1,070 research outputs found
Dissipative Processes in the Early Universe: Bulk Viscosity
In this talk, we discuss one of the dissipative processes which likely take
place in the Early Universe. We assume that the matter filling the isotropic
and homogeneous background is to be described by a relativistic viscous fluid
characterized by an ultra-relativistic equation of state and finite bulk
viscosity deduced from recent lattice QCD calculations and heavy-ion collisions
experiments. We concentrate our treatment to bulk viscosity as one of the
essential dissipative processes in the rapidly expanding Early Universe and
deduce the dependence of the scale factor and Hubble parameter on the comoving
time . We find that both scale factor and Hubble parameter are finite at
, revering to absence of singularity. We also find that their evolution
apparently differs from the one resulting in when assuming that the background
matter is an ideal and non-viscous fluid.Comment: 8 pages, 2 eps figure, Invited talk given at the 7th international
conference on "Modern Problems of Nuclear Physics", 22-25 September 2009,
Tashkent-Uzbekista
Matter-Antimatter Asymmetry in the Large Hadron Collider
The matter-antimatter asymmetry is one of the greatest challenges in the
modern physics. The universe including this paper and even the reader
him(her)self seems to be built up of ordinary matter only. Theoretically, the
well-known Sakharov's conditions remain the solid framework explaining the
circumstances that matter became dominant against the antimatter while the
universe cools down and/or expands. On the other hand, the standard model for
elementary particles apparently prevents at least two conditions out of them.
In this work, we introduce a systematic study of the antiparticle-to-particle
ratios measured in various and collisions over the last three
decades. It is obvious that the available experimental facilities turn to be
able to perform nuclear collisions, in which the matter-antimatter asymmetry
raises from at AGS to at LHC. Assuming that the final
state of hadronization in the nuclear collisions takes place along the
freezeout line, which is defined by a constant entropy density, various
antiparticle-to-particle ratios are studied in framework of the hadron
resonance gas (HRG) model. Implementing modified phase space and distribution
function in the grand-canonical ensemble and taking into account the
experimental acceptance, the ratios of antiparticle-to-particle over the whole
range of center-of-mass-energies are very well reproduced by the HRG model.
Furthermore, the antiproton-to-proton ratios measured by ALICE in
collisions is also very well described by the HRG model. It is likely to
conclude that the LHC heavy-ion program will produce the same particle ratios
as the program implying the dynamics and evolution of the system would not
depend on the initial conditions. The ratios of bosons and baryons get very
close to unity indicating that the matter-antimatter asymmetry nearly vanishes
at LHC.Comment: 9 pages, 5 eps-figures, revtex4-styl
Effects of quantum gravity on the inflationary parameters and thermodynamics of the early universe
The effects of generalized uncertainty principle (GUP) on the inflationary
dynamics and the thermodynamics of the early universe are studied. Using the
GUP approach, the tensorial and scalar density fluctuations in the inflation
era are evaluated and compared with the standard case. We find a good agreement
with the Wilkinson Microwave Anisotropy Probe data. Assuming that a quantum gas
of scalar particles is confined within a thin layer near the apparent horizon
of the Friedmann-Lemaitre-Robertson-Walker universe which satisfies the
boundary condition, the number and entropy densities and the free energy
arising form the quantum states are calculated using the GUP approach. A
qualitative estimation for effects of the quantum gravity on all these
thermodynamic quantities is introduced.Comment: 15 graghes, 7 figures with 17 eps graph
Deconfinement and freezeout boundaries in equilibrium thermal models
In different approaches, the temperature-baryon density plane of QCD matter
is studied for deconfinement and chemical freezeout boundaries. Results from
various heavy-ion experiments are compared with the recent lattice simulations,
the effective QCD-like Polyakov linear-sigma model, and the equilibrium thermal
models. Along the entire freezeout boundary, there is an excellent agreement
between the thermal model calculations and the experiments. Also, the thermal
model calculations agree well with the estimations deduced from the Polyakov
linear-sigma model (PLSM). At low baryonic density or high energies, both
deconfinement and chemical freezeout boundaries are likely coincident and
therefore the agreement with the lattice simulations becomes excellent as well,
while at large baryonic density, the two boundaries become distinguishable
forming a phase where hadrons and quark-gluon plasma likely coexist.Comment: 8 pages, 2 figures, accepted for publication in AHE
Thermodynamics of viscous Matter and Radiation in the Early Universe
Assuming that the background geometry is filled with free gas consisting of
matter and radiation and no phase transitions being occurred in the early
Universe, we discuss the thermodynamics of this {\it closed} system using
classical approaches. We find that essential cosmological quantities, such as
Hubble parameter , scale factor and curvature parameter , can be
derived from this simple model, which on one hand fulfills and entirely obeys
the laws of thermodynamics. On the other hand, the results are compatible with
the Friedmann-Lemaitre-Robertson-Walker model and the Einstein field equations.
