8037

7472

كارشناسي ارشد

ذرات بنيادي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1391

هشت،70ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

بهروز ميرزا

غلامرضا خسروي

20/7/92

منصور حقيقت، مسلم زارعي

فيزيك

ID7472

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Laws of thermodynamics for the future singularities in F R gravity Hamideh Nadi h nadi@ph iut ac ir Date of Submission January 23 2013 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor s Name Dr B mirza Email mirza@cc iut ac ir Abstract General theory of relativity has been known as a main theory in description of many cosmic observations Observational data indicates that the universe is expanding with a positive acceleration Dark energy is used as a main candidate for explanation of this accelerated expansion Existence of dark energy may lead to some kind of singularities in the Friedmann equations The type of singularities are related to the behavior of pressure energy density and scale factor In a new scenario which is called Little Rip the energy density increase with time however the time that the singularity appears is shifted to infinite large values Features of Little Rip are similar to the universe that ends up with type I singularity but in this case time of occurrence of the singularity is infinite There are some physical effects that can moderate the finite time future singularities One of them is the varying speed of light According to varying speed of light theory light is traveling faster in the very early periods of the existence of the universe In this thesis we will show that the varying speed of light as a function the universe s life time can change the behavior of type I and type II singularities Also we will investigate the varying speed of light effect in a Little Rip scenario Modified theories of gravity have been proposed as a candidate to explain accelerated expansion of the universe In the recent years F R theory has been studied as the simplest modified theory of gravity In this theory the gravitational action described by an arbitrary function of scalar curvature R F R gravity generates all four known types of the future singularities It is possible to obtain all F R theories corresponding to the future singularities Also the Little Rip scenario may be formulated in this theory We will obtain the specific model for Little Rip cosmology in F R modified theory There is a fundamental relation between gravity and thermodynamics Therefore one of ways that we can examine the correctness of one model is to investigate the laws of thermodynamics in that model We will investigate the second law of thermodynamics in near to the future finite time singularities and in the model that we have obtained for Little Rip F R cosmology Key Words Einstein field equations Friedmann equations Singularity Little Rip Varying speed of light Einstein Hilbert action Modified gravity Laws of thermodynamics PDF created with pdfFactory trial version www pdffactory com PDF created with pdfFactory trial version www pdffactory com

بهروز ميرزا

غلامرضا خسروي

منصور حقيقت، مسلم زارعي