49,726 research outputs found

### Partial Breaking of N=2 Supersymmetry and Decoupling Limit of Nambu-Goldstone Fermion in U(N) Gauge Model

We study the N=1 U(N) gauge model obtained by spontaneous breaking of N=2
supersymmetry. The Fayet-Iliopoulos term included in the N=2 action does not
appear in the action on the N=1 vacuum and the superpotential is modified to
break discrete R symmetry. We take a limit in which the Kahler metric becomes
flat and the superpotential preserves non-trivial form. The Nambu-Goldstone
fermion is decoupled from other fields but the resulting action is still N=1
supersymmetric. It shows the origin of the fermionic shift symmetry in N=1 U(N)
gauge theory.Comment: 10 pages,revised version to appear in Nuclear Physics

### Single-Particle Spin-Orbit Strengths of the Nucleon and Hyperons by SU6 Quark-Model

The quark-model hyperon-nucleon interaction suggests an important
antisymmetric spin-orbit component. It is generated from a color analogue of
the Fermi-Breit interaction dominating in the one-gluon exchange process
between quarks. We discuss the strength S_B of the single-particle spin-orbit
potential, following the Scheerbaum's prescription. Using the SU6 quark-model
baryon-baryon interaction which was recently developed by the Kyoto-Niigata
group, we calculate NN, Lambda N and Sigma N G-matrices in symmetric nuclear
matter and apply them to estimate the strength S_B. The ratio of S_B to the
nucleon strength S_N =~ -40 MeV*fm^5 is (S_Lambda)/(S_N) =~ 1/5 and
(S_Sigma)/(S_N) =~ 1/2 in the Born approximation. The G-matrix calculation of
the model FSS modifies S_Lambda to (S_Lambda)/(S_N) =~ 1/12. For S_N and
S_Sigma, the effect of the short-range correlation is comparatively weak
against meson-exchange potentials with a short-range repulsive core. The
significant reduction of the Lambda single-particle potential arises from the
combined effect of the antisymmetric LS force, the flavor-symmetry breaking
originating from the strange to up-down quark-mass difference, as well as the
effect of the short-range correlation. The density dependence of S_B is also
examined.Comment: 26 page

### A Numerical Study of Spectral Flows of Hermitian Wilson-Dirac Operator and the Index Theorem in Abelian Gauge Theories on Finite Lattices

We investigate the index of the Neuberger's Dirac operator in abelian gauge
theories on finite lattices by numerically analyzing the spectrum of the
hermitian Wilson-Dirac operator for a continuous family of gauge fields
connecting different topological sectors. By clarifying the characteristic
structure of the spectrum leading to the index theorem we show that the index
coincides to the topological charge for a wide class of gauge field
configurations. We also argue that the index can be found exactly for some
special but nontrivial configurations in two dimensions by directly analyzing
the spectrum.Comment: 13 pages, 3 figures, minor modifications including typos, a reference
adde

### Baryon-baryon interactions in the SU6 quark model and their applications to light nuclear systems

Interactions between the octet-baryons (B8) in the spin-flavor SU6 quark
model are investigated in a unified coupled-channels framework of the
resonating-group method (RGM). The interaction Hamiltonian for quarks consists
of the phenomenological confinement potential, the color Fermi-Breit
interaction with explicit flavor-symmetry breaking (FSB), and effective-meson
exchange potentials of scalar-, pseudoscalar- and vector-meson types. The model
parameters are determined to reproduce the properties of the nucleon-nucleon
(NN) system and the low-energy cross section data for the hyperon-nucleon (YN)
interactions. The NN phase shifts and many observables for the NN and YN
interactions are nicely reproduced. Properties of these B8 B8 interactions are
analyzed through the G-matrix calculations. The B8 B8 interactions are then
applied to some of few-baryon systems and light Lambda-hypernuclei in a
three-cluster Faddeev formalism using two-cluster RGM kernels. An application
to the three-nucleon system shows that the quark-model NN interaction can give
a sufficient triton binding energy with little room for the three-nucleon
force. The hypertriton Faddeev calculation indicates that the attraction of the
Lambda N interaction in the 1S0 state is only slightly more attractive than
that in the 3S1 state. In the application to the alpha alpha Lambda system, the
energy spectrum of 9 Lambda Be is well reproduced using the alpha alpha RGM
kernel. The very small spin-orbit splitting of the 9 Lambda Be excited states
is also discussed. In the Lambda Lambda alpha Faddeev calculation, the NAGARA
event for 6 Lambda Lambda He is found to be consistent with the quark-model
Lambda Lambda interaction.Comment: 77 pages, 33 figures, review article to be published in Prog. Part.
Nucl. Phy

### Ability of stabilizer quantum error correction to protect itself from its own imperfection

The theory of stabilizer quantum error correction allows us to actively
stabilize quantum states and simulate ideal quantum operations in a noisy
environment. It is critical is to correctly diagnose noise from its syndrome
and nullify it accordingly. However, hardware that performs quantum error
correction itself is inevitably imperfect in practice. Here, we show that
stabilizer codes possess a built-in capability of correcting errors not only on
quantum information but also on faulty syndromes extracted by themselves.
Shor's syndrome extraction for fault-tolerant quantum computation is naturally
improved. This opens a path to realizing the potential of stabilizer quantum
error correction hidden within an innocent looking choice of generators and
stabilizer operators that have been deemed redundant.Comment: 9 pages, 3 tables, final accepted version for publication in Physical
Review A (v2: improved main theorem, slightly expanded each section,
reformatted for readability, v3: corrected an error and typos in the proof of
Theorem 2, v4: edited language

### Parsing a sequence of qubits

We develop a theoretical framework for frame synchronization, also known as
block synchronization, in the quantum domain which makes it possible to attach
classical and quantum metadata to quantum information over a noisy channel even
when the information source and sink are frame-wise asynchronous. This
eliminates the need of frame synchronization at the hardware level and allows
for parsing qubit sequences during quantum information processing. Our
framework exploits binary constant-weight codes that are self-synchronizing.
Possible applications may include asynchronous quantum communication such as a
self-synchronizing quantum network where one can hop into the channel at any
time, catch the next coming quantum information with a label indicating the
sender, and reply by routing her quantum information with control qubits for
quantum switches all without assuming prior frame synchronization between
users.Comment: 11 pages, 2 figures, 1 table. Final accepted version for publication
in the IEEE Transactions on Information Theor

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