NSF Question 16

 

16. Describe your personal, professional, or educational experiences or situations that have contributed to your desire to pursue advanced study in science, mathematics, or engineering.  Review the instructions for the Previous Research Experience Form to avoid duplicating information. Type single-spaced using 10-point font size or larger. There is a 1-page limit.

 

 

     My recent experiences involving science writing and its connections to my research have substantially contributed to my desire to continue pursuing a career in theoretical astrophysics.  For the past year, I have worked as a staff writer for the Berkeley Scientific Journal, a bi-annual undergraduate-run science journal published on campus at UC Berkeley.  Thus far, I have written an article for each of the past two issues, one dealing with quantum computation and its suggestive support for the many worlds interpretation of quantum mechanics, and the other focusing on the special importance of the fundamental constants of physics for life.  Writing these articles has represented the culmination of my lifelong interest in popular science, drawing upon the inspiration I’ve received from authors like Brian Greene, Lee Smolin, David Deutsch, James Gleick, Richard Dawkins, and Timothy Ferris, to name several of those most influential to me.  In the future, I hope to continue to publish articles in science magazines and eventually author popular science books, both of which have provided a much needed source of inspiration and motivation, along with a big picture perspective that neither my courses or research could provide on their own.

     Of the authors mentioned above, I have actually had the chance to meet half of them, via public lectures and various informal talks on campus here at Berkeley.  One such experience that helped to convince me I am on the right track as a potential theoretical physicist, came after a talk given by Brian Greene, a Columbia University theoretical physicist and expert on Superstring theory, a topic on which he authored the recent best-seller, “The Elegant Universe”.  Superstring theory itself postulates that space has extra dimensions that are tightly curled up at the microscopic level.  Having studied the expansion of the space through my research, I’ve often wondered, if the universe is expanding, “Where does that new space actually come from?”  With this in mind, after the talk, I approached Brian Greene and asked him if one could think of the expansion of space as being due to the slow unfolding of these tightly curled up higher dimensional spaces, and had anyone ever thought of looking into that before?  After pausing for a moment, he said yes, one could certainly think of it that way, and as far as he knew, no one had ever conceived of it in those terms.  He then told me that it would be cutting edge research, although it would probably take a lifetime.  Hearing that, at the very least, I may have been the first to think of something like this, and hearing it from one of the worlds leading experts in the field, is something that can not help but lift one’s spirits.

     Recently, events regarding the second article that I wrote for the Berkeley Scientific Journal and its connection to my research have also helped to lift my spirits.  As described in more detail in the research experience essay, for over two years I have been doing research in astrophysics searching for supernova explosions with Professor Alex Filippenko.  We meet regularly on Wednesdays for our research group meetings and the atmosphere is usually quite informal, as we traditionally eat pizza, talk about recent observations, and whatever theoretical astrophysics topics come up.  I can not deny that the relaxed and intellectually supportive atmosphere of the group has significantly influenced my decision to pursue a career in astrophysics.  But in particular, in a group meeting several weeks ago, with no notice whatsoever, Alex says, “Andy, why don’t you give us a talk about your article in the Berkeley Scientific Journal.” which had just been published.  Although I had not expected it and therefore had not prepared anything, I was quite excited about giving an impromptu presentation, and in the end, I gave quick half-hour talk which led to a group discussion lasting over two hours.  I had previously done a formal presentation discussing my research at an undergraduate research poster session run by the Berkeley Society of Physics Students, but this particular experience was even more rewarding.  Whether the setting is formal or informal, any opportunity to present ideas that interest you to a genuinely receptive audience is something to be treasured.  And from a purely practical standpoint, with journal talks, colloquia, and, of course, oral exams, similar on the spot presentations will undoubtedly be crucial in graduate school and beyond.

     As it happened, the content of my article made it particularly relevant to be having this discussion with Alex at that time.  My article discusses the idea of the “fine tuning” of the fundamental constants of physics, where even tiny changes in the numerical values of constants like the speed of light and Newton’s gravitational constant could easily lead to a universe quite un-hospitable to life.  For example, small tweaking of the parameters could lead to universes without stars or stable chemical elements, which are undoubtedly crucial prerequisites for life as we know it.  These ideas, and the question of whether the universe is indeed fine-tuned for the existence of life, formed the subject matter of a public debate between Alex and Frank Shu, also a Professor of Astronomy at UC Berkeley.  The debate was part of an event called “Wonderfest”, a bay area forum where various scientific experts came to debate important scientific and philosophical issues.  Sitting in the audience and watching Alex and Frank engage in intellectual sparring, I was particularly struck by the fact that I had inadvertently given Alex a quick review of the subject through my article and impromptu talk a few weeks earlier.  As the whole set of events unfolded, I could not help but thinking that it may not be so unlikely that, someday, it will be me up there in Alex’s shoes.  It is indeed my desire to be a scientist like Alex who is relentlessly enthusiastic about debating these types of philosophical questions in a setting so conducive to the spirit of discovery.  In addition to seeing Alex in this debate, I have been fortunate to work with him in several contexts, as a researcher, a student, and as a teaching assistant for an introductory astronomy course taught by him.  There is no question that Alex has been a mentor for me, and considerably influenced my desire to continue to pursue a career in astrophysics.

