Parameter Definition and 352 Threads

Homework Statement Using Friedmann equations find the parameter of deceleration q_0 using relative densities \Omega_M,\ \Omega_R,\ \Omega_\Lambda. Homework Equations Friedmann equations, deceleration parameter: q_0=-\frac{\ddot{a_0}a_0}{\dot{a_0}^2} The Attempt at a Solution So from...

Hi, I am trying to fit sample data to a Johnson SU distribution in S-Plus. It seems not many people use S-Plus, so if you are familiar with R then you could help as well. The code that I have is: [FONT="Courier New"]f.Jsu.fun.takeslist(x,g,l,r,e) which is a function I have made that...

I am currently doing a course on CNC Programming (GCode, MCode and also APT Programming). The course is almost over and we are going to have an Exam at the end. The Exam is mostly writing programs but would also have a few theory questions. One of the questions asked in previous exams has been...

Homework Statement Elimnate the parameter to find a rectangular equation of the curve. x=sin t, y= csc t Homework Equations I believe trignometric identities are relevant to this problem. cscx=1/sinx The Attempt at a Solution csc x =1/ sin x thus y=1/x Is this the answer...

Hi everyone, I've got a one-dimensional non-autonomous ODE of the following form: dy / dx = f(x,y;w) x_{0} = g(w) y_{0} = h(x_{0};w) --- i.e., w is a parameter that influences both the derivative dy/dx along with both coordinates in the initial condition (x_{0},y_{0}). I basically want to...

I would appreciate a little help with a parametric equation please. Example. x = t + 1y = 3t - 2 I want to eliminate t x = t + 1 so I change the sides t = x - 1 I now bring in the second equation y = 3t - 2 = 3(x - 1) - 2 = 3x - 5 y = 3x - 5 The above I have understood, but my next...

Any problem of collision can be solved using four equations: Conservation of momentum and energy, impulsive forces and impact parameter (distance between center of masses of the particle taken perpendicular to velocity). I can solve problems using first three cases. But how to analyse a problem...

[FONT="Times New Roman"]I need to derive the lattice parameter in terms of the Zn-S separation distance, l. I looked up the value and I've found it to be a = \frac{4}{\sqrt{3}}l The way that I started my derivation was saying that each tetrahedron has a sulfide ion in the center, so then we...

EDIT: Figured it out. Stupid me. I should have solved in terms of x, giving me x=1-(y+3)^2 as my answer. Homework Statement x= 1−t^{2}, y= t−3, −2 ≤ t ≤ 2 Eliminate the parameter to find a Cartesian equation of the curve for −5 ≤ y ≤ −1 Homework Equations N/A The Attempt at a Solution...

Hi, I'm not exactly sure how to solve the following non-homogeneous ODE by variation of parameters. Solve the given non-homogeneous ODE by the variation of parameters: x^2y" + xy' -1/4y = 3/x + 3x Can someone please point me in the right direction? Help will be much appreciated...

My situation is as follows: I have a set of points in a bounded three-dimensional space. Simply put, each point has an X, Y and Z coordinate. I'm looking for a mathematical parameter that (globally) expresses how well the points are distributed over the space. The parameters should take the X...

What is a parameter regression in modeling?

According to Peterdonis in an old thread According to Matterwave in https://www.physicsforums.com/showthread.php?t=573589 msg #11: Peterdonis said Time is a parameter in non-relativistic QM while as a coordinate in relativistic QM/QFT. But Matterwave said parameter and coordinate has...

Greetings everyone , Can anyone point me into the right direction on how to come out with a value/ expression for the density parameter of a radiation dominated universe. Things that I know of/ can recall are: Friedmann equation : 8/3 \pi G ρ R^2 -kc^2 Also when radiation dominates...

Homework Statement A mass of 1000 kg drops from a height of 10.0 m onto a platform of negligible mass. It is desired to design a spring and damper on which to mount the platform so that it will settle to a new equilibrium position 2.00 m below its original position as quickly as possible...

Homework Statement a) Eleminate the parameter to find a Cartesian equation of the curve. b) Sketch the curve and indicate with an arrow the direction in which the curve is traced as the parameter increases. Homework Equations x = 2cosh(t) y = 5sinh(t) cosh^2(x) - sinh^2(x) = 1...

