3,614 research outputs found
Beyond conventional factorization: Non-Hermitian Hamiltonians with radial oscillator spectrum
The eigenvalue problem of the spherically symmetric oscillator Hamiltonian is
revisited in the context of canonical raising and lowering operators. The
Hamiltonian is then factorized in terms of two not mutually adjoint factorizing
operators which, in turn, give rise to a non-Hermitian radial Hamiltonian. The
set of eigenvalues of this new Hamiltonian is exactly the same as the energy
spectrum of the radial oscillator and the new square-integrable eigenfunctions
are complex Darboux-deformations of the associated Laguerre polynomials.Comment: 13 pages, 7 figure
Se and I status in pregnant ewes from a pastoral system and the effect of supplementation with Se and I or only Se on wool quality of lambs
Australian Merino ewes and lambs producing fine fibre wool for export are raised in the north-west of Uruguay in
pasture-based systems. We studied the status of selenium and iodine in pregnant Merino ewes (10 per treatment)
grazing in natural pasture, in natural pasture and supplemented with Se (0.1 mg Se/kg dry matter intake) and I (1
mg I/kg dry matter intake), or in natural pasture and supplemented with Se alone (0.1 mg Se/kg dry matter intake), during the last 30 days of gestation. Further, we evaluated the performance and wool quality of their
offspring. Content of Se and I in natural pasture, in the sera of pregnant ewes, and in the wool of their offspring
and levels of thyroidal hormones—TSH, T4, and free T3 (FT3)—in the sera of pregnant ewes were determined.
The performance of lambs and the commercial parameters of fine fibre wool produced were measured. Results
showed normal Se levels in serum (0.12–0.15 mg/l) in the ewes grazing in natural pasture (0.07–0.09 mg/kg DM)
during late pregnancy. The observed increase in Se content in the pasture at lambing (0.11–0.16 mg/kg DM)
improved serum Se levels (0.216 mg/l); however, the serum levels were not affected by the supplementation.
I content in pasture showed adequate levels (0.50–0.60 mg/kg DM), which were reflected in the blood serum
values 30 days prior to lambing (0.197–0.208 mg/l). However, at lambing, the I content in blood serum decreased
(0.150 mg/l). Further, the supplementation did not modify the serum I levels (0.163–0.175 mg/l). An increase in
FT3 levels in ewes at lambing could be associated with the increase in Se content in pasture and/or the adequate I content in pasture. No effect of supplementation was observed. Lambs showed good results regarding the quality of fine fibre wool and performance after supplementation with Se and I or Se alone and exhibited slightly
improved Se and I content in wool. In conclusion, natural pasture provides adequate status in Se and I for the
Merino ewes and their offspring without any additional beneficial effects of supplementation with Se and I or only Se
On the geometry of closed G2-structure
We give an answer to a question posed recently by R.Bryant, namely we show
that a compact 7-dimensional manifold equipped with a G2-structure with closed
fundamental form is Einstein if and only if the Riemannian holonomy of the
induced metric is contained in G2. This could be considered to be a G2 analogue
of the Goldberg conjecture in almost Kahler geometry. The result was
generalized by R.L.Bryant to closed G2-structures with too tightly pinched
Ricci tensor. We extend it in another direction proving that a compact
G2-manifold with closed fundamental form and divergence-free Weyl tensor is a
G2-manifold with parallel fundamental form. We introduce a second symmetric
Ricci-type tensor and show that Einstein conditions applied to the two Ricci
tensors on a closed G2-structure again imply that the induced metric has
holonomy group contained in G2.Comment: 14 pages, the Einstein condition in the assumptions of the Main
theorem is generalized to the assumption that the Weyl tensor is
divergence-free, clarity improved, typos correcte
Entropy, Topological Theories and Emergent Quantum Mechanics
[EN] The classical thermostatics of equilibrium processes is shown to possess a quantum mechanical dual theory with a finite dimensional Hilbert space of quantum states. Specifically, the kernel of a certain Hamiltonian operator becomes the Hilbert space of quasistatic quantum mechanics. The relation of thermostatics to topological field theory is also discussed in the context of the approach of the emergence of quantum theory, where the concept of entropy plays a key role.Research supported by grant No. ENE2015-71333-R (Spain).Cabrera, D.; Fernández De Córdoba Castellá, PJ.; Isidro San Juan, JM.; Vazquez Molina, J. (2017). Entropy, Topological Theories and Emergent Quantum Mechanics. Entropy. 19(3). https://doi.org/10.3390/e19030087S19
Extended WKB method, resonances and supersymmetric radial barriers
Semiclassical approximations are implemented in the calculation of position
and width of low energy resonances for radial barriers. The numerical
integrations are delimited by t/T<<8, with t the period of a classical particle
in the barrier trap and T the resonance lifetime. These energies are used in
the construction of `haired' short range potentials as the supersymmetric
partners of a given radial barrier. The new potentials could be useful in the
study of the transient phenomena which give rise to the Moshinsky's diffraction
in time.Comment: 12 pages, 4 figures, 3 table
The G_2 sphere over a 4-manifold
We present a construction of a canonical G_2 structure on the unit sphere
tangent bundle S_M of any given orientable Riemannian 4-manifold M. Such
structure is never geometric or 1-flat, but seems full of other possibilities.