     As people continue to ask me why I am doing astrophysics, I have realized that at the heart of it, the philosophical implications behind it all are really what drive me.  Simply put, I want to understand how the universe works and contribute to its understanding as much as I can in my lifetime.  How old is the universe?  What is driving the expansion of the universe?  What sets the values of the Fundamental Constants of Physics?  These are the kinds of questions that continue to make this field worthwhile, despite the large number of overwhelmingly esoteric steps involved in gaining a decent understanding of our current best answers to these questions.  Recently, I have been fortunate to experience a genuine convergence between my courses, my research, and my efforts at science writing, which have all related directly towards answering these types of questions.  As a taste of what is likely to come in graduate school and the rest of my career, this convergence has solidified my desire to pursue advanced study in theoretical astrophysics and strengthened my eventual hope of making a significant contribution to my field.

 

References:

1. Friedman, Andy. “The Fabric of Reality.”  Berkeley Scientific Vol. 5 Issue 1. Spring 2001, pp. 28-30  

2. Friedman, Andy. “Fundamental Constants of Physics: The Genes of the Universe.” Berkeley Scientific Vol. 5 Issue 2. Fall 2001, pp.

    100-104.

 

NSF Question 17

 

17. Describe your experiences in the following: Integrating research and education (for example, participating in and encouraging discovery at various levels); advancing diversity in science (for example, contributing to the participation of underrepresented groups); contributing to your community (both scholarly and social). Type single-spaced using 10-point font size or larger. There is a 1-page limit.

 

 

     My experiences with science writing and teaching have allowed me to integrate my research with education and make contributions to both the scientific community and the general public, in ways which I hope to continue throughout my career in astrophysics.  Such endeavors can also be helpful aids towards advancing diversity in science, and have been so to some degree in my previous experience. 

     As discussed in the previous essay, for over a year I have worked as a staff writer for the Berkeley Scientific Journal, (BSJ) where I have written a science article for each of the past two issues.  One major motivation I have for writing is simply to give back to the community of potential readers, scientists and non-scientists alike.  Well before I became certain I would pursue a career in science, popular science writings had inspired me to creative thought in ways that few other reading choices could.  And as a scientist, what these books and articles have done that neither my academic courses or, until recently, my research has done, is to put the things I am doing into a well-conceived big picture perspective.  In helping us to perform such personal reflection and place our roles as scientists in the proper context, these writings fill a genuine need in the scientific community.  Scientists who do not step away from themselves and perform a meta-analysis of what they are doing and why they are doing it are simply doing themselves and their peers a disservice.  It is in this sense that I view popular science works as terribly important, not only as means toward communicating important scientific ideas to the general public, but also as a sort of glue that holds the scientific community itself together via social and intellectual common ground.  As a beginning science writer, it is in this spirit that I strive to emulate those who have so deeply influenced me, and draw upon their inspiration to eventually make my own impact upon both the scientific community and the community at large. 

     In addition to writing for BSJ, I have also done graphic design work for the journal, designing the journal covers and selected graphics for both the Spring and Fall 2001 issues.  I have found that the careful use of graphical images can be an extremely useful tool towards communicating scientific ideas to the general public or even an expert audience.  While cover art is often more of a practical advertisement for the internal content of a science magazine or book, graphics related to the article itself can be crucial at making the article an effective means of communication.  As an example of what I have done, in my most recent article, I needed to create a graphic to help convey the essence of superstring theory, which happens to postulate that space has at least 6 extra dimensions hidden at the microscopic level.  Since a six-dimensional object is inherently impossible to draw, I decided to produce a schematic illustration designed purely to convey the complexity of the higher dimensional object.  I ended up taking a sufficiently complex two-dimensional geometrical design I had drawn, wrapping it around a sphere using graphics programs, and then texturing the surface with bumps and depressions corresponding to changes in brightness in my initial drawing.  What resulted was an unearthly image that served its purpose quite well. For more details and other BSJ graphics, see http://www.ugastro.berkeley.edu/~friedman/AndysWebPage/BerkeleyScientificJournal.html.  By continuing to create graphical aids like these that help illustrate scientific concepts, I hope to further contribute to the community of science readers.

