# gst: scrambling does not necessitate chaos.

<< Focusing on semiclassical systems, (AA) show that the parametrically long exponential growth of out-of-time order correlators (OTOCs), also known as scrambling, does not necessitate chaos. Indeed, scrambling can simply result from the presence of unstable fixed points in phase space, even in an integrable model. >>

Tianrui Xu, Thomas Scaffidi, Xiangyu Cao. Does scrambling equal chaos? arXiv:1912.11063v1 [cond-mat.stat-mech] Dec 23, 2019.

https://arxiv.org/abs/1912.11063

# phys: three forms of ambiguity in the definition of entanglement

<< A more general definition (of entanglement) was published by Thaller, (B. Thaller, Advanced Visual Quantum Mechanics, (Springer 2005) p218) "A state of a compound system is called entangled if it cannot be written as a single tensor product of subsystem states. A state in the product form is called unentangled or separable."  >>

The paper << discusses experiments with single-particle systems, some of whose states appear to be entangled. (..) Three forms of ambiguity are discussed. The choice of state-space and its dimensions is a matter of taste. There is not an a-priori natural partitioning of the state-space. The observables are not necessarily experimentally accessible and only determined by theory-laden extrapolation from experimental results. >>

Robert Shaw. Single-particle entanglement and three forms of ambiguity. arXiv:1912.11349v1 [physics.hist-ph]. Dec 22, 2019

https://arxiv.org/abs/1912.11349

# life: squeezing jaraca' (Bothrops jararaca)

<< Dozens of poisonous snake species, including the jararaca, thrive in Brazil's hot and humid climate. >>

<< Venom is extracted from each snake once a month in a delicate and potentially dangerous process. >>

Brazil milks deadly snakes for their life-saving venom.  Dec 10, 2019.

https://m.phys.org/news/2019-12-brazil-deadly-snakes-life-saving-venom.html

# behav: backward walking, navigational uncertainties (among Cataglyphis velox)

<< Current opinion in insect navigation assumes that animals need to align with the goal direction to recognise familiar views and approach it. Yet, ants sometimes drag heavy food items backward to the nest and it is still unclear to what extent they rely on visual memories while doing so. >>

<< ants do indeed recognise and use the learnt visual scenery to guide their path while walking backward. In addition, the results show that backward homing ants estimate their directional certainty by combining visual familiarity with other cues such as their path integrator and the time spent backward. >>

Sebastian Schwarz, Leo Clement, et al.  How do backward walking ants (Cataglyphis velox) cope with navigational uncertainty? doi: 10.1101/2019.12.16.877704. Dec 17, 2019.

https://www.biorxiv.org/content/10.1101/2019.12.16.877704v1

# life: a case of extreme swing (3): he's impeachable/ impeached, or (maybe) not

<< Now that the House of Representatives has voted to impeach President Donald Trump, what is the constitutional status of the two articles of impeachment? Must they be transmitted to the Senate to trigger a trial, or could they be held back by the House until the Senate decides what the trial will look like, as Speaker Nancy Pelosi has hinted?  The Constitution doesn’t say how fast the articles must go to the Senate. Some modest delay is not inconsistent with the Constitution, or how both chambers usually work. >>

<< Strictly speaking, "impeachment" occurred – and occurs - when the articles of impeachment are presented to the Senate for trial. And at that point, the Senate is obliged by the Constitution to hold a trial. >>

Noah Feldman. Trump Isn’t Impeached Until the House Tells the Senate

According to the Constitution, impeachment is a process, not a vote.  Dec 19,  2019. 

https://www.bloomberg.com/view/articles/2019-12-19/trump-impeachment-delay-could-be-serious-problem-for-democrats

Also

"extreme swing" in FonT

https://flashontrack.blogspot.com/search?q=extreme+swing

# gst: the complex dynamics of a transition

<< The transition state is a central concept of chemistry (..) Everything we think about in reactions really hinges on the structure of the transition state, which we cannot directly observe. >> Robert Field.

<< there are two different mechanisms competing for transition states, >>

<< there are additional reaction mechanisms beyond those two, >>

Chemists glimpse the fleeting 'transition state' of a reaction. 

Massachusetts Institute of Technology. Dec 16, 2019.

https://m.phys.org/news/2019-12-chemists-glimpse-fleeting-transition-state.html

# gst: a hexagonal pattern of six cyclones (Jupiter, by NASA)

<< In this annotated infrared image, six cyclones form a hexagonal pattern around a central cyclone at Jupiter's south pole. The image was generated from data collected by NJASA’s Juno spacecraft on Nov. 4, 2019 >>

Tony Greicius. NASA's Juno Navigators Enable Jupiter Cyclone Discovery.  Dec. 13, 2019. 

https://www.nasa.gov/feature/jpl/nasas-juno-navigators-enable-jupiter-cyclone-discovery

A New Cyclone Joins the Jovian Fray.  NASA. Dec 12, 2019. 

https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA23558