3,699 research outputs found
A theory of orbit braids
This paper upbuilds the theoretical framework of orbit braids in
by making use of the orbit configuration space , which enriches the
theory of ordinary braids, where is a connected topological manifold of
dimension at least 2 with an effective action of a finite group and the
action of on is trivial. Main points of our work include as follows. We
introduce the orbit braid group , and show that it is
isomorphic to a group with an additional endowed operation (called the extended
fundamental group of ), formed by the homotopy classes of some paths
(not necessarily closed paths) in , which is an essential extension
for fundamental groups. The orbit braid group is
large enough to contain the fundamental group of and other various
braid groups as its subgroups. Around the central position of
, we obtain five short exact sequences weaved in a
commutative diagram. We also analyze the essential relations among various
braid groups associated to those configuration spaces , and
. We finally consider how to give the presentations of orbit braid
groups in terms of orbit braids as generators. We carry out our work by
choosing with typical actions of and
. We obtain the presentations of the corresponding orbit
braid groups, from which we see that the generalized braid group
actually agrees with an orbit braid group and is a subgroup of
another orbit braid group. In addition, the notion of extended fundamental
groups is also defined in a general way in the category of topology and some
characteristics extracted from the discussions of orbit braids are given.Comment: 30 pages, minor changes and corrections in section
Hopping conductance and macroscopic quantum tunneling effect in three dimensional Pb(SiO) nanogranular films
We have studied the low-temperature electrical transport properties of
Pb(SiO) ( being the Pb volume fraction) nanogranular films
with thicknesses of 1000 nm and spanning the dielectric,
transitional, and metallic regions. It is found that the percolation threshold
lies between 0.57 and 0.60. For films with 0.50, the
resistivities as functions of temperature obey
relation ( being the local
superconducting gap and the Boltzmann constant) below the superconducting
transition temperature (7 K) of Pb granules. The value of the gap
obtained via this expression is almost identical to that by single electron
tunneling spectra measurement. The magnetoresistance is negative below
and its absolute value is far larger than that above at a certain field.
These observations indicate that single electron hopping (or tunneling), rather
than Cooper pair hopping (or tunneling) governs the transport processes below
. The temperature dependence of resistivities shows reentrant behavior for
the 0.500.57 films. It is found that single electron hopping (or
tunneling) also dominates the low-temperature transport process for these
films. The reduction of the single electron concentration leads to an
enhancement of the resisivity at sufficiently low temperature. For the
0.600.72 films, the resistivities sharply decrease with
decreasing temperature just below , and then show dissipation effect with
further decreasing temperature. Treating the conducting paths composed of Pb
particles as nanowires, we have found that the data below can be
well explained by a model that includes both thermally activated phase slips
and quantum phase slips.Comment: 8 pages, 6 figure
Perfect state transfer and efficient quantum routing: a discrete-time quantum walk approach
We show a perfect state transfer of an arbitrary unknown two-qubit state can
be achieved via a discrete-time quantum walk with various settings of coin
flippings, and extend this method to distribution of an arbitrary unknown
multi-qubit entangled state between every pair of sites in the
multi-dimensional network. Furthermore, we study the routing of quantum
information on this network in a quantum walk architecture, which can be used
as quantum information processors to communicate between separated qubits.Comment: 6 pages, 2 figure
Quantum security computation on shared secrets
Ouyang et al. proposed an threshold quantum secret sharing scheme,
where the number of participants is limited to , and the
security evaluation of the scheme was carried out accordingly. In this paper,
we propose an threshold quantum secret sharing scheme for the number of
participants in any case ( ). The scheme is based on a quantum
circuit, which consists of Clifford group gates and Toffoli gate. We study the
properties of the quantum circuit in this paper and use the quantum circuit to
analyze the security of the scheme for dishonest participants
Crossing-changeable braids from chromatic configuration spaces
Motivated by the work in [15], this paper deals with the theory of the braids
from chromatic configuration spaces. This kind of braids possess the property
that some strings of each braid may intersect together and can also be
untangled, so they are quite different from the ordinary braids in the sense of
Artin. This enriches and extends the theory of ordinary braids.Comment: 17 pages, It has been accepted for publication in SCIENCE CHINA
Mathematic
A secret sharing scheme on p^2 -dimensional quantum system
In this paper, we give the mutually unbiased bases on the p^2 -dimensional
quantum system where p is an odd prime number, and construct the corresponding
unitary transformation based on the properties of these mutually unbiased
bases. Then, we construct a (N,N) threshold secret sharing scheme using unitary
transformation between these mutually unbiased bases, and analyze the scheme's
security by several ways, for example, intercept-and-resend attack,
entangle-and-measure attack, Trojan horse attack, and so on. Using our method,
we construct a single-particle quantum protocol involving only one qudit, and
the method shows much more scalability than other schemes.Comment: 14 page