     In regard to teaching, this semester I have had the opportunity work as a teaching assistant for Astronomy 10, UC Berkeley’s introductory Astronomy course taught by Alex Filippenko.  Teaching in this setting is excellent preparation for the inevitable teaching responsibilities I will have in graduate school, and it will undoubtedly help me become a better lecturer, wherever I eventually find myself in the academic world.  And with Astronomy 10 especially, as an introductory breadth course, I am learning a great deal about how to communicate scientific ideas to what amounts to an approximate version of the general public in a much more personal context than through science writing alone.  I am constantly learning from my students where I can improve my explanations and teaching style, and with their help, I have vastly improved my confidence in my own knowledge of astronomy.  As a result, I have found myself constantly reconnected to what is fundamentally so exhilarating about the subject.  The captured sense of wonder on a student’s face as they struggle with the expansion of the universe or an imagined fall into a black hole is, in a sense, why we astronomers are doing any of this in the first place.  I have also had the opportunity in recent weeks to discuss with my students both my supernova research and how it relates to my recent article.  It is especially rewarding to see how students discover how to fit these concepts together, grasping the connections between distant supernova explosions, the expansion rate of the universe, the fundamental constants of physics, and the fact that we humans exist to explore and question such a universe.  This seems to me to be the essence of the integration of research and education.

     In regard to advancing diversity in science, to be perfectly honest, teaching an introductory astronomy course does not exactly qualify as community outreach.  But it is certainly a taste of what impact I can make upon the lives of individual students, in inspiring them to explore these ideas in the future.  And although I have had the opportunity to teach students with diverse backgrounds, I can not claim credit for their presence as students at UC Berkeley.  The most I can say is that if I have in any way inspired an underrepresented student to continue to pursue science, then I have done the best I could toward advancing diversity. 

     In addition to my discussion sections, I have also been doing volunteer tutoring at The Astronomy Learning Center, (TALC), whose inception and continued existence is due largely to the efforts of John Johnson, the head TA for Astronomy 10.  In this setting, we encourage group and individual board work by students in a relaxed and supportive intellectual environment.  Independent of Astronomy 10, I have also done group and individual tutoring in Physics and Astronomy as a volunteer at the Student Learning Center (SLC) on campus.  Many of the students who come to both TALC and the SLC happen to come from underrepresented portions of the population.  The fact that many of these students find themselves in need of extra help is largely a reflection of sociological conditions in the country as a whole.  As it is, in reality, these students are just as bright as any of their peers at Berkeley, as evidenced in my experience, at TALC especially, by the significant number of serious intellectual discussions I have engaged in with curious students of all backgrounds.

      For the most part, as science professionals, we have the luxury of viewing our colleagues simply as intellectual human beings, independent of our individual sociological backgrounds.  In this sense, the scientific enterprise is perhaps unique in its wholeheartedly egalitarian and merit based approach to advancing knowledge.  In an ideal world, all groups would thus be equally represented in this endeavor.  As it is, women and minority groups are still clearly underrepresented, and this problem must be addressed.  To this end, as a student and teacher, I have always been willing to help all who are interested without discrimination, and there is no doubt that I will carry that mindset for the rest of my career.  As a decent human being, this is simply the least I can do.  But purely as a scientist, I also want to explore and publicize the types of questions that promote the most crucial kinds of intellectual growth and discovery that science has to offer.  In addition to publishing peer reviewed journal articles on my research and engaging in popular science writing, I want to write textbooks, give public talks, and lead seminars.  Through research, writing, teaching, and whatever other avenues present themselves, in the end, I want make a lasting contribution to my community, and be a communicator of scientific ideas in as many ways as possible.

 

Proposed Plan of Research Form

 


Applicant: Friedman, Andrew

In a clear, concise, and original statement, describe any research interests you may pursue while on fellowship tenure. Your statement should demonstrate your understanding of research principles necessary to pursue these interests and explain the relationship to your previous research, if any. Present your plan with a clear hypothesis or questions to be asked by the research. If you have not yet formulated a plan of research, your statement should include a description of one question that interests you and an analysis of how you think the question may best be answered. A listing of courses alone is not sufficient. Research topics discussed in your proposed plan may be used in determining eligibility.  Type single space using 10 point font size or larger. There is a 2-page limit, including references.

 

     As a graduate student in theoretical astrophysics, I am primarily interested in critically examining the theoretical foundations behind some of the major results of the observational research group I have been involved with as an undergraduate at UC Berkeley.  As described in more detail in my research experience essay, since January of 1999, I have been working in astrophysics as a member of the Lick Observatory Supernova Search group at UC Berkeley, headed by Professor Alex Filippenko.  Under the auspices of the High Z supernova search team, we use observations of Type Ia supernovae to test various cosmological models, and specifically, to measure the acceleration rate of the universe.  The recent supernova results along with independent data gathered from cosmic microwave background (CMB) measurements suggest that the expansion of the universe is accelerating.  Initially, this result was the antithesis of the decelerating universe that was expected.  Indeed, it has been controversial enough throughout to force both my group and another independent supernova group to become our own harshest critics, and act quite cautiously in regard to taking the results on face value.  As such, we have tested for several major systematic errors, including chemical evolution of the Type Ia progenitor systems, and reddening by interstellar dust, and found that our results are largely unaffected.  And now that we have independent CMB data which is consistent with the supernova results, the astronomical community largely accepts that the universe is accelerating.  The supernova results are far from dogma, but they are beginning to be incorporated into the curriculum of advanced astrophysics courses and newer textbooks, for example.  As a theorist, in the cautious spirit of the scientists I have been fortunate to learn from, I would like to critically ask the question, “Is there any other effect which could be mimicking what we interpret to be cosmological acceleration?”  In other words, are these results physical, or an artifact of an incorrect interpretation stemming from an incomplete understanding of fundamental physics?  Since I have not yet completely formulated a detailed research plan, in this proposal, I will primarily discuss why this is an important and reasonable question and broadly outline several potential avenues of theoretical research along these lines that I hope to pursue in graduate school.

