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I don't get it.

  • by crumb_bum
  • posted Jun 02, 2008
  • 21 Comments

I don't get why it's so great.
I'd like to be in the loop too, please.

Watch this
SoulfumeInc

you will be in the loop when you stop saying "i dont get it."

HW.

^my thoughts exactly

HW.

^my thoughts exactly

ginetteginette
ginetteginette profile pic Alumni

i thought this blog was being sarcastic, my bad.

mezo
mezo profile pic Alumni

That phrase makes me so mad, I shake.

Maltzmania
Maltzmania profile pic Alumni

you should ask kayce she's in the loop

EZFL
EZFL profile pic Alumni

Kookaberry
Kookaberry profile pic Alumni

Argumentation theory was once based upon foundationalism, a theory of knowledge (epistemology) in the field of philosophy. It sought to find the grounds for claims in the forms (logic) and materials (factual laws) of a universal system of knowledge. As argument scholars gradually rejected the idealism in Plato and Kant, and jettisoned with it the idea that argument premises take their soundness from formal philosophical systems, the field broadened. Karl R. Wallace's seminal essay ("The Substance of Rhetoric: Good Reasons," Quarterly Journal of Speech(1963) 44. led many scholars to study "marketplace argumentation," that is the ordinary arguments of ordinary people. The seminal essay on marketplace argumentation is Anderson, Ray Lynn, and C. David Mortensen, "Logic and Marketplace Argumentation." Quarterly Journal of Speech 53 (1967): 143-150. This line of thinking led to a natural alliance with late developments in the sociology of knowledge. Some scholars drew connections with recent developments in philosophy, namely the pragmatism of John Dewey and Richard Rorty. Rorty has called this shift in emphasis "the linguistic turn."

In this new hybrid approach argumentation is used with or without empirical evidence to establish convincing conclusions about issues which are moral, scientific, epistemic, or of a nature in which science alone cannot answer. Out of pragmatism and many intellectual developments in the humanities and social sciences, "non-philosophical" argumentation theories grew which located the formal and material grounds of arguments in particular intellectual fields. These theories include informal logic, social epistemology, ethnomethodology, speech acts, the sociology of knowledge, the sociology of science, and social psychology. These new theories are not non-logical or anti-logical. They find logical coherence in most communities of discourse. These theories are thus often labelled "sociological" in that they focus on the social grounds of knowledge.

Kookaberry
Kookaberry profile pic Alumni

Baron-Cohen, in his capacity as Director of the Autism Research Centre at Cambridge, developed the EQ SQ paradigm as a consequence of his research into the causality of autism. Baron-Cohen argues that an individual with autism or Asperger syndrome, viewed in the construct of the EQ SQ Theory, may have an extreme S-type brain, with good systemizing and poor empathizing behaviors. The fact that most autistics are male, by a factor of 4 to 1, seems to support the EQ SQ Theory about the possible origins of autism.[2][3] He claims that people with Asperger Syndrome excel at systemizing and are less capable of empathizing.[1][4]

Kookaberry
Kookaberry profile pic Alumni

The overarching physical insight behind string theory is the holographic principle, which states that the description of the oscillations of the surface of a black hole must also describe the space-time around it. Holography demands that a low-dimensional theory describing the fluctuations of a horizon will end up describing everything that can fall through, which can be anything at all. So a theory of a black hole horizon is a theory of everything.

A-priori, finding even one consistent holographic description seems like a long-shot, because it would be a disembodied nonlocal description of quantum gravity. In string theory, not only is there one such description, there are several different ones, each describing fluctuations of horizons with different charges and dimensions, and all of them logically fit together. So the same physical objects and interactions can be described by the fluctuations of one-dimensional black hole horizons, or by three dimensional horizons, or by zero-dimensional horizons. The fact that these different descriptions describe the same physics is overwhelming evidence that string theory is consistent.

An ordinary astronomical black hole does not have a convenient holographic description, because it has a Hawking temperature. String theories are formulated on cold black holes, which are those which have as much charge as possible. The first holographic theory discovered described the scattering of one-dimensional strings, tiny loops of vibrating horizon charged with a two-form vector potential which makes a charged black hole a one-dimensional line. Fluctuations of this line horizon describe all matter, so every elementary particle can be described by a mode of oscillation of a very small segment or loop of string. The string-length is approximately the Planck length, but can be significantly bigger when the strings are weakly interacting.

All string theories predict the existence of degrees of freedom which are usually described as extra dimensions. Without fermions, bosonic strings can vibrate in a flat but unstable 26 dimensional space time. In a superstring theory with fermions, the weak-coupling (no-interaction) limit describes a flat stable 10 dimensional space time. Interacting superstring theories are best thought of as configurations of an 11 dimensional supergravity theory called M-theory where one or more of the dimensions are curled up so that the line-extended charged black holes become long and light.