A year ago I learned in multi-var calc about curvature, and since then I've wondered something. It came up again today when my dad tried to talk to me about curvature like it was the second derivative. :P Is there a way, or at least any attempt or resource at all, about parameterizing a...

Can someone give me the intuition behind not using time as a parameter for a Cycloid.

What's the order parameter in quasi crystals? Only the broken rotational symmetry?

If Hubble’s constant H0 = da/a does not change in time between two times t0 and t, how does the cosmological scale factor a(t) vary between these times? This is from a past exam paper, and being quite honest I don't even know where to start with it. Any help would be appreciated. So far...

Homework Statement For which parameter \alpha\in\mathbb{R} the function: f(x, y)= \begin{cases}|x|^\alpha \sin(y),&\mbox{ if } x\ne 0;\\ 0, & \mbox{ if } x=0\end{cases} is differentiable at the point (0, 0)? The Attempt at a Solution For α<0, the function is not continue at (0, 0)...

Homework Statement Starting with the equation below, I need to: - Show that there is a range of values for a for which Ωm≈1 - Derive expressions for the values of a at the endpoints of this range. Homework Equations Ωm(a) = Ωm0/[Ωm0+Ωr0/a+Ωv0a3]. (0 signifies present day values, m=matter...

I am new to lasers. In the expression for q parameter, 1/q = 1/R - j(λ/πw^2) how did we come to know that w(z) is a measure of decrease in field amplitude E with distance? I can't feel it. Does the gaussian beam itself contract to the minimum diameter? Shouldn't a lens be required for this...

In class the other day, my professor had written this as part of the lecture notes: Thus, this definition was mentioned as part of methods. He then went on to show an example of this as in the following: public class Dog { private Collar _ collar; public Dog(Collar collar) {...

valence Z=1, lattice param a = 4.05 conductivity = 1.76e7 . What's the avg time between collisions of a conduction electron in this metal (bcc structure).really have no idea lol

Dear all, As u know, one of the best potentials for quintessence is V=[M]^[4+\alpha] [\phi]^[-\alpha] They usually call M, THE MASS PARAMETER. Who knows what is the value of M for now?

Why will the Hubble parameter only decrease to .85 of today's Hubble parameter?

Welcome Using MLE I found that estimator \alpha parametr from Rayleigh distribution is described by formula \hat{\alpha}=\sqrt{\frac{\sum_{n}^{i=1}x_i^2}{2n}} but I can't proof that this estimator is consistent estimator. Would you be mind and help me with my problem.

Hi, Let us assume that Hubble's Constant H is really constant. Therefore: a' / a = H where a is the scale factor. The solution to this equation is: a(t) = exp(H t) This equation describes an accelerating universe with deceleration parameter q given by: q = - a'' a / a'^2 =...

It now looks like the Immirzi parameter has a critical value which is determined numbertheoretically, not by the Bekenstein-Hawking S = A/4. It used to be that with LQG the IP appeared multiplicatively in S = A/4 so that the value of the IP had to be ADJUSTED to get the S = A/4 equation...

I have a set of data points {xi,yi} where each yi is a Gamma distributed variable where both the shape k and scale \theta depend on i. I then fit the data points with a power law model y=a(x)b. I would like to know the probability distributions for the fit parameters a and b. Is...

I have the parametric function x(t) = (1-t^2)/(1+t^2), y(t) = 2t/(1+t^2) and need to eliminate the parameter and find a Cartesian equation. I've tried to substitute t = tan u, then x(t) = cos(2u) and y(t) = tan(2u). From that I get y = sin(2x)/x. However, when I entered the original...

Please teach me this: How to understand the smallness of mass while the mass parameter diverge rapidly in renormalization group flow because the mass term in Lagrangian is the relevant operator.By the way,are there always exist the fix point of renormalization group flow in any QTF Theory,or in...

Hi... The variation of the total energy with increasing the lattice constant (a), the minimum value of the lattice constant correspond to what degree of temperature? Nawzad A.