     First of all, disregarding for a moment my personal bias, it is not unreasonable to speak of the accelerating universe results as one of the most important recent discoveries in all of physics, and, quite possibly, all of science.  It is not inconceivable that, if the results hold up, the leaders of the relevant projects could merit a shared Nobel Prize in physics within the next decade.  When a scientific result this groundbreaking is released, an honest scientist thus has to meet the idea with a reasonable amount of skepticism.  We are in this field to answer fundamental questions about the past, present, and future state of the universe as a whole, and these cosmological questions are philosophically and scientifically important enough that we owe it to ourselves and the scientific community to subject any major results to sufficient peer reviewed criticism.  And beyond that, it is not unreasonable to say that we actually owe it to humanity to make a sincere effort at critical examination.  Granted, most United States or World citizens might value esoteric astronomical discoveries, such as, say, measuring the Neutrino mass, with comparatively low regard, but for a publicly accessible result such as one that says, “The universe is roughly 14-15 billion years old.” or, “The universe is accelerating in its expansion.”, a large number of people are actually sincerely interested and affected.  Regardless of the esoteric foundations of the supernova results, the idea of the expanding and accelerating universe happens to be quite conducive to the public imagination.  It is within this big picture context that I am motivated to investigate the validity of this result, aside from its pure scientific interest.  If the universe is accelerating in its expansion, or if it is simply coasting along, these are reasonable things for an educated human being to be aware of, just as it is reasonable to understand that the universe likely began a finite time in the past at the Big Bang.

     But just as it is reasonable to continue subjecting the Big Bang model to stricter and stricter tests, this result, as a comparative toddler, should in no way be spared from a similar gauntlet of critiques.  First of all, there are several motivations for the idea that, while the data analysis underlying the supernova results may be robust, the assumptions that research groups have adopted in interpreting the results may be in need of revision.  The idea that the data analysis may be robust comes from the fact that it is statistically unlikely that the independent data analyses done by the High Z Team, the Supernova Cosmology Project, and the MAXIMA, BOOMERanG, and DASI cosmic microwave background collaborations are all intrinsically flawed, yet somehow still in agreement.  But if the shared theoretical assumptions made by the all the groups are flawed at some level, the interpretation of the results would be in question, even if we assume perfect data analysis.  The assumptions stem from our current understanding of Einstein’s theory of General Relativity.

     In the current interpretation, the acceleration is caused by Einstein’s newly resurrected cosmological constant L, which was originally an ad hoc repulsive gravitational term thrown in to Einstein’s Field Equations in order to keep the universe static, as Einstein believed it to be at the time.  It now serves as a repulsive gravitational force (cosmic antigravity) which causes the expansion of the universe to accelerate.  The idea of the cosmological constant being a real, physical quantity has left a large number of scientists uneasy for several reasons.  When we apply standard particle physics theory, which treats the natural Planck energy density of the vacuum as the physical basis for the cosmological constant, L, we get a number that is 10120 orders of magnitude larger than what we observe, quite possibly the most numerically discrepant prediction in the history of science!  If the independent supernova and CMB results are as robust as they seem, this clearly signifies that we are likely to require significant change in our understanding of fundamental physics in order to describe what, in fact, L actually is.  As it stands, our fundamental physics gives us an answer that is bordering on ridiculous.

     This alone naturally leads one to consider that maybe we are being fooled somehow, observing an effect that looks like L and cosmological acceleration, but is in fact, some other new physical phenomenon altogether.  Granted, this would defer the problem of what L is to some other source, but if the other source is more amenable to and consistent with theoretical and observational tests, then as good scientists, we can learn to live without L.  This is not to deny the possibility that L is real, (in fact, it is still our best bet thus far), but as honest scientists, we must continue to be our own harshest critics and seriously consider the possibility that General Relativity is flawed, and that the L we think we are seeing is actually an artifact of some other yet to be understood physical process.

