13 research outputs found
On the statistical-mechanical meaning of the Bousso bound
The Bousso entropy bound, in its generalized form, is investigated for the
case of perfect fluids at local thermodynamic equilibrium and evidence is found
that the bound is satisfied if and only if a certain local thermodynamic
property holds, emerging when the attempt is made to apply the bound to thin
layers of matter. This property consists in the existence of an ultimate lower
limit l* to the thickness of the slices for which a statistical-mechanical
description is viable, depending l* on the thermodynamical variables which
define the state of the system locally. This limiting scale, found to be in
general much larger than the Planck scale (so that no Planck scale physics must
be necessarily invoked to justify it), appears not related to gravity and this
suggests that the generalized entropy bound is likely to be rooted on
conventional flat-spacetime statistical mechanics, with the maximum admitted
entropy being however actually determined also by gravity.
Some examples of ideal fluids are considered in order to identify the
mechanisms which can set a lower limit to the statistical-mechanical
description and these systems are found to respect the lower limiting scale l*.
The photon gas, in particular, appears to seemingly saturate this limiting
scale and the consequence is drawn that for systems consisting of a single
slice of a photon gas with thickness l*, the generalized Bousso bound is
saturated. It is argued that this seems to open the way to a peculiar
understanding of black hole entropy: if an entropy can meaningfully (i.e. with
a second law) be assigned to a black hole, the value A/4 for it (where A is the
area of the black hole) is required simply by (conventional) statistical
mechanics coupled to general relativity.Comment: 6 pages. Some editing and the addition of a reference. This version,
ideally corresponding to the published one, contains 4 corrections to it,
with two of them (p.3, line 19 and p.6, line 10 of this version) with
semantic relevanc
A proof of the Bekenstein bound for any strength of gravity through holography
The universal entropy bound of Bekenstein is considered, at any strength of
the gravitational interaction. A proof of it is given, provided the considered
general-relativistic spacetimes allow for a meaningful and inequivocal
definition of the quantities which partecipate to the bound (such as system's
energy and radius). This is done assuming as starting point that, for assigned
statistical-mechanical local conditions, a lower-limiting scale l* to system's
size definitely exists, being it required by holography through its
semiclassical formulation as given by the generalized covariant entropy bound.
An attempt is made also to draw some possible general consequences of the l*
assumption with regards to the proliferation of species problem and to the
viscosity to entropy density ratio. Concerning the latter, various fluids are
considered including systems potentially relevant, to some extent, to the
quark-gluon plasma case.Comment: 13 pages. v2: the title is modified; the discussion is strengthened
and made more concise (10pp). v3: some short clarifications adde
Monetary conditions and banks’ behaviour in the Czech Republic
This paper examines the impact of monetary conditions on the risk-taking behaviour of banks in the Czech Republic by analysing the comprehensive credit register of the Czech National Bank. Our duration analysis indicates that expansionary monetary conditions promote risk-taking among banks. At the same time, a lower interest rate during the life of a loan reduces its riskiness. While seeking to assess the association between banks’ appetite for risk and the short-term interest rate we answer a set of questions related to the difference between higher liquidity versus credit risk and the effect of the policy rate conditioned on bank and borrower characteristics.This work was supported by the Czech national Bank (Research Project No. C4/2009) and the Grant Agency of the Czech Republic projects GA CR No. 14-02108S and No. P402/12/G097)