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Dynamical Evolution of Collapsing Stellar Systems in F R Gravity

Thesis Info

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Author

Yousaf, Zeeshan

Program

PhD

Institute

University of the Punjab

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2015

Thesis Completion Status

Completed

Subject

Mathemaics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/9585/1/Zeeshan_Yousaf_Math_2015_Univ_of_the_Punjab_11.04.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725929751

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This thesis is devoted to study the dynamical instability of some relativistic collapsing self-gravitating structures with both Newtonian and post-Newtonian approximations in metric f(R) gravity. In this setting, we consider evolution of spherical, cylin- drical and restricted axial stellar systems ¯lled with expansion and expansion-free adiabatic/non-adiabatic matter con¯gurations. We analyze the role of adiabatic index (sti®ness parameter) in the instability constraints of these self-gravitating structures. We construct dynamical equation using contracted Bianchi identities of the e®ective dark sources as well as usual matter distribution. The perturbation approach is ap- plied on physical variables and then formulate modi¯ed versions of collapse equation which leads to instability constraints at both N and pN regimes. We ¯rst consider spherically and cylindrically symmetric spacetimes ¯lled with charged and uncharged expansion-free anisotropic matter distributions. It is found that the adiabatic index does not have any role in the expansion-free evolution within N and pN approximations. Rather, this range is governed by pressure anisotropy, ra- dial pro¯le of system energy density, f(R) model and electric charge (for charged distribution). We also explore the role of heat radiations in non-viscous charged spherical and cylindrical systems as well as shearing viscous uncharged axial relativis- tic interior. It is found that heat radiations try to decrease stability of the evolving systems, while viscosity tends to increase system stability. The electromagnetic ¯eld decreases instability regions for charged spherical systems while its opposite e®ects have been observed for cylindrical collapsing self-gravitating systems. We conclude that f(R) dark energy sources coming up from the well-known f(R) models a®ect xi xii the whole dynamical behavior of collapsing systems due to its repulsive nature. Finally, we study the factors involved in the energy density irregularities of rela- tivistic planar °uid distribution in the presence of Palatini f(R) corrections. For this purpose, we develop a link between the Weyl scalar and structural properties of the system by a couple of di®erential equations. We also investigate the e®ects of Palatini f(R) terms in the formulation of structure scalars obtained by orthogonal splitting of the Riemann tensor in general relativity. We then identify the parameters which produce energy density irregularities in expansion and expansion-free dissipative as well as non-dissipative matter distributions. It is found that particular combinations of the matter variables lead to irregularities in an initially homogeneous °uid dis- tribution. We conclude that Palatini f(R) extra corrections tend to decrease the inhomogeneity, thereby imparting stability to the self-gravitating system.
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تیرا سوہنا پاک خیال

تیرا سوہنا پاک خیال
رہندا ہر دم میرے نال
اندروں باہروں جو ہِک ہوون
اوہ بندے نیں خال خال
اثر نسل تک جاری رہندا
جیہڑا ہووے حرام دا مال
عاشق تپ جد کندن ہووے
ہکو جئے نیں ہجر وصال
روندے روندے سو جاندے نیں
ڈھیر غریباں دے کئی بال
سار نہ پچھی یار سجن نے
گزرے کتنے ماہ و سال

عہد نبوی میں مذہبی تعلیم کے رجحانات کا تحقیقی مطالعہ

Education is a very important aspect of human life. Muslims were strongly believed on Religious Education. It was considered mandatory for spiritually life here in this world and here after. This article “Research Study of Religious Education Trends in the Prophet (PBUH) Era” introduces the concept of “education” with its definition from Oxford Dictionary and by Muslims philosophers. The “Education System” is also defined with its main components and its objectives in the light of sayings by various Muslim intellectuals. Then, the education system in the Prophet (PBUH) Era is discussed in detail. The role of Prophet (PBUH) and his companions and their effects are also discussed. It also studies the main objectives of Religious Education, its curriculum, the role of Mosque and the relation between teacher and student. Lastly, the current education system of Pakistan is analyzed critically and a few suggestions are given to make it a better one.

