658 research outputs found
Superconductivity in CoO Layers and the Resonating Valence Bond Mean Field Theory of the Triangular Lattice t-J model
Motivated by the recent discovery of superconductivity in two dimensional
CoO layers, we present some possibly useful results of the RVB mean field
theory applied to the triangular lattice. Away from half filling, the order
parameter is found to be complex, and yields a fully gapped quasiparticle
spectrum. The sign of the hopping plays a crucial role in the analysis, and we
find that superconductivity is as fragile for one sign as it is robust for the
other. NaCoOHO is argued to belong to the robust case, by
comparing the LDA Fermi surface with an effective tight binding model. The high
frequency Hall constant in this system is potentially interesting, since it is
pointed out to increase linearly with temperature without saturation for T
T.Comment: Published in Physical Review B, total 1 tex + 9 eps files. Erratum
added as separate tex file on November 7, 2003, a numerical factor corrected
in the erratum on Dec 3, 200
The su(N) XX model
The natural su(N) generalization of the XX model is introduced and analyzed.
It is defined in terms of the characterizing properties of the usual XX model:
the existence of two infinite sequences of mutually commuting conservation laws
and the existence of two infinite sequences of mastersymmetries. The
integrability of these models, which cannot be obtained in a degenerate limit
of the su(N)-XXZ model, is established in two ways: by exhibiting their R
matrix and from a direct construction of the commuting conservation laws. We
then diagonalize the conserved laws by the method of the algebraic Bethe
Ansatz. The resulting spectrum is trivial in a certain sense; this provides
another indication that the su(N) XX model is the natural generalization of the
su(2) model. The application of these models to the construction of an
integrable ladder, that is, an su(N) version of the Hubbard model, is
mentioned.Comment: 16 pages, TeX and harvmac (option b). Minor corrections, accepted for
publication in Nuclear Physics
A Class of Parameter Dependent Commuting Matrices
We present a novel class of real symmetric matrices in arbitrary dimension
, linearly dependent on a parameter . The matrix elements satisfy a set
of nontrivial constraints that arise from asking for commutation of pairs of
such matrices for all , and an intuitive sufficiency condition for the
solvability of certain linear equations that arise therefrom. This class of
matrices generically violate the Wigner von Neumann non crossing rule, and is
argued to be intimately connected with finite dimensional Hamiltonians of
quantum integrable systems.Comment: Latex, Added References, Typos correcte
Kinetic Antiferromagnetism in the Triangular Lattice
We show that the motion of a single hole in the infinite Hubbard model
with frustrated hopping leads to weak metallic antiferromagnetism of kinetic
origin. An intimate relationship is demonstrated between the simplest versions
of this problem in 1 and 2 dimensions, and two of the most subtle many body
problems, namely the Heisenberg Bethe ring in 1-d and the 2-dimensional
triangular lattice Heisenberg antiferromagnet.Comment: 10 pages, 2 figures, 5 supplementary figures; Figures fixe
Including a phase in the Bethe equations of the Hubbard model
We compute the Bethe equations of generalized Hubbard models, and study their
thermodynamical limit. We argue how they can be connected to the ones found in
the context of AdS/CFT correspondence, in particular with the so-called
dressing phase problem. We also show how the models can be interpreted, in
condensed matter physics, as integrable multi-leg Hubbard models.Comment: 30 page
Response of rice varieties to short-day treatment
Synchronisation of flowering was effected in fifty rice varieties, ranging from early to very late duration, by giving 8 light hours photoperiod to 30 days old seedlings for 20 days. The results showed that the later the type, the greater was its response to photoperiod and regression value of photoperiod response over the normal duration of the varieties was approximately 1.0
PreMa: Predictive Maintenance of Solenoid Valve in Real-Time at Embedded Edge-Level
In industrial process automation, sensors (pressure, temperature, etc.),
controllers, and actuators (solenoid valves, electro-mechanical relays, circuit
breakers, motors, etc.) make sure that production lines are working under the
pre-defined conditions. When these systems malfunction or sometimes completely
fail, alerts have to be generated in real-time to make sure not only production
quality is not compromised but also safety of humans and equipment is assured.
In this work, we describe the construction of a smart and real-time edge-based
electronic product called PreMa, which is basically a sensor for monitoring the
health of a Solenoid Valve (SV). PreMa is compact, low power, easy to install,
and cost effective. It has data fidelity and measurement accuracy comparable to
signals captured using high end equipment. The smart solenoid sensor runs
TinyML, a compact version of TensorFlow (a.k.a. TFLite) machine learning
framework. While fault detection inferencing is in-situ, model training uses
mobile phones to accomplish the `on-device' training. Our product evaluation
shows that the sensor is able to differentiate between the distinct types of
faults. These faults include: (a) Spool stuck (b) Spring failure and (c) Under
voltage. Furthermore, the product provides maintenance personnel, the remaining
useful life (RUL) of the SV. The RUL provides assistance to decide valve
replacement or otherwise. We perform an extensive evaluation on optimizing
metrics related to performance of the entire system (i.e. embedded platform and
the neural network model). The proposed implementation is such that, given any
electro-mechanical actuator with similar transient response to that of the SV,
the system is capable of condition monitoring, hence presenting a first of its
kind generic infrastructure
Fermionic R-Operator and Integrability of the One-Dimensional Hubbard Model
We propose a new type of the Yang-Baxter equation (YBE) and the decorated
Yang-Baxter equation (DYBE). Those relations for the fermionic R-operator were
introduced recently as a tool to treat the integrability of the fermion models.
Using the YBE and the DYBE for the XX fermion model, we construct the fermionic
R-operator for the one-dimensional (1D) Hubbard model. It gives another proof
of the integrability of the 1D Hubbard model. Furthermore a new approach to the
SO(4) symmetry of the 1D Hubbard model is discussed.Comment: 25 page
The Origin of Degeneracies and Crossings in the 1d Hubbard Model
The paper is devoted to the connection between integrability of a finite
quantum system and degeneracies of its energy levels. In particular, we analyze
in detail the energy spectra of finite Hubbard chains. Heilmann and Lieb
demonstrated that in these systems there are crossings of levels of the same
parameter independent symmetry. We show that this apparent violation of the
Wigner-von Neumann noncrossing rule follows directly from the existence of
nontrivial conservation laws and is a characteristic signature of quantum
integrability. The energy spectra of Hubbard chains display many instances of
permanent (at all values of the coupling) twofold degeneracies that cannot be
explained by parameter independent symmetries. We relate these degeneracies to
the different transformation properties of the conserved currents under spatial
reflections and the particle-hole transformation and estimate the fraction of
doubly degenerate states. We also discuss multiply degenerate eigenstates of
the Hubbard Hamiltonian. The wave functions of many of these states do not
depend on the coupling, which suggests the existence of an additional parameter
independent symmetry.Comment: 25 pages, 12 figure
Magnetization plateaux in an extended Shastry-Sutherland model
We study an extended two-dimensional Shastry-Sutherland model in a magnetic
field where besides the usual Heisenberg exchanges of the Shastry-Sutherland
model two additional SU(2) invariant couplings are included. Perturbative
continous unitary transformations are used to determine the leading order
effects of the additional couplings on the pure hopping and on the long-range
interactions between the triplons which are the most relevant terms for small
magnetization. We then compare the energy of various magnetization plateaux in
the classical limit and we discuss the implications for the two-dimensional
quantum magnet SrCu(BO).Comment: 8 pages, Proceedings of the HFM2008 Conferenc
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