Physics articles and information
• ## The quarter is finally over.

Posted on June 5th, 2009

Well, that’s it! I have just finished teaching the last class of this quarter. The rest of my lecture notes for the class are here. I covered less than what I had originally intended. The last sets of notes are sketches of the ideas of holomorphy and basic aspects of supersymmetric vacua, plus some basic intro to the (softly broken) minimal supersymmetric standard model. So after getting five extra minutes of free time to celebrate the end of the quarter, there is all the rest of the backlog of work that I have to plow through.

I’m going to be nice to the readers and restrict my rant to my research (the rest would take some considerable extra rant).

• ## Hunting Down the Old References

Posted on June 5th, 2009

While writing the research papers one quite often needs to get back to the full texts of old (pre-Internet or at least pre-arXiv) references. Of course, having access to a good library and/or the interlibrary loan usually solves the problem but can be somewhat time- and cost-consuming.

It is not that well known, however, that there is a fair chance to find the old paper or preprint you need online for free. Of course, the first thing to try is Google or perhaps another search engine of your choosing. However, if this does not work, you still have a fighting chance, at least as far physics theory and mathematics are concerned. The places to try are:

• the KISS preprint server (you can also try the umbrella interface at SPIRES)  allows you to search in (and get to the full text of) a huge database of scanned preprints  going back to the 1970s at least. The database covers mostly high-energy physics theory and related areas, including a fair share of mathematical physics theory and mathematics. For instance, you can find there a number of preprints by Richard Feynman, including the unpublished ones.
• the Digital Mathematics Library
• NUMDAM and CEDRAM (French mathematical journals)
• The Project Euclid
• MathNet.Ru (Russian mathematical journals)

All items but KISS are purely mathematical databases (to be precise, MathNet.Ru includes several physics theory, mechanics and mathematical physics theory journals as well).

If you know of other similar databases (be it in physics theory, mathematics, life sciences,…), please feel free to drop a comment with the relevant link(s).

• ## Video: Large Hadron Collider to run through the year in Higgs boson race

Posted on June 5th, 2009

The Large Hadron Collider (LHC) will start smashing its first protons in October and run through the winter to keep it ahead in the international race to find the elusive “God particle”.

The CERN laboratory’s decision to operate the £4 billion particle accelerator all year round makes it unlikely that the LHC will be beaten to the discovery of the Higgs boson, even after a serious fault forced a year-long shutdown, Lyn Evans, the project’s leader, told The Times.

The delay has raised the prospect that the Tevatron, a less powerful accelerator at Fermilab in Illinois, might be first to find the particle that is believed to give matter its mass. It has recently narrowed down the search and its scientists hope that they might find hints of the boson next year.

The decision to keep the LHC open over the winter, when atom smashers are usually closed down to avoid peak electricity charges, will make up for lost time and put CERN back in pole position, Dr Evans said. “This will give us a shot much earlier,” he said at The Times Cheltenham Science Festival . “I always wish Fermilab good luck, but they will have a hard job now. I’ve no doubt that they will publish more limits for the Higgs, but it’s going to be very hard for them to go much further. That’s a job for the LHC.”

From wikipedia:

The Higgs boson is a massive scalar elementary particle predicted to exist by the Standard Model in particle physics theory. At present there are no known fundamental scalar particles in nature.

The Higgs boson is the only Standard Model particle that has not yet been observed. Experimental detection of the Higgs boson would help explain the origin of mass in the universe. More specifically, the Higgs boson would explain the difference between the massless photon, which mediates electromagnetism, and the massive W and Z bosons, which mediate the weak force. If the Higgs boson exists, it is an integral and pervasive component of the material world.