The inclusion of finite bulk viscosity coefficient derives to important changes
in all these cosmological quantities. Accordingly, our picture about the
evolution of the Universe and its astrophysical consequences seems to be a
subject of a radical revision. We find that strongly depends on the
thermodynamics of background matter. The time scale, at which negative
curvature might take place, depends on the relation between the matter content
and the total energy. Using quantum and statistical approaches, we assume that
the size of the Universe is given by the volume occupied one particle and one
photon. Different types of their interactions are taken into account.
Expressions for and are introduced. Therefore, the expansion of the
Universe turns to be accessible.Comment: 9 pages, 2 figures (3 eps graphs
The way forward to public health in Gulf Cooperation Council (GCC) countries: a need for public health systems and law
Introduction: Public health systems in the Gulf Cooperation Council (GCC) Countries are not well established. The existing systems do not match with the current health challenges and with the use of innovative technology in healthcare (diagnosis, treatment or rehabilitation). This paper is intended to give an overview of the public health situation in these countries. It discusses the need for effective and integrated system of public health laws that plays important role in addressing high priorities in public health. Conclusion: The GCC countries have the infrastructure for estab¬lishing a national public health system. However it needs an effective integrated and organized mechanism to shape this system; based on acceptable guidelines and criteria in such a way that they are institutional and capable of meeting the population needs.
This system should be cost- effective and investment in health sector should be looked upon as a sustained investment in human and societal development. Despite the great efforts exerted and achievements made, there are great challenges ahead that can be overcome by exhibiting a strong political will and having a united approach of all stakeholders
Application of Machine Learning Techniques to Predict Teenage Obesity Using Earlier Childhood Measurements from Millennium Cohort Study
Obesity is a major global concern with more than 2.1 billion people overweight or obese worldwide, which amounts to almost 30% of the global population. If the current trend continues, the overweight and obese population is likely to increase to 41% by 2030. Individuals developing signs of weight gain or obesity are also at the risk of developing serious illnesses such as type 2 diabetes, respiratory problems, heart disease, stroke, and even death. It is essential to detect childhood obesity as early as possible since children who are either overweight or obese in their younger age tend to stay obese in their adult lives. This research utilises the vast amount of data available via UK's millennium cohort study to construct machine learning driven framework to predict young people at the risk of becoming overweight or obese. The focus of this paper is to develop a framework to predict childhood obesity using earlier childhood data and other relevant features. The use of novel data balancing technique and inclusion of additional relevant features resulted in sensitivity, specificity, and F1-score of 77.32%, 76.81%, and 77.02% respectively. The proposed technique utilises easily obtainable features making it suitable to be used in a clinical and non-clinical environment
Integrating the HFACS Framework and Fuzzy Cognitive Mapping for In-Flight Startle Causality Analysis
This paper discusses the challenge of modeling in-flight startle causality as a precursor to enabling the development of suitable mitigating flight training paradigms. The article presents an overview of aviation human factors and their depiction in fuzzy cognitive maps (FCMs), based on the Human Factors Analysis and Classification System (HFACS) framework. The approach exemplifies system modeling with agents (causal factors), which showcase the problem space's characteristics as fuzzy cognitive map elements (concepts). The FCM prototype enables four essential functions: explanatory, predictive, reflective, and strategic. This utility of fuzzy cognitive maps is due to their flexibility, objective representation, and effectiveness at capturing a broad understanding of a highly dynamic construct. Such dynamism is true of in-flight startle causality. On the other hand, FCMs can help to highlight potential distortions and limitations of use case representation to enhance future flight training paradigms
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