Bally, John

I discovered the Aspen Center for Physics during summer 1971. I was still an undergraduate student at the University of California at Berkeley and between my junior and senior years. During a two-month long motorcycle tour of the West, I ended up in Aspen where I spent nearly a month camping. I discovered the Center during my first day. The staff was kind enough to let me use the library and sit in on the occasional discussion during this period. The experiences during my weeks in Aspen contributed to my decision to apply for graduate school in physics and astronomy and my love of Colorado's mountains (we own a home in Breckenridge, Colorado). After earning my PhD at the University of Massachusetts (the first on the FCRAO 14 meter mm-wave telescope), I spent 12 years at AT&T Bell Laboratories in the Radio Physics Research Department (in the group that discovered the Cosmic Microwave Background 15 years before I arrived there in 1980). I moved to the University of Colorado at Boulder in January 1992 where I am a professor in the Department of Astrophysical and Planetary Sciences. ACP played a pivotal role in motivating me to become an astrophysicist. I've returned to attend quite a few workshops and meetings over the years (though not recently) where discussions with colleagues inspired many of my papers. Aspen remains one of my favorite places on the planet and the ACP one of the most creative environments for a scientist.

Baskaran, Ganapathy

My visit to Aspen in the summer of 1987, coincided with the beginning of an exciting era in the field of high temperature superconductivity. Aspen was beautiful - flowers, bees, breeze mixed with music, mountains, hiking, plenty of physics and the company of excellent physicists. Thanks to P.W. Anderson, I was deeply involved with him from the start, in his Resonating Valence Bond (RVB) theory of high Tc superconductivity. The Aspen environment enabled me to give an expression to my involvement, in the form of a hand-drawn picture card that I sent to Anderson on July 20, 1987. Aspen and its somewhat romantic atmosphere catalyzed this expression.

Looking back, my sketch anticipates the relevance of RVB ideas, not only to cuprates but also to systems such as organics, heavy fermions, graphene, etc. In the last 25 years, the role of RVB ideas in other systems is gradually gaining prominence. Impurity band superconductivity in boron doped diamond (analogue of Si:P, one of the flowers in the sketch), is arguably a striking example. Does the big flower in the sketch below, `aromatic ring compounds' stand for superconducting ET-salts and some C60 compounds (discovered in the 90's which are in a fundamental way Mott insulator based?

Anderson has added this sketch in the concluding section of an article he wrote in, Modern Physics in America - A Michelson-Morley Centennial Symposium' Eds. W. Fickinger and K.L. Kowalski, (AIP Conference Proceedings 169, American Institute of Physics 1988). Anderson concludes, "I close with a postcard that my collaborator, Baskaran, sent me from Aspen. He is Tamil and doesn't pronounce the English language the same way the rest of us do - so RVB becomes a question - and this is the answer. As far as we know, certainly these are B's, but maybe there are some B's hanging around in a lot of other interesting places."

Bena, Iosif

I came to Aspen at the end of the first year of my first postdoc, for a workshop devoted to time in string theory. I did my PhD in a place where a lot of research was devoted to black holes in string theory, but somehow the subject had never gotten close to my heart. In Aspen I heard a talk by Samir Mathur, which contained some rudimentary ideas of what was later to become the so-called fuzzball proposal for black holes, and had some extensive discussions with him afterwards on the patio (I had him as a professor during my undergrad studies at MIT, and he probably still had painful memories of trying to decipher my unintelligible handwriting). These discussions really changed my view of black hole physics, and during them I also realized that I can use my exotic-brane-configuration skills to construct the geometries that Samir Mathur had conjectured should give the microstates of black holes. This field has been the centerline of my research ever since, and this all began from a discussion on the Aspen patio almost nine years ago.

Bender, Carl M.

The ACP did have a big impact on my career: Around 1975 I gave a talk in the summer. Gell-Mann was in the audience, and during and after my talk he made lots of positive comments about my work. In the audience was a professor from Washington University, who remembered my talk and especially Gell-Mann's comments. So, when a senior job opening appeared at Washington University, I was invited to visit and was immediately offered the job. I'm still there!

