14,135 research outputs found
Exceptional points and photonic catastrophe
Exceptional points (EPs) with a global collapse of pairs of eigenfunctions
are shown to arise in two locally-coupled and spatially-extended optical
structures with balanced gain and loss. Global collapse at the EP deeply
changes light propagation, which becomes very sensitive to small changes of
initial conditions or system parameters, similarly to what happens in models of
classical or quantum catastrophes. The implications of global collapse for
light behavior are illustrated by considering discrete beam diffraction and
Bloch oscillation catastrophe in coupled waveguide lattices.Comment: 5 pages, 4 figure
Implications of the Pseudo-Dirac Scenario for Ultra High Energy Neutrinos from GRBs
The source of Ultra High Energy Cosmic Rays (UHECR) is still an unresolved
mystery. Up until recently, sources of Gamma Ray Bursts (GRBs) had been
considered as a suitable source for UHECR. Within the fireball model, the UHECR
produced at GRBs should be accompanied with a neutrino flux detectable at the
neutrino telescope such as IceCube. Recently, IceCube has set an upper bound on
the neutrino flux accompanied by GRBs about 3.7 times below the prediction. We
investigate whether this deficit can be explained by the oscillation of the
active neutrinos to sterile neutrinos en route from the source to the detectors
within the pseudo-Dirac scenario. We then discuss the implication of this
scenario for diffuse supernova relic neutrinos.Comment: 14 pages, 5 figures; v2: figures added, discussion improved, matches
the version published in JCA
Erasing the orbital angular momentum information of a photon
Quantum erasers with paths in the form of physical slits have been studied
extensively and proven instrumental in probing wave-particle duality in quantum
mechanics. Here we replace physical paths (slits) with abstract paths of
orbital angular momentum (OAM). Using spin-orbit hybrid entanglement of photons
we show that the OAM content of a photon can be erased with a complimentary
polarization projection of one of the entangled pair. The result is the
(dis)appearance of azimuthal fringes based on whether the \which-OAM"
information was erased. We extend this concept to a delayed measurement scheme
and show that the OAM information and fringe visibility are complimentary
Study of attosecond delays using perturbation diagrams and exterior complex scaling
We describe in detail how attosecond delays in laser-assisted photoionization
can be computed using perturbation theory based on two-photon matrix elements.
Special emphasis is laid on above-threshold ionization, where the electron
interacts with an infrared field after photoionization by an extreme
ultraviolet field. Correlation effects are introduced using diagrammatic
many-body theory to the level of the random-phase approximation with exchange
(RPAE). Our aim is to provide an ab initio route to correlated multi-photon
processes that are required for an accurate description of experiments on the
attosecond time scale. Here, our results are focused on photoionization of the
M -shell of argon atoms, where experiments have been carried out using the
so-called RABITT technique. An influence of autoionizing resonances in
attosecond delay measurements is observed. Further, it is shown that the delay
depends on both detection angle of the photoelectron and energy of the probe
photon.Comment: 36 pages, 10 figure
A Staged Muon-Based Neutrino and Collider Physics Program
We sketch a staged plan for a series of muon-based facilities that can do
compelling physics at each stage. Such a plan is unique in its ability to span
both the Intensity and Energy Frontiers as defined by the P5 sub-panel of the
US High Energy Physics Advisory Committee. This unique physics reach places a
muon-based facility in an unequaled position to address critical questions
about the nature of the Universe.Comment: Contribution to the CERN Council Open Symposium on European Strategy
for Particle Physics, 10-12 Sept. 2012, Krakow, Polan
Discovery of Proton Decay: A Must for Theory, a Challenge for Experiment
It is noted that, but for one missing piece -- proton decay -- the evidence
in support of grand unification is now strong. It includes: (i) the observed
family-structure, (ii) the meeting of the gauge couplings, (iii)
neutrino-oscillations, (iv) the intricate pattern of the masses and mixings of
all fermions, including the neutrinos, and (v) the need for as a
generator, to implement baryogenesis. Taken together, these not only favor
grand unification but in fact select out a particular route to such
unification, based on the ideas of supersymmetry, SU(4)-color and left-right
symmetry. Thus they point to the relevance of an effective string-unified
G(224) or SO(10)-symmetry.
A concrete proposal is presented, within a predictive
SO(10)/G(224)-framework, that successfully describes the masses and mixings of
all fermions, including the neutrinos - with eight predictions, all in
agreement with observation. Within this framework, a systematic study of proton
decay is carried out, which pays special attention to its dependence on the
fermion masses, including the superheavy Majorana masses of the right-handed
neutrinos. The study shows that a conservative upper limit on the proton
lifetime is about (1/2 - 1) yrs, with
being the dominant decay mode, and as a distinctive feature,
being prominent. This in turn strongly suggests that an improvement in the
current sensitivity by a factor of five to ten (compared to SuperK) ought to
reveal proton decay. Otherwise some promising and remarkably successful ideas
on unification would suffer a major setback.Comment: LaTex file 29 pages, no figures. Minor correction
Period-tripling subharmonic oscillations in a driven superconducting resonator
We have observed period-tripling subharmonic oscillations, in a
superconducting coplanar waveguide resonator operated in the quantum regime,
. The resonator is terminated by a tunable inductance
that provides a Kerr-type nonlinearity. We detected the output field
quadratures at frequencies near the fundamental mode, GHz, when the resonator was driven by a current at with an
amplitude exceeding an instability threshold. The output radiation was
red-detuned from the fundamental mode. We observed three stable radiative
states with equal amplitudes and phase-shifted by . The
downconversion from to is strongly enhanced by resonant
excitation of the second mode of the resonator, and the cross-Kerr effect. Our
experimental results are in quantitative agreement with a model for the driven
dynamics of two coupled modes
Observation of Fermi-Pasta-Ulam-Tsingou Recurrence and Its Exact Dynamics
One of the most controversial phenomena in nonlinear dynamics is the reappearance of initial
conditions. Celebrated as the Fermi-Pasta-Ulam-Tsingou problem, the attempt to understand how these
recurrences form during the complex evolution that leads to equilibrium has deeply influenced the entire
development of nonlinear science. The enigma is rendered even more intriguing by the fact that integrable
models predict recurrence as exact solutions, but the difficulties involved in upholding integrability for a
sufficiently long dynamic has not allowed a quantitative experimental validation. In natural processes,
coupling with the environment rapidly leads to thermalization, and finding nonlinear multimodal systems
presenting multiple returns is a long-standing open challenge. Here, we report the observation of more than
three Fermi-Pasta-Ulam-Tsingou recurrences for nonlinear optical spatial waves and demonstrate the
control of the recurrent behavior through the phase and amplitude of the initial field. The recurrence period
and phase shift are found to be in remarkable agreement with the exact recurrent solution of the nonlinear
Schrödinger equation, while the recurrent behavior disappears as integrability is lost. These results identify
the origin of the recurrence in the integrability of the underlying dynamics and allow us to achieve one of
the basic aspirations of nonlinear dynamics: the reconstruction, after several return cycles, of the exact
initial condition of the system, ultimately proving that the complex evolution can be accurately predicted in
experimental conditions
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