     It has been recently suggested by a group at the University of New South Wales in Sydney, Australia, (Murphy, Webb et. al.) that observations of (Quasi-Stellar Object) QSO absorption lines out to high redshift may indicate that the dimensionless Hydrogen fine structure constant a may be changing in time.   (Where a = e2/c = (electric charge) 2/ (Planck’s constant x the speed of light) ).  Some theorists, notably John D. Barrow, and Joao Magueijo, have pointed out that this may mimic the behavior of L in a fashion that is consistent with observations.  As any serious research team must do, the UNSW group is waiting for other independent groups to confirm their results, and until then, one can not merely accept the results without criticism.  But the theoretical motivations for a changing a, along with the robust statistical tests employed by the UNSW group at the very least make this observational result suggestive enough to prompt further theoretical investigation, even before the result is either confirmed or constrained by future independent observations.  As one of the possible explanations for what we interpret as L, a theory that allows for varying a, and indeed any of the other physical constants, is an avenue which may be legitimately explored.

     A priori, there are no reasons why the “constants” of physics should not be allowed to change, so it is at least reasonable to investigate the explanatory power of theories in which they can vary, and apply observational tests when possible.  Although a theory of changing constants is not part of the current standard view, it is not a new idea in any sense.  Indeed, scientists as far back as Eddington, Dirac, and Wheeler gave serious consideration to space and time variation of the speed of light and Newton’s Gravitational Constant, for example.   Modern day theories such as string theory that attempt to unify gravity with the other fundamental forces, naturally contain extra compactified spatial dimensions whose scales determine the values of the fundamental constants.  Since we have no a priori reason to expect that the scales of the extra dimensions will remain constant as the expansion of the universe proceeds, variation in the values of the constants is a natural prediction of such theories.  Whether such unifying theories are worthwhile is another question entirely, but suffice it to say that string theory and its brethren are our current best attempts at a unified theory of quantum gravity, and their preliminary theoretical findings are suggestive and compelling enough to take very seriously.   In addition to the previously mentioned Barrow and Magueijo, Andreas Albrecht, one of the founders of the modern theory of inflationary cosmology, has seriously considered varying speed of light (VSL) models and how they would impact our current understanding of cosmology.  Albrecht has taken the stance that he is not investigating VSL models because he is convinced they are correct, rather, he is doing so to offset the fact that no serious modern opposing theory to cosmological inflation has arisen.   Rather than trying to sell a pet theory, Albrecht is simply trying to keep science honest when it comes to our cosmological theories.   It is in this spirit that I hope to analyze the supernova results in graduate school.

     Some would object to the idea of resorting to a theory of changing constants to explain away L because it would seem to decisively undermine the basis of fundamental physics as we know it.  First of all, treating the “constants” as constant will always be an excellent local approximation.  Local classical physics thus remains unharmed.  It is only on the largest cosmological scales and in our Standard Model of Particle physics where we will require significant revision. As it stands, no one will deny that the standard model of particle physics is incomplete.  It has yet to incorporate gravity into its quantum mechanical framework with electromagnetism and the strong and weak nuclear forces.  Few will deny that our understanding of gravity in, say, thirty years, is bound to be significantly different from our current understanding.  And we have already concluded that if the independent supernovae and CMB results are not intrinsically in error, and L is real, we are already in the same situation.   Fundamental physics must change in either case.   If we must choose between two theories that may both be consistent with observations, one must consider which theory possesses greater explanatory power.  It may be that a changing fine structure constant, or some other combination of changing constants can mimic the behavior of L, and explain what is physically happening in a more logical and consistent fashion.  Or it may not.  The point is that the question is of great scientific interest, regardless of what the result may be.  In other words, even if theories with changing physical constants end up being terribly wrong, we can not help but learn some interesting physics through their investigation.  As a long-term theoretical goal, I would love to help formulate a general theory of changing constants, to help provide a framework within which further observational groups like the Lick Observatory Supernova Search group, the High Z Team and the UNSW group can test whether the constants do vary in space and time, and evaluate their impact on our cosmological models.

     Although, as a theorist, I plan to become involved with more fundamental questions that I can possibly predict at present, the idea that the cosmological constant could be a mirage, possibly replaced by a new paradigm of fundamental physics where the constants can vary, is a topic that highly interests me.   Having been a researcher working in the supernova field for several years now, as a potential theorist, I would genuinely like to see the results through, whatever their eventual interpretation may be.  It is my hope that, regardless of their eventual interpretation, the supernova results will act as a springboard toward a new and better understanding of fundamental physics, where yet again, astronomical observations cause us to radically revise our understanding of nature.  The phenomenon is not unprecedented: Hoyle’s prediction of the resonant Triple Alpha level required for the formation of Carbon 12, the solution to the Solar Neutrino Problem, the Binary Pulsar and bending of starlight during a total solar eclipse as a test of Einstein’s theory of General Relativity, to name a few.  The list is simply too large for this page, and as a hopeful theorist, I would love nothing more than to help add to it.  In graduate school and beyond, it is with this mindset that I hope to be a part of that tradition of unbridled theoretical investigation.

 

References:   (See Also the Research Experience References )

 

1.

Albrecht, A. Cosmology with a time-varying speed of light. To appear in the proceedings of COSMO98  ( astro-ph/9904185 14 Apr 1999)

2.

