131 research outputs found
Measurement of Time-of-Arrival in Quantum Mechanics
It is argued that the time-of-arrival cannot be precisely defined and
measured in quantum mechanics. By constructing explicit toy models of a
measurement, we show that for a free particle it cannot be measured more
accurately then , where is the initial kinetic
energy of the particle. With a better accuracy, particles reflect off the
measuring device, and the resulting probability distribution becomes distorted.
It is shown that a time-of-arrival operator cannot exist, and that approximate
time-of-arrival operators do not correspond to the measurements considered
here.Comment: References added. To appear in Phys. Rev.
Estimating the uncertainties of strain and damage analysis by X-ray diffraction in ion implanted MoO3
N/
Single-particle nonlocality and entanglement with the vacuum
We propose a single-particle experiment that is equivalent to the
conventional two-particle experiment used to demonstrate a violation of Bell's
inequalities. Hence, we argue that quantum mechanical nonlocality can be
demonstrated by single-particle states. The validity of such a claim has been
discussed in the literature, but without reaching a clear consensus. We show
that the disagreement can be traced to what part of the total state of the
experiment one assigns to the (macroscopic) measurement apparatus. However,
with a conventional and legitimate interpretation of the measurement process
one is led to the conclusion that even a single particle can show nonlocal
properties.Comment: 6 pages, 5 figure
Measuring the Spectra of High Energy Neutrinos with a Kilometer-Scale Neutrino Telescope
We investigate the potential of a future kilometer-scale neutrino telescope
such as the proposed IceCube detector in the South Pole, to measure and
disentangle the yet unknown components of the cosmic neutrino flux, the prompt
atmospheric neutrinos coming from the decay of charmed particles and the
extra-galactic neutrinos, in the 10 TeV to 1 EeV energy range.
Assuming a power law type spectra,
, we quantify the discriminating
power of the IceCube detector and discuss how well we can determine magnitude
() as well as slope () of these two components of the high
energy neutrino spectrum, taking into account the background coming from the
conventional atmospheric neutrinos.Comment: 21 pages, 7 figure
Faraday rotation in graphene
We study magneto--optical properties of monolayer graphene by means of
quantum field theory methods in the framework of the Dirac model. We reveal a
good agreement between the Dirac model and a recent experiment on giant Faraday
rotation in cyclotron resonance. We also predict other regimes when the effects
are well pronounced. The general dependence of the Faraday rotation and
absorption on various parameters of samples is revealed both for suspended and
epitaxial graphene.Comment: 10 pp; v2: typos corrected and references added, v3, v4: small
changes and more reference
Long-Baseline Study of the Leading Neutrino Oscillation at a Neutrino Factory
Within the framework of three-flavor neutrino oscillations, we consider the
physics potential of \nu_e --> \nu_\mu appearance and \nu_\mu --> \nu_\mu
survival measurements at a neutrino factory for a leading oscillation scale
\delta m^2 ~ 3.5 \times 10^{-3} eV^2. Event rates are evaluated versus baseline
and stored muon energy, and optimal values discussed. Over a sizeable region of
oscillation parameter space, matter effects would enable the sign of \delta m^2
to be determined from a comparison of \nu_e --> \nu_\mu with \bar\nu_e -->
\bar\nu_\mu event rates and energy distributions. It is important, therefore,
that both positive and negative muons can be stored in the ring. Measurements
of the \nu_\mu --> \nu_\mu survival spectrum could determine the magnitude of
\delta m^2 and the leading oscillation amplitude with a precision of O(1%--2%).Comment: 33 pages, single-spaced Revtex, uses epsf.sty, 14 postscript figures.
Added references, expanded conclusions, improved figs. 13 and 14. Version to
be published in Phys. Rev.
Towards an applied metaecology
The complexity of ecological systems is a major challenge for practitioners and decision-makers who work to avoid, mitigate and manage environmental change. Here, we illustrate how metaecology – the study of spatial interdependencies among ecological systems through fluxes of organisms, energy, and matter – can enhance understanding and improve managing environmental change at multiple spatial scales. We present several case studies illustrating how the framework has leveraged decision-making in conservation, restoration and risk management. Nevertheless, an explicit incorporation of metaecology is still uncommon in the applied ecology literature, and in action guidelines addressing environmental change. This is unfortunate because the many facets of environmental change can be framed as modifying spatial context, connectedness and dominant regulating processes - the defining features of metaecological systems. Narrowing the gap between theory and practice will require incorporating system-specific realism in otherwise predominantly conceptual studies, as well as deliberately studying scenarios of environmental change.We thank FAPESP (grants 2014/10470-7 to AM, 2013/04585-3 to DL, 2013/50424-1 to TS and 2015/18790-3to LS), CNPq (Productivity Fellowships 301656/2011-8 to JAFDF,308205/2014-6 to RP, 306183/2014-5 to PIP and 307689/2014-0 to VDP), the National Science Foundation (DEB 1645137 toJGH), the Natural Sciences and Engineering Council of Canada (SJL,PPN), and the Academy of Finland (grants 257686 and 292765 toMC) for support. This work contributes to the Labex OT-Med (no.ANR-11-LABX-0061), funded by the French government throughthe A*MIDEX project (no. ANR-11-IDEX-0001-02)
Many body physics from a quantum information perspective
The quantum information approach to many body physics has been very
successful in giving new insight and novel numerical methods. In these lecture
notes we take a vertical view of the subject, starting from general concepts
and at each step delving into applications or consequences of a particular
topic. We first review some general quantum information concepts like
entanglement and entanglement measures, which leads us to entanglement area
laws. We then continue with one of the most famous examples of area-law abiding
states: matrix product states, and tensor product states in general. Of these,
we choose one example (classical superposition states) to introduce recent
developments on a novel quantum many body approach: quantum kinetic Ising
models. We conclude with a brief outlook of the field.Comment: Lectures from the Les Houches School on "Modern theories of
correlated electron systems". Improved version new references adde
The effects of introducing the Amazonian squirrel monkey on the behavior of the northeast marmoset
Agricultural crops in the diet of bearded capuchin monkeys, Cebus libidinosus Spix (Primates: Cebidae), in forest fragments in southeast Brazil
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