Study of Genetic Variants for Inherited Ocular Disorders in Sindhi Inbred Pedigrees

The inherited ocular disorders are the leading cause of vision impairment, eye degeneration, and dysfunction worldwide. The most of the ocular diseases are inherited as autosomal recessive traits and are in populations where endogamous marriages are common. Identification of disease causing gene and pathogenic variants are of great importance for screening of carriers and management of the disease, moreover, it is fundamental to understand the underlying mechanisms of diseases and thus pave the path for successful therapeutic approaches to cure the disease. This study was aimed to find genetic and molecular basis of enrolled consanguineous pedigrees affected with inherited ocular disorders. Fifty four consanguineous families affected with oculo cutaneous albinism, Retinitis pigmentosa and congenital glaucoma were enrolled from various areas of Sindh province. Detailed family history was recorded and pedigrees were drawn. Genomic DNA was extracted from whole blood for genetic studies. Homozygosity mapping was performed for the most common loci and genes. Frequent mutations were screened through ARMS assays. The disease causing and candidate genes were Sanger sequenced. The whole exome sequencing was carried out on selected unlinked families, data were analyzed and desired variants were filtered out. In-slico bioinformatics tools were used to access the pathogenicity of the novel variants and protein structures were modeled to compare wild and mutant proteins. Disease causing genes were identified in twenty eight families, whereas twenty six families were remained unresolved. Mutations in three genes OCA2, TYR and MC1R, associated with albinism, were found in 14 (14/19) families. Four novel variants c.1056A>C, p.Arg352Ser, c.1322A>G, p.Asp441Gly, c.987C>AGA, p.Gln339Aspfs*2, c.1951 +4A>G were found in OCA2 gene including three reported variants. One novel c.1037 -18 T>G and three reported variants were found in TYR gene, whereas one reported variant was found in the MC1R gene. Moreover 10 families with congenital glaucoma were screened. Four PCG causing mutation were found in CYP1B1 gene, including 1 novel allele, c.1048 C>A, p.Pro350Thr and three known, variants. c.1572G>A, p.Arg390His was remained the frequent PCG causing mutation in CYP1B1 gene. Twenty five families affected with non-syndromic RP and 6 with syndromic RP were analyzed. Five disease causing variants were found in Bardet Biedl Syndrome associated genes in 6 10 syndromic RP families. One novel nonsense variant was detected in c.223C>T, p.Arg75*, in BBS9 gene and four reported variants in MKKS ,BBS1 and BBS2 . Homozygosity mapping was done for common RP loci in the nineteen families with non-syndromic retinitis pigmentosa and were found unlinked. Two families were selected for the whole exome sequencing, and two different candidate genes were identified in each. The pathogenic variant 1708C>G, p.Arg570Gly in MARK3 was found responsible for low eye vision and phthisis phenotype in the VI-12 family. The functional studies of MARK3 gene on animal model support the findings in humans. The second family LURP-33 revealed the pathogenic variant, c.75C>A, p.Asp25Glu in novel chloride like gene, CLCC1, segregated in five affected individuals. The Cl channels play important function in the retinal structure in mice and its dysfunction leads to cause retinal degeneration. In-slico functional studies indicate the pathogenic nature of the CLCC1 variant; however, detailed study of CLCC1 knock out animals may further help to understand its function and role in causing RP. In the present study, OCA2 37% (7/19) was the frequently mutated gene causing OCA in Sindhi population followed by TYR mutations 31% (6/19). CYP1B1 was the most common gene causing PCG with a recurrent mutation, p.R390H in patients having different ethnic groups. Furthermore, Retinitis pigmentosa showed genetic heterogeneity as compared to other disorders studied here. Just MKKS gene mutation was found twice in two families with BBS, whereas, 68% (17/25) RP families were remained unlinked to common RP genes. Identification of two novel candidate gene in Sindhi consanguineous pedigrees causing RP and phthisis indicate genetic heterogeneity and may help to explore novel mechanisms of normal vision and pathophysiology of the phenotype caused by the mutation in MARK3 and CLCC1 genes. The findings may help to provide genetic counseling to affected families and may facilitate to develop cost effective, rapid diagnostic procedures for carrier screening for common mutations.