7,668 research outputs found
Comment on "Equivalence of the variational matrix product method and the density matrix renormalization group applied to spin chains"
Dukelsky, Mart\'in-Delgado, Nishino and Sierra (Europhys. Lett., 43, 457
(1998) - hereafter referred to as DMNS) investigated the matrix product method
(MPM), comparing it with the infinite-size density matrix renormalization group
(DMRG). For equivalent basis size, the MPM produces an improved variational
energy over that produced by DMRG and, unlike DMRG, produces a
translationally-invariant wavefunction. The DMRG results presented were
significantly worse than the MPM, caused by a shallow bound state appearing at
the join of the two DMRG blocks. They also suggested that the DMRG results can
be improved by using an alternate superblock construction for
the last few steps of the calculation. In this comment, we show that the DMRG
results presented by DMNS are in error and the artificial bound state produced
by the standard superblock configuration is very small even for states
kept. In addition, we calculate explicitly the energy and wavefunction for the
superblock structure and verify that the energy coincides
with that of the MPM, as conjectured by S. Ostlund and S. Rommer (Phys. Rev.
Lett., 75, 3537 (1995)).Comment: 2 pages, 1 eps figure included. eps.cls include
Galaxy rotations from quantised inertia and visible matter only
It is shown here that a model for inertial mass, called quantised inertia, or
MiHsC (Modified inertia by a Hubble-scale Casimir effect) predicts the
rotational acceleration of the 153 good quality galaxies in the SPARC dataset
(2016 AJ 152 157), with a large range of scales and mass, from just their
visible baryonic matter, the speed of light and the co-moving diameter of the
observable universe. No dark matter is needed. The performance of quantised
inertia is comparable to that of MoND, yet it needs no adjustable parameter. As
a further critical test, quantised inertia uniquely predicts a specific
increase in the galaxy rotation anomaly at higher redshifts. This test is now
becoming possible and new data shows that galaxy rotational accelerations do
increase with redshift in the predicted manner, at least up to Z=2.2.Comment: 9 pages, 2 figures. Published in Astrophys Space Sc
Inertia from an asymmetric Casimir effect
The property of inertia has never been fully explained. A model for inertia
(MiHsC or quantised inertia) has been suggested that assumes that 1) inertia is
due to Unruh radiation and 2) this radiation is subject to a Hubble-scale
Casimir effect. This model has no adjustable parameters and predicts the cosmic
acceleration, and galaxy rotation without dark matter, suggesting that Unruh
radiation indeed causes inertia, but the exact mechanism by which it does this
has not been specified. The mechanism suggested here is that when an object
accelerates, for example to the right, a dynamical (Rindler) event horizon
forms to its left, reducing the Unruh radiation on that side by a Rindler-scale
Casimir effect whereas the radiation on the other side is only slightly reduced
by a Hubble-scale Casimir effect. This produces an imbalance in the radiation
pressure on the object, and a net force that always opposes acceleration, like
inertia. A formula for inertia is derived, and an experimental test is
suggested.Comment: 7 pages, 1 figure. Accepted by EPL (Europhysics Letters) on the 11th
February, 201
Can the Podkletnov effect be explained by quantised inertia?
The Podkletnov effect is an unexplained loss of weight of between 0.05% and
0.07% detected in test masses suspended above supercooled levitating
superconducting discs exposed to AC magnetic fields. A larger weight loss of up
to 0.5% was seen over a disc spun at 5000 rpm. The effect has so far been
observed in only one laboratory. Here, a new model for inertia that assumes
that inertial mass is caused by Unruh radiation which is subject to a
Hubble-scale Casimir effect (called MiHsC or quantised inertia) is applied to
this anomaly. When the disc is exposed to the AC magnetic field it vibrates
(accelerates), and MiHsC then predicts that the inertial mass of the nearby
test mass increases, so that to conserve momentum it must accelerate upwards
against freefall by 0.0029 m/s^2 or 0.03% of g, about half of the weight loss
observed. With disc rotation, MiHsC predicts an additional weight loss, but 28
times smaller than the rotational effect observed. MiHsC suggests that the
effect should increase with disc radius and rotation rate, the AC magnetic
field strength (as observed), and also with increasing latitude and for lighter
discs.Comment: 8 pages, 1 figure. To appear in the SPESIF-2011 conference
proceedings, in Physics Procedi
Testing quantised inertia on galactic scales
Galaxies and galaxy clusters have rotational velocities apparently too fast
to allow them to be gravitationally bound by their visible matter. This has
been attributed to the presence of invisible (dark) matter, but so far this has
not been directly detected. Here, it is shown that a new model that modifies
inertial mass by assuming it is caused by Unruh radiation, which is subject to
a Hubble-scale (Theta) Casimir effect predicts the rotational velocity (v) to
be: v^4=2GMc^2/Theta (the Tully-Fisher relation) where G is the gravitational
constant, M is the baryonic mass and c is the speed of light. The model
predicts the outer rotational velocity of dwarf and disk galaxies, and galaxy
clusters, within error bars, without dark matter or adjustable parameters, and
makes a prediction that local accelerations should remain above 2c^2/Theta at a
galaxy's edge.Comment: 7 pages, 1 figure. Accepted for publication in Astrophysics and Space
Science on 27/7/201
The Non-Abelian Density Matrix Renormalization Group Algorithm
We describe here the extension of the density matrix renormalization group
algorithm to the case where Hamiltonian has a non-Abelian global symmetry
group. The block states transform as irreducible representations of the
non-Abelian group. Since the representations are multi-dimensional, a single
block state in the new representation corresponds to multiple states of the
original density matrix renormalization group basis. We demonstrate the
usefulness of the construction via the one-dimensional Hubbard model as the
symmetry group is enlarged from , up to .Comment: Revised version discusses the Hubbard model with SO(4) symmetr
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Stochastic Hosting Capacity in LV Distribution Networks
Hosting capacity is defined as the level of penetration that a particular technology can connect to a distribution network without causing power quality problems. In this work, we study the impact of solar photovoltaics (PV) on voltage rise. In most cases, the locations and sizes of the PV are not known in advance, so hosting capacity must be considered as a random variable. Most hosting capacity methods study the problem considering a large number of scenarios, many of which provide little additional information. We overcome this problem by studying only cases where voltage constraints are active, with results illustrating a reduction in the number of scenarios required by an order of magnitude. A linear power flow model is utilised for this task, showing excellent performance. The hosting capacity is finally studied as a function of the number of generators connected, demonstrating that assumptions about the penetration level will have a large impact on the conclusions drawn for a given network
Magnetism in the dilute Kondo lattice model
The one dimensional dilute Kondo lattice model is investigated by means of
bosonization for different dilution patterns of the array of impurity spins.
The physical picture is very different if a commensurate or incommensurate
doping of the impurity spins is considered. For the commensurate case, the
obtained phase diagram is verified using a non-Abelian density-matrix
renormalization-group algorithm. The paramagnetic phase widens at the expense
of the ferromagnetic phase as the -spins are diluted. For the incommensurate
case, antiferromagnetism is found at low doping, which distinguishes the dilute
Kondo lattice model from the standard Kondo lattice model.Comment: 11 pages, 2 figure
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