Bennemann, Karl

We spent a wonderful summer in Aspen, due to meeting so many of my former students (J. Schmalian, D. Morr, et. al.) as well as former teachers (D. Pines, H. Frauenfelder, S. Berry, et. al.). I felt back at home in the US and almost forgot physics for a while. I walked every day along the river to the Center, discovered a short cut, and using this, I got one day, as viewed by the secret police, too close to former Secretary of State Albright and former President Clinton who were guests of a party in a beautiful garden close to the Aspen Institute and along my short-cut walk. However, responding, "I am only a simple physicist," and a guest of the Aspen Center for Physics, saved me, and maybe this event taught me too, to avoid always the lovely short-cuts in theory. Tempus fugit, but may the Center live forever!

Biermann, Peter L.

I have been at Aspen many times, and of all these visits one sticks in my mind as especially fruitful, and that was in September 2005, my last visit. At that time I talked a lot with Alex Kusenko, with a paper in PRL as a result. This paper speculated that dark matter could be a right–handed neutrino of a few keV; we showed that this could result in much earlier star formation than normally expected. The hypothesis has surprisingly not only survived, but has found increasing support from a number of galaxy observations. Without Aspen this paper might not have been written.

Bludman, Sidney

I have participated in ACP since 1963, and have co-organized summer workshops on neutrino physics and astrophysics, on cosmic rays, and on cosmology. I have acknowledged ACP and my summer collaborators in many publications.

Best wishes to you and the Center for a Happy New Year.

Bouwknegt, Peter

The Aspen Center for Physics embodies everything that persuaded me to become a physicist; doing research in a relaxed atmosphere, surrounded by breathtaking nature and good–natured and inspiring colleagues. I have written some of my best papers, and established long–lasting friendships, whilst visiting the Center. While I haven't been able to visit the Center in recent times, it is always high on my wish–list, and I wouldn't hesitate to visit again in future if the opportunity arises. My sincerest congratulations with the 50th anniversary, and particular thanks to all the fantastic staff of the ACP, in particular Jane Kelly, for making my stays memorable, over and over again. I hope there's many more years to come. The ACP provides an invaluable service to the physics community.


My first time in Aspen was in the summer 2001. I had just published one of the most cited papers of mine, and I had a great opportunity to discuss and deepen understanding and implications of those results with the best researchers active in that field. Four years later, I attended one more time the summer Aspen workshop, and a nice work came out from the interaction with colleagues of mine, afterwards published on PRL. A very special scientific community I'm indeed referring to, where physics “was taken care of” as it always should be: theory and experiment getting closely along, one pushing the other to the next advancing step. Within a community where handing down of competences between different generations, respect, and friendship were the perfect ingredients to make so many young people to grow up as researchers and as men and women. That Aspen workshop was also the first long one I was attending to, after my daughter Anna's birth. I decided to take the tiny Anna with me, “convincing” (it turned out quite easy I should say) my parents to accompany us. Anna and I have been so happy there together for a full month. That was also the first overseas trip of my mum and dad ever – I took them to Arches too one Sunday I remember - and I think that a few employers in Aspen supermarkets still remember an old man gesticulating salt and cherries while speaking a solid incomprehensible italian. So, Aspen has represented for me an ideal environment, with great and nice personnel taking care of us, where to play good physics, growing up as a researcher, strengthen friendship relations and live memorable personal experiences. Thanks!

Cline, David B.

I started to attend the Aspen Center during the time of the Super Conducting Super Collider and learned of the wonderful chance to sort of think “outside the box.” For example, at one Aspen meeting John Learned, Kirk MacDonald and I dreamed up the idea of a 100 kiloton Liquid Argon TPC for Neutrino physics (LANNDD) and published the first paper. It is now one of the two detector concepts for the US Long Baseline Neutrino Experiment (LBNL) and strongly supported by NSF and DOE. Also our own 600 Ton LAr detector ICARUS is taking data at the Gran Sasso Laboratory. I also attended a meeting on Ultra High Energy Neutrinos that was very useful. Mainly I have worked on Dark Matter detection for several summers. I work on XENON 100, the largest dark matter detector in the world. Every summer I go to Aspen, I end up writing a published research paper on the work I have done there. Recently I have been exploring the claims of the existence of low mass WIMPs and have provided two papers on the subject. We hold our own Dark Matter Symposium at Marina Del Ray (LA) that is very popular and this year we will emphasize low mass WIMPs.The Aspen experience is totally unique. Normally we are very busy teaching, doing administration and research. While some of this continues at Aspen, there is the chance to think of new ideas or explore in more detail current experimental and theoretical claims. This experience is unique. The chance to discuss advanced concept with other experts is invaluable.

