Stephon Alexander

The Last Day

I'm sitting here in a Cafe on a drizzly day in the Castro district; my last day in San Francisco.
Yesterday, I went by my offices at SLAC and Stanford's ITP on campus, for the last time. I was pleased to bid farewell to BJ Bjorken, Michael Peskin, Lenny Susskind and Steve Shenker. BJ is truly amazing; our interaction was all about physics as usual. We were discussing my latest research project, which is looking into experimental ways to detect parity violation in gravity. Two years ago I wrote a paper which argued that the origin of matter over anit-matter in our universe is a direct consequence of the fact that space-time is chiral (in 3-dimensions reflection asymmetric). While the model is pretty and all that (mathematically consistent), the only reason why we should believe it is, of course, through some experimental signature. So BJ was being a critical ear for my arguments as to why parity violation should show up in the cosmic microwave background radiation.

Some of you out there have expressed confusion about the common lore of structure formation (galaxies, stars) in the universe. So let me take some time give a simple (yet accurate) description of this process.

When we look at the night sky with powerful telescopes we see that in every direction objects such as galaxies are moving away from us at a speed proportional to their distance from us. This is the famous Hubble redshift relationship, which confirmed the prediction of Einstein’s Relativity that the universe is expanding. Think of baking raisin bread. As the bread expands, every raisin appears to move away from every other raisin; if you were living on a raisin, the other raisins would play the role of the receding galaxies. The cool thing is that every other raisin would perceive the same thing about the other raisins (that the other raisins are moving away at a rate proportional to the distance). So analogously galaxies really aren't moving away from each other like we think, instead the space itself is stretching (analogous to our rising raising bread in the oven), an immediate consequence of general relativity (space-time itself is dynamical and is influenced by matter and energy)

Hubble's law tells us that way back in the past (billions of years ago) the universe was denser and hotter. So hot that all the matter had disintegrated into pure radiation energy. So how did the radiation filled universe turn into matter? The answer to these questions rests on a simple fact about gravity; it’s the only force that’s purely attractive. Before we go on I have to admit that I lied to you. We know from condensed matter physics experiments, that matter and radiation under extreme pressures and temperatures (temperature divided by frequency is proportional to Planck's constant) that substance becomes subject to the physics of quantum mechanics. So in the past our universe was a quantum soup of pure radiation energy. The uncertainty principle tells us that this radiation will vibrate. This vibration will affect gravity in such a way that the attractive force of gravity eventually leads these vibrations (quantum fluctuations) to collapse. This collapse is often called a Jean's instability. The cool thing is that we can calculate this effect and make predictions to compare to observations of the fluctuation of this quantum radiation in the past with the WMAP satellite data.

The collapse of this radiation-matter complex in the early universe eventually develops into stars and galaxies. There are puzzles still unresolved in this picture, such as: How did the universe begin expanding in the first place? What happened before the 'beginning'? What is the meaning of before? (What is physical time?) Etc. Etc.

To answer these questions we really need to understand the nature of gravity fully in terms of quantum gravity.

Well this is why I'm going off to Penn State, to work with the great Abhay Ashtekar at the Center for Geometry and Quantum Gravity; where the focus is in constructing a theory of quantum gravity and its cosmological and other experimental consequences. I hope to keep you updated.

Well I must sign out for now. Before I go, I ask you all to please take a look at webpage below and keep those less fortunate close to heart during the holiday season and the rest of the year.
Tsunami Relief

On Einstein and Voodoo

Once again I'm at the stage of a research project where I have to buckle down and calculate. Many of you might have this idea that theoretical physicists love to pin their pen to the paper and run symbolic marathons endlessly. Well I'm not the one. I actually dislike doing calculations (o.k. I'm telling a half-truth). Months of visualization exercises, which leave me either giddy or experiencing motion illusions, have come to a disappointing end. That stage of trying to imagine the physics and get a grip on that speckle of 'reality' is where I find joy in my work. But this time there was a glitch in my process.

So I've made friends with a few cognitive psychologists at Stanford. They do research on trying to understand, among many other things, how we got to be so smart; how is it that humans can create ideas like differential topology and superstring theory? When I first heard that people were actually doing research on 'abstract domains' concerned with the type of thinking that I do, I got a bit weary. But as time went by (and after debating with my cogsci pals for a while) I finally swallowed the fact that I have an organ called the Brain.

One day while going for my ritual run at the top of Potrero hill, to relax my brain from a dreary calculation marathon, an Einstein quote crossed my mind: "The most incomprehensible thing about the Universe is that it's comprehensible." Just think about that- I think it’s profound.

That quote triggered the stunningly bizarre realization that my Brain and all the damn Neurons and such are firing away to create the very physics and math that I suppose is so fundamental. If indeed we can come up with physical law and mathematics which make predictions about our universe during an epoch billions of years before humans existed, then whatever underlies the functioning of our Brains to generate such ‘incomprehensible’ tasks has (based on logical grounds) to be more fundamental than the theories that we create.