Long light strings can vibrate at different resonant frequencies, and each resonant frequency describes a different type of particle.[8] So in string limits, any elementary particle should be thought of as a tiny vibrating line, rather than as a point. The string can vibrate in different modes just as a guitar string can produce different notes, and every mode appears as a different particle: electron, photon, gluon, etc.
Levels of magnification: Macroscopic level, molecular level, atomic level, subatomic level, string level.
Levels of magnification: Macroscopic level, molecular level, atomic level, subatomic level, string level.

The only way in which strings can interact is by splitting and combining in a smooth way. It is impossible to introduce arbitrary extra matter, like point particles which interact with strings by collisions, because the particles can fall into the black hole, so holography demands that it must show up as a mode of oscillation. The only way to introduce new matter is to find gravitational backgrounds where strings can scatter consistently, or to add boundary conditions, endpoints for the strings. Some of the backgrounds are called NS-branes, which are extreme-charged black hole sheets of different dimensions. Other charged black-sheet backgrounds are the D-branes, which have an alternate description as planes where strings can end and slide. When the strings are long and light, the branes are classical and heavy. In other limits where the strings become heavy, some of the branes can become light.

Since string theory is widely believed to be a consistent theory of quantum gravity, many hope that it correctly describes our universe, making it a theory of everything. There are known configurations which describe all the observed fundamental forces and matter but with a zero cosmological constant and some new fields. There are other configurations with different values of the cosmological constant, which are metastable but long-lived. This leads many to believe that there is at least one metastable solution which is quantitatively identical with the standard model, with a small cosmological constant, which contains dark matter and a plausible mechanism for inflation. It is not yet known whether string theory has such a solution, nor how much freedom the theory allows to choose the details. Because of this, string theory has not yet made practically falsifiable predictions that would allow it to be experimentally tested.

The full theory does not yet have a satisfactory definition in all circumstances, since the scattering of strings is most straightforwardly defined by a perturbation theory. The complete quantum mechanics of high dimensional branes is not easily defined, and the behavior of string theory in cosmological settings (time-dependent backgrounds) is not fully worked out. It is also not clear if there is any principle by which string theory selects its vacuum state, the space-time configuration which determines the properties of our universe (see string theory landscape).

Kookaberry
Kookaberry profile pic Alumni

. If the number of particles is less than the number of thermally accessible states, for high temperatures and low densities, the particles will all be in different states. In this limit the gas is classical. As the density increases or the temperature decreases, the number of accessible states per particle becomes smaller, and at some point more particles will be forced into a single state than the maximum allowed for that state by statistical weighting. From this point on, any extra particle added will go into the ground state.

To calculate the transition temperature at any density, integrate over all momentum states the expression for maximum number of excited particles p/1-p:

\, N = V \int {d^3k \over (2\pi)^3} {p(k)\over 1-p(k)} = V \int {d^3k \over (2\pi)^3} {1 \over e^{k^2\over 2mT}-1}
\, p(k)= e^{-k^2\over 2mT}.

The integral, when evaluated, with the factors of kB and ℏ restored by dimensional analysis, gives the critical temperature formula of the preceding section. It can be seen that this integral defines the critical temperature and particle number corresponding to the conditions of zero chemical potential (μ=0 in the Bose–Einstein statistics distribution).

[edit] The Gross-Pitaevskii equation

Main article: Gross-Pitaevskii equation

The state of the BEC can be described by the wavefunction of the condensate \psi(\vec{r}). For a system of this nature, |\psi(\vec{r})|^2 is interpreted as the particle density, so the total number of atoms is N=\int d\vec{r} |\psi(\vec{r})|^2

Provided essentially all atoms are in the condensate (that is, have condensed to the ground state), and treating the bosons using Mean field theory, the energy (E) associated with the state \psi(\vec{r}) is:

E=\int d\vec{r}\left[\frac{\hbar^2}{2m}|\nabla\psi(\vec{r})|^2+V(\vec{r})|\psi(\vec{r})|^2+\frac{1}{2}U_0|\psi(\vec{r})|^4\right]

Minimising this energy with respect to infinitesimal variations in \psi(\vec{r}), and holding the number of atoms constant, yields the Gross-Pitaevski equation (GPE) (also a non-linear Schrödinger equation):

i\hbar\frac{\partial \psi(\vec{r})}{\partial t} = \left(-\frac{\hbar^2\nabla^2}{2m}+V(\vec{r})+U_0|\psi(\vec{r})|^2\right)\psi(\vec{r})

where:

\,m is the mass of the bosons,
\,V(\vec{r}) is the external potential,
\,U_0 is representative of the inter-particle interactions.

The GPE provides a good description the behavior of the BEC's and is the approach often applied to their theoretical analysis.

Kookaberry
Kookaberry profile pic Alumni

Make sense now?

Kookaberry
Kookaberry profile pic Alumni

I heart Bose-Einsetein condensates

Kookaberry
Kookaberry profile pic Alumni

lol @ my awful spelling

crumb_bum

i get it now. thanks!

ntopp

It's just a neat-looking design of a fantasy product.

Solari

You're not supposed to get it; you're just supposed to pretend you get it so you can feel superior to those who admit they don't get it. This is the secret of Threadless.

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