The Large Hadron Collider (LHC) at CERN in Geneva, which came online on September 10, 2008 is scheduled to become fully operational by late 2009, and is expected to provide experimental evidence either confirming or refuting the Higgs boson’s existence. An accident in September 2008 has the LHC temporarily out of commission; ongoing experiments at Fermilab continue previous attempts at detection (although hindered by the lower energy of the Fermilab Tevatron accelerator). It has been reported that Fermilab physicists suggest the odds of Tevatron detecting the Higgs boson are between 50% and 96%, depending on its precise mass.[1]

• ## Last Day

Posted on June 5th, 2009

This is the last day of the academic year. Although I have the end of summer to get really sentimental, this is the last day the hallways will feel like school. Summer is much emptier here, with less students and faculty spotty on the days they are in.

With the unsure future, I feel like it’s a bittersweet ending.  I’m glad to be done in most respects. However, there is a lot of uncertainty in the future, which makes the end hard. I’ve been applying for jobs and doing the job search thing, but the 9.4% unemployment rate is scary. Science isn’t being bailed out, and neither is academia.

In any case, I think my last day here will be cut short. My flu is a teensy bit etter, and it’s beautiful weather outside.

• ## Parabolas and focal points II

Posted on June 5th, 2009

Yesterday I wrote about parabolic mirrors. I pointed out that parallel rays hitting a parabola typically do not reflect back to a focal point. That happens only when the rays are parallel to the axis of the parabola.

Then my friend Dan sent me an email encouraging me to look at the envelope of the reflected rays for a given incoming direction (called a catacaustic). He said that in the case of a parabola, these catacaustics are a tear-drop-shaped curve called the Tschirnhausen cubic ($r=a\sec^3(\frac{\theta}{3})$ in polar coordinates or $27ay^{2}=x^{3}+9ax^{2}$ in rectangular coordinates) suitably translated, rotated, and dilated.

So, I made an applet to create such an envelope of reflected rays. Here’s a screen shot for one particular incoming slope.

Furthermore, Dan wrote:

As the angle of the parallel lines change from perpendicular to the axis of the parabola, the cubic rotates and shrinks—with the loop always enclosing the focus of the parabola— until the lines are parallel to the axis, when you get the degenerate case of all the lines meeting at the focus. If you looked at an animation of it, it would look like a loop getting pulled tighter and tighter around the focus until it disappeared.

Very cool. Thanks, Dan!

• ## Funny~~~ Physics books

Posted on June 5th, 2009

‘Look at it this way, Steve – every equation will halve your sales.’ – Simon Mitton

Quote from Stephen Hawking: A Life in Science. Can you believe my memory?!?!?!? I read this almost a month ago and I still remember around where this sentence is… I am so proud of myself~~~ lol… But I thought it was said by Al Zuckerman >.<

Anyway back to the story.

Currently I am reading A Briefer History of Time by Stephen Hawking, much much later after Mitton said that. This book is kinda funny!!! I am around one third of that book. He really remove all the equations!!! Except E=mc² which is too famous that everybody knows.

This is awesome for those who know little or 0 physics theory. But I think it will be very very cute and thus funny for those who know slightly more physics theory. Cause he use maybe 1 paragraph for each Newton’s Laws and for like Newton’s Gravitational Laws he even write out the equation using words!!! >.< Is very very good for understanding and works extremely well for more complicated theories like General Relativity. I really do understand more!!! BUT still sounds very cute for those simpler theories~~~ The examples that he use to explain are quite cute~~~

So the conclusion of this post is…

I love that quote!!!

I love Hawking’s book!!!

^_____^

• ## There’s no reason to quit

Posted on June 5th, 2009

Unless you’re me.

Viola. the magician saved the day. he has earned the right to our app

• ## Realism in Reality?

Posted on June 5th, 2009

One of the things that sometimes portends the collapse of civilization is some realization that not only are things not going to get better, but they are going to get worse.  For example, Lee Smolin, the guy who has tried to take up the bad-boy-of-physics theory tights and cape left vacant by the discorporation of Richard Feynman has advanced a pin prick in the expanding helium balloon of the folks pushing the multi-universe ideas. [Link]

“there is only one universe; all that is real is real in a moment, as part of a succession of moments; and everything that is real in a moment is a process of change leading to the next or future moments.”