This realization depressed me. I felt for a while that I was in the wrong field. I bet that if Einstein was still with us, based on his quote, he would have gone into Cognitive Psychology or Voodoo.

Cosmologist meets Cosmetologist

The other day while doing a calculation at a Cafe and frustratingly twisting my fledgling dreads, I noticed this tall guy with long dreads. I approached him and said, "Excuse me, your dreads are cool, how do I get mine like that?"
He responded, "The only person that can do it is Rhonda, she manages this spot in the Lakeside district of Oakland called Nappy or Not"
I was down.

So here I am sitting in Rhonda's salon while Rhonda is applying a 'secret' locking technique to my hair. Her fingers move like a Spanish guitarist. I'm having a blast here in Nappy or Not. It feels like back home in the Bronx; folk telling jokes, good soul music in the background and lots of gossip-good stuff that is.

I tried to withhold my professional status-shamefully, I told a half-truth, that I'm a musician. But eventually it came out that I do cosmology. The ladies in the salon were all over it. It turns out that Rhonda is into metaphysical things-after all she is a cosmetologist-I think of it as a subfield in Observational Cosmology. They actually require a liscence to do their jobs, unlike cosmologists.

If you're ever in the Bay area and want to get the 'baddest' hairdo on the west coast and a good time, you gotta come hang with Rhonda and the crew at Nappy or Not (E18th St & Park Blvd.)

Holla.

hip hop cosmologist

Due to a lack of genuine ideas in physics, I've resorted to producing rap beats on my Mac for the time being. It's amazing how far music production software and hardware have gone. One of the most famous rap songs, "Paid in Full", by Eric B. and Rakim, was done on a $100 Casio '80s CZ-100 keyboard; those you see nowadays in pawn shops for $15. The beat was produced by Marley Marl and found its way into pop music; remember Susanne Vega's famous song with that phat rap beat, or how about Enigma's Gregorian Chant-the same beat, all done on a cheap toy synthesizer. Forget the need for hardware! When I was in Afrika Bamabatta's studio back in the 80's, I remember seeing racks of hardware with cables strangling each other until they reached the humongous speakers at the corner of the studio.

I say all this because now with one piece of software, I can reproduce the effects of a full racked recording studio worth tens of thousands of dollars. I can make music on Airplane flights to conferences and talks. I know, you're concerned that I'll have a career change and become a rap producer. Not that I'm envious of Kanye West, but the thought of playing with this cool new software, making beats and getting paid on the order of $50,000 for each one is very tempting. But, I'll have to be as talented as Kanye. Anyway, in the meanwhile, I might write my lectures over some phat ass beats. I'll have my students deliver freestyle oral exams... that’s it, I’ll be the first hip hop cosmologist. Oh well, back to my backreaction calculation.

Complexity of Simplicity

Over the last 30 years in the field of cosmology, physicists have reached the consensus that our physical
Universe, which spans the size of 3000 Mega Parsecs (1 Parsec is on the order of 10 Trillion miles), began its life some 14 billion years ago from a primordial quantum soup. A few milliseconds before that epoch (known as the radiation dominated era) microwave data tells us that the universe underwent an extremely rapid expansion of space- from the size of an atom to the size we see today! The initial conditions during this so-called inflationary epoch were remarkably simpler than the universe, let alone world in which we inhabit.

I have spent the last 5 years of my research career working on the details of the inflationary epoch. I am still befuddled by the following question: How did all this complexity arise? In other words, was complexity
part of the blueprint of the universe. Surely, from the point of view of the inflationary paradigm the answer is no. Therefore, something is missing from my point of view in the study of the 'early universe'. I think that part of the problem is related to the conceptual problems in quantum mechanics in the context of inflation. For one thing, we know that the quantum fluctuations generated during inflation (which are responsible for the generation of galaxies), while having a simple description mathematically (they are scale invariant) suffer the same foundational problems of the collapse of the wavefunction. What is this problem?

Quantum mechanics tells us that all the information about a physical system is encoded in a wave pattern of potentiality. When this system is observed (and it could be observed in many different ways)
all of the potentiality is manifested into one singular observable. The physical system once coexisting in
a probability wave of all possibilities 'collapses' into (by the act of observation) into one thing. The only problem for inflation here is where or what is the observer?

Well enough of this, perhaps my friends in CogSci can help resolve this paradox-Whence the complexity.

