370 research outputs found
A cooperative-relational approach to digital libraries
Copyright @ 2007 Springer-Verlag, Berlin HeidelbergThis paper presents a novel approach to model-driven development of Digital Library (DL) systems. The overall idea is to allow Digital Library systems designers (e.g. information architects, librarians, domain experts) to easily design such systems by using a visual language. We designed a Domain Specific Visual Language for such a purpose and developed a framework supporting it; this framework helps designers by automatically generating code for the defined Digital Library system, so that they do not have to get involved into technical issues concerning its deployment. In our approach, both Human-Computer Interaction and Computer Supported Collaborative Work techniques are exploited when generating interfaces and services for the specific Digital Library domain
Compactification and signature transition in Kaluza-Klein spinor cosmology
We study the classical and quantum cosmology of a 4+1-dimensional space-time
with a non-zero cosmological constant coupled to a self interacting massive
spinor field. We consider a spatially flat Robertson-Walker universe with the
usual scale factor and an internal scale factor associated with
the extra dimension. For a free spinor field the resulting equations admit
exact solutions, whereas for a self interacting spinor field one should resort
to a numerical method for exhibiting their behavior. These solutions give rise
to a degenerate metric and exhibit signature transition from a Euclidean to a
Lorentzian domain. Such transitions suggest a compactification mechanism for
the internal and external scale factors such that in the
Lorentzian region. The corresponding quantum cosmology and the ensuing
Wheeler-DeWitt equation have exact solutions in the mini-superspace when the
spinor field is free, leading to wavepackets undergoing signature change. The
question of stabilization of the extra dimension is also discussed.Comment: 12 pages, 1 figure, to appear in Annals of Physic
The Mathematical Universe
I explore physics implications of the External Reality Hypothesis (ERH) that
there exists an external physical reality completely independent of us humans.
I argue that with a sufficiently broad definition of mathematics, it implies
the Mathematical Universe Hypothesis (MUH) that our physical world is an
abstract mathematical structure. I discuss various implications of the ERH and
MUH, ranging from standard physics topics like symmetries, irreducible
representations, units, free parameters, randomness and initial conditions to
broader issues like consciousness, parallel universes and Godel incompleteness.
I hypothesize that only computable and decidable (in Godel's sense) structures
exist, which alleviates the cosmological measure problem and help explain why
our physical laws appear so simple. I also comment on the intimate relation
between mathematical structures, computations, simulations and physical
systems.Comment: Replaced to match accepted Found. Phys. version, 31 pages, 5 figs;
more details at http://space.mit.edu/home/tegmark/toe.htm
Measurements of the -Dependence of the Proton and Neutron Spin Structure Functions g1p and g1n
The structure functions g1p and g1n have been measured over the range 0.014 <
x < 0.9 and 1 < Q2 < 40 GeV2 using deep-inelastic scattering of 48 GeV
longitudinally polarized electrons from polarized protons and deuterons. We
find that the Q2 dependence of g1p (g1n) at fixed x is very similar to that of
the spin-averaged structure function F1p (F1n). From a NLO QCD fit to all
available data we find at
Q2=5 GeV2, in agreement with the Bjorken sum rule prediction of 0.182 \pm
0.005.Comment: 17 pages, 3 figures. Submitted to Physics Letters
Research of working area development parameters in conditions of deep steep deposit finalizing
ĐŃŃиПанО ŃĐžŃĐźŃНи ŃОСŃĐ°Ń
ŃĐ˝ĐşŃ ĐžĐąâŃĐźŃ ĐˇĐ°ĐżĐ°ŃŃв кОŃиŃниŃ
кОпаНин в ĐżŃикОнŃŃŃĐ˝ŃĐš ŃĐ° гНийиннŃĐš СОнŃ. ĐŃŃанОвНонО Ń
Đ°ŃĐ°ĐşŃĐľŃ Đ˛ĐżĐťĐ¸Đ˛Ń ĐżĐ°ŃаПоŃŃŃв Đ´ĐžŃОйки гНийОкиŃ
ĐşŃŃŃĐžŃпадниŃ
ŃĐžĐ´ĐžĐ˛Đ¸Ń Đ˛ŃĐ´ĐşŃиŃиП ŃпОŃОйОП на Đ´ĐžŃŃĐťŃно ĐżĐžĐťĐžĐśĐľĐ˝Đ˝Ń ĐżĐžŃĐžŃниŃ
ŃĐ° ĐżŃОокŃниŃ
кОнŃŃŃŃв каŃâŃŃŃ. ĐŃŃанОвНонО, ŃĐž наКПонŃиК ŃĐľŃоднŃĐš кОоŃŃŃŃŃĐ˝Ń ŃОСкŃĐ¸Đ˛Ń Đ´ĐžŃŃгаŃŃŃŃŃ ĐżŃи ĐźŃĐ˝ŃПаНŃĐ˝ĐžĐźŃ ĐˇĐ˝Đ°ŃĐľĐ˝Đ˝Ń ŃŃПи ОйŃŃĐłŃв кОŃиŃĐ˝ĐžŃ ĐşĐžĐżĐ°ĐťĐ¸Đ˝Đ¸ ĐżŃикОнŃŃŃĐ˝ĐžŃ ĐˇĐžĐ˝Đ¸ НоМаŃОгО Ń Đ˛Đ¸ŃŃŃОгО йОкŃв ĐżĐžĐşĐťĐ°Đ´Ń Đ˛ ĐżŃОокŃĐ˝ĐžĐźŃ ĐżĐžĐťĐžĐśĐľĐ˝Đ˝Ń. ĐаКПонŃиК пОŃĐžŃниК кОоŃŃŃŃŃĐ˝Ń ŃОСкŃĐ¸Đ˛Ń Đ´ĐžŃŃгаŃŃŃŃŃ ĐżŃи ĐźŃĐ˝ŃПаНŃĐ˝ĐžĐźŃ ĐˇĐ˝Đ°ŃĐľĐ˝Đ˝Ń ŃŃПи ОйŃŃĐłŃв кОŃиŃĐ˝ĐžŃ ĐşĐžĐżĐ°ĐťĐ¸Đ˝Đ¸ ĐżŃикОнŃŃŃĐ˝ĐžŃ ĐˇĐžĐ˝Đ¸ НоМаŃОгО Ń Đ˛Đ¸ŃŃŃОгО йОкŃв пОкНадŃ, Đ° ŃакОМ ŃОйОŃОгО йОŃŃŃ ĐşĐ°Ń'ŃŃŃ Đ˛ пОŃĐžŃĐ˝ĐžĐźŃ ĐżĐžĐťĐžĐśĐľĐ˝Đ˝Ń