Albrecht, A.., Magueijo, J.  A time varying speed of light as a solution to cosmological puzzles.  Phys.Rev. D59 (1999) 043516          

3.

Barrow, J.D., Magueijo, J. Can a changing alpha explain the Supernovae results?, to be published in Ap.J.Lett,  ( astro-ph/9907354,  22 Feb 2000 )

4.

Barrow, J.D., Magueijo, J. Varying- alpha Theories and Solutions to the Cosmological Problems, Phys. Lett. B443 (1998) 104 

5.

Barrow, J.D., et. al., The Behavior of Varying-Alpha Cosmologies, Submitted to PRD  ( astro-ph/0109414, 24 Sep 2001 )

6.

Murphy, M.T., Webb J.K et. al. Possible evidence for a variable fine structure constant from QSO absorption lines: motivations, analysis and results,  MNRAS in press, ( astro-ph/0012419, 4 Sep 2001 )

7.

Sandvik, H.B, Barrow, J.D., Magueijo, J. A Simple Varying-alpha Cosmology, Submitted for publication in Phys.Rev.Lett, ( astro-ph/0107512, 26 Jul 2001 )

8.

Webb, J.K. et. al. A Search for Time Variation of the Fine Structure Constant, Phys.Rev.Lett. 82 (1999) 884-887

9.

Webb J.K,  Murphy, M.T et. al. Further Evidence for Cosmological Evolution of the Fine Structure Constant, Phys.Rev.Lett. 87 (2001) 091301

 

 

 

Previous Research Experience Form

 

Applicant: Friedman, Andrew

Describe any scientific research activities in which you have participated, such as experience in undergraduate research programs, or research experience gained through summer or part time employment or in work-study programs, or other research activities, either academic or job-related. Explain the purpose of the research and your specific role in the research, including the extent to which you worked independently and/or as part of a team. In your statement, distinguish between undergraduate and graduate research experience. If you have no direct research experience, describe any activities that you believe have prepared you to undertake research. At the end of your statement, list any publications and/or presentations made at national and/or regional professional meetings.  Type single space using 10 point font size or larger. There is a 2-page limit, including references.

 

     Since January of 1999, I have been doing research in Astrophysics as a member of the Lick Observatory Supernova Search (L.O.S.S) team with Professor Alex Filippenko at the University of California, Berkeley.  We work under the larger auspices of the High Z (i.e. high redshift) Supernova Search Team, headed by Dr. Brian Schmidt at the Australian National University in Canberra.  The big picture goal of the group is to discover large numbers of Type Ia supernovae in distant galaxies, determine their spectra and light curves from follow up observations, and use them to do cosmology.  My research has focused on both searching for supernovae and performing photometry on the follow up observations to obtain the supernova’s light curves, which plot its apparent brightness as a function of time in several different filters (U,B,V,R and I bands).  These light curves are then used to test various cosmological models, and specifically, to measure the acceleration rate of the universe.  Since Edwin Hubble’s 1929 discovery that almost all galaxies are redshifted, and are thus receding from us, we have known that the universe is expanding.  The major result of the High Z Team, which was announced first in 1998, is that the supernovae we observed are consistently 10-15% dimmer than what we would expect from a coasting expanding universe, implying that they were actually farther away than expected, and thus that the expansion of the universe may actually be accelerating. 

     When I joined the group in early 1999, the result was even more controversial than it is now because it flew in the face of conventional wisdom that the universe was surely decelerating, as gravity should eventually overcome the energy from the initial expansion. The results also resurrected serious interest in Einstein’s Cosmological Constant L, which in theory could provide a cosmic antigravity force, which resists normal gravity and causes the acceleration.  As it happened, the accelerating universe results were obtained independently through work done by the Supernova Cosmology Project headed by Dr. Saul Perlmutter at the Lawrence Berkeley National Laboratories.  This gave both of our groups more confidence in a result that initially, neither team was willing to believe, let alone publicize to the astronomical community.  Since then, crucial independent tests of the possible cosmological models have been performed using data from the Cosmic Microwave Background (CMB), most notably from the MAXIMA, BOOMERanG, and DASI experiments.  These results are also consistent with the supernovae results.  Thus the present consensus from the astronomical community is that we have an accelerating universe with a nonzero cosmological constant, and an unwieldy list of questions regarding the true physical basis for this phenomenon.

     To use supernovae to answer cosmological questions, we first look at a its spectra to determine its redshift and see if we can classify it as a Type Ia.  We use Type Ia supernovae in particular because there is strong theoretical basis for the idea that all Type Ia supernovae can be treated as “standard candles”, in the sense that their intrinsic brightness does not vary much amongst populations of Type Ia’s exploding over cosmological timescales and thus at different redshifts.  Assuming that Type Ia supernovae are perfect standard candles, we can use them as relatively robust cosmological distance indicators. Traditionally, we get a distance by measuring the supernova’s apparent peak brightness from its observed light curve, and comparing it with that of other Type Ia’s that exploded in galaxies whose distance we have determined independently, for example using Cepheid variable stars.  Knowing both the distance and the intrinsic brightness of the supernova, we can compare the apparent brightness we observe to the apparent brightness we would expect to see from models with or without cosmological acceleration, and test which model is most consistent with observations.

