1,530 research outputs found
Planck-Scale Corrections to Friedmann Equation
Recently, Verlinde proposed that gravity is an emergent phenomenon which
originates from an entropic force. In this work, we extend Verlinde's proposal
to accommodate generalized uncertainty principles (GUP), which are suggested by
some approaches to \emph{quantum gravity} such as string theory, black hole
physics and doubly special relativity (DSR). Using Verlinde's proposal and two
known models of GUPs, we obtain modifications to Newton's law of gravitation as
well as the Friedmann equation. Our modification to the Friedmann equation
includes higher powers of the Hubble parameter which is used to obtain a
corresponding Raychaudhuri equation. Solving this equation, we obtain a leading
Planck-scale correction to Friedmann-Robertson-Walker (FRW) solutions for the
equation of state.Comment: 15 pages, no figure, to appear in Central Eur.J.Phys. arXiv admin
note: text overlap with arXiv:1301.350
Minimal Length, Friedmann Equations and Maximum Density
Inspired by Jacobson's thermodynamic approach[gr-qc/9504004], Cai et al
[hep-th/0501055,hep-th/0609128] have shown the emergence of Friedmann equations
from the first law of thermodynamics. We extend Akbar--Cai derivation
[hep-th/0609128] of Friedmann equations to accommodate a general entropy-area
law. Studying the resulted Friedmann equations using a specific entropy-area
law, which is motivated by the generalized uncertainty principle (GUP), reveals
the existence of a maximum energy density closed to Planck density. Allowing
for a general continuous pressure leads to bounded curvature
invariants and a general nonsingular evolution. In this case, the maximum
energy density is reached in a finite time and there is no cosmological
evolution beyond this point which leaves the big bang singularity inaccessible
from a spacetime prospective. The existence of maximum energy density and a
general nonsingular evolution is independent of the equation of state and the
spacial curvature . As an example we study the evolution of the equation of
state through its phase-space diagram to show the existence of
a maximum energy which is reachable in a finite time.Comment: 15 pages, 1 figure, minor revisions, To appear in JHE
Removal of Fixed-valued Impulse Noise based on Probability of Existence of the Image Pixel
This paper proposes a new approach for restoring images distorted by fixed-valued impulse noise. The detection process is based on finding the probability of existence of the image pixel. Extensive investigations indicate that the probability of existence of a pixel in an original image is bounded and has a maximum limit. The tested pixel is judged as original if it has probability of existence less than the threshold boundary. In many tested images, the proposed method indicates that the noisy pixels are detected efficiently. Moreover, this method is very fast, easy to implement and has an outstanding performance when compared with other well-known methods. Therefore, if the proposed filter is added as a preliminary stage to many filters, the final results will be improved
The Models of Legal Education: Implication for Saudi Arabia
The model of any type of education is very important for learning and every type of learning requires a different approach. This research explores the Socratic method, the Case Method, the Problem-Based Method, Clinical Legal Education and Lecture Approach for legal education. It also discusses the merits and demerits of each educational model in the legal education context. It was observed that all teaching methods were complementary to each another and that legal education requires a mix of all as per the subject matter and resource-availability of education institutions. This research also identified the legal education model in Saudi Arabia. Saudi Arabia predominately adopted the lecture approach due to historical dependence on French-educated Egyptian professors. The lecture approach is very traditional and has more demerits as compared to merits with rote learning. Therefore, we suggest the Kingdom use a mixed approach for legal education for maximum advantage
The Impact of Accounting Disclosure on the Efficiency of Investment Decisions in Sudanese Banks (2007 to 2017)
The present study aimed at investigating the Sudanese reality regarding the application of the international standards to financial disclosure and their impact on the efficiency of investment decisions as well as clarifying the significance of financial reports in decision making at the internal and external levels of the bank. The study adopted the inductive approach, the deductive approach, validity test, the historical approach to analyze literature review, and the descriptive analytical approach utilizing case study method. Results of the study revealed that the bank counts on credible, scientific, and accurate data when applying accounting disclosure. Consequently, investment decisions will be properly made. Additionally, it helps the bank provide financial reports and statement on its current financial status which reinforce the credibility of the reports submitted to the investors. The study recommended fostering modern methods in accounting system to evaluate and to reach the proper and real value of assets. Moreover, the level of disclosure in the reports should be increased and the financial statements should be transparent and available to all beneficiary. Keywords: Accounting disclosure, efficiency, investment, Sudanese bank
Tendering in Assignment of the Administrative Contract: A Comparison of Egyptian Tender Law and Saudi Government Tenders and Procurement Law
Administrative contracts are conducted to meet government agencies' requirements in terms of procurement, which is done by tendering. The government infrastructure demand and day-to-day other needs are contracted with vendors, who render their services by applying the announced tender. Hence, the legal framework related to tendering is very important, which protects the legal rights of tender authority and vendors. This present research aims to explore the tendering law in Saudi Arabia and Egypt, having a close legal framework regarding tendering. Egypt is carrying the tender law of 1998, which is updated in 2018 recently. Moreover, tendering in Saudi Arabia depends on the Government Tenders and Procurement Law (GTPL) of 2019, which is updated from the previous version of GTPL 2006. The research explores the basic structure of the procurement system and tendering in both systems, including the discussions on procurement agency, tendering methods, basic tendering regulations, public-private partnership, transparency issue, and tendering with foreigners' bidders. Also, the recent improvements in both tendering systems are discussed. The research traces many similarities and differences in both tendering systems and suggests taking help from each other's experiences
Collocation algorithms and error analysis for approximate solutions of ordinary differential equations
PhD ThesisThis thesis is mainly concerned with an error analysis of
numerical methods for two point boundary value problems. in particular
for the method of collocation using polynomial and certain piecewise
polynomial bases.
As in previous work on strict error bounds an operator
theoretical approach is taken. The setting for the theory and the
principal results for later use are firstly considered. Then two types
of 'a posteriori' error bounds are developed. These"bounds are made
computable by relating the inverse of the approximating operator to the
inverse of certain matrices formed in the actual application of the
approximation method.
The application of this theory to the numerical solution of
linear two point boundary value problems is then considered. It is
demonstrated how the differential equation can be split to fit into the
setting required by the theory. It is also demonstrated how the global
and the piecewise collocation method can be expressed in terms of a
projection method applied to the operator equation. The conditions
required by the theory are expressed in terms of continuity requirements
on the coefficients of the differential equation and in terms of the
distribution of the collocation points. In examining these bounds on
a variety of problems. it is noticed that with some problems the
conditions for applicability may not hold except for more points than one
actually required to obtain a satisfactory solution. To improve the
applicability. the theory is reconsidered with a different splitting
of the differential equation. The method of collocation is expressed
accordingly in terms of a new projection operator which is proved to
have some nice properties in practice. This new approach is then compared with the original one and it is shown to be superior on various problems.
By examining the inverse differential operator and the residual
improved error bounds and estimates are shown to be obtainable. These
estimates are tested in a large variety of examples and some graphs
are presented to describe their behaviour in more detail. Finally
these estimates are used to develop various adaptive mesh selection
algorithms for solving two point boundary value problems. These
strategies are tested and compared in several representative examples
and some conclusions are drawn.
The thesis concludes with a brief review of the work with an
indication of possible improvements and extensions
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