Scale Definition and 721 Threads

Hi, everybody! I can not really understand the particular behavior of the sin2thw with respect to the scale (like on the plot below). Clearly there are three regimes from the left to the right: a plato, a degradation and a steep rise. But why exactly does the curve behave like this? The...

From Introduction to Cosmology by Matt Roos, he wanted to derive the Hubble parameter in terms of the scale factor. From the Friedmann's equation, ##\frac{R'^2 + kc^2}{R^2} = \frac{8πG}{3}ρ## The density parameter is ##~Ω(a) = \frac{8πG}{3H_o^2}ρ(a)~## and let ##~Ω_k = \frac{-kc^2}{H_o^2}##...

Hello! Could anybody help me? My wondering seems so trivial, but I can't skip it. They say that since u and d quarks are much lighter than QCD scale(~200MeV), in reality we can consider the QCD Lagrangian has an approximate global chiral symmetry with respect to these two flavors. At first, it...

Hey everyone, I understand how to normalize a second order system, but I wanted to know if the same steps are taken when the parameters of the system are not scalar but matrices. For example where the parameter phi, and gamma are both 3x3 matrices and X is a 3x1 vector. From what I've see...

In this video: The professor at the end (at about 7:28), used the formula for scale factor and redshift as a(t) = 1/z, instead of the actual one a(t) = 1/1+z. And when we apply both of them, they give very different results. So, how could the professor use the first formula, which we were...

Below Planck scale means inside the Planck scale, and above Planck scale means outside of Planck scale? If the term is correct.. why doesn't quantum gravity theory like Loop Quantum Gravity affect low energy experiments above the Planck scale (outside of Planck scale)? Quantum field theory is...

Please can someone explain the difference between the decibel (dB) scale and the adjusted decibel scale (dBA scale) and why the dBA scale is used in preference to the dB scale. I've been stuck on this for ages and can't seem to understand the difference

I'm not following what justifications mean and which one is bigger or smaller... There is a drawing in this problem but here's the rest: "The scale factor from A to B is 41.6%. Justify why A is a scale drawing of B and why it's an enlargement of B. Include the scale factor in your justification"

Hi. I was wondering if experiments on the Planck length (about 10-35 m) are possible or not. If it is possible, what kind of experiment would that be? If it's not, then what is the problem? Or what is need to be done? Thanks.

The thermal efficiency of a reversible heat engine is solely a function of the temperature of the two reservoirs. η = f(θH,θC) = 1 - (QC/QH) (QC/QH) = 1 - f(θH,θC) (QC/QH) = Ψ(θH,θC) The simplest function that can be used is T1/T2 (QC/QH) = T1/T2 In order to define the Kelvin scale we assign a...

Homework Statement A class of interesting theories are invariant under the scaling of all lengths by ##x^{\mu} \rightarrow (x')^{\mu}=\lambda x^{\mu}## and ##\phi(x) \rightarrow \phi'(x) = \lambda^{-D}\phi(\lambda^{-1}x)##. Here ##D## is called the scaling dimension of the field. Consider...

Question: By what factor has the linear size-scale of the Universe changed between when the light was emitted from the galaxy and now? The question gives the red shift z and I have the equation linear size scale = 1 / 1 + z and I know how to calculate the linear size scale. But I'm a little...

Homework Statement A star experiences a sudden increase in pressure to a new value P'. Taking the average density as ρ and the radius R, estimate the time scale of expansion of the star. (Ignore gravity altogether). Homework Equations The only thing I can see in my notes that may (or may not)...

Hi, In a problem I have been working on for a while now I have found that I want to find the function satisfying the functional relation f(x)n f(a - x) = 1 for n = 1 I believe I have proven that f(x) = x/(a - x). On this page is an answer I do not quite understand. One of the prerequisits...

Having a bit of trouble estimating total scale uncertainty. In this experiment, I used four precision weights (error << scale resolution). Each weight has a known mass and is weighted on a scale 20 different times. Therefore, for each weight, I have a mean scale measurement, a standard...

