1,346 research outputs found
Passivity-Based Control of Human-Robotic Networks with Inter-Robot Communication Delays and Experimental Verification
In this paper, we present experimental studies on a cooperative control
system for human-robotic networks with inter-robot communication delays. We
first design a cooperative controller to be implemented on each robot so that
their motion are synchronized to a reference motion desired by a human
operator, and then point out that each robot motion ensures passivity.
Inter-robot communication channels are then designed via so-called scattering
transformation which is a technique to passify the delayed channel. The
resulting robotic network is then connected with human operator based on
passivity theory. In order to demonstrate the present control architecture, we
build an experimental testbed consisting of multiple robots and a tablet. In
particular, we analyze the effects of the communication delays on the human
operator's behavior
Finite Higgs mass without Supersymmetry
We identify a class of chiral models where the one-loop effective potential
for Higgs scalar fields is finite without any requirement of supersymmetry. It
corresponds to the case where the Higgs fields are identified with the
components of a gauge field along compactified extra dimensions. We present a
six dimensional model with gauge group U(3)xU(3) and quarks and leptons
accomodated in fundamental and bi-fundamental representations. The model can be
embedded in a D-brane configuration of type I string theory and, upon
compactification on a T^2/Z_2 orbifold, it gives rise to the standard model
with two Higgs doublets.Comment: 28 pages, 4 figures, uses axodraw. Some typos corrected and
references rearrange
The Origin of Spontaneous Symmetry Breaking in Theories with Large Extra Dimensions
We suggest that the electroweak Higgs particles can be identified with
extra-dimensional components of the gauge fields, which after compactification
on a certain topologically non-trivial background become tachyonic and
condense. If the tachyonic mass is a tree level effect, the natural scale of
the gauge symmetry breaking is set by the inverse radius of the internal space,
which, in case of the electroweak symmetry, must be around TeV. We
discuss the possibility of a vanishing tree level mass for the Higgs. In such a
scenario the tachyonic mass can be induced by quantum loops and can be
naturally smaller than the compactification scale. We give an example in which
this possibility can be realized. Starting from an Einstein--Yang--Mills theory
coupled to fermions in 10-dimensions, we are able to reproduce the spectrum of
the Standard Model like chiral fermions and Higgs type scalars in 4-dimensions
upon compactifying on . The existence of
a monopole solution on and a self dual U(1) instanton on
are essential in obtaining chiral fermions as well as
tachyonic or massless scalars in 4-dimensions. We give a simple rule which
helps us to identify the presence of tachyons on the monopole background on
.Comment: 33 pages. Version accepted for publication in Phys.Rev.
MUTANTS OF NONPRODUCER CELL LINES TRANSFORMED BY MURINE SARCOMA VIRUS : III. DETECTION AND CHARACTERIZATION OF RNA SPECIFIC FOR HELPER AND SARCOMA VIRUSES
BALB/3T3 cells transformed by the Kirsten sarcoma virus (nonvirus producer BALB/3T3 cells) and mutant cell lines derived therefrom by treatment with bromodeoxyuridine (BrdU) were analyzed for expression of virus-specific RNA using single-stranded DNA transcripts of Rauscher leukemia virus (RLV), a virus activated in one of the cell lines (58-2T), and Ki-SV-specific DNA transcript; the latter transcript after removal of all sequences cross-reactive with RLV RNA. The Rauscher virus DNA detected multiple copies of viral RNA in virus-producing cells (∼2.5 x 103/cell) whether infected with RLV or activated to produce virus with BrdU. Nonproducer (NP) cells and normal BALB cells showed small numbers of RNA genomes (70–250/cell) and only partial saturation of the transcript. The intracellular RNA sedimented at 35S (main peak) with a variable minor peak at 20S with the exception of one mutant cell, M-43-2 (main peak at 26–27S). The 58-2T transcript reacted preferentially in NP cells and their derivatives with biphasic kinetics suggesting the possibility of sequences specific for the original transforming virus. The size of Ki-SV specific sequences were 30S in mutant cells whether or not complete virus was being produced and independent of in vivo transplantability
Measurement of the mass of the Ï„ lepton
The mass of the τ lepton has been measured at the Beijing Electron-Positron Collider using the Beijing Spectrometer. A search near threshold for e^+e^-→τ^+τ^- was performed. Candidate events were identified by requiring that one τ decay via τ→eνν¯, and the other via τ→μνν¯. The mass value, obtained from a fit to the energy dependence of the τ^+τ^- cross section, is m_τ=1776.9_(-0.5)^(+0.4)±0.2 MeV
Radiative and Semileptonic B Decays Involving Higher K-Resonances in the Final States
We study the radiative and semileptonic B decays involving a spin-
resonant with parity for and for
in the final state. Using the large energy effective theory (LEET)
techniques, we formulate transition form factors in the large
recoil region in terms of two independent LEET functions
and , the values of
which at zero momentum transfer are estimated in the BSW model. According to
the QCD counting rules, exhibit a dipole
dependence in . We predict the decay rates for ,
and . The
branching fractions for these decays with higher -resonances in the final
state are suppressed due to the smaller phase spaces and the smaller values of
. Furthermore, if the spin of
becomes larger, the branching fractions will be further suppressed due to the
smaller Clebsch-Gordan coefficients defined by the polarization tensors of the
. We also calculate the forward backward asymmetry of the decay, for which the zero is highly insensitive to the
-resonances in the LEET parametrization.Comment: 27 pages, 4 figures, 7 tables;contents and figures corrected, title
and references revise
Radiative brane-mass terms in D>5 orbifold gauge theories
A gauge theory with gauge group G defined in D>4 space-time dimensions can be
broken to a subgroup H on four dimensional fixed point branes, when
compactified on an orbifold. Mass terms for extra dimensional components of
gauge fields A_i (brane scalars) might acquire (when allowed by the brane
symmetries) quadratically divergent radiative masses and thus jeopardize the
stability of the four-dimensional theory. We have analyzed Z_2
compactifications and identified the brane symmetries remnants of the higher
dimensional gauge invariance. No mass term is allowed for D=5 while for D>5 a
tadpole \epsilon^{ij}F_{ij}^\alpha can appear when there are U_\alpha(1)
factors in H. A detailed calculation is done for the D=6 case and it is
established that the tadpole is related, although does not coincide, with the
U_\alpha(1) anomaly induced on the brane by the bulk fermions. In particular,
no tadpole is generated from gauge bosons or fermions in real representationsComment: 12 pages, 2 figures, axodraw.sty. v2: important typoes corrected and
reference added. v3: logarithmic corrections to tadpole include
Dynamic ATR-FTIR and TEM study of the resin-dentin interface in Reactmer Bond
Abstract no. 895published_or_final_versio
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