546 research outputs found
Signature Change by GUP
We revisit the issue of continuous signature transition from Euclidean to
Lorentzian metrics in a cosmological model described by FRW metric minimally
coupled with a self interacting massive scalar field. Then, using a
noncommutative phase space of dynamical variables deformed by Generalized
Uncertainty Principle (GUP) we show that the signature transition occurs even
for a model described by FRW metric minimally coupled with a free massless
scalar field accompanied by a cosmological constant. This indicates that the
continuous signature transition might have been easily occurred at early
universe just by a free massless scalar field, a cosmological constant and a
noncommutative phase space deformed by GUP, without resorting to a massive
scalar field having an {\it ad hoc} complicate potential. We also study the
quantum cosmology of the model and obtain a solution of Wheeler-DeWitt equation
which shows a good correspondence with the classical path.Comment: 14 pages, to be published in IJMP
Co-incorporation of biodegradable wastes with crop residues to reduce nitrate pollution of groundwater and decrease waste disposal to landfill
Return of high nitrogen (N) content crop residues to soil, particularly in autumn, can result in environmental pollution resulting from gaseous and leaching losses of N. The EU Landfill Directive will require significant reductions in the amounts of biodegradable materials going to landfill. A field experiment was set up to examine the potential of using biodegradable waste materials to manipulate losses of N from high N crop residues in the soil. Leafy residues of sugar beet were co-incorporated into soil with materials of varying C:N ratios, including molasses, compactor waste, paper waste, green waste compost and cereal straw. The amendment materials were each incorporated to provide approximately 3.7 t C per hectare. The most effective material for reducing nitrous oxide (N2O) production and leaching loss of NO3− was compactor waste, which is the final product from the recycling of cardboard. Adding molasses increased N2O and NO3− leaching losses. Six months following incorporation of residues, the double rate application of compactor waste decreased soil mineral N by 36 kg N per hectare, and the molasses increased soil mineral N by 47 kg N per hectare. Compactor waste reduced spring barley grain yield by 73% in the first of years following incorporation, with smaller losses at the second harvest. At the first harvest, molasses and paper waste increased yields of spring barley by 20 and 10% compared with sugar beet residues alone, and the enhanced yield persisted to the second harvest. The amounts of soil mineral N in the spring and subsequent yields of a first cereal crop were significantly correlated to the lignin and cellulose contents of the amendment materials. Yield was reduced by 0.3–0.4 t/ha for every 100 mg/g increase in cellulose or lignin content. In a second year, cereal yield was still reduced and related to the cellulose content of the amendment materials but with one quarter of the effect. Additional fertilizer applied to this second crop did not relieve this effect. Although amendment materials were promising as tools to reduce N losses, further work is needed to reduce the negative effects on subsequent crops which was not removed by applying 60 kg/ha of fertilizer N
MULTI-DIMENSIONAL COSMOLOGY AND DSR–GUP
A multi-dimensional cosmology with FRW type metric having four-dimensional spacetime and d-dimensional Ricci-flat internal space is considered with a higher-dimensional cosmological constant. The classical cosmology in commutative and Doubly Special Relativity–Generalized Uncertainty Principle (DSR–GUP) contexts is studied and the corresponding exact solutions for negative and positive cosmological constants are obtained. In the positive cosmological constant case, it is shown that unlike the commutative as well as GUP cases, in DSR–GUP case both scale factors of internal and external spaces after accelerating phase will inevitably experience decelerating phase leading simultaneously to a big crunch. This demarcation from GUP originates from the difference between the GUP and DSR–GUP algebras. The important result is that unlike GUP which results in eternal acceleration, DSR–GUP at first generates acceleration but prevents the eternal acceleration at late-times and turns it into deceleration
Black hole thermodynamics and modified GUP consistent with doubly special relativity
We study the black hole thermodynamics and obtain the correction terms for
temperature, entropy, and heat capacity of the Schwarzschild black hole,
resulting from the commutation relations in the framework of {\it Modified
Generalized Uncertainty Principle} suggested by {\it Doubly Special
Relativity}.Comment: 13 pages, 6 figures, minor revision, references adde
Multi-Dimensional Cosmology and GUP
We consider a multidimensional cosmological model with FRW type metric having
