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How a single stretched polymer responds coherently to a minute oscillation in fluctuating environments: An entropic stochastic resonance
Within the cell, biopolymers are often situated in constrained, fluid
environments, e.g., cytoskeletal networks, stretched DNAs in chromatin. It is
of paramount importance to understand quantitatively how they, utilizing their
flexibility, optimally respond to a minute signal, which is, in general,
temporally fluctuating far away from equilibrium. To this end, we analytically
study viscoelastic response and associated stochastic resonance in a stretched
single semi-flexible chain to an oscillatory force or electric field. Including
hydrodynamic interactions between chain segments, we evaluate dynamics of the
polymer extension in coherent response to the force or field. We find power
amplification factor of the response at a noise-strength (temperature) can
attain the maximum that grows as the chain length increases, indicative of an
entropic stochastic resonance (ESR). In particular for a charged chain under an
electric field, we find that the maximum also occurs at an optimal chain
length, a new feature of ESR. The hydrodynamic interaction is found to enhance
the power amplification, representing unique polymer cooperativity which the
fluid background imparts despite its overdamping nature. For the slow
oscillatory force, the resonance behavior is explained by the chain undulation
of the longest wavelength. This novel ESR phenomenon suggests how a biopolymer
self-organizes in an overdamping environment, utilizing its flexibility and
thermal fluctuations
Black Hole as a Wormhole Factory
On general grounds, one may argue that a black hole stops radiation at the
Planck mass, where the radiated energy is comparable to the black hole's mass.
And also, it has been argued that there would be a "wormhole-like" structure,
known as "space-time foam", due to large fluctuations below the Planck length.
In this paper, as an explicit example, we consider an exact classical solution
which represents nicely those two properties in a recently proposed quantum
gravity model based on different scaling dimensions between space and time
coordinates. The solution, called "Black Wormhole", consists of two different
states, depending on its mass M and an IR parameter omega: For the black hole
state, a non-traversable wormhole occupies the interior region of the black
hole around the singularity at the origin, whereas for the wormhole state, the
interior wormhole is exposed to an outside observer as the black hole horizon
is disappeared from evaporation. The black hole state becomes thermodynamically
stable as it approaches to the merge point where the interior wormhole throat
and the black hole horizon merges, and the Hawking temperature vanishes at the
exact merge point. This solution suggests the "Generalized Cosmic Censorship"
by the existence of a wormhole-like structure which protects the naked
singularity even after the black hole evaporation. One could understand the
would-be wormholes inside the black hole horizon as the results of microscopic
wormholes created by "negative" energy quanta which have entered the black hole
horizon in Hawking radiation processes: The quantum black hole could be a
wormhole factory. It is found that this speculative picture may be consistent
with the recent "ER=EPR" proposal for resolving the recent black hole
entanglement debates.Comment: Added some more words on (1) the transition between the black hole
phase and wormhole phase and (2) the notion of a wormhole "factory" in Fig.
5. Updated references, Accepted in PL
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