinetic, and back to Magenticfluids
-
J-Z Zhu
Relaxation of Galerkin-Truncated Gyrokinetic, and back to Magenticfluids
J-Z Zhu
11:30 - 12:00
Room: Nordita lecture room
The gyrokinetic absolute equilibrium will be reviewed. Some numerical results of gyrokinetic simulations will be presented. Two-fluid magneticfluid absolute equilibrium is used to investigate two-fluid effects, effects of various helicities et al. This talk try to bring some new insights into the kinetic and two-fluid effects in magnetized plasma turbulence in fusion device, space and astrophysics.
12:00
Condensates in two dimensional turbulence
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C-K Chan
Condensates in two dimensional turbulence
C-K Chan
12:00 - 12:30
Room: Nordita lecture room
We derive and numerically confirm that the saturation of energy condensation in two-dimensional turbulence is governed by the balance between forcing and small-scale dissipation. The time scale of saturation is inversely proportional to the viscosity but the saturation energy level is determined by both viscosity and the forcing scale. It is shown that, because the energy dissipation is proportional to the enstrophy, which itself is a conserved quantity in the ideal case, it is necessary to resolve the enstrophy spectrum to achieve numerical consistency. We also find that the movement of the condensate vortices can be described as Brownian motion of an inertial particle. [arXiv:1109.6937v1]
14:30
On the Evolution of Texts: An Introduction to Stemmatology
-
T Roos
On the Evolution of Texts: An Introduction to Stemmatology
T Roos
14:30 - 15:30
Room: Nordita lecture room
15:30
Nothing new under the burning sun? Climate and verbs in North-West Semitic
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O. Wikander
Nothing new under the burning sun? Climate and verbs in North-West Semitic
O. Wikander
15:30 - 16:30
Room: Nordita lecture room
Wednesday, 19 October 2011
09:00
Time Scales, Persistence, and Dynamic Multiscaling in Turbulence
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R. Pandit
(
IISc, Bangalore
)
Time Scales, Persistence, and Dynamic Multiscaling in Turbulence
R. Pandit
(
IISc, Bangalore
)
09:00 - 09:45
Room: Nordita lecture room
09:45
Orientation of non-symmetric particles in axisymmetric random flows
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D. Vincenzi
Orientation of non-symmetric particles in axisymmetric random flows
D. Vincenzi
09:45 - 10:15
Room: Nordita lecture room
10:45
Navier-Stokes in hyperbolic plane
-
ENS, Lyon Gawedzki
Navier-Stokes in hyperbolic plane
ENS, Lyon Gawedzki
10:45 - 11:15
Room: Nordita lecture room
11:15
Axial dipolar dynamo action in Taylor-Green vortex
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M-E Brachet
Axial dipolar dynamo action in Taylor-Green vortex
M-E Brachet
11:15 - 11:45
Room: Nordita lecture room
11:45
Role of polymers in the mixing of Rayleigh-Taylor turbulence
-
A Mazzino
Role of polymers in the mixing of Rayleigh-Taylor turbulence
A Mazzino
11:45 - 12:15
Room: Nordita lecture room
The role of polymer additives on Rayleigh-Taylor turbulence is investigated by means of direct numerical simulations (DNS) of Oldroyd-B viscoelastic model. The dynamics of polymer elongations follows adiabatically the self-similar evolution of the turbulent mixing layer and shows the appearance of a strong feedback on the flow which originates a cut off for polymer elongations. The viscoelastic effects on the mixing properties of the flow are twofold. Mixing is appreciably enhanced at large scales (the mixing layer growth-rate is larger than that of the purely Newtonian case) and depleted at small scales (thermal plumes are more coherent with respect to the Newtonian case). The observed speed up of the thermal plumes, together with an increase of the correlations between temperature field and vertical velocity, contributes to a significant enhancement of heat transport. Our findings are consistent with a scenario of drag reduction induced by polymers.
14:30
Life at high Reynolds number
-
M Jensen
Life at high Reynolds number
M Jensen
14:30 - 15:00
Room: Nordita lecture room
15:00
A Lie-group mean-field theory for turbulent channel and pipe flow
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Xi Chen
A Lie-group mean-field theory for turbulent channel and pipe flow
Xi Chen
15:00 - 15:30
Room: Nordita lecture room
16:00
Round table discussions
Round table discussions
16:00 - 17:00
Room: Nordita lecture room
Thursday, 20 October 2011
09:30
Structures versus statistics in turbulence, resolution of old quarrel
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G. Falkovich
Structures versus statistics in turbulence, resolution of old quarrel
G. Falkovich
09:30 - 10:15
Room: Nordita lecture room
10:45
Turbulence in non-integer dimensions by fractal Fourier decimation
-
U. Frisch
Turbulence in non-integer dimensions by fractal Fourier decimation
U. Frisch
10:45 - 11:30
Room: Nordita lecture room
11:30
The tyger phenomenon for the Galerkin truncated Burgers equation.
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S.S. Ray
(
Obs Nice
)
The tyger phenomenon for the Galerkin truncated Burgers equation.
S.S. Ray
(
Obs Nice
)
11:30 - 12:00
Room: Nordita lecture room
12:00
On form and growth
-
J Wettlaufer
(
NORDITA and Yale
)
On form and growth
J Wettlaufer
(
NORDITA and Yale
)
12:00 - 12:30
Room: Nordita lecture room
14:30
Inverse energy cascade in 3d isotropic and homogeneous turbulence
-
L Biferale
Inverse energy cascade in 3d isotropic and homogeneous turbulence
L Biferale
14:30 - 14:50
Room: Nordita lecture room
Friday, 21 October 2011
09:30
Population dynamics in compressible flows
-
R. Benzi
Population dynamics in compressible flows
R. Benzi
09:30 - 10:15
Room: Nordita lecture room
10:45
Lagrangian/Eulerian estimate of turbulent breakup of small particles
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A. Lanotte
Lagrangian/Eulerian estimate of turbulent breakup of small particles
A. Lanotte
10:45 - 11:15
Room: Nordita lecture room
11:15
The size of the region of analyticity of solutions to the two-dimensional Euler equation
-
V. Zheligovsky
The size of the region of analyticity of solutions to the two-dimensional Euler equation
V. Zheligovsky
11:15 - 11:45
Room: Nordita lecture room