Jacobe supta

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9 years, 333 days

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These are replies submitted by escorpsy


I am soory for the late. at the maple file attached here I describe the procedure  step by step. I hope it has enough clarification.

Thank you for your time 


First of all, I really appreciate your help.

I know what is happening physically but dont know how to translate to maple language.

let me try to explain what is happening there ,

we have a differential equation (3.3) ( i replaced theta by t ) , you solved numerically ( with your values for paramters M,l,C,Q,a,w) and find r against t diagram . now auther insert that in (3.2) then integrated  ( with theta_0=0.16 and r(0.159) ) and studied the relation between (3.2) and (2.6 T not t) that is figure 3 .

well how to find r(t) from your plot and integrate (3.2)


thank you for your help


actually this differential equation is equation 3.3 In the below paper which authors solved numerically..



thanks for the point you indicated , it was really crucial point .


considering your point i did two example , i think i have problem with one of them.



thanks in advance



uptodated worksheet

still no answer !!

@Carl Love  @tomleslie @Preben Alsholm


my goal is to find the values of alpha and beta and gamma and lambda so that can solve equations ( and so now i have two equations f(alpha,beta,gamma,lambda,w)=0 and g(alpha,beta,gamma,lambda,w)=0 by and respectively , so there is exist the values of alpha and beta and gamma and lambda so that can solve de2 and corrected equations ?


how can i check this case ?


thank you guys

@tomleslie @Preben Alsholm


i have 5 differential equation which this one is one of them , so this differential equations are very complicated i guess a solution as above and put in equations to see what's happening.


this one is another one and i did your method for getting better looking result but still it has ugly face !



** i corrected the worksheet**


diff(A(r),r)^2 is correct or (diff(A(r),r))^2 for A'^2 ?


can numerical method for differential equation help us for this equations ?



thank you in advance guys



thanks so much , its looking so pretty now . i see Q ( its a constant , actually it is phi_0) is not involved in result equation , is not it strange ?

i reinstalled maple and the problem solved !


well i obtained the variation of the action i attached with respect to g_[~mu,~nu] but want to know that it is correct or not.

N[mu](x[~nu]) is unit time like four velocity and phi is brans-dicke scalar field and acction is written with Lorentzian signature(-,+,+,+)and omega is dicke



thank you for your time.


best regards

@Torre in general i mean can we obtain the field equation of an action by variation ? e.g. f(R) gravity.

@ecterrab for (3) i obtained different solution . what is my problem ?



@ecterrab thank you for your comprehensive help. i appricione of the my problem now is how to define f(R) which R is function of a(t) that contravariant derivative or covariant derivative consider its dependence to t . eg. its easy to compute 00 and 11 components of the field equations that i attached handy. T_00 = rho_m+rho_r and T_11=0. and F is derivative of f with respect to R. but how can i define them so that 00 and 11 components of field equations obtain as the pic i attached.

guys with which command and how to calculate for example μ=0 and ν=0 for R_μρνσ+R_ρν g_σμ-R_ρσ g_νμ-R_μν g_σρ+R_μσ g_νρ +R[g_μν g_σρ -g_μσ g_νρ] Covariantderivative^ρ Covariantderivative^σ  f.  where f is a function of R. for a (-dt+dx+dy+dz) metric

thx again and again



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