15,808 research outputs found
A Strictly Single-Site DMRG Algorithm with Subspace Expansion
We introduce a strictly single-site DMRG algorithm based on the subspace
expansion of the Alternating Minimal Energy (AMEn) method. The proposed new MPS
basis enrichment method is sufficient to avoid local minima during the
optimisation, similarly to the density matrix perturbation method, but
computationally cheaper. Each application of to in the
central eigensolver is reduced in cost for a speed-up of ,
with the physical site dimension. Further speed-ups result from cheaper
auxiliary calculations and an often greatly improved convergence behaviour.
Runtime to convergence improves by up to a factor of 2.5 on the Fermi-Hubbard
model compared to the previous single-site method and by up to a factor of 3.9
compared to two-site DMRG. The method is compatible with real-space
parallelisation and non-abelian symmetries.Comment: 9 pages, 6 figures; added comparison with two-site DMR
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TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
Study of the charge correlation function in one-dimensional Hubbard heterostructures
We study inhomogeneous one-dimensional Hubbard systems using the density
matrix renormalization group method. Different heterostructures are
investigated whose configuration is modeled varying parameters like the on-site
Coulomb potential and introducing local confining potentials. We investigate
their Luttinger liquid properties through the parameter K_rho, which
characterizes the decay of the density-density correlation function at large
distances. Our main goal is the investigation of possible realization of
engineered materials and the ability to manipulate physical properties by
choosing an appropriate spatial and/or chemical modulation.Comment: 6 pages, 7 figure
Abelian and non-abelian symmetries in infinite projected entangled pair states
We explore in detail the implementation of arbitrary abelian and non-abelian
symmetries in the setting of infinite projected entangled pair states on the
two-dimensional square lattice. We observe a large computational speed-up;
easily allowing bond dimensions in the square lattice Heisenberg model
at computational effort comparable to calculations at without
symmetries. We also find that implementing an unbroken symmetry does not
negatively affect the representative power of the state and leads to identical
or improved ground-state energies. Finally, we point out how to use symmetry
implementations to detect spontaneous symmetry breaking.Comment: 18 pages, submitted to SciPost Physic
Mixed-signal CNN array chips for image processing
Due to their local connectivity and wide functional capabilities, cellular nonlinear networks (CNN) are excellent candidates for the implementation of image processing algorithms using VLSI analog parallel arrays. However, the design of general purpose, programmable CNN chips with dimensions required for practical applications raises many challenging problems to analog designers. This is basically due to the fact that large silicon area means large development cost, large spatial deviations of design parameters and low production yield. CNN designers must face different issues to keep reasonable enough accuracy level and production yield together with reasonably low development cost in their design of large CNN chips. This paper outlines some of these major issues and their solutions
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