Classical and Quantum Gravity 2009

The most read articles of 2009 in the journal Classical and Quantum Gravity -- see under JULY :-)

JANUARY
What is a particle?
D Colosi and C Rovelli
http://www.iop.org/EJ/abstract/0264-9381/26/2/025002

FEBRUARY
Arithmetical chaos and quantum cosmology
L A Forte
http://www.iop.org/EJ/abstract/0264-9381/26/4/045001

MARCH
Local Hawking temperature for dynamical black holes
S A Hayward, R Di Criscienzo, M Nadalini, L Vanzo and S Zerbini
http://www.iop.org/EJ/abstract/0264-9381/26/6/062001

APRIL
The double pulsar system: a unique laboratory for gravity
M Kramer and N Wex
http://www.iop.org/EJ/abstract/0264-9381/26/7/073001

MAY
LISA Pathfinder: the experiment and the route to LISA
M Armano et al.
http://www.iop.org/EJ/abstract/0264-9381/26/9/094001

JUNE
Status of NINJA: the Numerical INJection Analysis project
L Cadonati et al.
http://www.iop.org/EJ/abstract/0264-9381/26/11/114008

JULY
What is the entropy of the universe?
P H Frampton, S D H Hsu, T W Kephart and D Reeb
http://www.iop.org/EJ/abstract/0264-9381/26/14/145005

AUGUST
Testing gravitational-wave searches with numerical relativity waveforms: results from the first Numerical INJection Analysis (NINJA) project
B Aylott et al.
http://www.iop.org/EJ/abstract/0264-9381/26/16/165008

SEPTEMBER
Polarized spots in anisotropic open universes
R Sung and P Coles
http://www.iop.org/EJ/abstract/0264-9381/26/17/172001

OCTOBER
Present status of the Penrose inequality
M Mars
http://www.iop.org/EJ/abstract/0264-9381/26/19/193001

NOVEMBER
The information paradox: a pedagogical introduction
S D Mathur
http://www.iop.org/EJ/abstract/0264-9381/26/22/224001

DECEMBER
Casimir energy and gravitomagnetism
F Sorge
http://www.iop.org/EJ/abstract/0264-9381/26/23/235002

What is the entropy of the universe?

P H Frampton, S D H Hsu, T W Kephart and D Reeb

http://www.iop.org/EJ/abstract/0264-9381/26/14/145005

Abstract. Standard calculations suggest that the entropy of our universe is dominated by black holes, whose entropy is of order their area in Planck units, although they comprise only a tiny fraction of its total energy. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. Therefore, assuming unitarity in black hole evaporation, the standard results suggest that the largest uncertainty in the future quantum state of the universe is due to the Hawking radiation from evaporating black holes. However, the entropy of the matter precursors to astrophysical black holes is enormously less than that given by area entropy. If unitarity relates the future radiation states to the black hole precursor states, then the standard results are highly misleading, at least for an observer that can differentiate the individual states of the Hawking radiation.