3,801 research outputs found
Nonlinear Effects in Easement Valuation
Rules of thumb have been developed to assist appraisers in dealing with the uncertainties that abound when easement values must be estimated. An economic analysis of one popular rule-of-thumb technique, based on a fixed percentage of the value of a hypothetical fee simple interest in the affected land, reveals that such methodology could not generally be expected to yield meaningful results. If a rule of thumb were to be employed, its use would be more supportable if the underlying assumptions reflected the nonlinear structure of land values.
Topological Color Codes and Two-Body Quantum Lattice Hamiltonians
Topological color codes are among the stabilizer codes with remarkable
properties from quantum information perspective. In this paper we construct a
four-valent lattice, the so called ruby lattice, governed by a 2-body
Hamiltonian. In a particular regime of coupling constants, degenerate
perturbation theory implies that the low energy spectrum of the model can be
described by a many-body effective Hamiltonian, which encodes the color code as
its ground state subspace. The gauge symmetry
of color code could already be realized by
identifying three distinct plaquette operators on the lattice. Plaquettes are
extended to closed strings or string-net structures. Non-contractible closed
strings winding the space commute with Hamiltonian but not always with each
other giving rise to exact topological degeneracy of the model. Connection to
2-colexes can be established at the non-perturbative level. The particular
structure of the 2-body Hamiltonian provides a fruitful interpretation in terms
of mapping to bosons coupled to effective spins. We show that high energy
excitations of the model have fermionic statistics. They form three families of
high energy excitations each of one color. Furthermore, we show that they
belong to a particular family of topological charges. Also, we use
Jordan-Wigner transformation in order to test the integrability of the model
via introducing of Majorana fermions. The four-valent structure of the lattice
prevents to reduce the fermionized Hamiltonian into a quadratic form due to
interacting gauge fields. We also propose another construction for 2-body
Hamiltonian based on the connection between color codes and cluster states. We
discuss this latter approach along the construction based on the ruby lattice.Comment: 56 pages, 16 figures, published version
The physics of dipolar bosonic quantum gases
This article reviews the recent theoretical and experimental advances in the
study of ultracold gases made of bosonic particles interacting via the
long-range, anisotropic dipole-dipole interaction, in addition to the
short-range and isotropic contact interaction usually at work in ultracold
gases. The specific properties emerging from the dipolar interaction are
emphasized, from the mean-field regime valid for dilute Bose-Einstein
condensates, to the strongly correlated regimes reached for dipolar bosons in
optical lattices.Comment: Review article, 71 pages, 35 figures, 350 references. Submitted to
Reports on Progress in Physic
Search for Yukawa Production of a Light Neutral Higgs Boson at LEP
Within a Two-Higgs-Doublet Model (2HDM) a search for a light Higgs boson in
the mass range of 4-12 GeV has been performed in the Yukawa process e+e- -> b
bbar A/h -> b bbar tau+tau-, using the data collected by the OPAL detector at
LEP between 1992 and 1995 in e+e- collisions at about 91 GeV centre-of-mass
energy. A likelihood selection is applied to separate background and signal.
The number of observed events is in good agreement with the expected
background. Within a CP-conserving 2HDM type II model the cross-section for
Yukawa production depends on xiAd = |tan beta| and xihd = |sin alpha/cos beta|
for the production of the CP-odd A and the CP-even h, respectively, where tan
beta is the ratio of the vacuum expectation values of the Higgs doublets and
alpha is the mixing angle between the neutral CP-even Higgs bosons. From our
data 95% C.L. upper limits are derived for xiAd within the range of 8.5 to 13.6
and for xihd between 8.2 to 13.7, depending on the mass of the Higgs boson,
assuming a branching fraction into tau+tau- of 100%. An interpretation of the
limits within a 2HDM type II model with Standard Model particle content is
given. These results impose constraints on several models that have been
proposed to explain the recent BNL measurement of the muon anomalous magnetic
moment.Comment: 24 pages, 9 figures, Submitted to Euro. Phys. J.
