scholarly journals Dynamical constraints on RG flows and cosmology

2019 ◽  
Vol 2019 (12) ◽  
Author(s):  
Daniel Baumann ◽  
Daniel Green ◽  
Thomas Hartman
Keyword(s):  
Dynamical Constraints

Dynamical Constraints on Using Precise Spike Timing to Compute in Recurrent Cortical Networks

2008 ◽  
Vol 20 (4) ◽  
pp. 974-993 ◽  
Author(s):  
Arunava Banerjee ◽  
Peggy Seriès ◽  
Alexandre Pouget
Keyword(s):  
Dynamical System ◽  
Initial Conditions ◽  
Internal State ◽  
Spike Timing ◽  
Spiking Neurons ◽  
Spatiotemporal Patterns ◽  
Cortical Networks ◽  
Temporal Precision ◽  
Cortical Areas ◽  
Dynamical Constraints

Several recent models have proposed the use of precise timing of spikes for cortical computation. Such models rely on growing experimental evidence that neurons in the thalamus as well as many primary sensory cortical areas respond to stimuli with remarkable temporal precision. Models of computation based on spike timing, where the output of the network is a function not only of the input but also of an independently initializable internal state of the network, must, however, satisfy a critical constraint: the dynamics of the network should not be sensitive to initial conditions. We have previously developed an abstract dynamical system for networks of spiking neurons that has allowed us to identify the criterion for the stationary dynamics of a network to be sensitive to initial conditions. Guided by this criterion, we analyzed the dynamics of several recurrent cortical architectures, including one from the orientation selectivity literature. Based on the results, we conclude that under conditions of sustained, Poisson-like, weakly correlated, low to moderate levels of internal activity as found in the cortex, it is unlikely that recurrent cortical networks can robustly generate precise spike trajectories, that is, spatiotemporal patterns of spikes precise to the millisecond timescale.

scholarly journals Gaia DR2 reveals a very massive runaway star ejected from R136

2018 ◽  
Vol 619 ◽  
pp. A78 ◽  
Author(s):  
D. J. Lennon ◽  
C. J. Evans ◽  
R. P. van der Marel ◽  
J. Anderson ◽  
I. Platais ◽  
...  
Keyword(s):  
Lower Limit ◽  
Proper Motion ◽  
Evolutionary History ◽  
Massive Star ◽  
Position Angle ◽  
Proper Motions ◽  
Central Cluster ◽  
Dynamical Constraints ◽  
Runaway Stars ◽  
Gaia Dr2

A previous spectroscopic study identified the very massive O2 III star VFTS 16 in the Tarantula Nebula as a runaway star based on its peculiar line-of-sight velocity. We use the Gaia DR2 catalog to measure the relative proper motion of VFTS 16 and nearby bright stars to test if this star might have been ejected from the central cluster, R136, via dynamical ejection. We find that the position angle and magnitude of the relative proper motion (0.338±0.046 mas yr−1, or approximately 80±11 km s−1) of VFTS 16 are consistent with ejection from R136 approximately 1.5±0.2 Myr ago, very soon after the cluster was formed. There is some tension with the presumed age of VFTS 16 that, from published stellar parameters, cannot be greater than 0.9+0.3−0.2 Myr. Older ages for this star would appear to be prohibited due to the absence of He I lines in its optical spectrum, since this sets a firm lower limit on its effective temperature. The dynamical constraints may imply an unusual evolutionary history for this object, perhaps indicating it is a merger product. Gaia DR2 also confirms that another very massive star in the Tarantula Nebula, VFTS 72 (alias BI 253; O2 III-V(n)((f*)), is also a runaway on the basis of its proper motion as measured by Gaia. While its tangential proper motion (0.392±0.062 mas yr−1 or 93±15 km s−1) would be consistent with dynamical ejection from R136 approximately 1 Myr ago, its position angle is discrepant with this direction at the 2σ level. From their Gaia DR2 proper motions we conclude that the two ∼100 M⊙ O2 stars, VFTS 16 and VFTS 72, are fast runaway stars, with space velocities of around 100 km s−1 relative to R136 and the local massive star population. The dynamics of VFTS 16 are consistent with it having been ejected from R136, and this star therefore sets a robust lower limit on the age of the central cluster of ∼1.3 Myr.

