1,136 research outputs found
Detecting photon-photon scattering in vacuum at exawatt lasers
In a recent paper, we have shown that the QED nonlinear corrections imply a
phase correction to the linear evolution of crossing electromagnetic waves in
vacuum. Here, we provide a more complete analysis, including a full numerical
solution of the QED nonlinear wave equations for short-distance propagation in
a symmetric configuration. The excellent agreement of such a solution with the
result that we obtain using our perturbatively-motivated Variational Approach
is then used to justify an analytical approximation that can be applied in a
more general case. This allows us to find the most promising configuration for
the search of photon-photon scattering in optics experiments. In particular, we
show that our previous requirement of phase coherence between the two crossing
beams can be released. We then propose a very simple experiment that can be
performed at future exawatt laser facilities, such as ELI, by bombarding a low
power laser beam with the exawatt bump.Comment: 8 pages, 6 figure
Entanglement as a source of black hole entropy
We review aspects of black hole thermodynamics, and show how entanglement of
a quantum field between the inside and outside of a horizon can account for the
area-proportionality of black hole entropy, provided the field is in its ground
state. We show that the result continues to hold for Coherent States and
Squeezed States, while for Excited States, the entropy scales as a power of
area less than unity. We also identify location of the degrees of freedom which
give rise to the above entropy.Comment: 12 pages, latex, 5 figures. Invited talk by SD at `Recent
Developments in Gravity' (NEB XII), Nafplion, Greece, 30 June 2006. To appear
in Journal of Physics: Conference Series; V2: References added, Minor changes
to match published versio
Reality, measurement and locality in Quantum Field Theory
It is currently believed that the local causality of Quantum Field Theory
(QFT) is destroyed by the measurement process. This belief is also based on the
Einstein-Podolsky-Rosen (EPR) paradox and on the so-called Bell's theorem, that
are thought to prove the existence of a mysterious, instantaneous action
between distant measurements. However, I have shown recently that the EPR
argument is removed, in an interpretation-independent way, by taking into
account the fact that the Standard Model of Particle Physics prevents the
production of entangled states with a definite number of particles. This result
is used here to argue in favor of a statistical interpretation of QFT and to
show that it allows for a full reconciliation with locality and causality.
Within such an interpretation, as Ballentine and Jarret pointed out long ago,
Bell's theorem does not demonstrate any nonlocality.Comment: 15 pages. Published versio
On Unitarity Based Relations Between Various Lepton Family Violating Processes
Simple "unitarity inspired" relations between two- and three-body lepton
flavor violating decays are noted and discussed. In the absence of
cancellations, the existing strong bounds on and severly constrain two-body lepton flavor violating decays.Comment: 5 pages, 3 figure
Manufacture and Test of the Prototype 5 T Superconducting Undulator for the LHC Synchrotron Radiation Profile Monitor
A superconducting undulator wound with Nb-Ti based conductor, will be used in the LHC as a key part of the synchrotron radiation profile monitor system. Two undulators are needed, one per each circulating beam, providing 5 T in a 60 mm bore over two periods of 280 mm each. A full scale prototype has been designed and successfully tested in the end of 2004. In this paper, the electromagnetic and the mechanical design of the undulator are summarized. The fabrication of the prototype is described and the successful cold test results, both power test and magnetic flux density measurements, are reported
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