The Problem of Time

I forget who said it, but the quote goes something like this:
"Even Einstein, the master of time, ran out of it"
I know thats cruel of me. But I have a good point. The fact is that Einstein was never a master of time.
We all know by now that Einstein discovered a deep and permament insight into the nature of space and time. He called this framework General Relativity. No longer was space and time some empty stage that things move about; it is dynamical and can fluctuate, bend, form singularities, evaporate etc. Just like Maxwell equations govern how electric and magnetic fields behave in the presence of charged entities, the Einstein field equations tell us (in a very complicated set of equations) how space and time will behave in the presence of matter and energy. Well enough of the is pedagogy. My point is that the Einstein equations can be rewritten in a form where time does not exist. How could this be? General Relativity is based on a fundamental principle which simply states that the laws of physics do not change if you make a shift in the reference frame of the system under study. Objects will fall on Mars as well as on Earth (albeit at different rates). Mathematically speaking this means that the theory has a specific symmetry, called
diffeomorphism invariance. This means that I can relabel a function with different coordinate systems but the function will always look the same (stated naively). It turns out that the Einstein equation has a diffeomorphism symmetry related to shifting time forwards or backwards and the laws of physics according to General relativity does not care. Therefore, time is gone!

What does this mean? Why does there seem to be physical time? More on that later.

H& H vs. Jerry's

Bagels have become an integral part of my existence.  I was in N.Y yesterday and went through the daytime hell to get my dozen H & H bagles to bring back.  As you all know by now, I'm a Trini by birth and curry is our soul capital.  This changed after frequenting Jerry's bagels, which was across the street from my High School, De Witt Clinton.  There was a time that the area was predominantly Jewish some 40 years ago.  Later the area got mixed up with Latinos and Caribbean folk.  Lets say that the KFC across the street couldn't compete with Jerrys.

I took for granted all the amazing things my daily bus ride to school spanned.  The ride originated on E233 on White Plains road, a predominantly Jamaican spot.  Then the bus circumscribed the hilly side of the Woodlawn cemetary.  It was only years later when I became an admirerer of Jazz history that I learned that many great Jazz musicians chose to be buried next to each other in Woodlawn, such as Miles Davis, Duke Ellington, Coleman Hawkins, Milt Jackson, Slide Hampton, King Oliver , Cootie Williams, Florence Mills-to name a few.  Then the bus covered some of the Riverdale golf course onward to Bainbridge ave, where the house of pain Irish hoods roamed.  In the mornings groups of us would walk across the Montiofiore Hospital's campus toward Jerome ave where our high school stood.  This was especially influential on a lot of us, seeing doctors and interns busting to Jerry's for their fix.  It amazes me that 5 of my class mates are now practicing at Montiofiore, still getting their Jerry high. 

Just yesterday I brought back some bagels to share with my good friend, Lera.   These were H & H (a Manhattan based bagel claiming to be the "best in the world")  Now, I know that folk from Brooklyn claim theirs is the best.  But have y'all had a Jerry's...Give the Bronx some dap

hangin out with the homies

I'm out here in N.Y.C, my hometown. Last night I had a great time reuniting with my two pals from
the graduate school days at Brown, Kamran and Hahn. They are both Neuroscientist doing amazing research on neuron signal detection. Their research is like doing particle physics experiments on of the Brain-real deep stuff. Kamran was a string theorist and after his PhD with David Lowe, he went to Cal Tech to work with Christolph Koch. Hahn started his life as an applied mathematitian working with Fields medalist David Mumford. Yeah me and these guys still blow me away. I had a nice discussion with them about the precision experiments (putting in detectors into a single neuron while the organism is alive!)

I have this deep admiration for people working at the frontiers of brain sciences.

Other than that, I'm doing this calculation which shows that gravitons can lead to cooper pairing of neutrinos (Majorana) I wont tell you yet what it's for.

Out of the Cave II

Yeah, I know, you feel betrayed. But I've had very good reasons. I must admit, I've been a sloth, not making my daily entries and keeping in touch you all in blogland. I really can't talk too much about the physics problem I've been working; evaporating the few brain cells I have left. But I will say that It's a totally cool and unexpected way of explaining neutrino masses! Can you guess. I'll give you a hint, its related to cosmic Inflation. . .

Otherwise, I'm doing all the things that a new assistant professor does. Luckily I don't have to teach for the first semester. But I'm working hard on grant proposals-what a pain. Any suggestions from those that crossed this path?

playing with ideas

I'm in my typical state of mind-not feeling too smart. About what you may wonder? First I must share the good news. It seems like my cosmological constant resolution is looking good in the eyes of the referee of my paper! I can't talk too much about this-but so far so good. But there is this other nagging thing that has occupied my mind for the past few weeks. It has to do with the Cosmic Microwave Background Radiation (CMBR) and whether or not there is parity violation present in it. To answer this question, I will have to figure out a clever way of analyzing the data which takes into account foreground noise which could also contribute to parity violation. Needless to say that I'm not an expert on analyzing the WMAP (Wilkinson Microwave Anisotropy Probe) data. So I've been trying to convince Professor Sarah Church and her Post doc Dr. Melanie Bowden to join a collaboration with me and Peskin. It will be very cool if there is parity violation on large scales. I believe that this may be a way of testing the baryon asymmetry idea I published two years ago. Time will tell...