98 research outputs found
Intersection rules, dynamics and symmetries
We consider theories containing gravity, at most one dilaton and form field
strengths. We show that the existence of particular BPS solutions of
intersecting extremal closed branes select the theories, which upon dimensional
reduction to three dimensions possess a simple simply laced Lie group symmetry
G. Furthermore these theories can be fully reconstructed from the dynamics of
such branes and of their openings. Amongst such theories are the effective
actions of the bosonic sector of M-theory and of the bosonic string. The BPS
intersecting brane solutions form representations of a subgroup of the group of
Weyl reflections and outer automorphisms of the triple Kac-Moody extension G+++
of the G algebra, which cannot be embedded in the overextended Kac-Moody
subalgebra G++ characterising the cosmological Kasner solutions.Comment: Latex 30 pages, 3 figure
The Frobenius formalism in Galois quantum systems
Quantum systems in which the position and momentum take values in the ring
and which are described with -dimensional Hilbert space, are
considered. When is the power of a prime, the position and momentum take
values in the Galois field , the position-momentum phase space is
a finite geometry and the corresponding `Galois quantum systems' have stronger
properties. The study of these systems uses ideas from the subject of field
extension in the context of quantum mechanics. The Frobenius automorphism in
Galois fields leads to Frobenius subspaces and Frobenius transformations in
Galois quantum systems. Links between the Frobenius formalism and Riemann
surfaces, are discussed
Persistent spin splitting of a two-dimensional electron gas in tilted magnetic fields
By varying the orientation of the applied magnetic field with respect to the
normal of a two-dimensional electron gas, the chemical potential and the
specific heat reveal persistent spin splitting in all field ranges. The
corresponding shape of the thermodynamic quantities distinguishes whether the
Rashba spin-orbit interaction RSOI, the Zeeman term or both dominate the
splitting. The interplay of the tilting of the magnetic field and RSOI resulted
to an amplified splitting in weak fields. The effects of changing the RSOI
strength and the Landau level broadening are also investigated.Comment: 10 pages, 5 figure
Quantum non-demolition (QND) modulation of quantum interference
We propose an experiment where quantum interference between two different
paths is modulated by means of a QND measurement on one or both the arm of the
interferometer. The QND measurement is achieved in a Kerr cell. We illustrate a
scheme for the realisation of this experiment and some further developments.Comment: accepted for publicatio
Search for Charged Higgs Bosons at LEP
A search for pair-produced charged Higgs bosons is performed with the L3
detector at LEP using data collected at centre-of-mass energies between 189 and
209GeV, corresponding to an integrated luminosity of 629.4/pb. Decays into a
charm and a strange quark or into a tau lepton and its neutrino are considered.
No significant excess is observed and lower limits on the mass of the charged
Higgs boson are derived at the 95% confidence level. They vary from 76.5 to
82.7GeV, as a function of the H->tv branching ratio
Search for Doubly-Charged Higgs Bosons at LEP
Doubly-charged Higgs bosons are searched for in e^+e^- collision data
collected with the L3 detector at LEP at centre-of-mass energies up to 209 GeV.
Final states with four leptons are analysed to tag the pair-production of
doubly charged Higgs bosons. No significant excess is found and lower limits at
95% confidence level on the doubly-charged Higgs boson mass are derived. They
vary from 95.5 GeV to 100.2 GeV, depending on the decay mode. Doubly-charged
Higgs bosons which couple to electrons would modify the cross section and
forward-backward asymmetry of the e^+e^- -> e^+e^- process. The measurements of
these quantities do not deviate from the Standard Model expectations and
doubly-charged Higgs bosons with masses up to the order of a TeV are excluded
Flavour Independent Search for Neutral Higgs Bosons at LEP
A flavour independent search for the CP-even and CP-odd neutral Higgs bosons
h and A is performed in 624/pb of data collected with the L3 detector at LEP at
centre-of-mass energies between 189 and 209GeV. Higgs boson production through
the e^+e^- -> Z h and the e^+e^- ->h A processes is considered and decays of
the Higgs bosons into hadrons are studied. No significant signal is observed
and 95% confidence level limits on the hZZ and hAZ couplings are derived as a
function of the Higgs boson masses. Assuming the Standard Model cross section
for the Higgs-strahlung process and a 100% branching fraction into hadrons, a
95% confidence level lower limit on the mass of the Higgs boson is set at
110.3GeV
Standard Model Higgs Boson with the L3 Experiment at LEP
Final results of the search for the Standard Model Higgs boson are presented
for the data collected by the L3 detector at LEP at centre-of-mass energies up
to about 209 GeV. These data are compared with the expectations of Standard
Model processes for Higgs boson masses up to 120 GeV. A lower limit on the mass
of the Standard Model Higgs boson of 112.0 GeV is set at the 95 % confidence
level. The most significant high mass candidate is a Hnunu event. It has a
reconstructed Higgs mass of 115 GeV and it was recorded at root(s)=206.4 GeV
Higgs Candidates in e+e- Interactions at root(s) = 206.6 GeV
In a search for the Standard Model Higgs boson, carried out on 212.5 pb-1 of
data collected by the L3 detector at the highest LEP centre-of-mass energies,
including 116.5 pb-1 above root(s) = 206GeV, an excess of candidates for the
process e+e- -> Z* -> HZ is found for Higgs masses near 114.5GeV. We present an
analysis of our data and the characteristics of our strongest candidates.Comment: Footnote added, matches the version to be published in Physics
Letters
Search for Charged Higgs Bosons in e+e- Collisions at Centre-of-Mass Energies up to 202 GeV
A search for pair-produced charged Higgs bosons is performed with the L3
detector at LEP using data collected at centre-of-mass energies between 192 and
202 GeV, corresponding to an integrated luminosity of 233.2 pb^-1. Decays into
a charm and a strange quark or into a tau lepton and its neutrino are
considered. The observed events are consistent with the expectations from
Standard Model background processes. Including data taken at lower
centre-of-mass energies, lower limits on the charged Higgs mass are derived at
the 95% confidence level. They vary from 67.4 to 79.9GeV as a function of the
H^+/- --> tau nu branching ratio
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