4,343 research outputs found
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
Pseudo-observables in electroweak Higgs production
We discuss how the leading electroweak Higgs production processes at the LHC,
namely vector-boson fusion and Higgs+W/Z associated production, can be
characterized in generic extensions of the Standard Model by a proper set of
pseudo-observables (PO). We analyze the symmetry properties of these PO and
their relation with the PO set appearing in Higgs decays. We discuss in detail
the kinematical studies necessary to extract the production PO from data, and
present a first estimate of the LHC sensitivity on these observables in the
high-luminosity phase. The impact of QCD corrections and the kinematical
studies necessary to test the validity of the momentum expansion at the basis
of the PO decomposition are also discussed.Comment: 34 pages, 12 figures, 1 tabl
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
Exploring the flavour structure of the MSSM with rare K decays
We present an extensive analysis of rare K decays, in particular of the two
neutrino modes K+->pi+ nu nu-bar and KL->pi0 nu nu-bar, in the Minimal
Supersymmetric extension of the Standard Model. We analyse the expectations for
the branching ratios of these modes, both within the restrictive framework of
the minimal flavour violation hypothesis and within a more general framework
with new sources of flavour-symmetry breaking. In both scenarios, the
information that can be extracted from precise measurements of the two neutrino
modes turn out to be very useful in restricting the parameter space of the
model, even after taking into account the possible information on the mass
spectrum derived from high-energy colliders, and the constraints from B-physics
experiments. In the presence of new sources of flavour-symmetry breaking,
additional significant constraints on the model can be derived also from the
two KL->pi0 l+l- modes.Comment: 22 pages, 10 figures (high quality figures available on request
TOXICITY OF PREDNISOLONE, DEXAMETHASONE AND THEIR PHOTOCHEMICAL DERIVATIVES ON AQUATIC ORGANISMS
Light exposure of aqueous suspensions of prednisolone and dexamethasone causes their partial phototransformation.
The photoproducts, isolated by chromatographic techniques, have been identified by spectroscopic means.
Prednisolone, dexamethasone and their photoproducts have been tested to evaluate their acute and chronic toxic effects
on some freshwater chain organisms. The rotifer Brachionus calyciflorus and the crustaceans Thamnocephalus platyurus
and Daphnia magna were chosen to perform acute toxicity tests, while the alga Pseudokircheneriella subcapitata (formerly
known as Selenastrum capricornutum) and the crustacean Ceriodaphnia dubia to perform chronic tests. The
photochemical derivatives are more toxic than the parent compounds. Generally low acute toxicity was found. Chronic
exposure to this class of pharmaceuticals caused inhibition of growth population on the freshwater crustacean C. dubia
while the alga P. subcapitata seems to be less affected by the presence of these drugs
Minimal Flavour Violation and Beyond
We review the formulation of the Minimal Flavour Violation (MFV) hypothesis
in the quark sector, as well as some "variations on a theme" based on smaller
flavour symmetry groups and/or less minimal breaking terms. We also review how
these hypotheses can be tested in B decays and by means of other
flavour-physics observables. The phenomenological consequences of MFV are
discussed both in general terms, employing a general effective theory approach,
and in the specific context of the Minimal Supersymmetric extension of the SM.Comment: 14 pages, 5 figures. Review to appear in "Top and flavour physics in
the LHC era" - Special Issue of The European Physical Journal
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
B_{s,d} -> l^+ l^- and K_L -> l^+ l^- in SUSY models with non-minimal sources of flavour mixing
We present a general analysis of B_{s,d}-> l^+ l^- and K_L -> l^+ l^- decays
in supersymmetric models with non-minimal sources of flavour mixing. In spite
of the existing constraints on off-diagonal squark mass terms, these modes
could still receive sizeable corrections, mainly because of Higgs-mediated
FCNCs arising at large tan(beta). The severe limits on scenarios with large
tan(beta) and non-negligible {tilde d}^i_{R(L)}-{d-tilde}^j_{R(L)} mixing
imposed by the present experimental bounds on these modes and Delta B=2
observables are discussed in detail. In particular, we show that scalar-current
contributions to K_L -> l^+ l^- and B-{bar B} mixing set non-trivial
constraints on the possibility that B_s -> l^+ l^- and B_d -> l^+ l^- receive
large corrections.Comment: 18 pages, 4 figures (v2: minor changes, published version
Less Minimal Flavour Violation
We consider the approximate U(2)^3 flavour symmetry exhibited by the quark
sector of the Standard Model and all its possible breaking terms appearing in
the quark Yukawa couplings. Taking an Effective Field Theory point of view, we
determine the current bounds on these parameters, assumed to control the
breaking of flavour in a generic extension of the Standard Model at a reference
scale Lambda. In particular, a significant bound from epsilon'/epsilon is
derived, which is relevant to Minimal Flavour Violation as well. In the
up-quark sector, the recently observed CP violation in D -> pi+ pi-, K+ K-
decays might be accounted for in this generic framework, consistently with any
other constraint.Comment: 15 pages, 1 figur
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