     However, comparison between high and low redshift supernovae in different environments is necessary to justify the assumption that Type Ia supernovae can indeed be used as reliable standard candles. Other effects, such as evolution of the chemical composition of successive generations of these objects, or reddening by interstellar dust could in theory change the intrinsic brightness of Type Ia supernovae as a function of redshift.   Testing this assumption and providing the foundation for the understanding the high redshift supernovae is a primary focus of the particular supernova search that I am involved in.  We look for nearby, low redshift supernovae, (Z < 0.1), whose spectra and light curves we determine and then compare and combine with those of the high redshift supernovae found by the High Z Team.  By comparing both high and low redshift supernovae, we can test for chemical evolution of the progenitor systems, and extend our tests of cosmological models to regimes that require both high and low redshift data points.

     That said, if we want to use these supernovae to do cosmology, the first thing one must do in such a project is to find them!   Our team, which includes several undergraduates, searches for supernovae aided by IRAF (Image Reduction and Analysis Facility) image processing software specifically designed to find possible supernova candidates.  Our data consists of CCD images that come from the Katzman Automatic Imaging Telescope (KAIT) located at Lick Observatory.  The state of the art program I work with, which was designed by my direct superior, Assistant Research Astronomer Weidong Li, sifts through images of as many as 1000 galaxies a night. However, the program itself is still not sensitive enough to detect many supernovae, so it requires a careful observer to check through the images and verify possible good candidates.  In doing so, I use various IRAF programs to compare the current images with template images of the same host galaxy taken previously to determine whether there is indeed something new and re-observable in the CCD image, as opposed to a fleeting asteroid or cosmic ray, for example.   For promising candidates, I instruct KAIT remotely to automatically re-observe the image to make sure that the apparent supernova is still in the field of view, and can sometimes even get same day verification.  I am happy to say I have been fortunate to discover seven supernovae in the past semesters.  Pictures of the supernovae (1999bh, 1999bx, 1999ej, 1999gb, 200fa, 2001L, and 2001ae) can be found on the KAIT website at http://astron.berkeley.edu/~bait/kait_lwd.html under 1999, 2000, and 2001 discoveries.  Once we make a discovery, it is announced with our name as discoverer, via an IAU circular (International Astronomical Union) e-mail to a large fraction of the astronomical community. 

     I took a six-month break from the group during the Spring 2000 semester when I studied abroad at the University of New South Wales in Sydney, Australia.   Since returning, I’ve continued working with the Filippenko group on a new research project in addition to the supernova search, where I am learning how to perform photometry, the precise measurement of the brightness of astronomical objects.  I am in the process of working with Weidong Li, our resident expert on KAIT and key technical member of our group, to learn how to perform aperture and point-spread-function (PSF) fitting photometry on individual supernovae.  I start with a data set of dozens of follow up CCD observations in different filters taken by KAIT starting from the date of discovery and extending for several months to a year.  I then perform photometry on each image in order to produce the supernova’s light curves in all the relevant filters.  I am currently working with IRAF software packages, graphing scripts, occasionally Microsoft Excel, and several programs written by Weidong Li with the long term goal of producing light curves for as many as 30 Type Ia supernovae.  I now spend most of my time in the group focusing on the photometry project, while occasionally helping to train new undergraduates to do the supernova search.

     To begin the process, I did photometry on a “practice” supernova (SN 2000cx), that occurred far from its host galaxy, and compared my light curves with the data that Weidong had already reduced, getting consistent results.  That particular supernova has been discussed in great detail in the recent paper by Weidong and Alex, (Li & Filippenko 2001) listed in the references.  I am now in the process of learning galaxy subtraction, to deal with supernovae that occur closer to their host galaxy, and currently working with Supernovae 1998dh.  Galaxy subtraction is necessary because we want to isolate the light coming from the supernova alone and remove contaminating light from the host galaxy.  If we have template images of the galaxy taken before the supernova explosion, this process is straightforward.  In most cases, however, we do not, which means we must wait a year or so until the supernova fades and then take a calibration image of the host galaxy which we can then subtract from our supernova images.  During the rest of this semester, and in the Spring before I attend graduate school, I plan to continue working with the group and apply the techniques of galaxy subtraction and PSF photometry to generate the light curves for supernova 1998dh and a number of the 30 or so Type Ia supernovae who we have followed extensively with KAIT.  Most of them have data that are simply waiting idly while we try to get good calibration images of the host galaxy, without which we can't even begin to do any of the galaxy subtraction or photometry.  I also plan to help train the new undergraduates in the group, so we can efficiently approach the task of reducing the considerable about of supernova data we have.  