Cohn, Joanne

Paul Ginsparg and I were chatting outside on the lawn at the ACP during a 1991 summer workshop, about the international preprint collection and distribution list I had been running for about a year and a half. The preprints were filling up people's emails––he suggested it should be automated, and I invited him to try. The next day he reported he'd just written some scripts to do this, and we worked out a transfer of my network to his planned system. A few months later the arXiv (at that point an ftp site) went live.

Copeland, Ed

I have many happy memories of Aspen from both a physics and personal perspective. It was where I started working with Tom Kibble on the evolution of cosmic strings in 1990, and later in 2005 where I began working on my review on dark energy. It is also where I sat on the lawn in August 1990 along with other members of the Center listening to Margaret Thatcher speaking in the tent of the Aspen Music Festival about the need to end divisions between the East and West, and in one added sentence saying the invasion of Kuwait by Iraq could not be allowed to succeed. Long lasting friendships have emerged from Aspen trips. It remains my family's favourite place; there is something very special about the afternoon/evening barbecues where all the participants gather with their families and everyone mixes in a lovely informal atmosphere.

Delgado, Antonio

My visits to the ACP have always been a pleasure and after those visits my scientific production has improved a lot. The atmosphere at ACP is wonderful for good collaborations and great discussions. Keep on with the good work.

Dine, Michael

I have had several very enjoyable stays at the Center, but the most memorable was my first, just a year into my first postdoctoral appointment. Apart from facilitating a project which I was formulating at the time, conversations at the Center led me to three issues which have been central to my subsequent career in theoretical physics: Higgs physics, the cosmological constant and neutrino physics, especially the MSW effect. The participants included not only David Gross, Leonard Susskind and Tom Appelquist, but also a delegation from ITEP –– my first encounter with Polyakov, Volshin, Vainshtein and others. This was still in the Soviet era, and this opportunity was extraordinary.

Dodelson, Scott

I am a physicist today because of The Aspen Center for Physics. After finishing my PhD, I spent my first year as a postdoc in an office by myself, struggling to produce a couple of papers but feeling very isolated. I was unhappy and began applying for jobs outside of physics. My first break came when I was accepted to the Aspen summer program. There I met a dozen people my age all interested in the same things as I was. We went on hikes together, organized pot lucks every night, played volleyball, and discussed physics. I started a fruitful and long–lasting collaboration with another postdoc, who ironically was from my institution. At one of our last potlucks, as we listened to someone strumming a guitar and finalized our research plans, I turned to my new colleague and said, “This is what I want to be when I grow up.”

Elser, Veit

During the late summer of 2012, Veit communicated with his students at the start of the fallsemester via this blog.

Faraggi, Alon

Without a doubt Aspen provides a special and unique environment to pursue one's interests. I have been fortunate to visit Aspen twice for periods of two weeks. The first in Summer 2006 when I embarked on my work with Marco Matone on formulating quantum mechanics from an equivalence postulate. This is a particular piece of work that I am proud of, which I believe sets the stage for the proper formulation of quantum gravity. The second visit was in Summer 2004, while I was developing the systematic classification of heterotic string vacua. This led to the observation of spinor–vector duality in heterotic string compactifications, and is still very much under development.

Feng, Jonathan

I came to Aspen for the first five summers after graduate school. I once played the trumpet, and the first summer, I think I knew about as many people in the music tent as I did at the Center for Physics. I remember summers filled with physics and music: one day a Canadian Brass master class followed by a talk on supersymmetry, the next day a lecture on dark matter followed by an oxygen tank–aided Bobby McFerrin. These days, I don't get to Aspen as much, but when I do, I often still feel like a kid in two candy stores at once.

