# Monthly Archives: March 2010

## Quark gluon plasma and gauge/gravity duality

The talk started out on viscosity of fluids, like when a plate is sliding across a fluid spread across a stationary plate. There was a graphic showing how the fluid formed a ‘gradient’ as the top layer of fluid had to move faster to keep up with the top plate, while the bottom fluid did not really want to move, but eventually the top fluid managed to drag it along.

Then this moved into the viscosity of gases, and eventually arrived at Maxwell’s formula for viscosity of dilute gas and how pressure of the gas does not matter. There was a quick aside as the speaker mentioned how Robert Boyle might have conducted an experiment along the same lines, using a pendulum suspended inside of a vacuum, where despite changes in pressure no visible difference in the swing of the pendulum could be detected. Robert Boyle also thought to do other things, like stick a butterfly into the vacuum jar and see what happened…

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The reason for the viscosity of dilute gas not being affected by pressure had to do with “mass density” (I think). So even though the gas is more spread out the speeds it is bouncing around at increase. (I think).

This was just the introduction. Then discussion moved onto Quantum Cromo Dynamics, lots of phase diagrams and energy density / c2. And c in this case is something like mass density in the general description of viscosity.

Filed under Events

## Extra Derivative Tips

General Concepts which are useful Some extra Derivative Tricks Derivatives of Trig Functions Filed under MAT 131

## Trigonometric Function Graphs

Filed under MAT 131

## Newtons Method for Square roots

(pages 131 – 132 in text book)

Set allowed Error variable

if guess2 –x < error { Square root found }
guess = (x/guess + guess) /2
else, guess again…

Function must be written in line by line order, unless you write a header for the function above main.

Use Function prototyping to avoid having to write your code in bottom up order.  Function prototyping is placing the header for the function above main.

The .h files represent header files! only the functions actually included in your code are taken and inserted into your compiled code.

You can restrict access to functions by prototyping a function inside of another function. Don’t actually write the function body into another function though.

Filed under CSE 130

## Potential Energy, Conservative Force Field

﻿Poential Energy is represented by the symbol U.

U = mgh
Wby Gravity = -ΔU
ΔU = UFinal – UInitial = 0 – mgh = -mgh
ΔU = -mgh = Wby Gravity = ΔKE

What is important is the change in potential energy.

-ΔU = (UFinal – UInitial) = Wdone by Gravity = ΔKE = KEFinal – KEInitial

Lost Potential Energy = gained Kinetic Energy

KEFinal + UFinal = KEinitial + UInitial

Total Mechanical Energy is Conserved

Conservative Force Field: Total work done about a closed path sums to ZERO.

Friction Force is non-conservative (You do not get energy back in a closed path)

Imagine how force looks as a ball is dropped from the sky. think of dy as the many very small distances it travels over to fall to the ground. dW is the very small but of work

ΔU = -W = -F
dU = -dW  = -Fy
dydU/dy = -Fy
U(y)=mgy

Read this “The potential Energy with respect to height is equal to mass times gravity times height.

Now what about stretched springs? This story is a little different. The force exerted to do work grows as the spring stretch’s further. If you draw a graph, the potential energy of the spring as it is compressed and stretched would form a parabola.

Now what about a child on a slide? The component of gravity parallel to the slide is mg cos θ. It is doing work. θ is changing all the time, as the mass of the child moves along the slide.

Filed under PHY 125

## Chapter 6 – Centrifugal Acceleration Review How to convert acceleration in terms of g Centrifugal velocity equals two pi R over time.

Time equals one over frequency (number of revolutions per second) Centrifugal force, on an object not experiencing forces along the y axis (Car driving in circle, etc…) Centrifugal force, on an object experiencing forces along the x and y axis (ball spun horizontally above your head)

When you spin a ball vertically, at the top of the circle, the tension force can be at minimum, 0, or else the ball will fall out of the sky, thanks to gravity. This means, the velocity of the ball overhead is equal to: The max pull at the bottom of the circle is equal to: For banking turns, Friction Force μ could be μ static or μ kinetic. It is the coefficient of Friction

Conic Pendulum Filed under PHY 125

## Work – Constant Force, and Changing Force

Work increases or decreases over displacement. 1. Kinetic Energy equals one half mass times velocity squared
2. Work equals change in Kinetic Energy, which is equivalent to final kinetic energy minus initial kinetic energy.
3. Work equals force over displacement (If the force and displacement are parallel).
4. Work equals Force over displacement times cos theta (If the force and displacement are at an angle to each other. Theta is the angle formed from Force and displacement). Force is an example of a Dot Product or Scalar Product of two vectors, for example vector’s A and B. 1. Vector A dot product Vector B is equal to the scalar value of magnitude A times magnitude B times cos theta.
2. Work (scalar value) equals the dot product of Force times displacement, which is equal to magnitude of Force times magnitude of displacement times cos Theta.
3. Dot Products distribute.

So the point of learning about dot products is that work, can be broken down into it’s component parts, Fx, Fy, Fz and dx, dy, dz and you can use these component parts to find out the angle theta. If we think about a spring and the work done to pull a spring open, the Force needed to continue pulling the spring grows, the further you pull on the spring This makes the Force Applied equal to a constant “k” times displacement x.    Filed under PHY 125

## Automatic Local Variables

Automatic Local Variables

• Variables defined inside a function
• Created each time a function is called
• Initialized and get a value each time
• Accessible inside function they are declared in only.
• Not available outside the function

The Stack Frame keeps an activation record For Example

Main variables
—————
Printf variables
—————
Another Function Variables

And so on.

Language translation is done by the compiler
Language implementation is done by the stack

Variable Scope
Score refers to the area of a program for which a  variable is defined

Global Variable

• Declared above main
• Constants tend to be global
• No need to pass global var’s

Filed under CSE 130

## Derivatives and Implicit Differentiation

How do you find two tangent lines passing through a point? The point is not a point on the line! So decide on an arbitrary point on the line and call it f(a). Then solve for the slope m in terms of a (Find f’(a)). Then plug in your values and solve for the tangent line at the two points. Derivative Example Problems Rule: Apply log rules when you see logs!!!!!! (You want to expand as much as possible)

Implicit Differentiation

We briefly started to talk about implicit differentiation. So a function is y=f(x). or “y as described by function f with respect to point x equals”. And this seems to be the key here. So we started using this new notation for derivatives, instead of the usual f prime. To start, look at a very easy example, x2. y equals x2 which is the same as, f(x) equals x2, which says that y = f(x).” “The derivative of the function which equals y with respect to point x equals f prime, which is equivalent to the derivative of x2 equal 2x.”

Filed under MAT 131

## Holographic Superfluidity and Superconductivity

I went to a talk today in the Physics department. It is interesting in that I did not understand most of it, but at the same time I felt like I will be able to understand it eventually. Also, someone asked: “What dimension are we in?” Answer: Just 3 + 1

So, here are the interesting terms I heard today. I’ll need to investigate these further. Perhaps they will make good train reading.

• QCP – Quantum Critical Point
• QPT – Quantum Phase Transition
• Nerst effect
• dyonic black hole
• cyclotron resonance
• Lorenzen (sp?) z=1
• phenomenological – Need a dictionary for this
• quiver: L263 (Included a neat picture)
• gluino field
• Holographic Phase Transition
• charged scalar field
• abelion gauge field
• tachyonic
• BPS bound
• modulus

I better take a few chemistry classes too or at least read a few textbooks.