I have always thought that grading on a scale is stupid. When a teacher/professor grades tests based on a scale, the teacher grades each student based on their performance compared to other students. This is a stupid way to do things because it can both cause some students who know the...

In the spring 2016 issue of the Johns Hopkins Magazine, there is a non-technical article (in graphic novel format) about a new instrument, dubbed CLASS, which is intended to detect "pinwheel patterns" caused by gravitational waves originating in the inflation era acting on the CBR. If these...

The charge of an electron is -e in energy scales well into the atomic scale. At infinitesimal scales it becomes infinite. This relation must be continuous for re-normalization to work, thus the intermediate value theorem asserts that it attains all values between at some energy level. I want to...

Hello all; Just thought I'd throw a brainstorming question to all you smart guys out there about a subject I know only from the youtube videos I've just come across. Large scale electricity generation from piezoelectricity. I'm aware that this technology is used mostly on a small scale...

On very small scales, an object's kinetic energy tells you its temperature, and on larger scales, an object's kinetic energy tells you its velocity. Where's the cut off? I mean, velocity is relativistic, but temperature... isn't... is it? Also, black body radiation decreases a body's temperature...

In my undergraduate days I remember learning about the double slit experiment etc. in quantum mechanics. And I'm only now starting to learn about the Standard model. So there are these fields; higgs, electro-magnetic, strong and weak nuclear. So if a photon is a perturbation in the...

I'm going to perform a small scale electrolysis experimenter of water. I want to find out how the rates of the gases are produced when the amount of electrolyte added to the water is changed. I'm going to use baking soda (NaHCO3) as the electrolyte but I just wanted to make sure that I won't be...

As any RF engineer knows the radial antenna is something pure theoretical. But as someone who loves physics an idea came to my mind. Please tell me if this would work and if not, why does it fail to work. So: Assuming we have an atom with 8 valence electrons which is hit with 8 photons with...

scientists have observed light acting as waves on a macroscopic scale before the quantum characteristics of particles were discovered. My question is what sets apart the macroscopic wavelike characteristcs of light apart from other matter waves? This may be a stupid question but can the...

Let's assume a universe like ours which after inflation expands decelerated and accelerated thereafter. How will the ratio Hubble length ##1/H## to scalefactor ##a## evolve over time? And how could one calculate the time dependence of this ratio. Any help appreciated.

Homework Statement The aim is to find a solution for the scale factor in a Robertson Walker Metric with a scalar field and a Lagrange multiplier. Homework Equations I have this action S=-\frac{1}{2}\int...

Homework Statement A trailer carrying a boat is supported by a scale which initially reads 48 kg. The boat (and therefore its centre of gravity) is moved 0.15 m further back on the trailer. The scale now reads 37 kg. Find the mass of the boat (Ignore the 6.0 m distance because it was not given...

Homework Statement let's say you have a regular bathroom scale, which we know measures the normal force that it exerts on a person aka. apparent weight. Now let's say that we didn't know that it measured the normal force when a object was on it. Obviously we still know that the only two forces...

Hi, I'm doing a project and an looking at building a small weigh scale and measure about 40lbs max (even lesser is ok as I'm learning). I'm looking for load cell thickness of 5mm or less (:smile:). I've one kitchen scale that I opened but that load cell is bigger. I looked at the web and found...

Hi all -- can anyone offer a qualitative explanation of why it is that couplings run with the energy in *relativistic* quantum theory, and not in non-relativistic? Some insight here would be much appreciated. Thanks.

Homework Statement IMPORTANT:There is an error in the statement.α and β are in C not K 2. Homework Equations R=Ro(1 +αt+βt2) The Attempt at a Solution I really don't know what to do because if I isolate t in the equation it will give me the temperature on the ideal gas scale whereas the...

I'm doing a lab where we use three strings connected to a ring, with each string attached to separate spring scales. What would be sources of error in this? And how does friction affect my results?

I'm currently doing a design for my final year studies and it's regarding esterification process. My proposed reactor is CSTR, operating at a temperature of 60C and 400 kPa. Reactants are methanol and jatropha oil with sulphuric acid catalyst. For a commercial scale production of biodiesel...