Ford, Eric

ACP workshops have long–lasting impact. For example, during the 2008 summer workshop on “Characteristics and Habitability of Super Earths,” I collaborated closely with two postdocs. The ideas we developed while at the ACP grew and grew, culminating in a paper published in 2011. The benefits of this type of long–term collaboration probably aren't reflected in publication and citation counts. (In case anyone is keeping track, the paper I'm referring to is at

ACP summer workshops provide an opportunity to sit down in front of a blackboard with colleagues, day after day, allowing you to exploit their diverse areas of expertise and make connections that you simply would not find otherwise.

Freed, Dan

For over 20 years now the Aspen Center for Physics has opened its doors to mathematicians whose work has deep connections to theoretical physics. I have been a co–organizer of a series of workshops (six so far) which bring together mathematicians and physicists. Interaction between scientists from different fields is especially difficult––there are cultural and language barriers on top of the usual technical struggles. The open–ended structure of the Aspen Center provides the time and space to overcome these hurdles. The leisurely lecture schedule, an open architecture which fosters discussion, and the communal activities all contribute to the scientific output. Not only has my time there inspired many of my own projects and collaborations, but I have also witnessed that effect on others time after time. Happy 50th and many more!

Greenside, Henry

I have only spent two previous summers at Aspen, both on workshops related to the theme of physics and biology. The first workshop (organized by Mike Cross and Herbie Levine, I think that was in 1999) brought nonequilibrium pattern formation researchers together with biologists to explore possible common territory and that played a big role in my shifting my research interests to theoretical neuroscience, my current interest. (It was at that first workshop that I met for the first time a Duke colleague, Larry Katz, who later let me spend a sabbatical in his Duke lab, and helped me to learn about mammalian olfaction.) As many others have mentioned, the informal and beautiful environment of the Center and surrounding area greatly stimulated many interesting discussions and was also a valuable chance for me to learn and explore new ideas and techniques. Mike Cross and I also enjoyed many discussions and several hikes in Aspen that led to our writing an introductory graduate text on nonequilibrium pattern formation.

I would like to mention one amusing incident: on the first day of the 2003 workshop, before people knew who belonged to which workshop, I was eating lunch at one of the lunch tables with various people and the question came up about what each of us was working on. Several of us said "brains" and others then said, "I am working on branes too!" It took a while for us to realize that the two kinds of brains/branes had nearly nothing in common. Rather sadly, the neuroscience-oriented physicists and string theorists largely stayed apart for the remaining weeks of the workshops.

Gronau, Michael

I am very glad to summarize my several visits at the Aspen Center of Physics by stressing their great inspiration and stimulating effect on my research work.

In my first visit to the ACP in summer 1983 (when I recall Lincoln Wolfenstein proposing modestly his seminal CKM parametrization) I started a long-term collaboration with Jonathan Rosner, first studying heavy neutrinos and then turning our attention to heavy quark physics. Our work at the Center in summer 1983 resulted in a review summarizing methods for obtaining limits on heavy neutral leptons [Phys. Rev. D 29, 2539 (1984)]. Much of our joint work in subsequent years on B and D meson physics was stimulated by discussions and joint work we had done when meeting at the Center in the summers of 1988, 1990, 1993, 1995, 2001, 2003 and 2011.

I recall the summer of 1990 as a crucial point in the course of studying CP violation in B meson decays. That summer I met David London, who had been Rosner's PhD student in the mid ‘80s. We were interested in similar problems. Shortly before our meeting, independently we had written two papers [Phys. Lett. 223, 267 (1989) and Phys. Rev. Lett. 63, 1451 (1989)] stressing the role played by QCD penguin amplitudes in time-dependent neutral B meson CP asymmetries. We were seeking methods eliminating what we then called “penguin pollution." We found a beautiful method based on isospin symmetry which we applied immediately to B → ππ[Phys. Rev. Lett. 65, 3381 (1990)] and then to other processes. This seminal paper (so far accumulating 757 citations) provided the most precise method for determining the CP violating phase α.

