4,574 research outputs found
Nonlinear internal models for output regulation
In this paper we show how nonlinear internal models can be effectively used
in the design of output regulators for nonlinear systems. This result provides
a significant enhancement of the non-equilibrium theory for output regulation,
which we have presented in the recent paper entitled "Limit Sets, Zero
Dynamics, and Internal Models in the Problem of Nonlinear Output Regulation"
Robust Asymptotic Stabilization of Nonlinear Systems with Non-Hyperbolic Zero Dynamics
In this paper we present a general tool to handle the presence of zero
dynamics which are asymptotically but not locally exponentially stable in
problems of robust nonlinear stabilization by output feedback. We show how it
is possible to design locally Lipschitz stabilizers under conditions which only
rely upon a partial detectability assumption on the controlled plant, by
obtaining a robust stabilizing paradigm which is not based on design of
observers and separation principles. The main design idea comes from recent
achievements in the field of output regulation and specifically in the design
of nonlinear internal models.Comment: 30 pages. Preliminary versions accepted at the 47th IEEE Conference
on Decision and Control, 200
Cluster Dynamical Mean-Field Methods for d-wave Superconductors: the Role of Geometry
We compare the accuracy of two cluster extensions of Dynamical Mean-Field
Theory in describing d-wave superconductors, using as a reference model a
saddle-point t-J model which can be solved exactly in the thermodynamic limit
and at the same time reasonably describes the properties of high-temperature
superconductors. The two methods are Cellular Dynamical Mean-Field Theory,
which is based on a real-space perspective, and Dynamical Cluster
Approximation, which enforces a momentum-space picture by imposing periodic
boundary conditions on the cluster, as opposed to the open boundary conditions
of the first method. We consider the scaling of the methods for large cluster
size, but we also focus on the behavior for small clusters, such as those
accessible by means of present techniques, with particular emphasis on the
geometrical structure, which is definitely a relevant issue in small clusters.Comment: 11 pages, 10 figure
Rotationally-invariant slave-bosons for Strongly Correlated Superconductors
We extend the rotationally invariant formulation of the slave-boson method to
superconducting states. This generalization, building on the recent work by
Lechermann et al. [Phys. Rev. B {\bf 76}, 155102 (2007)], allows to study
superconductivity in strongly correlated systems. We apply the formalism to a
specific case of strongly correlated superconductivity, as that found in a
multi-orbital Hubbard model for alkali-doped fullerides, where the
superconducting pairing has phonic origin, yet it has been shown to be favored
by strong correlation owing to the symmetry of the interaction. The method
allows to treat on the same footing the strong correlation effects and the
interorbital interactions driving superconductivity, and to capture the physics
of strongly correlated superconductivity, in which the proximity to a Mott
transition favors the superconducting phenomenon.Comment: 18 pages, 7 figure
The rare decay B --> X_s l^+ l^- to NNLL precision for arbitrary dilepton invariant mass
We present a new phenomenological analysis of the inclusive rare decay . In particular, we present the first calculation of the NNLL
contributions due to the leading two-loop matrix elements, evaluated for
arbitrary dilepton invariant mass. This allows to obtain the first NNLL
estimates of the dilepton mass spectrum and the lepton forward-backward
asymmetry in the high region, and to provide an
independent check of previously published results in the low region. The numerical impact of these NNLL corrections in the
high-mass region () amounts to -13% in the
integrated rate, and leads to a reduction of the scale uncertainty to .
The impact of non-perturbative contributions in this region is also discussed
in detail.Comment: 40 pages, 12 figures. v2: extended phenomenological discussion;
results unchanged; published versio
Flavour symmetries in the SMEFT
We analyse how and flavour symmetries act on the Standard
Model Effective Field Theory, providing an organising principle to classify the
large number of dimension-six operators involving fermion fields. A detailed
counting of such operators, at different order in the breaking terms of both
these symmetries, is presented. A brief discussion about possible deviations
from these two reference cases, and a simple example of the usefulness of this
classification scheme for high- analyses at the LHC, are also presented.Comment: 31 pages, 13 Table
Electromagnetism in nonleptonic weak interactions
We construct a low-energy effective field theory that permits the complete
treatment of isospin-breaking effects in nonleptonic weak interactions to
next-to-leading order. To this end, we enlarge the chiral Lagrangian describing
strong and Delta S=1 weak interactions by including electromagnetic terms with
the photon as additional dynamical degree of freedom. The complete and minimal
list of local terms at next-to-leading order is given. We perform the one-loop
renormalization at the level of the generating functional and specialize to K
-> pi pi decays.Comment: 17 pages, 1 figure; 2 references added, final version for publication
in Nucl. Phys.
Glycometabolic Alterations in Secondary Adrenal Insufficiency: Does Replacement Therapy Play a Role?
Secondary adrenal insufficiency (SAI) is a potentially life-threatening endocrine disorder due to an impairment of corticotropin (ACTH) secretion from any process affecting the hypothalamus or pituitary gland. ACTH deficit can be isolated or associated with other pituitary failures (hypopituitarism). An increased mortality due to cardiovascular, metabolic, and infectious diseases has been described in both primary and secondary adrenal insufficiency. However, few studies have provided compelling evidences on the underlying mechanism in SAI, because of the heterogeneity of the condition. Recently, some studies suggested that inappropriate glucocorticoid (GCs) replacement therapy, as for dose and/or timing of administration, may play a role. Hypertension, insulin resistance, weight gain, visceral obesity, increased body mass index, metabolic syndrome, impaired glucose tolerance, diabetes mellitus, dyslipidemia have all been associated with GC excess. These conditions are particularly significant when SAI coexists with other pituitary alterations, such as growth hormone deficiency, hypogonadism, and residual tumor. Novel regimen schemes and GC preparations have been introduced to improve compliance and better mimick endogenous cortisol rhythm. The controlled trials on the improved replacement therapies, albeit in the short-term, show some beneficial effects on cardiovascular risk, glucose metabolism, and quality of life. This review examines the current evidence from the available clinical trials investigating the association between different glucocorticoid replacement therapies (type, dose, frequency, and timing of treatment) and glycometabolic alterations in SAI
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