Updated Nucleosynthesis Constraints on Unstable Relic Particles
We revisit the upper limits on the abundance of unstable massive relic
particles provided by the success of Big-Bang Nucleosynthesis calculations. We
use the cosmic microwave background data to constrain the baryon-to-photon
ratio, and incorporate an extensively updated compilation of cross sections
into a new calculation of the network of reactions induced by electromagnetic
showers that create and destroy the light elements deuterium, he3, he4, li6 and
li7. We derive analytic approximations that complement and check the full
numerical calculations. Considerations of the abundances of he4 and li6 exclude
exceptional regions of parameter space that would otherwise have been permitted
by deuterium alone. We illustrate our results by applying them to massive
gravitinos. If they weigh ~100 GeV, their primordial abundance should have been
below about 10^{-13} of the total entropy. This would imply an upper limit on
the reheating temperature of a few times 10^7 GeV, which could be a potential
difficulty for some models of inflation. We discuss possible ways of evading
this problem.Comment: 40 pages LaTeX, 18 eps figure
The asymmetry of the proton in a Pion Cloud Model approach
We study the asymmetry of the proton in a model approach
in which hadronic fluctuations of the nucleon are generated through gluon
splitting and recombination mechanisms. Within this framework, it is shown that
the
asymmetry of the proton is consistently described by including only
nucleon fluctuations to and bound states. Predictions
of the model closely agree with the recent experimental data of the E866/NuSea
Collaboration.Comment: Final version. To appear in Phys. Rev.
Search for tau -> e gamma decay at Belle
We have searched for the lepton-flavor-violating decay tau -> e gamma using a
data sample of 86.7/fb collected with the Belle detector at the KEKB asymmetric
e^+ e^- collider. No evidence for a signal is obtained, and we set an upper
limit for the branching fraction Br(tau -> e gamma) < 3.9 x 10^-7 at the 90%
C.L.Comment: 11 pages, 10 figures, ReVTeX4, eps
Flavor Decomposition of the Polarized Quark Distributions in the Nucleon from Inclusive and Semi-inclusive Deep-inelastic Scattering
Spin asymmetries of semi-inclusive cross sections for the production of
positively and negatively charged hadrons have been measured in deep-inelastic
scattering of polarized positrons on polarized hydrogen and 3He targets, in the
kinematic range 0.023<x<0.6 and 1 GeV^2<Q^2<10 GeV^2. Polarized quark
distributions are extracted as a function of x for up $(u+u_bar) and down
(d+d_bar) flavors. The up quark polarization is positive and the down quark
polarization is negative in the measured range. The polarization of the sea is
compatible with zero. The first moments of the polarized quark distributions
are presented. The isospin non-singlet combination Delta_q_3 is consistent with
the prediction based on the Bjorken sum rule. The moments of the polarized
quark distributions are compared to predictions based on SU(3)_f flavor
symmetry and to a prediction from lattice QCD.Comment: 14 pages, 6 figures (eps format), 10 tables in Latex New version
contains tables of asymmetries and correlation matri
Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV
A search is presented for physics beyond the standard model (BSM) in final
states with a pair of opposite-sign isolated leptons accompanied by jets and
missing transverse energy. The search uses LHC data recorded at a
center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to
an integrated luminosity of approximately 5 inverse femtobarns. Two
complementary search strategies are employed. The first probes models with a
specific dilepton production mechanism that leads to a characteristic kinematic
edge in the dilepton mass distribution. The second strategy probes models of
dilepton production with heavy, colored objects that decay to final states
including invisible particles, leading to very large hadronic activity and
missing transverse energy. No evidence for an event yield in excess of the
standard model expectations is found. Upper limits on the BSM contributions to
the signal regions are deduced from the results, which are used to exclude a
region of the parameter space of the constrained minimal supersymmetric
extension of the standard model. Additional information related to detector
efficiencies and response is provided to allow testing specific models of BSM
physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO
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