Being highly excited by our findings, David and I decided to tackle at Aspen the difficult problem of extracting the weak phase ϒ from CP asymmetry measurements in B decays. We proposed a method based on the interference between b → u‾cs and b → c‾us amplitudes contributing to B → DK decays and related processes. Our paper, Phys. Lett. B 253, 483 (1991) (with 488 citations), followed shortly afterwards by Phys. Lett. B 265, 172 (1991) (with 676 citations), became the cornerstone for other variants providing together the most accurate method of determining ϒ in tree-dominated B decays.

I can only hope that these precise determinations of CP violating phases, combined with other CKM constraints, will eventually lead to deviations from the CKM framework, pointing a direction for physics beyond the Standard Model.

Guhathakurta, Raja

I have many fond memories from my various trips to Aspen – some to winter meetings and some to summer workshops/meetings (with generous amounts of skiing and hiking/biking thrown in of course). Two things, in particular, stick out in my mind as having special significance in my career.

The first of these is in–depth discussions with my collaborators/students on our Andromeda research project. I can think of a few specific ideas that were born out of these discussions and these have led to a series of papers and extensive and productive collaborations.

The second memory is of the winter “Physics Café.” Matthias Steinmetz and I spent an hour or so one evening fielding questions about dark matter from a group of adults. There was a second event the following summer, “Journey Back to the Big Bang,” in which Kathryn Johnston and I fielded questions from a large group of school children on the patio at the Aspen Center for Physics. This second event was filmed and subsequently shown on the local public television station. I'm very passionate about public speaking and give a lot of public lectures. These two events at Aspen really helped fuel this passion.

Congratulations on the ACP's 50th anniversary!

Harrison, Michael J.

ACP came to be an intellectual lifesaver for me since its inception! As a newly appointed assistant professor at Michigan State University in the early sixties my attempts to juggle teaching duties and research met with an acceptable measure of success only because of summer times at ACP, and the absence there of the distraction of teaching obligations and committee work. The stimulation and encouragement of others at ACP was also a very large factor. Soon after an early summer at ACP, my first graduate student and I produced a theoretical Physical Review Letter which was based on an idea conceived in Aspen, and subsequently verified in others' experiments.

Much later in my career, after I had served as dean of Lyman Briggs College at Michigan State University, a brief stay at ACP encouraged me to begin research in biological physics. I currently work on the theoretical physics of viruses and their replication in disease, but retired from teaching at age 75.

Hiller, Desmond John

I attended an Aspen workshop on “Taking Supernova Cosmology into the Next Decade” in August of 2010. This workshop was beneficial to my research in several ways. It allowed me to meet and interact with experts in the field – a field that was relatively new to me at that time. Discussions with other researchers in the field helped to clarify important concepts and issues. In addition, the talks and discussions revealed important research questions, and further emphasized the need for additional sophisticated modeling of Type Ia supernovae (SNe) to better understand their fundamental properties and the basic physics involved in the production of their spectra. Although my published SN research has concentrated on core–collapse SNe, a paper on modeling Type Ia SNe with my radiative transfer code, CMFGEN, is in preparation. I appreciated the relaxed atmosphere of the Aspen workshop – too many other conferences/workshops are packed with presentations, leaving little time for researchers to interact as they do in Aspen.

Holm, Darryl

1979 was the start of my work on geometry in continuum mechanics. I remember that Cecile Dewitt was very encouraging and that her appreciation of my project meant a lot to me.

Was 1984 the year when we were evacuated from our hotels in the middle of the night because of mudslides? I remember that Allan and Louise Kaufman took me in when my hotel was declared unsafe.

Holz, Daniel

I first visited Aspen as an undergraduate (I snuck in* “illegally,” but felt very welcome). It was a revelation, showing me that physics was incredibly fun and social: free–wheeling discussions over lunch, or during long afternoon hikes, or during dinners hosted by various participants which ran to all hours. By the end of my three weeks I was hooked, both on the Center and on physics. My subsequent visits have only reinforced my initial impressions. The ACP is a unique environment. My visits leave me stimulated and refreshed, and often represent my most productive and fertile periods. The fundamental flaw of the Center is that we're not allowed to just move in permanently.