Reinvestigation of the electron fraction and electron Fermi energy of neutron star
In this work, we reinvestigate the electron fraction and electron
Fermi energy of neutron stars, based on our previous work of Li et
al.(2016), in which we firstly deduced a special solution to , and
then obtained several useful analytical formulae for and matter
density within classical models and the relativistic mean field(RMF)
theory using numerically fitting. The advantages of this work include the
following aspects:(1) The linear functions are substituted for the nonlinear
exponential functions used in the previous work. This method may be more
simple, and closer to realistic equation of state\,(EoS) of a neutron star(NS),
because there are linear or quasi-linear relationships between number fractions
of leptons and matter density, which can be seen by solving NS EoS; (2)we
introduce a dimensionless variable \,(,
is the standard saturated nuclear density), which greatly reduces
the scope of the fitting coefficients;(3)we present numerical errors including
absolute and relative deviations between the data and fit. By numerically
simulating, we have obtained several analytical formulae for and
for both APR98 and RMF models. Combining these analytical formulae with the
special solution, we can calculate the value of for any given
matter density. Since and are important in assessing cooling
rate of a NS and the possibility of kaon/pion condensation in the NS interior,
this study could be useful in the future study on the thermal evolution of a
NS.Comment: 3 figures, 3 tables , and We welcome any comment you might have about
the content, To be published in Astron. Nach
CPOT: Channel Pruning via Optimal Transport
Recent advances in deep neural networks (DNNs) lead to tremendously growing
network parameters, making the deployments of DNNs on platforms with limited
resources extremely difficult. Therefore, various pruning methods have been
developed to compress the deep network architectures and accelerate the
inference process. Most of the existing channel pruning methods discard the
less important filters according to well-designed filter ranking criteria.
However, due to the limited interpretability of deep learning models, designing
an appropriate ranking criterion to distinguish redundant filters is difficult.
To address such a challenging issue, we propose a new technique of Channel
Pruning via Optimal Transport, dubbed CPOT. Specifically, we locate the
Wasserstein barycenter for channels of each layer in the deep models, which is
the mean of a set of probability distributions under the optimal transport
metric. Then, we prune the redundant information located by Wasserstein
barycenters. At last, we empirically demonstrate that, for classification
tasks, CPOT outperforms the state-of-the-art methods on pruning ResNet-20,
ResNet-32, ResNet-56, and ResNet-110. Furthermore, we show that the proposed
CPOT technique is good at compressing the StarGAN models by pruning in the more
difficult case of image-to-image translation tasks.Comment: 11 page
The inner 40 pc Radial Distribution of the Star formation Rate for a nearby Seyfert 2 galaxy M51
We investigate spatially resolved specific star formation rate (SSFR) in the
inner 40 pc for a nearby Seyfert 2 galaxy, M51 (NGC 5194) by analyzing
spectra obtained with the \emph{Hubble Space Telescope (HST)} Space Telescope
Imaging Spectrograph (STIS). We present 24 radial spectra measured along the
STIS long slit in M51, extending \sim 1\arcsec from the nucleus (i.e., -41.5
pc to 39.4 pc). By the simple stellar population synthesis, the stellar
contributions in these radial optical spectra are modeled. Excluding some
regions with zero young flux fraction near the center (from -6 pc to 2 pc), we
find that the mean flux fraction of young stellar populations (younger than
24.5 Myr) is about 9 \%, the mean mass fraction is about 0.09\%. The young
stellar populations are not required in the center inner 8 pc in M51,
suggesting a possible SSFR suppression in the circumnuclear region ( 10
pc) from the feedback of active galactic nuclei (AGNs). The radial distribution
of SSFR in M51 is not symmetrical with respect to the long slit in STIS. This
unsymmetrical SSFR distribution is possibly due to the unsymmetrical AGN
feedback in M51, which is related to its jet.Comment: 9 pages, 4 figures, published in Research in Astron. Astrophy
Measurements of Radon Concentrations Using CR-39 Detectors in China JinPing Underground Laboratory (2015-2016)
Radon background is one of the most critical influences on the ultra-low
background and rare-event physical experiments in underground laboratories. To
conduct a comprehensive investigation of the radon concentrations in China
JinPing underground Laboratory (CJPL), long-term cumulative measurements were
carried out using time-integrated passive radon dosimeters containing CR-39
solid-state nuclear track detectors at four sites of CJPL-I. The measurements
lasted from May 30,2015 to March 16,2016, a total of 290 days, and the total
effective measurement time is 6,953 hours. In the main experiment hall equipped
with the ventilation system, the average annual radon concentrations were
(55+/-7) Bq m^-3, (58+/-10) Bq^m-3and (53+/-9) Bq m^-3 in three locations
respectively. In the storage tunnel without any radon reduction facility, the
average annual radon concentrations increased to (345+/-15) Bq m^-3, reflecting
the original average annual radon concentration levels in the underground
laboratory. Compared with the measured results in the period from 2010 to 2011,
the average radon concentration in the main experimental hall was reduced from
(86+/-25) Bq m^-3 to (58+/-10) Bq m^-3 due to the well-running ventilation
system. Compared with other international underground laboratories, radon
concentrations in CJPL-I were at an intermediate level and can meet the demand
for low background and rare-event physical experiments
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