9,205 research outputs found
Gauge invariance and hadron structure
We prove that the {\em gauge dependent} gluon spin, gluon and quark orbital
angular momenta operators have {\em gauge invariant} expectation values on
hadron states with {\em definite} momentum and polarization, therefore the
conventional decomposition of nucleon spin into contributions from the spin and
orbital angular momentum of quark and gluon is {\em gauge independent}. Similar
conclusions apply to the {\em gauge dependent} quark momentum and kinetic
energy operators, and accordingly nucleon momentum and mass structures.Comment: This revised version gives a complete, comprehensive proof of our
conclusion, and explains why the specific calculations of Hoodbhoy, Ji and Lu
(hep-ph/9808305) do not necessarily contradict our theore
A quantum-copying machine for equatorial qubits
Bu\v{z}ek and Hillery proposed a universal quantum-copying machine (UQCM)
(i.e., transformation) to analyze the possibility of cloning arbitrary states.
The UQCM copies quantum-mechanical states with the quality of its output does
not depend on the input. We propose a slightly different transformation to
analyze a restricted set of input states. We impose the conditions (I) the
density matrices of the two output states are the same, and that (II) the
distance between input density operator and the output density operators is
input state independent. Using Hilbert-Schmidt norm and Bures fidelity, we show
that our transformation can achieves the bound of the fidelity.Comment: Latex file, 11 page
Spin content of the nucleon in a valence and sea quark mixing model
A dynamical valence and sea quark mixing model is shown to fit the baryon
ground state properties as well as the spin content of the nucleon. The
relativistic correction and the transition
terms induced by the quark axial vector current
in this model space is responsible for the
quark spin reduction.Comment: 11 pages, Latex, one figure, to be published in Phys. Rev. C5
Prototype of Readout Electronics for the ED in LHAASO KM2A
The KM2A(one kilometer square extensive air shower array) is the largest
detector array in the LHAA- SO(Large High Altitude Air Shower Observatory)
project. The KM2A consists of 5635 EDs(Electromagnetic particle Detectors) and
1221 MDs(Muon Detectors). The EDs are distributed and exposed in the wild. Two
channels, Anode and Dynode, are employed for the PMT(photomultiplier tube)
signal readout. The readout electronics proposed in this paper aims at the
accurate charge and arrival time measurement of the PMT signals, which cover a
large amplitude range from 20P.E(photoelectrons) to 2x10^5 P.E. By using the
Trigger-less architecture, we digitize signals close to the PMTs. All digitized
data is transmitted to DAQ(Data Acquisition) via the simplified WR(White
Rabbit) protocol. Compared with traditional high energy experiments,
high-precision of time measurement in such a large area and suppression of
temperature effects in the wild become the key techniques. Experiments show
that the design has fulfilled the requirements in this project.Comment: 6 pages, 12 figure
Some Problems in Defining Functional Integration over the Gauge Group
We find that sometimes the usual definition of functional integration over
the gauge group through limiting process may have internal difficulties.Comment: 2 pages revtex, no figur
A Note on Functional Integral over the Local Gauge Group
We evaluated some particular type of functional integral over the local gauge
group C^{\infty}({\bf R}^n, U(1)) by going to a discretized lattice. The
results explicitly violates the property of the Haar measure. We also analysed
the Faddeev-Popov method through a toy example. The results also violates the
property of the Haar measure.Comment: 7 pages, Revte
A Note on Invariant Measure on the Local Gauge Group
In this paper we investigated the problem of the existence of invariant
meaures on the local gauge group. We prove that it is impossible to define a
{\it finite} translationally invariant measure on the local gauge group
(where is an arbitrary matrix Lie group).Comment: 4 pages, REVTE
Dynamics of Josephson junction systems in the computational subspace
The quantum dynamics of the Josephson junction system in the computational
subspace is investigated. A scheme for the controlled not operation is given
for two capasitively coupled SQUIDs. In this system, there is no systematic
error for the two qubit operation. For the inductively coupled SQUIDs, the
effective Hamiltonian causes systematic errors in the computational subspace
for the two qubit operation. Using the purterbation theory, we construct a more
precise effective Hamiltonian. This new effective Hamiltonian reduces the
systematic error to the level much lower than the threshold of the fault
resilent quantum computation
Quantization of gauge theory for gauge dependent operators
Based on a canonically derived path integral formalism, we demonstrate that
the perturbative calculation of the matrix element for gauge dependent
operators has crucial difference from that for gauge invariant ones. For a
gauge dependent operator what appears in the Feynman diagrams
is not itself, but the gauge-transformed one , where characterizes the specific gauge
transformation which brings any field variable into the particular gauge which
we have adopted to quantize the gauge theory using the canonical method. The
study of the matrix element of gauge dependent operators also reveals that the
formal path integral formalism for gauge theory is not always reliable.Comment: 4 pages revtex, no figure, multicol styl
A universal cloner allowing the input to be arbitrary states in symmetric subspace
A generalized universal quantum cloning machine is proposed which allows the
input to be arbitrary states in symmetric subspace. And it reduces to the
universal quantum cloning machine (UQCM) if the input are identical pure
states. The generalized cloner is optimal in the sense we compare the input and
output reduced density operators at a single qubit. The result for qubits is
extended to arbitrary-dimensional states.Comment: Revtex, 5 page
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