4-dimensional space-time and -dimensional Ricci-flat internal space sectors
with a higher dimensional cosmological constant. We study the classical
cosmology in commutative and GUP cases and obtain the corresponding exact
solutions for negative and positive cosmological constants. It is shown that
for negative cosmological constant, the commutative and GUP cases result in
finite size universes with smaller size and longer ages, and larger size and
shorter age, respectively. For positive cosmological constant, the commutative
and GUP cases result in infinite size universes having late time accelerating
behavior in good agreement with current observations. The accelerating phase
starts in the GUP case sooner than the commutative case. In both commutative
and GUP cases, and for both negative and positive cosmological constants, the
internal space is stabilized to the sub-Planck size, at least within the
present age of the universe. Then, we study the quantum cosmology by deriving
the Wheeler-DeWitt equation, and obtain the exact solutions in the commutative
case and the perturbative solutions in GUP case, to first order in the GUP
small parameter, for both negative and positive cosmological constants. It is
shown that good correspondence exists between the classical and quantum
solutions.Comment: 21 pages, 15 figures, minor revision, references adde
Issues of Cost & Access in Canada’s Health Care System: Lessons for the Civil Justice System
There are numerous examples of rethinking costs in the Canadian health care system. Three of these provide us with a sense of why there might be useful lessons for the civil justice system
Activation rate uniformity in a bilateral IVNAA facility for two anthropomorphic phantoms
Activation rate uniformity is the first property which is considered in the design of a prompt γ-ray in vivo neutron activation analysis facility. Preliminary studies on the activation rate distribution in the body can be done by use of Monte Carlo codes, such as the MCNP. In this paper, different bilateral configurations of an IVNAA system are considered in order to improve the activation rate uniformity in a water phantom measuring 32 cm x 100 cm x 16 cm. In the best case, uniformity parameters are U = 1.003 and R = 1.67, with the mean activation rate of 1.85×10-6 cm-3. In more accurate calculations, the water phantom is replaced by a body model. The model in question is a 5 year-old ORNL phantom filled with just soft tissue. For uniformity studies, the internal organs are not simulated. Finally, uniformity parameters in this case are U = 1.005 and R = 12.2
Thermo-mechanical properties of commercially available epoxy resins for structural applications
Externally bonded (EB) or Near-Surface-Mounted (NSM) composite reinforcements are
often bonded to a cementitious substrate by means of commercially available epoxies. These twocomponent-
resins are generally ‘cold-curing’ (at room temperature), having however the ability to cure
faster under elevated temperatures. One application requesting such an accelerated curing process is the
gradient anchorage for strengthening of concrete structures with prestressed CFRP laminates, based on a
purely concrete/epoxy/CFRP connection without any mechanical devices.
This paper resumes the investigation on several crucial thermo-mechanical parameters of different epoxy
resins, such as glass-transition temperatures, directional tensile strength and elastic modulus. It is for
instance demonstrated that an accelerated curing process or an increasing specimen age implicate a higher
glass transition temperature. Strength and stiffness development is faster in case high temperatures are
applied; the final values with growing age however are below the ones for specimens cured only at room
temperature. Initial mixing under vacuum on the other hand induces higher strength and stiffness values.
Eventually, it is shown that an accelerated curing of a cold-curing epoxy increases the porosity of the
latter, possibly implying durability issues
Cosmology of Dirac-Born-Infeld dRGT massive gravity
We introduce the cosmological analysis of the Dirac-Born-Infeld dRGT massive
gravity theory which is a new extension of de Rham-Gabadadze-Tolley (dRGT)
massive gravity. In this theory, we consider the Dirac-Born-Infeld (DBI) scalar
field which is coupled to the graviton field. Moreover, we perform the
cosmological background equations, and we demonstrate the self-accelerating
background solutions. We show that the theory consists of self-accelerating
solutions with an effective cosmological constant. In the following, we exhibit
tensor perturbations analyses and achieve the dispersion relation of
gravitational waves. We analyze the propagation of gravitational perturbation
in the Friedmann-Lema\^itre-Robertson-Walker cosmology in the DBI dRGT massive
gravity. Finally, we present the vector and scalar perturbations to show the
stability conditions of the theory.Comment: arXiv admin note: text overlap with arXiv:2204.0559
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