9,510 research outputs found
Probing Dark Energy with the Kunlun Dark Universe Survey Telescope
Dark energy is an important science driver of many upcoming large-scale
surveys. With small, stable seeing and low thermal infrared background, Dome A,
Antarctica, offers a unique opportunity for shedding light on fundamental
questions about the universe. We show that a deep, high-resolution imaging
survey of 10,000 square degrees in \emph{ugrizyJH} bands can provide
competitive constraints on dark energy equation of state parameters using type
Ia supernovae, baryon acoustic oscillations, and weak lensing techniques. Such
a survey may be partially achieved with a coordinated effort of the Kunlun Dark
Universe Survey Telescope (KDUST) in \emph{yJH} bands over 5000--10,000 deg
and the Large Synoptic Survey Telescope in \emph{ugrizy} bands over the same
area. Moreover, the joint survey can take advantage of the high-resolution
imaging at Dome A to further tighten the constraints on dark energy and to
measure dark matter properties with strong lensing as well as galaxy--galaxy
weak lensing.Comment: 9 pages, 6 figure
Perfect State Transfer in Laplacian Quantum Walk
For a graph and a related symmetric matrix , the continuous-time
quantum walk on relative to is defined as the unitary matrix , where varies over the reals. Perfect state transfer occurs
between vertices and at time if the -entry of
has unit magnitude. This paper studies quantum walks relative to graph
Laplacians. Some main observations include the following closure properties for
perfect state transfer:
(1) If a -vertex graph has perfect state transfer at time relative
to the Laplacian, then so does its complement if is an integer multiple
of . As a corollary, the double cone over any -vertex graph has
perfect state transfer relative to the Laplacian if and only if . This was previously known for a double cone over a clique (S. Bose,
A. Casaccino, S. Mancini, S. Severini, Int. J. Quant. Inf., 7:11, 2009).
(2) If a graph has perfect state transfer at time relative to the
normalized Laplacian, then so does the weak product if for any
normalized Laplacian eigenvalues of and of , we have
is an integer multiple of . As a corollary, a weak
product of with an even clique or an odd cube has perfect state
transfer relative to the normalized Laplacian. It was known earlier that a weak
product of a circulant with odd integer eigenvalues and an even cube or a
Cartesian power of has perfect state transfer relative to the adjacency
matrix.
As for negative results, no path with four vertices or more has antipodal
perfect state transfer relative to the normalized Laplacian. This almost
matches the state of affairs under the adjacency matrix (C. Godsil, Discrete
Math., 312:1, 2011).Comment: 26 pages, 5 figures, 1 tabl
Coupled atomic-molecular condensates in a double-well potential: decaying molecular oscillations
We present a four-mode model that describes coherent photo-association (PA)
in a double-well Bose-Einstein condensate, focusing on the molecular
populations in certain parameters. Our numerical results predict an interesting
strong-damping effect of molecular oscillations by controlling the particle
tunnellings and PA light strength, which may provide a promising way for
creating a stable molecular condensate via coherent PA in a magnetic
double-well potential.Comment: 6 pages, 4 figures, submitte
Mass Hierarchy Determination Using Neutrinos from Multiple Reactors
We report the results of Monte Carlo simulations of a medium baseline reactor
neutrino experiment. The difference in baselines resulting from the 1 km
separations of Daya Bay and Ling Ao reactors reduces the amplitudes of 1-3
oscillations at low energies, decreasing the sensitivity to the neutrino mass
hierarchy. A perpendicular detector location eliminates this effect. We
simulate experiments under several mountains perpendicular to the Daya Bay/Ling
Ao reactors, considering in particular the background from the TaiShan and
YangJiang reactor complexes. In general the hierarchy can be determined most
reliably underneath the 1000 meter mountain BaiYunZhang, which is 44.5 km from
Daya Bay. If some planned reactors are not built then nearby 700 meter
mountains at 47-51 km baselines gain a small advantage. Neglecting their low
overhead burdens, hills near DongKeng would be the optimal locations. We use a
weighted Fourier transform to avoid a spurious dependence on the high energy
neutrino spectrum and find that a neural network can extract quantities which
determine the hierarchy marginally better than the traditional RL + PV.Comment: 22 pages, added details on the neural network (journal version
Extrapolation Method for the No-Core Shell Model
Nuclear many-body calculations are computationally demanding. An estimate of
their accuracy is often hampered by the limited amount of computational
resources even on present-day supercomputers. We provide an extrapolation
method based on perturbation theory, so that the binding energy of a large
basis-space calculation can be estimated without diagonalizing the Hamiltonian
in this space. The extrapolation method is tested for 3H and 6Li nuclei. It
will extend our computational abilities significantly and allow for reliable
error estimates.Comment: 8 pages, 7 figures, PRC accepte
Three Kinds of Special Relativity via Inverse Wick Rotation
Since the special relativity can be viewed as the physics in an inverse Wick
rotation of 4-d Euclid space, which is at almost equal footing with the 4-d
Riemann/Lobachevski space, there should be important physics in the inverse
Wick rotation of 4-d Riemann/Lobachevski space. Thus, there are three kinds of
special relativity in de Sitter/Minkowski/anti-de Sitter space at almost equal
footing, respectively. There is an instanton tunnelling scenario in the
Riemann-de Sitter case that may explain why \La be positive and link with the
multiverse.Comment: 3 pages, no figures, to appear in Chin. Phys. Let
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