3,775 research outputs found
A new screening function for Coulomb renormalization
We introduce a new screening function which is useful for the few-body
Coulomb scattering problem in ``screening and renormalization'' scheme. The new
renormalization phase factor of the screening function is analytically shown.
The Yukawa type of the screening potential has been used in several decades, we
modify it to make more useful. As a concrete example, we compare the
proton-proton scattering phase shifts calculated from these potentials. The
numerical results document that high precision calculations of the
renormalization are performed by the new screening function.Comment: 4 pages, 8 figure
Quantum Computer Using Coupled Quantum Dot Molecules
We propose a method for implementation of a quantum computer using artificial
molecules. The artificial molecule consists of two coupled quantum dots stacked
along z direction and one single electron. One-qubit and two-qubit gates are
constructed by one molecule and two coupled molecules, respectively.The ground
state and the first excited state of the molecule are used to encode the |0>
and |1> states of a qubit. The qubit is manipulated by a resonant
electromagnetic wave that is applied directly to the qubit through a microstrip
line. The coupling between two qubits in a quantum controlled NOT gate is
switched on (off) by floating (grounding) the metal film electrodes. We study
the operations of the gates by using a box-shaped quantum dot model and
numerically solving a time-dependent Schridinger equation, and demonstrate that
the quantum gates can perform the quantum computation. The operating speed of
the gates is about one operation per 4ps. The reading operation of the output
of the quantum computer can be performed by detecting the polarization of the
qubits.Comment: 18 pages, 7 figures, submitted to Jpn. J. Appl. Phys, please send
your e-mail to Nan-Jian Wu <[email protected]
Unknotting numbers and triple point cancelling numbers of torus-covering knots
It is known that any surface knot can be transformed to an unknotted surface
knot or a surface knot which has a diagram with no triple points by a finite
number of 1-handle additions. The minimum number of such 1-handles is called
the unknotting number or the triple point cancelling number, respectively. In
this paper, we give upper bounds and lower bounds of unknotting numbers and
triple point cancelling numbers of torus-covering knots, which are surface
knots in the form of coverings over the standard torus . Upper bounds are
given by using -charts on presenting torus-covering knots, and lower
bounds are given by using quandle colorings and quandle cocycle invariants.Comment: 26 pages, 14 figures, added Corollary 1.7, to appear in J. Knot
Theory Ramification
Separability of a Low-Momentum Effective Nucleon-Nucleon Potential
A realistic nucleon-nucleon potential is transformed into a low-momentum
effective one (LMNN) using the Okubo theory. The separable potentials are
converted from the LMNN with a universal separable expansion method and a
simple Legendre expansion. Through the calculation of the triton binding
energies, the separability for the convergence of these ranks is evaluated. It
is found that there is a tendency for the lower momentum cutoff parameter
of LMNN to gain good separability.Comment: 6 pages, 1 tabl
Equivalent hyperon-nucleon interactions in low-momentum space
Equivalent interactions in a low-momentum space for the , and interactions are calculated, using the SU quark model
potential as well as the Nijmegen OBEP model as the input bare interaction.
Because the two-body scattering data has not been accumulated sufficiently to
determine the hyperon-nucleon interactions unambiguously, the construction of
the potential even in low-energy regions has to rely on a theoretical model.
The equivalent interaction after removing high-momentum components is still
model dependent. Because this model dependence reflects the character of the
underlying potential model, it is instructive for better understanding of
baryon-baryon interactions in the strangeness sector to study the low-momentum
space interactions.Comment: 9 pages, 13 figures, accepted for publication in Phys. Rev.
Contributions of -exchange, -exchange, and contact three-body forces in NNLO ChEFT to H
Faddeev calculations of hypertriton (H) separation energy are
performed, incorporating all next-to-next-to-leading-order NN
three-body forces (3BFs) in chiral effective field theory: -exchange,
-exchange, and contact interactions. The -exchange and contact
interactions are rewritten in a form suitable for evaluating partial-wave
matrix elements. The -deuteron folding potentials constructed from
these 3BFs are evaluated to demonstrate their contributions to \h3t. The
-exchange interaction provides an attractive effect in which the d-state
component of the deuteron wave function plays an important role. The attractive
contribution tends to cancel the repulsive ones from the -exchange and
contact 3BFs. Faddeev calculations show that the net effect of the 3BFs to the
\h3t separation energy is small in a range between to keV, depending
on the NN interaction used. Although these results are based on speculative
low-energy constants, they can serve as a reference for further investigations.Comment: 6 pages, 4 figure
Faddeev Calculation of H Incorporating 2{\pi} Exchange NN Interaction
Faddeev calculations of hypertriton (H) separation energy are
performed, incorporating -exchange NN three-baryon force.
Repulsive contributions of the three-baryon force in the order of 50 100
keV are found, depending on the NN interactions employed. The effect is not
negligible compared with the small separation-energy of H and is
essential to gauge the two-body N interactions.Comment: 6 pages, 3 Figure
Partial-wave expansion of three-baryon interactions in chiral effective field theory
An expression of partial wave expansion of three-baryon interactions in
chiral effective field theory is presented. The derivation follows the method
by Hebeler et al. [Phys. Rev. C{\bf 91}, 044001 (2015)], but the final
expression is more general. That is, a systematic treatment of the higher-rank
spin-momentum structure of the interaction becomes possible. Using the derived
formula, a -deuteron folding potential is evaluated. This information
is valuable for inferring the possible contribution of the
three-baryon forces to the hypertriton as the basis of further studies by
sophisticated Faddeev calculations. A microscopic understanding of
three-baryon forces together with two-body interactions is
essential for the description of hypernuclei and neutron-star matter.Comment: 7 pages, 4 figure
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