Automatic artificial ventilation therapy using the ARDSNet protocol enforcing dynamical constraints

2017 ◽  
Author(s):  
Anake Pomprapa ◽  
Philipp A. Pickerodt ◽  
Wolfgang Braun ◽  
Martin Russ ◽  
Moritz B.T. Hofferberth ◽  
...  
Keyword(s):  
Artificial Ventilation ◽  
Dynamical Constraints

The high-resolution spectroscopy of dissociating molecules

1990 ◽  
Vol 332 (1625) ◽  
pp. 297-307 ◽  
Keyword(s):  
High Resolution ◽  
Energy Flow ◽  
Energy State ◽  
Reaction Dynamics ◽  
Theoretical Models ◽  
Spectroscopic Studies ◽  
High Resolution Spectroscopy ◽  
Bond Breaking ◽  
Vibrational Levels ◽  
Dynamical Constraints

Results from spectroscopic studies of the vibrational levels of dissociating molecules and from state-selected, state-resolved photofragmentation spectroscopy are presented. The extent of energy flow among the modes of a molecule is explored through the couplings, or lack thereof, revealed by high-resolution spectroscopy. The dynamics of energy flow during bond breaking are revealed by photofragment excitation spectroscopy and by product energy state distributions. These completely resolved data provide sensitive tests of dynamical constraints such as vibrational or rotational adiabaticity and thus of theoretical models for unimolecular reaction dynamics.

scholarly journals DYNAMICAL CONSTRAINTS ON THE MASSES OF THE NUCLEAR STAR CLUSTER AND BLACK HOLE IN THE LATE-TYPE SPIRAL GALAXY NGC 3621

2008 ◽  
Vol 690 (1) ◽  
pp. 1031-1044 ◽  
Author(s):  
Aaron J. Barth ◽  
Louis E. Strigari ◽  
Misty C. Bentz ◽  
Jenny E. Greene ◽  
Luis C. Ho
Keyword(s):  
Black Hole ◽  
Spiral Galaxy ◽  
Star Cluster ◽  
Late Type ◽  
Dynamical Constraints ◽  
The Masses

scholarly journals KMOS3D: DYNAMICAL CONSTRAINTS ON THE MASS BUDGET IN EARLY STAR-FORMING DISKS

2016 ◽  
Vol 831 (2) ◽  
pp. 149 ◽  
Author(s):  
Stijn Wuyts ◽  
Natascha M. Förster Schreiber ◽  
Emily Wisnioski ◽  
Reinhard Genzel ◽  
Andreas Burkert ◽  
...  
Keyword(s):  
Mass Budget ◽  
Star Forming ◽  
Dynamical Constraints

Incorporation of time continuity into subsynoptic analysis by using dynamical constraints

Tellus ◽  
1978 ◽  
Vol 30 (6) ◽  
pp. 496-516 ◽  
Author(s):  
John M. Lewis ◽  
Stephen C. Bloom
Keyword(s):  
Dynamical Constraints

The Maximum Caliber Variational Principle for Nonequilibria

2020 ◽  
Vol 71 (1) ◽  
pp. 213-238 ◽  
Author(s):  
Kingshuk Ghosh ◽  
Purushottam D. Dixit ◽  
Luca Agozzino ◽  
Ken A. Dill
Keyword(s):  
Variational Principle ◽  
Complex Systems ◽  
Cell Motility ◽  
Maximum Entropy ◽  
Network Traffic ◽  
Neuronal Firing ◽  
Gene Circuits ◽  
Reaction Coordinates ◽  
Dynamical Constraints

Ever since Clausius in 1865 and Boltzmann in 1877, the concepts of entropy and of its maximization have been the foundations for predicting how material equilibria derive from microscopic properties. But, despite much work, there has been no equally satisfactory general variational principle for nonequilibrium situations. However, in 1980, a new avenue was opened by E.T. Jaynes and by Shore and Johnson. We review here maximum caliber, which is a maximum-entropy-like principle that can infer distributions of flows over pathways, given dynamical constraints. This approach is providing new insights, particularly into few-particle complex systems, such as gene circuits, protein conformational reaction coordinates, network traffic, bird flocking, cell motility, and neuronal firing.

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