25,030 research outputs found
Positive ion temperatures above the F-layer maximum
Positive ion temperatures above F layer maximum from Ariel I satellite ion mass analyze
Model-Independent Determinations of B -> D l nu , D* l nu Form Factors
We present nonperturbative, model-independent parametrizations of the
individual QCD form factors relevant to B -> D* l nu and B -> D l nu decays.
These results follow from dispersion relations and analyticity, without
recourse to heavy quark symmetry. To describe a form factor with two percent
accuracy, three parameters are necessary, one of which is its normalization at
zero recoil, F(1). We combine the individual form factors using heavy quark
symmetry to extract values for the product |V_{cb}| F(1) from B -> D* l nu data
with negligible extrapolation uncertainty.Comment: uses harvmac and epsf, 22 pages, 3 eps figures include
Black hole formation in core-collapse supernovae and time-of-flight measurements of the neutrino masses
In large stars that have exhausted their nuclear fuel, the stellar core collapses to a hot and dense proto-neutron star that cools by the radiation of neutrinos and antineutrinos of all flavors. Depending on its final mass, this may become either a neutron star or a black hole. Black hole formation may be triggered by mass accretion or a change in the high-density equation of state. We consider the possibility that black hole formation happens when the flux of neutrinos is still measurably high. If this occurs, then the neutrino signal from the supernova will be terminated abruptly (the transition takes ≲0.5 ms). The properties and duration of the signal before the cutoff are important measures of both the physics and astrophysics of the cooling proto-neutron star. For the event rates expected in present and proposed detectors, the cutoff will generally appear sharp, thus allowing model-independent time-of-flight mass tests for the neutrinos after the cutoff. If black hole formation occurs relatively early, within a few (∼1) seconds after core collapse, then the expected luminosities are of order LBH=1052 erg/s per flavor. In this case, the neutrino mass sensitivity can be extraordinary. For a supernova at a distance D=10 kpc, SuperKamiokande can detect a ν̅e mass down to 1.8 eV by comparing the arrival times of the high-energy and low-energy neutrinos in ν̅e+p→e++n. This test will also measure the cutoff time, and will thus allow a mass test of νμ and ντ relative to ν̅e. Assuming that νμ and ντ are nearly degenerate, as suggested by the atmospheric neutrino results, masses down to about 6 eV can be probed with a proposed lead detector of mass MD=4 kton (OMNIS). Remarkably, the neutrino mass sensitivity scales as (D/LBHMD)1/2. Therefore, direct sensitivity to all three neutrino masses in the interesting few-eV range is realistically possible; there are no other known techniques that have this capability
Two Flavour QCD Phase Transition
Results on the phase transition in QCD with two flavours of light staggered
fermions from an ongoing simulation are presented. We find the restoration of
the chiral SU(2) x SU(2) symmetry, but not of the axial U_A(1) symmetry.Comment: LaTeX2e, amstex package. 4 pages, 2 figures. Talk presented at the
10th International Conference on Problems of Quantum Field Theory, Crime
Flexible high speed codec
The project's objective is to develop an advanced high speed coding technology that provides substantial coding gains with limited bandwidth expansion for several common modulation types. The resulting technique is applicable to several continuous and burst communication environments. Decoding provides a significant gain with hard decisions alone and can utilize soft decision information when available from the demodulator to increase the coding gain. The hard decision codec will be implemented using a single application specific integrated circuit (ASIC) chip. It will be capable of coding and decoding as well as some formatting and synchronization functions at data rates up to 300 megabits per second (Mb/s). Code rate is a function of the block length and can vary from 7/8 to 15/16. Length of coded bursts can be any multiple of 32 that is greater than or equal to 256 bits. Coding may be switched in or out on a burst by burst basis with no change in the throughput delay. Reliability information in the form of 3-bit (8-level) soft decisions, can be exploited using applique circuitry around the hard decision codec. This applique circuitry will be discrete logic in the present contract. However, ease of transition to LSI is one of the design guidelines. Discussed here is the selected coding technique. Its application to some communication systems is described. Performance with 4, 8, and 16-ary Phase Shift Keying (PSK) modulation is also presented
A synoptic view of ionic constitution above the F-layer maximum
Ionic composition above F layer maximum from Ariel I satellite ion mass spectromete
Thermocapillary effects in driven dewetting and self-assembly of pulsed laser-irradiated metallic films
In this paper the lubrication-type dynamical model is developed of a molten,
pulsed laser-irradiated metallic film. The heat transfer problem that
incorporates the absorbed heat from a single beam or interfering beams is
solved analytically. Using this temperature field, we derive the 3D long-wave
evolution PDE for the film height. To get insights into dynamics of dewetting,
we study the 2D version of the evolution equation by means of a linear
stability analysis and by numerical simulations. The stabilizing and
destabilizing effects of various system parameters, such as the peak laser beam
intensity, the film optical thickness, the Biot and Marangoni numbers, etc. are
elucidated. It is observed that the film stability is promoted for such
parameters variations that increase the heat production in the film. In the
numerical simulations the impacts of different irradiation modes are
investigated. In particular, we obtain that in the interference heating mode
the spatially periodic irradiation results in a spatially periodic film rupture
with the same, or nearly equal period. The 2D model qualitatively reproduces
the results of the experimental observations of a film stability and spatial
ordering of a re-solidified nanostructures
Quantum lost property: a possible operational meaning for the Hilbert-Schmidt product
Minimum error state discrimination between two mixed states \rho and \sigma
can be aided by the receipt of "classical side information" specifying which
states from some convex decompositions of \rho and \sigma apply in each run. We
quantify this phenomena by the average trace distance, and give lower and upper
bounds on this quantity as functions of \rho and \sigma. The lower bound is
simply the trace distance between \rho and \sigma, trivially seen to be tight.
The upper bound is \sqrt{1 - tr(\rho\sigma)}, and we conjecture that this is
also tight. We reformulate this conjecture in terms of the existence of a pair
of "unbiased decompositions", which may be of independent interest, and prove
it for a few special cases. Finally, we point towards a link with a notion of
non-classicality known as preparation contextuality.Comment: 3 pages, 1 figure. v2: Less typos in text and less punctuation in
titl
Dynamic study of adhesively bonded double lap composite joints
Composite structures may be subjected to high loading rates in naval applications.Hence, the composite assembly’s dynamic behaviour needs investigation. This paperpresents an investigation on the structural rate dependent behaviour of adhesivelybounded double lap joints. High rate tests showed ringing in the force/displacementcurves. An attempt was made to determine the origins of this phenomenon
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