*Editorial Note from ACP – don't try this!

Iida, Kei

In 1998, Setsuo Ichimaru and Katsuhiko Sato, my supervisors, kindly recommended me to apply to the ACP summer program just after I got D.Sc. in Tokyo with a thesis entitled “Phase transitions in high–density matter and neutron star evolution.” I was fortunate enough to participate in the program and talk with Gordon Baym about quark matter. After a while, Gordon kindly allowed me to stay in Urbana one year and half as a visiting postdoc. In Urbana, I worked with Gordon on color superconductivity, which turns out to be a turning point of my career.

Joglekar, Yogesh

I visited ACP for a graphene workshop in June 2008. I am interested in engaging young students in research, and that summer, as a young Assistant Professor, I was mentoring a freshman, Stephen Wolf. At the ACP, I spent about an hour each morning in the library, walking the trails behind the ACP, and thinking about theoretical problems that could be tackled by young students.

Today, the paper* with Mr. Wolf is a standard reference on memristors. My group routinely publishes Physical Review papers with only high–school and undergraduate co–authors (the youngest one being a 13–year–old), and NSF supports my graphene research and the outreach with a CAREER grant. The ACP provided a calm, serene environment, without the daily distractions, so that I could focus on what was really interesting to me.

* Y.N. Joglekar and S.J. Wolf, Eur. J. Phys. 30, 661 (2009). The support by the ACP is acknowledged in this paper.

Kayser, Boris

During the 29 years I was at the National Science Foundation (NSF), I was in charge of the NSF funding of the Aspen Center for Physics. Rather than recount some of my own experiences in Aspen, I would like to respond from that perspective. While at NSF, I often said that I felt the NSF grant to the ACP to be one of the very most valuable grants in the entire NSF Theoretical Physics Program. I think so still. Thanks to the vision of its founders, the insight and dedication of its leaders, and the skill and warmth of its staff, the ACP is extremely effective at promoting the exchange of ideas on which progress in physics depends. This Center also does a great deal to strengthen the sense of community and common purpose within physics. May its good work, and its wonderful impact, never end.

Kohn, Robert V.

My two weeks at the “Patterns on Thin Sheets” program in Aug/Sept 2010 were extremely stimulating and useful. I came hoping to make new contacts with the physics community in this area, and I was not disappointed. Discussions with Benjamin Davidovitch (Univ of Massachusetts, one of the workshop's organizers) were particularly productive, leading to continued interaction that has had a great deal of influence on my research. I liked ACP's laid–back style, which left plenty of time for one–on–one discussion. Also very welcome were the “show and tell” sessions organized by the workshop leadership, which helped me find the people whose interests were closest to mine.

Kolda, Christopher

I've always enjoyed my time at Aspen, but most especially the rhythm of the day, with a few talks, but lots of time for interaction and for quiet thinking. But those talks, few as they are, have played a vital role for me. On more than one occasion I've been asked to speak on a subject which was only peripherally related to what I had intended to work on while at Aspen. And on those occasions I've found the interactions before, during and after the talk helped to launch my research in completely new directions. I never come back from Aspen working on the same problems that I brought with me, an unexpected benefit that few other environments can provide.

Kravtsov, Andrey

I've been coming to the Aspen Center for Physics regularly over the last ten years and have always been awed by the amazing atmosphere of the place. The atmosphere is almost magical and is extremely conducive for creative work, generating new ideas, and starting new collaborations. I have witnessed several times when discussions during regular discussion sessions at the Center or during skiing on the lift, or during hikes have turned into papers. One of my most successful, and high-impact projects on the form of the Halo Occupation Distribution (Kravtsov et al. 2004) have been started and carried out largely during a three-week workshop at the ACP in the summer of 2003, where myself and several key collaborators were present and worked together. Many of my other projects have likewise benefited from participation in the Aspen conferences and workshops. The ACP is a priceless asset to the physics and astrophysics communities!
Kravtsov, A.V., Berlind, A., Wechsler, R. et al. 2004, The Astrophysical Journal, Volume 609, Issue 1, pp. 35-49