Can anyone provide a good reference which gives the G-L parameter for YBCO (a) along the ab-plane of the sample and (b) along the c-axis? I've been to the depths of Google Scholar and back and found nothing, so any help would be much appreciated. :)

hello everyone, :wink: one short question. it is said function sqrt() takes argument inside the parenthesis. sometimes word parameter is also used. are they interchangeable? i am speaking in terms of c++. is int main() has any similarity to math functions such as f(x)=2x+7. but the problem...

Hi, I am doing question A2/15 B2/23 (specifically part (ii)) at the top of page 50 here: http://www.maths.cam.ac.uk/undergrad/pastpapers/2001/Part_2/list_II.pdf I have done everything up to and including showing the impact parameter is given by b=h/E, but I am having trouble doing parts (a)...

I would like to discuss a puzzle I'm wondering about in loopy approaches to quantum gravity. The puzzle is roughly as follows: The Immirzi parameter (IP) is a strange constant that appears in loopy approaches. Calculations of black hole entropy in loopy approaches seem to need to fix the IP...

let be the integrals \int_{0}^{\infty}dxx^{2} (x-a)^{1/2}=I1 and \int_{0}^{\infty}dxx^{2} (x-a)^{-1/2}=I2 is then correct that I2= 2\frac{dI1}{da} whenever applying a regularization scheme , is it correct to differentiate with respct to external parameters ??

Can anyone tell me where I can find a basic T parameter table for RF design. One with the T parameters for shunt impedence in coaxial, series capacitance in coaxial, coaxial of length l etc...

Homework Statement Hi Guys, I try to find the range for parameters phi1 and phi2 were the autoregressive process below is stationary. We have the process X(t)+phi1*X(t-1)+phi2X(t-2)=Epsilon(t) (1) Homework Equations We get the characteristic polynomial F(z)=z^2+phi1*z+phi2 (2) The...

Hi folks, I'm taking a class in statistical mechanics out of Sethna's text. Part of the course involves student presentations. I've settled on his chapter on order parameters, broken symmetry and topology. Its a relatively short chapter and I'd like to read some more. I'm looking for...

An estimate of 0.94/tPlanck for the maximum reached by the Hubble parameter was given by Ashtekar and Sloan here (based on Loop qc): http://arxiv.org/abs/0912.4093 Loop quantum cosmology and slow roll inflation Abhay Ashtekar, David Sloan (Submitted on 21 Dec 2009) "In loop quantum cosmology...

Simple question hopefully. What was the initial value for the Hubble parameter immediately following the big bang (or ending of inflationary epoch)? I presume the initial velocity of expansion was lightspeed and started slowing from there.

Hi, I've heard it said that for Schwarzschild spacetimes, then the coordinate 'r' is an affine parameter for radial null geodesics in the region exterior to the horizon. It seems weird to me that one of the coords is an affine parameter. How can this be seen? I know that the radial null...

When you see something like f(x,·,·), how are you supposed to interpret it? Sorry, I can't give example, the only places I've seen have been using it informally. I read, http://www.reddit.com/r/math/comments/995dl/ask_math_reddit_what_does_the_dot_in_this/ , but can't find a definitive answer.

Homework Statement Suppose z is complex number with |z| = 1 (also assume that z is not 1 + 0*i) Let z = a + b*i where a and b are real numbers. Find a real parameter, t, such that z = (t-i)/(t+i), where i = sqrt(-1) Homework Equations |z| = sqrt(a^2+b^2) The Attempt at...

Hello everyone, As is known to all, the order parameter for the ferromagnetic case in the Landau expression is chosen as the magnetization. This is easy to understand. But for the antiferromagnetic case, what is the order parameter? People told me it was magnetic moment on the sublattice. But...

Homework Statement For alpha particles of 7.7 MeV, what impact parameter will result in a deflection of 2 degrees for a thin gold foil? Homework Equations impact parameter equation, b=\frac{kq_{\alpha}Q}{m_{\alpha}v^{2}}cot\frac{\theta}{2} The Attempt at a Solution Pretty easy, just plug...

Homework Statement Calculate dhkl and vc for the (111) direction of germanium. Homework Equations dhkl=a/sqrt(h2+k2+l2) vc=unit cell volume=a1dot(a2xa3) or vc=structure form factor/density The Attempt at a Solution dhkl=a/sqrt(3) I know how to solve this, I've just...