Imagine I have three space probes that I send out radially. They have a superluminal way to determine each other's relative position to each other instantaneously. If each one measures the relative position of the other two and comes up with an angle for them, how far away would they have to...

http://arxiv.org/abs/1503.09158 Is this a legitimite thing? I've never heard of 4th color charge or quark-lepton unification.

I am creating a gray-scale image of a 2000*2000 matrix using mat2gray and imshow command.But highest number of matrix entries that imshow can implement is 500*500 approximately.After that it shows------ "Warning: Image is too big to fit on screen; displaying at 8% > In...

Hi Everyone, I have a question about logarithmic sampling. I think I might have to go and review my Z-transforms, but maybe not. The reason I am doing this is because I am automating equipment which records the data over time, but I want the sampling to be done logarithmically. If I have an...

When experimenting with fusion, why do we always go so big and make extremely expensive reactors that take years to create and even construct facilities for? I've seen some failed attempts at making fusion happen in carbon nanotubes, failing in the sense that the carbon nanotubes are just...

I'm confused by the following passage in our book (translated). An alternative too choosing the normed tangent vectors ##\vec e_i = \frac{1}{h_1}\frac{\partial \vec r}{\partial u_i}## with scale factors ##h_i = \left| \frac{\partial \vec r }{\partial u_i} \right| ## is to choose the normal...

Homework Statement An earthquake with a magnitude of 5.4 is 39 times as intense as an aftershock that occurs 5 hours later. What is the magnitude of the aftershock. Homework Equations m=log_10(i/i_0) The Attempt at a Solution I know that I what to find the magnitude m=log_10(39/i_0) I am...

Homework Statement Lets say we have a series of balls and an eggs. All items have equal mass but are traveling at different velocities. Thus they have differing kinetic energies. Now, for each 'ball' object we have, we want to find an egg object with a similar kinetic energy. Let's say...

This is a physics question but since it is on a 'universal' scale, I will ask it here. Quantum entanglement. I was watching a panel discussion with Leonard Suskind and others leading theoretical physicists...also watched a Nova program presented by David Green, etc. In both there was a...

Homework Statement Find the two numerical values of λ such that \left(\begin{array}{cc}4&3\\1&2\end{array}\right) \left(\begin{array}{cc}u\\1\end{array}\right) =λ \left(\begin{array}{cc}u\\1\end{array}\right) Hence or otherwise find the equations of the two lines through the origin which...

Hi, So I am a little confused on the Planck scale. Correct me if I'm wrong (I hope this doesn't sound idiotic) but I believe that any field on a classical scale should be able to be quantized and work on a quantum scale/Planck scale, where the Planck length and the Planck time are the...

Hi and welcome to my curious posts :) If a scale measures force then i assume it's measuring mass*acceleration, so does that mean that the scale is actually measuring my mass (like a balance does ), and then multiplying it by a 9.8m/s^2? Or how exactly is it built/programmed to work?

In the book "Statistical physics for cosmic structures" at p. 171 a read a definition of scale invariance (leading to the so called scale invariant power spectrum) given as the requirement that ##\sigma^2_M(R=R_H(t)) = constant##, where ##R_H(t)## is the horizon, i.e. the maximal distance that...

Hi guys, This question has me a bit stumped and I can't seem to find any methods on Google that would help me solve this: The last part of the question asks me to find the value of the scale factor, which in this equation I believe is 1.8. I know how to calculate percentage increases the...

Wabbit had an interesting comment in the "Aeon to Zeon" cosmology thread. Here's an excerpt, for more follow the link. I replied saying I'd start a separate thread.

Hey guys! I was reading the following paper http://arxiv.org/abs/hep-ph/0703260 for Georgi and I have a conceptual question about it. Howard Georgi was talking about this Unparticle Physics theory and at the base of his analysis is the principle of scale invariance. So Georgi is saying what if...

Homework Statement A 200g hamster sits on an 800 g wedge shaped block which in turn rests on a spring scale. An extra fine lubricating oil is sprayed on the top surface of the block, rendering it entirely frictionless, causing the hamster to slide down. Friction between the block and the scale...