Langacker, Paul

I have participated many times in the ACP summer and winter programs, but the most memorable dates back to around 1995 (I am not sure of the exact year). During a summer workshop Gary Steigman and I started an improved calculation of the cosmological constraints on the fractionally charged particles predicted in many string compactifications. The final result (that such states are unlikely) was what everyone (including ourselves) would have guessed, but we uncovered some interesting subtleties and loopholes. The work took a bit longer than we anticipated: we finished the calculation in 2011, at least 16 years later! I am quite proud of the paper. Good science sometimes takes time to carry out.

Leggett, Tony

I've enjoyed the hospitality of the ACP a number of times, but the one I remember most vividly was my first stay, in the summer of 1965, where I did the bulk of my work on the collective oscillations of a superfluid Fermi liquid. I particularly remember the bilateral discussions (not aboutphysics, but very wide-ranging) that were organized with some of the top-rank business executives who were staying at the Aspen Institute for Humanistic Studies, and also the inspiring conversations with my colleagueswhich took place above 14,000 feet – I'm convinced all the best physics gets done there! My congratulations on the 50th anniversary, and best wishes for the future.

Lorenzana, José

I stayed at the ACP in the summer of 2011. The visit was very inspiring for my research. I enjoyed the high quality time for discussions and the family friendly atmosphere. I came back home with my bag full of new ideas to develop. I interacted, created and strengthened links with many colleagues which had a strong influence on my research. ACP provides an ideal environment which is difficult to find at home, not only because it is hard to find the same critical mass to work with but also because daily obligations leave little space for creative thinking which is the most important part of our work.

McCray, Richard

From 1970–1985, I attended workshops at ACP almost every summer, and I have many memories of wonderful times there. For example, take summer 1970, when I was a new Assistant Professor at Harvard College Observatory. I was hiking up to Buckskin Pass with my wife. We stopped for lunch about halfway up, and I saw Hans Bethe with a group of women. I went over and introduced myself, just to say hello. But that wasn't enough for Prof. Bethe. He asked me what kind of research I was doing, and when I told him, he quizzed me for almost an hour. I was so flattered that such a great physicist would be so interested in my work, but also a bit uncomfortable because our conversation was keeping my wife and Prof. Bethe's companions waiting. But nobody seemed to mind. It was a glorious day, one of many such days in Aspen that I will never forget.

Miller, Cole

The Aspen Center for Physics has always been my favorite spot for summer workshops. Its atmosphere of informality, combined with the diversity of attendees and the unmatched natural environment, has led to multiple advances in my own research. Last summer, for example, my month there led to work that will result in six papers, including one that was entirely conceived, written, and submitted while at Aspen (a new idea for the formation of early supermassive black holes). Even beyond this direct impact, the many friendships and collaborations I have established while hiking up the Ute Trail, Aspen Mountain, or other destinations have immeasurably enriched both my career and my personal interactions. The ACP is a unique place; may it have an equally successful next 50 years!

Moler, Kathryn

Aspen is a unique place to think and collaborate, as well as delve into ongoing work around the world. I'm both an experimentalist and a mom with kids at home, so I prefer to keep my travel to a minimum. Aspen attracts the top theory postdocs, and good conversations with a half–dozen of the top theory postdocs is worth traveling to many conferences in terms of understanding the landscape of current progress.

Murthy, Tejas G.

The Aspen Center was an incredible experience for me. I am a beginning academic–engineer making a very difficult foray into physics. This was an opportunity to interact with experimentalists and theoreticians in the area of granular mechanics. Unexpectedly, one afternoon over lunch, a discussion on problems in labs turned into an intensive mentoring session on how to put a lab together. I am starting to see how important this advice was to me, I have really cherished it! I will avail myself of every opportunity to go back to Aspen, to those warm afternoons in spectacular surroundings talking about physics, and everything else with wonderful people.