72,980 research outputs found
Unitary Fermi Gas in a Harmonic Trap
We present an {\it ab initio} calculation of small numbers of trapped,
strongly interacting fermions using the Green's Function Monte Carlo method
(GFMC). The ground state energy, density profile and pairing gap are calculated
for particle numbers using the parameter-free "unitary"
interaction. Trial wave functions are taken of the form of correlated pairs in
a harmonic oscillator basis. We find that the lowest energies are obtained with
a minimum explicit pair correlation beyond that needed to exploit the
degeneracy of oscillator states. We find that energies can be well fitted by
the expression where is the
Thomas-Fermi energy of a noninteracting gas in the trap and is a
pairing gap. There is no evidence of a shell correction energy in the
systematics, but the density distributions show pronounced shell effects. We
find the value for the pairing gap. This is smaller
than the value found for the uniform gas at a density corresponding to the
central density of the trapped gas.Comment: 2 figures, 2 table
Remarks on flavour mixings from orbifold compactification
We consider 5d SU(5) GUT models based on the orbifold , and study the different possibilities of placing the SU(5) matter
multiplets in three possible locations, namely, the two branes at the two
orbifold fixed points and SU(5) bulk. We demonstrate that if flavour
hierarchies originate solely from geometrical suppressions due to wavefunction
normalisation of fields propagating in the bulk, then it is not possible to
satisfy even the gross qualitative behaviour of the CKM and MNS matrices
regardless of where we place the matter multiplets.Comment: 4 pages, Late
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Real-time decoding of question-and-answer speech dialogue using human cortical activity.
Natural communication often occurs in dialogue, differentially engaging auditory and sensorimotor brain regions during listening and speaking. However, previous attempts to decode speech directly from the human brain typically consider listening or speaking tasks in isolation. Here, human participants listened to questions and responded aloud with answers while we used high-density electrocorticography (ECoG) recordings to detect when they heard or said an utterance and to then decode the utterance's identity. Because certain answers were only plausible responses to certain questions, we could dynamically update the prior probabilities of each answer using the decoded question likelihoods as context. We decode produced and perceived utterances with accuracy rates as high as 61% and 76%, respectively (chance is 7% and 20%). Contextual integration of decoded question likelihoods significantly improves answer decoding. These results demonstrate real-time decoding of speech in an interactive, conversational setting, which has important implications for patients who are unable to communicate
K+ -> pi+ nu nu(bar) and FCNC from non-universal Z' bosons
Motivated by the E787 and E949 result for K+ -> pi+ nu nu(bar) we examine the
effects of a new non-universal right-handed Z' boson on flavor changing
processes. We place bounds on the tree-level FCNC from K-K(bar) and B-B(bar)
mixing as well as from the observed CP violation in kaon decay. We discuss the
implications for K -> pi nu nu(bar), B -> X nu nu(bar) and B -> tau+ tau-. We
find that existing bounds allow substantial enhancements in the K+ -> pi+ nu
nu(bar) rate, particularly through a new one-loop Z' penguin operator.Comment: Typos corrected, references added, version to appear in PR
U(1)-decoupling, KK and BCJ relations in SYM
We proved the color reflection relation, U(1)-decoupling, Kleiss-Kuijf and
Bern-Carrasco-Johansson relation for color-ordered Super
Yang-Mills theory using SYM version BCFW recursion relation,
which depends only on the general properties of super-amplitudes. This verified
the conjectured matter fields BCJ relation. We also show that color reflection
relation and U(1)-decoupling relation are special cases of KK relation, if we
consider the KK relation as a general relation, then the former two relations
come out naturally as the special cases.Comment: 17 page
Phenomenological study of the atypical heavy flavor production observed at the Fermilab Tevatron
We address known discrepancies between the heavy flavor properties of jets
produced at the Tevatron collider and the prediction of conventional-QCD
simulations. In this study, we entertain the possibility that these effects are
real and due to new physics. We show that all anomalies can be simultaneously
fitted by postulating the additional pair production of light bottom squarks
with a 100% semileptonic branching fraction.Comment: 30 pages, 13 figures, 3 tables. Submitted to Phys. Rev.
The NLO QCD Corrections to Meson Production in Decays
The decay width of to meson is evaluated at the next-to-leading
order(NLO) accuracy in strong interaction. Numerical calculation shows that the
NLO correction to this process is remarkable. The quantum
chromodynamics(QCD)renormalization scale dependence of the results is obviously
depressed, and hence the uncertainties lying in the leading order calculation
are reduced.Comment: 14 pages, 7 figures; references added; expressions and typos ammende
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