We start by the study of the most basic properties of our construction. The
structure is co-calibrated if, and only if, M is an Einstein manifold. The
fibres are always associative. In fact, the associated 3-form results from a
linear combination of three other volume 3-forms, one of which is the volume of
the fibres. We also give new examples of co-calibrated structures on well known
spaces. We hope this contributes both to the knowledge of special geometries
and to the study of 4-manifolds.Comment: 13 page
Morteros de albañilería con escombros de demolición
The possibility of recycling construction rubble, its technical and economic effectiveness, and the social and ecological impact they provide for our society is the reason and the starting point for an optimal exploitation of this aggregate in the manufacture of masonry mortar, since it has the same inherent properties as those obtained from the quarry aggregates, described in the Cuban standard NC52-79:93.
The work consists in the preparation and study of masonry mortars using recycled aggregates -demolition product-. Four volumetric dosages were prepared (1:4; 1:5; 1:6 y 1:8), which were submitted to physical and mechanical tests at 7, 28 and 60 days, adherence resistance at 28 days, and capillary absorption, obtaining similar results to those.La posibilidad real del reciclaje de escombros, su efectividad técnica, económica, y el impacto social y ecológico que proporciona a la sociedad, es nuestro punto de partida para lograr un óptimo aprovechamiento de este árido como futuro agregado fundamental en la obtención de un mortero de albañilería, capaz de tener como propiedades aquellas intrínsecas de los propios morteros obtenidos a partir de áridos de cantera y recogidos en la norma cubana NC52-79:93.
El trabajo consiste en la preparación y estudio de morteros de albañilería empleando árido reciclado -producto de demolición- como agregado. Se prepararon 4 dosificaciones volumétricas (1:4; 1:5; 1:6 y 1:8), las cuales fueron sometidas a ensayos físico-mecánicos al, 28 y 60 días, resistencia a la adherencia a 28 días, y absorción capilar, obteniéndose resultados comparables con los morteros de albañilería tradicionales
Chiral Symmetry and light resonances in hot and dense matter
We present a study of the scattering amplitude in the and
channels at finite temperature and nuclear density within a chiral
unitary framework. Meson resonances are dynamically generated in our approach,
which allows us to analyze the behavior of their associated scattering poles
when the system is driven towards chiral symmetry restoration. Medium effects
are incorporated in three ways: (a) by thermal corrections of the unitarized
scattering amplitudes, (b) by finite nuclear density effects associated to a
renormalization of the pion decay constant, and complementarily (c) by
extending our calculation of the scalar-isoscalar channel to account for finite
nuclear density and temperature effects in a microscopic many-body
implementation of pion dynamics. Our results are discussed in connection with
several phenomenological aspects relevant for nuclear matter and Heavy-Ion
Collision experiments, such as mass scaling vs broadening from dilepton
spectra and chiral restoration signals in the channel. We also
elaborate on the molecular nature of resonances.Comment: 14 pages, 14 figures. Contribution to Hard Probes 2008, Illa de A
Toxa, Spain, June 8th-14th 200
Comparison of extracellular and intracellular blood compartments highlights redox alterations in Alzheimer's and Mild Cognitive Impairment patients.
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