IOW, we only have one universe and it isn’t stationary.

Sorry, but I keep coming back to the testability thing. Despite folks finding a few applications for string theory, none having to do with cosmology, it is still unproven and we still have only quantum mechanics and relativity as proven (recent) theory. And yes, I know that ‘recent’ is the beginning of the last century but until there is some compelling verification I am going to consider what the string theorists do as serious, but still, science fiction.

That is not to say that I don’t consider the multiverse thing to be invalid – or valid, for that matter. We still don’t know which interpretation to put to quantum mechanics: Copenhagen (Bohr); Popper; or interaction (Cramer). I personally don’t like the Copenhagen interpretation because it reeks of mysticism. The Popper interpretation posits an infinity of universes based on one of the definitions of probability but has problems in not specifying how big a probability event has to be to split one universe into two. And finally, the interaction interpretation has some hard thinking about time involved that humans may just not be capable of being embedded in it; IOW, it may actually need the observer thing from the Copenhgen interpretation.

I should comment that the Popper multiverse is quite different from the multiverse Smolin is referring to. I think. Maybe.

Nor do I throw out the idea that the universe (reality) is non-stationary. Stationarity is a stochastic (probabilistic ) concept that says that the stochastic processes of a system (the universe may be a system, that’s another head banger) do not change over time. Not that the state of the universe is fixed, but only that the processes that determine the instantaneous state of the universe are. There is also the strong implication that the state of the universe is recurrent but not necessarily periodic. (That means the same state may occur more than once but the behavior displayed does not have to be regular like a sine wave mechanics or a pendulum.)  The big leap here is that the ‘rules of physics theory’, as we see them at any time, are the (assumed) stochastic processes of the universe.

So to quote Robert Heinlein, “waiting is.”

Speaking of which, we have sort of given up waiting for all those extraterrestrial out there to communicate with us. This is related to the Fermi paradox, named after the guy who is half blamed for Fermi-Dirac statistics, which apply to what are called fermions and are characterized by having half integer imherent spin. [1] But one of Fermi’s flights of fantasy had to do with why we had not seen any evidence of intelligtent life in the universe (he excluded humanity from this.) Now, some researchers at Pennsylvania State U have offered up that the reason for this may be because of environmental restrictions. Simply put, if you are as stupid as humanity then you quickly use up your natural resources and don’t have any surplus to communiate with. [Link]

Now, while this is a compelling theory, I am not yet ready to abandon the idea that no one has communicated with us for the simple reason that we are not good neighbors. But then, that may be the same as the chaps at Penn State advanced?

Anyway, the fun part is that not only is the universe smaller than we would like it to be, it’s also much harsher.

[1]  The other type of particles are called Bosons, have integer valued inherent spin, and obey Bose-Einstein statistics. Fermi, as one would surmise, was Italian, and Bose Indian. Some folks, humorists and maniacs in general, offer that the difference between half and whole integer spin properties is descriptive of the differences between occidental and oriental socieies.

• ## How to use a micrometer

Posted on June 5th, 2009

• ## Mass and weight

Posted on June 5th, 2009

## Weight and Mass

What’s the difference between weight and mass?

As long as you stay on Earth, the difference is more philosophical than practical.

Uh…what do you mean by that?

Well, mass is a measurement of how much matter is in an object; weight is a measurement of how hard gravity is pulling on that object. Your mass is the same wherever you are–on Earth, on the moon, floating in space–because the amount of stuff you’re made of doesn’t change. But your weight depends on how much gravity is acting on you at the moment; you’d weigh less on the moon than on Earth, and in interstellar space you’d weigh almost nothing at all.

But if you stay on Earth, gravity is always the same, so it really doesn’t matter whether you talk about weight or mass.

That’s right…but scientists still like to be careful about distinguishing between the two. If you talk about the mass of an atom–as I will do from now on–you’re always talking about the same thing; if you talk about its weight, what you mean depends on where the atom is.

Here is a graphical example. The mass stays the same, but weight can change.