124,336 research outputs found
Fisher matrix forecasts for astrophysical tests of the stability of the fine-structure constant
We use Fisher Matrix analysis techniques to forecast the cosmological impact
of astrophysical tests of the stability of the fine-structure constant to be
carried out by the forthcoming ESPRESSO spectrograph at the VLT (due for
commissioning in late 2017), as well by the planned high-resolution
spectrograph (currently in Phase A) for the European Extremely Large Telescope.
Assuming a fiducial model without variations, we show that ESPRESSO
can improve current bounds on the E\"{o}tv\"{o}s parameter---which quantifies
Weak Equivalence Principle violations---by up to two orders of magnitude,
leading to stronger bounds than those expected from the ongoing tests with the
MICROSCOPE satellite, while constraints from the E-ELT should be competitive
with those of the proposed STEP satellite. Should an variation be
detected, these measurements will further constrain cosmological parameters,
being particularly sensitive to the dynamics of dark energy.Comment: Phys. Lett. B (in press
A note on black hole entropy, area spectrum, and evaporation
We argue that a process where a fuzzy space splits in two others can be used
to explain the origin of the black hole entropy, and why a "generalized second
law of thermodynamics" appears to hold in the presence of black holes. We reach
the Bekenstein-Hawking formula from the count of the microstates of a black
hole modeled by a fuzzy space. In this approach, a discrete area spectrum for
the black hole, which becomes increasingly spaced as the black hole approaches
the Planck scale, is obtained. We show that, as a consequence of this, the
black hole radiation becomes less and less entropic as the black hole
evaporates, in a way that some information about its initial state could be
recovered.Comment: 4 pages, 2 figure
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