Search for Neutral Higgs Bosons in e+e- Collisions at sqrt(s) ~189GeV
A search for neutral Higgs bosons has been performed with the OPAL detector
at LEP, using approximately 170 pb-1 of e+e- collision data collected at
sqrt(s)~189GeV. Searches have been performed for the Standard Model (SM)
process e+e- to H0Z0 and the MSSM processes e+e- to H0Z0, A0h0. The searches
are sensitive to the b b-bar and tau antitau decay modes of the Higgs bosons,
and also to the MSSM decay mode h0 to A0A0. OPAL search results at lower
centre-of-mass energies have been incorporated in the limits we set, which are
valid at the 95% confidence level. For the SM Higgs boson, we obtain a lower
mass bound of 91.0 GeV. In the MSSM, our limits are mh>74.8GeV and mA>76.5GeV,
assuming tan(beta)>1, that the mixing of the scalar top quarks is either zero
or maximal, and that the soft SUSY-breaking masses are 1 TeV. For the case of
zero scalar top mixing, we exclude values of tan(beta) between 0.72 and 2.19.Comment: 38 pages, 15 figures, submitted Euro. Phys. J.
Measurement of triple gauge boson couplings from WW production at LEP energies up to 189 GeV
A measurement of triple gauge boson couplings is presented, based on W-pair
data recorded by the OPAL detector at LEP during 1998 at a centre-of-mass
energy of 189 GeV with an integrated luminosity of 183 pb^-1. After combining
with our previous measurements at centre-of-mass energies of 161-183 GeV we
obtain k_g=0.97 +0.20 -0.16, g_1^z=0.991 +0.060 -0.057 and lambda_g=-0.110
+0.058 -0.055, where the errors include both statistical and systematic
uncertainties and each coupling is determined by setting the other two
couplings to their SM values. These results are consistent with the Standard
Model expectations.Comment: 28 pages, 8 figures, submitted to Eur. Phys. J.
Measurement of the Hadronic Cross-Section for the Scattering of Two Virtual Photons at LEP
The interaction of virtual photons is investigated using the reaction e+e- ->
e+e- hadrons based on data taken by the OPAL experiment at e+e- centre-of-mass
energies sqrt(s_ee)=189-209 GeV, for W>5 GeV and at an average Q^2 of 17.9
GeV^2. The measured cross-sections are compared to predictions of the Quark
Parton Model (QPM), to the Leading Order QCD Monte Carlo model PHOJET to the
NLO prediction for the reaction e+e- -> e+e-qqbar, and to BFKL calculations.
PHOJET, NLO e+e- -> e+e-qqbar, and QPM describe the data reasonably well,
whereas the cross-section predicted by a Leading Order BFKL calculation is too
large.Comment: 30 pages, 10 figures, Submitted to Eur.Phys.J.
Search for Nearly Mass-Degenerate Charginos and Neutralinos at LEP
A search was performed for charginos with masses close to the mass of the
lightest neutralino in e+e- collisions at centre-of-mass energies of 189-209
GeV recorded by the OPAL detector at LEP. Events were selected if they had an
observed high-energy photon from initial state radiation, reducing the dominant
background from two-photon scattering to a negligible level. No significant
excess over Standard Model expectations has been observed in the analysed data
set corresponding to an integrated luminosity of 570pb-1. Upper limits were
derived on the chargino pair-productin cross-section, and lower limits on the
chargino mass were derived in the context of the Minimal Supersymmetric
Extension of the Standard Model for the gravity and anomaly mediated
Supersymmetry breaking scenarios.Comment: 26 pages, 9 figure
A Measurement of Semileptonic B Decays to Narrow Orbitally-Excited Charm Mesons
The decay chain b -> Bbar -> D^{**0} l nu X, D^{**0} -> D^{*+} pi^-, D^{*+}
-> D^0 pi^+, D^0 ->(Kpi or K3pi) is identified in a sample of 3.9 million
hadronic Z decays collected with the OPAL detector at LEP. The branching ratio
BR (b -> Bbar) x BR (Bbar -> D^0_1 l nu X) x BR (D^0_1 -> D^{*+} pi^-) is
measured to be (2.64 +- 0.79 (stat) +- 0.39 (syst)) X 10^-3 for the J^P = 1^+
(D^0_1) state. For decays into the J^P = 2^+ (D^{*0}_2) state, an upper limit
of 1.4 X 10^-3 is placed on the branching ratio at the 95% confidence level.Comment: 20 pages, 6 figure
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
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