     In the end, the completed analysis and light curves, along with a training primer discussing how to do KAIT photometry, should form the bulk of my senior honors thesis research.  When we eventually publish these light curves, I will end up as second or third author on a paper along with Weidong and Alex, where we present the addition of the new data to our sample.  The work is of considerable interest to astrophysics, especially to those in the supernova field, as we would effectively be extending the current useful database of nearby supernovae by roughly 30%.  In addition, our light curves are better sampled than those previously published (i.e. more follow up images, closely spaced in time), and would likely become the new “training set”, with which to compare all subsequent Type Ia supernovae light curves, providing even stricter tests of the accelerating universe results.  All in all, I feel like I am making a positive contribution to the group, learning a tremendous amount, and definitely preparing me for possible Astrophysics research in graduate school, although right now I am leaning significantly towards astrophysics theory rather than observational astronomy, due mostly to the huge number of tantalizing unsolved problems I have been introduced to in the context of both my academic and research experiences here at Berkeley.

     This semester, I have also been involved in the perpetual motion experience that is the UC Berkeley Undergraduate Infrared Astronomy Laboratory taught by Professor James Graham.  The amount I have learned in a mere 10 weeks has been exponential at the very least.   In order to write up my labs, I have had to develop a competent familiarity with the Unix operating system, become proficient programming in IDL (Interactive Data Language), and learn to use the LaTeX document formatting language, in addition to the conceptual core material of the lab.   The learning curve is pretty steep, and in a very short time we all become pseudo experts.  There are very few courses that can boast such things.  So far, in addition to Unix, IDL programming, and LaTeX, I have learned a tremendous amount regarding statistics, error analysis, CCD pixel array imaging, and how to take images of stars with a robotic telescope, (The Leuschner Observatory 30-inch telescope and Infared Camera).   These are some of the fundamental tools of a modern day astronomer.   

     The lab material has also been integrally related to my supernova research.  My last lab report, “Photometric observations with the Leuschner Telescope and Infrared Camera”, considerably solidified my understanding of the photometry I have done for supernovae.  Instead of simply using part of the massive IRAF software package infrastructure, or programs written by Weidong Li, this time I wrote the software to perform differential aperture photometry on individual stars from the ground up.  Even though using the programs clearly requires an understanding of the underlying theoretical motivations and major workings of the program, it is no substitute for writing the program yourself.  I have already applied what I have learned in this laboratory toward teaching some of the new undergraduates in my research group about differential photometry, hopefully providing them with a big picture view of what we are doing and why we are doing it in the first place.  On a broader level, the programming skills I acquire in this lab will be generally applicable to whatever topics I pursue as a theoretical astrophysicist.  But perhaps most importantly, through this lab, I am learning more about what it takes to write a concise, clear, and honest scientific paper, and to present my results to a community of my peers.  

 

Publications and Presentations:

1.

Li W.D., Filippenko A.V., Treffers R.R., Friedman A., et. al., “The Lick Observatory Supernova Search” Cosmic Explosions, 2000, ed. S. Holt and W.W. Zheng, New York, American Institute of Physics. pp. 103-105

2.

Li W.D., Filippenko A.V, and Friedman, A.   “Photometric Observations of 30 Nearby Type Ia Supernovae.”  Paper In progress.

3.

Last April, as part of my honors thesis, I spoke at the Berkeley Undergraduate Research Poster presentation organized by the  Society of Physics Students, discussing the accelerating universe results and my role in the supernova search.

 

Selected References:

1.

Filippenko A.V., Riess. A.G. Results from the High-Z Supernova Search Team., Proceedings of the 3rd International Symposium on Sources and Detection of Dark Matter in the Universe (DM98), Feb. 1998, ed. D. Cline and Phys.Rept. 307 (1998) 31-44, 

2.

Filippenko A.V., Riess. A.G. Evidence From Type Ia Supernova for an Accelerating Universe, to appear in Second Tropical Workshop on Particle Physics and Cosmology: Neutrino and Flavor Physics, ed. J. F. Nieves (New York: American Instit. of Phys.)

3.

Graham, James, and Treffers, R.R. An Infrared Camera for Leuschner Observatory and the Berkeley Undergraduate Astronomy Lab, Publications of the Astronomical Society of the Pacific, 113, pg. 607-621, May 2001.

4.

Li W.D., Filippenko A.V. et. al. The Unique Type Ia Supernova 2000cx in NGC 524, Accepted for pub. in Oct 2001 issue of PASP.

5.

Perlmutter S. et. al. Cosmology From Type Ia Supernovae, Bull.Am.Astron.Soc. 29 (1997) 1351

6.

Riess, A.G. , Filippenko A.V. et. al. Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant, Astron.J. 116 (1998) 1009-1038

7.

Schmidt, et. al. The High-Z Supernova Search: Measuring Cosmic Deceleration and Global Curvature of the Universe Using Type Ia Supernovae, Astrophys.J. 507 (1998) 46-63

 

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