2,210 research outputs found
Flight measurement and analysis of AAFE RADSCAT wind speed signature of the ocean
The advanced aerospace flight experiment radiometer scatterometer (AAFE RADSCAT) which was developed as a research tool to evaluate the use of microwave frequency remote sensors to provide wind speed information at the ocean surface is discussed. The AAFE RADSCAT helped establish the feasibility of the satellite scatterometer for measuring both wind speed and direction. The most important function of the AAFE RADSCAT was to provide a data base of ocean normalized radar cross section (NRCS) measurements as a function of surface wind vector at 13.9 GHz. The NRCS measurements over a wide parametric range of incidence angles, azimuth angles, and winds were obtained in a series of RADSCAT aircraft missions. The obtained data base was used to model the relationship between k sub u band radar signature and ocean surface wind vector. The models developed therefrom are compared with those used for inversion of the SEASAT-A satellite scatterometer (SASS) radar measurements to wind speeds
Complete Insecurity of Quantum Protocols for Classical Two-Party Computation
A fundamental task in modern cryptography is the joint computation of a
function which has two inputs, one from Alice and one from Bob, such that
neither of the two can learn more about the other's input than what is implied
by the value of the function. In this Letter, we show that any quantum protocol
for the computation of a classical deterministic function that outputs the
result to both parties (two-sided computation) and that is secure against a
cheating Bob can be completely broken by a cheating Alice. Whereas it is known
that quantum protocols for this task cannot be completely secure, our result
implies that security for one party implies complete insecurity for the other.
Our findings stand in stark contrast to recent protocols for weak coin tossing,
and highlight the limits of cryptography within quantum mechanics. We remark
that our conclusions remain valid, even if security is only required to be
approximate and if the function that is computed for Bob is different from that
of Alice.Comment: v2: 6 pages, 1 figure, text identical to PRL-version (but reasonably
formatted
On the power of two-party quantum cryptography
We study quantum protocols among two distrustful parties. Under the
sole assumption of correctness - guaranteeing that honest players
obtain their correct outcomes - we show that every protocol
implementing a non-trivial primitive necessarily leaks information to
a dishonest player. This extends known impossibility results to all
non-trivial primitives. We provide a framework for quantifying this
leakage and argue that leakage is a good measure for the privacy
provided to the players by a given protocol. Our framework also covers
the case where the two players are helped by a trusted third party. We
show that despite the help of a trusted third party, the players
cannot amplify the cryptographic power of any primitive. All our
results hold even against quantum honest-but-curious adversaries who
honestly follow the protocol but purify their actions and apply a
different measurement at the end of the protocol. As concrete
examples, we establish lower bounds on the leakage of standard
universal two-party primitives such as oblivious transfer
Model-based Cognitive Neuroscience: Multifield Mechanistic Integration in Practice
Autonomist accounts of cognitive science suggest that cognitive model building and theory construction (can or should) proceed independently of findings in neuroscience. Common functionalist justifications of autonomy rely on there being relatively few constraints between neural structure and cognitive function (e.g., Weiskopf, 2011). In contrast, an integrative mechanistic perspective stresses the mutual constraining of structure and function (e.g., Piccinini & Craver, 2011; Povich, 2015). In this paper, I show how model-based cognitive neuroscience (MBCN) epitomizes the integrative mechanistic perspective and concentrates the most revolutionary elements of the cognitive neuroscience revolution (Boone & Piccinini, 2016). I also show how the prominent subset account of functional realization supports the integrative mechanistic perspective I take on MBCN and use it to clarify the intralevel and interlevel components of integration
Implications of Hyperon Pairing for Cooling of Neutron Stars
The implications of hyperon pairing for the thermal evolution of neutron
stars containing hyperons are investigated. The outcome of cooling simulations
are compared for neutron star models composed only of nucleons and leptons,
models including hyperons, and models including pairing of hyperons. We show
that lambda and neutron pairing suppresses all possible fast neutrino emission
processes in not too massive neutron stars. The inclusion of lambda pairing
yields better agreement with X-ray observations of pulsars. Particularly, the
surface temperatures deduced from X-ray observations within the hydrogen
atmosphere model are more consistent with the thermal history of neutron stars
containing hyperons, if the critical temperature for the onset of lambda and
nucleon pairing is not too small.Comment: 7 pages, 3 figures. To be published in ApJL. The postscript and
additional tables can be found at
http://www.physik.uni-muenchen.de/sektion/suessmann/astro/cool/schaab.089
Magnetic field generated by r-modes in accreting quark stars
We show that the r-mode instability can generate strong toroidal fields in
the core of accreting millisecond quark stars by inducing differential
rotation. We follow the spin frequency evolution on a long time scale taking
into account the magnetic damping rate in the evolution equations of r-modes.
The maximum spin frequency of the star is only marginally smaller than in the
absence of the magnetic field. The late-time evolution of the stars which enter
the r-mode instability region is instead rather different if the generated
magnetic fields are taken into account: they leave the millisecond pulsar
region and they become radio pulsars.Comment: 8 pages, 8 figure
Cryptography in the Bounded Quantum-Storage Model
We initiate the study of two-party cryptographic primitives with unconditional
security, assuming that the adversary’s quantum memory is of bounded size. We show that oblivious
transfer and bit commitment can be implemented in this model using protocols where honest parties
need no quantum memory, whereas an adversarial player needs quantum memory of size at least n/2
in order to break the protocol, where n is the number of qubits transmitted. This is in sharp contrast
to the classical bounded-memory model, where we can only tolerate adversaries with memory of size
quadratic in honest players’ memory size. Our protocols are efficient and noninteractive and can be
implemented using today’s technology. On the technical side, a new entropic uncertainty relation
involving min-entropy is established
Improving the security of quantum protocols via commit-and-open
We consider two-party quantum protocols starting with a transmission
of some random BB84 qubits followed by classical messages. We show a
general compiler improving the security of such protocols: if the
original protocol is secure against an almost honest adversary, then
the compiled protocol is secure against an arbitrary computationally
bounded (quantum) adversary. The compilation preserves the number of
qubits sent and the number of rounds up to a constant factor. The
compiler also preserves security in the bounded-quantum-storage model
(BQSM), so if the original protocol was BQSM-secure, the compiled
protocol can only be broken by an adversary who has large quantum
memory and large computing power. This is in contrast to known
BQSM-secure protocols, where security breaks down completely if the
adversary has larger quantum memory than expected. We show how our
technique can be applied to quantum identification and oblivious
transfer protocols
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