1,007 research outputs found
Quantum Monte Carlo study of few- and many-body Bose systems in one and two dimensions
In this Thesis, we report a detailed study of the ground-state properties of
a set of quantum few- and many-body systems in one and two dimensions with
different types of interactions by using Quantum Monte Carlo methods.
Nevertheless, the main focus of this work is the study of the ground-state
properties of an ultracold Bose system with dipole-dipole interaction between
the particles. We consider the cases where the bosons are confined to a bilayer
and multilayer geometries, that consist of equally spaced two-dimensional
layers. These layers can be experimentally realized by imposing tight
confinement in one direction. We specifically address the study of new quantum
phases, their properties, and transitions between them. One expects these
systems to have a rich collection of few- and many-body phases because the
dipole-dipole interaction is anisotropic and quasi long-range.Comment: Author's PhD thesis defended on December 21st, 2020 at Universitat
Polit\`ecnica de Catalunya, Spain. Supervisors: Grigory Astrakharchik and
Jordi Boronat Medico. 148 pages. This dissertation is also available at
https://atenea-phd.upc.edu/mod/finalthesis/download.php?file=1fdcb9aad2c827491e96b7a142f2179
The role of potassium orbitals in the metallic behavior of K3picene
Detailed electronic structure calculations of picene clusters doped by
potassium modeling the crystalline K3picene structure show that while two
electrons are completely transferred from potassium atoms to the LUMO of
pristine picene, the third one remains closely attached to both material
components. Multiconfigurational analysis is necessary to show that many
structures of almost degenerate total energies compete to define the cluster
ground state. Our results prove that the 4s orbital of potassium should be
included in any interaction model describing the material. We propose a quarter
filled two orbital model as the most simple model capable of describing the
electronic structure of K-intercalated picene. Precise solutions obtained by a
development of Lanczos method show low energy electronic excitations involving
orbitals located at different positions. Consequently, metallic transport is
possible in spite of the clear dominance of interaction over hopping.Comment: 12 pages, 10 figures (6 of them really heavy
Few-body bound states of two-dimensional bosons
We study clusters of the type AB with in a
two-dimensional mixture of A and B bosons, with attractive AB and equally
repulsive AA and BB interactions. In order to check universal aspects of the
problem, we choose two very different models: dipolar bosons in a bilayer
geometry and particles interacting via separable Gaussian potentials. We find
that all the considered clusters are bound and that their energies are
universal functions of the scattering lengths and , for
sufficiently large attraction-to-repulsion ratios . When
decreases below , the dimer-dimer interaction
changes from attractive to repulsive and the population-balanced AABB and
AAABBB clusters break into AB dimers. Calculating the AAABBB hexamer energy
just below this threshold, we find an effective three-dimer repulsion which may
have important implications for the many-body problem, particularly for
observing liquid and supersolid states of dipolar dimers in the bilayer
geometry. The population-imbalanced ABB trimer, ABBB tetramer, and AABBB
pentamer remain bound beyond the dimer-dimer threshold. In the dipolar model,
they break up at where the atom-dimer interaction
switches to repulsion.Comment: 3 figure
Daily rainfall variability in the Spanish Mediterranean area
Ponencias presentadas en: 2nd European Conference on Applied Climatology (ECAC) celebrada en Viena del 19 al 23 de octubre de 2018
Sequencing of folding events in Go-like proteins
We have studied folding mechanisms of three small globular proteins: crambin
(CRN), chymotrypsin inhibitor 2 (CI2) and the fyn Src Homology 3 domain (SH3)
which are modelled by a Go-like Hamiltonian with the Lennard-Jones
interactions. It is shown that folding is dominated by a well-defined
sequencing of events as determined by establishment of particular contacts. The
order of events depends primarily on the geometry of the native state.
Variations in temperature, coupling strengths and viscosity affect the
sequencing scenarios to a rather small extent. The sequencing is strongly
correlated with the distance of the contacting aminoacids along the sequence.
Thus -helices get established first. Crambin is found to behave like a
single-route folder, whereas in CI2 and SH3 the folding trajectories are more
diversified. The folding scenarios for CI2 and SH3 are consistent with
experimental studies of their transition states.Comment: REVTeX, 12 pages, 11 EPS figures, J. Chem. Phys (in press
Does Circular Economy Affect Financial Performance? The Mediating Role of Sustainable Sup-ply Chain Management in the Automotive Industry
The implementation of stricter sustainable policies and the tightening of environmental laws are forcing manufacturing companies, particularly those that make up the automotive industry, to make changes and improvements involving Circular Economy (CE) practices. However, CE practices do not always lead to an improvement in firm performance. This study analyzes the effects of the implementation of CE practices on the financial performance (FIP) of manufacturing companies in the automotive industry of Mexico, considering the mediating effect exerted by sustainable supply chain management (SSCM). The proposed model is validated through PLS-SEM using a sample of 460 companies. The results show that the FIP is strengthened through the implementation of the CE and that this effect is mediated by the commitment of the company to promote a better SSCM. This study contributes to the CE and SSCM theories by providing evidence about the positive effect that the implementation of these activities has on the performance of the automotive industry and how a SSCM equally exerts a direct and indirect effect on this. In the same way, managers can use this study and its results to make their operations more efficient and to demonstrate the effects of sustainability on the financial performance of the company
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