819 research outputs found
On the notions of facets, weak facets, and extreme functions of the Gomory-Johnson infinite group problem
We investigate three competing notions that generalize the notion of a facet
of finite-dimensional polyhedra to the infinite-dimensional Gomory-Johnson
model. These notions were known to coincide for continuous piecewise linear
functions with rational breakpoints. We show that two of the notions, extreme
functions and facets, coincide for the case of continuous piecewise linear
functions, removing the hypothesis regarding rational breakpoints. We then
separate the three notions using discontinuous examples.Comment: 18 pages, 2 figure
Approximation of corner polyhedra with families of intersection cuts
We study the problem of approximating the corner polyhedron using
intersection cuts derived from families of lattice-free sets in .
In particular, we look at the problem of characterizing families that
approximate the corner polyhedron up to a constant factor, which depends only
on and not the data or dimension of the corner polyhedron. The literature
already contains several results in this direction. In this paper, we use the
maximum number of facets of lattice-free sets in a family as a measure of its
complexity and precisely characterize the level of complexity of a family
required for constant factor approximations. As one of the main results, we
show that, for each natural number , a corner polyhedron with basic
integer variables and an arbitrary number of continuous non-basic variables is
approximated up to a constant factor by intersection cuts from lattice-free
sets with at most facets if and that no such approximation is
possible if . When the approximation factor is allowed to
depend on the denominator of the fractional vertex of the linear relaxation of
the corner polyhedron, we show that the threshold is versus .
The tools introduced for proving such results are of independent interest for
studying intersection cuts
Thermodynamics of phase transition in higher dimensional AdS black holes
We investigate the thermodynamics of phase transition for
dimensional Reissner Nordstrom (RN)-AdS black holes using a grand canonical
ensemble. This phase transition is characterized by a discontinuity in specific
heat. The phase transition occurs from a lower mass black hole with negative
specific heat to a higher mass black hole with positive specific heat. By
exploring Ehrenfest's scheme we show that this is a second order phase
transition. Explicit expressions for the critical temperature and critical mass
are derived. In appropriate limits the results for dimensional
Schwarzschild AdS black holes are obtained.Comment: LaTex, 11 pages, 5 figures, To appear in JHE
The structure of the infinite models in integer programming
The infinite models in integer programming can be described as the convex
hull of some points or as the intersection of halfspaces derived from valid
functions. In this paper we study the relationships between these two
descriptions. Our results have implications for corner polyhedra. One
consequence is that nonnegative, continuous valid functions suffice to describe
corner polyhedra (with or without rational data)
Removal and degradation of mixed dye pollutants by integrated adsorption-photocatalysis technique using 2-D MoS2/TiO2 nanocomposite
Two-dimensional (2D) Molybdenum disulfide (MoS2) has become one of the most exciting areas of research for adsorbents due to its high surface area and abundant active sites. Mainly, 2D MoS2 show promising removal of textile dye pollutants by adsorption process, but it show high affinity for anionic type of dyes, that limits its performance in mixed dye pollutants treatment. Herein, we demonstrate an integrated approach to remove mixed dye pollutants (anionic and cationic) concurrently by combining adsorption and photocatalysis process. We synthesize MoS2/TiO2 nanocomposites for different weight percentages 2.5, 5, 10, 20, 30 and 50 wt% of pre-synthesized flower-like MoS2 nanoparticle by a two-step hydrothermal method. We demonstrate a new process of two-stage adsorption/photocatalysis using high wt% of MoS2 (Stage-I) and low wt% of MoS2 (Stage-II) nanocomposites. The proposed two-stage integrated adsorption and photocatalysis process using 50% and 2.5% of MoS2 coated TiO2, respectively showed complete removal of methylene blue dye ∼5 times faster than conventional single-stage (adsorption or photocatalysis) water treatment process. Furthermore, the feasibility of the proposed two-stage method in mixed dye pollutants removal (anionic and cationic) testified, which showed excellent performance even in doubling the dye pollutant concentration. This work brings a deeper insight into understanding the morphology and concentration of 2-D MoS2 in MoS2/TiO2 nanocomposite in tackling mixed dye pollutants and the possibilities of applying in textile dyeing industries wastewater treatment plants
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Brexit or Brand it? The Effects of Attitude Towards Brexit and Reshored Brands on Consumer Purchase Intention
Copyright © 2022 The Authors. Brexit has caused a seismic shift in the British socio-economic and political landscapes, creating widespread uncertainties, while simultaneously giving hope and national pride to millions. The decision by a number of organizations to reshore their production has opened a new era for business management that challenges the axiomatic assumption of the benefits of offshored production. Although reshoring predates Brexit, the link between the two in the British context is not just serendipitous and they are argued to have reasonable interlinkages. However, there is inadequate empirical evidence to suggest that British consumers’ attitude towards Brexit has any effect on their intention to purchase reshored brands. Through a mixed-methods study comprising a survey of 415 respondents and 20 in-depth interviews, this paper addresses this research gap. Findings suggest that corporate social responsibility (CSR) and consumer reshoring sentiment (CRS) have positive effects on consumers’ attitude towards reshored brands. Despite CRS's positive influence on attitude towards Brexit, the latter does not have any significant effects on the intention to purchase a reshored brand, which is positively influenced by the attitude towards the same brand. As such, companies should enhance the image of their brands and CSR in order to harness the benefits of reshoring.University of Western Australia, as part of the Wiley – The University of Western Australia agreement via the Council of Australian University Librarians
Entangled Dilaton Dyons
Einstein-Maxwell theory coupled to a dilaton is known to give rise to
extremal solutions with hyperscaling violation. We study the behaviour of these
solutions in the presence of a small magnetic field. We find that in a region
of parameter space the magnetic field is relevant in the infra-red and
completely changes the behaviour of the solution which now flows to an
attractor. As a result there is an extensive ground state
entropy and the entanglement entropy of a sufficiently big region on the
boundary grows like the volume. In particular, this happens for values of
parameters at which the purely electric theory has an entanglement entropy
growing with the area, , like which is believed to be a
characteristic feature of a Fermi surface. Some other thermodynamic properties
are also analysed and a more detailed characterisation of the entanglement
entropy is also carried out in the presence of a magnetic field. Other regions
of parameter space not described by the end point are also
discussed.Comment: Some comments regarding comparison with weakly coupled Fermi liquid
changed, typos corrected and caption of a figure modifie
Thermodynamics of Large N Gauge Theories with Chemical Potentials in a 1/D Expansion
In order to understand thermodynamical properties of N D-branes with chemical
potentials associated with R-symmetry charges, we study a one dimensional large
N gauge theory (bosonic BFSS type model) as a first step. This model is
obtained through a dimensional reduction of a 1+D dimensional SU(N) Yang-Mills
theory and we use a 1/D expansion to investigate the phase structure. We find
three phases in the \mu-T plane. We also show that all the adjoint scalars
condense at large D and obtain a mass dynamically. This dynamical mass protects
our model from the usual perturbative instability of massless scalars in a
non-zero chemical potential. We find that the system is at least meta-stable
for arbitrary large values of the chemical potentials in D \to \infty limit. We
also explore the existence of similar condensation in higher dimensional gauge
theories in a high temperature limit. In 2 and 3 dimensions, the condensation
always happens as in one dimensional case. On the other hand, if the dimension
is higher than 4, there is a critical chemical potential and the condensation
happens only if the chemical potentials are below it.Comment: 37 pages, 4 figures; v2: minor corrections, references added; v3:
minor corrections, to appear in JHE
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