2020-07-01

Classical Phase Space Densities for One or a Few Particles

This is the first time in several years that I've done a post about physics that didn't have to do with my research. This came about from thinking about applying techniques in statistical physics to game theory; although I still have a lot more to learn about that and need to do more to flesh out those ideas, it occurred to me in the process that I never had such a good intuition for the phase space density in classical mechanics, and notes that I've found online focus almost exclusively on the phase space density of a large number of particles in an explicitly statistical treatment. I intend to use this post to shed light on why this may be the case, help build intuition for how things like the Liouville equation work for simple systems of one or a few particles, and reinforce the notion that there is no classical analogue to the phenomenon of a multi-particle entangled quantum state yielding a mixed single-particle state under a partial trace. Follow the jump to see more.

2020-06-23

Book Review: "The Social Contract" by Jean-Jacques Rousseau

Now that I have been able to properly enjoy the summer, having essentially finished my PhD work, I've recently read the book The Social Contract by Jean-Jacques Rousseau (translated from French to English by Willmoore Kendall); this was a book that I got from a friend who moved away a few years ago, but never got around to reading until now. This is one of the classic texts of political philosophy from the European Enlightenment era, and came before many of the seminal events of world history, including the American & French Revolutions and the European colonization & subsequent independence of much of Asia, Africa, Australia, and South America. The author provides his own refutations of many of the arguments for hereditary monarchy and instead forcefully argues for a legislature, separate from the executive, that is conducted as a direct democracy, even while acknowledging that different circumstances for different states may suggest different forms & sizes for the executive. The book includes many examples from ancient & medieval European history, and while much of the discussion of cultures outside of Europe seems antiquated or racist to modern eyes, I imagine it was typical of its time & place.

It was really interesting to see such broad imagination of democratic & republican societies before they came to be in Europe & North America. However, the book itself is not an easy read: it basically feels like a polemical political treatise written in the terse style of the textbooks by the physicists Landau & Lifshitz, in which every definition and proposition must be carefully parsed & understood individually and also as part of a broader whole. The arguments are built up slowly, so patience is required too; frequently, I found myself wondering how the author could fail to acknowledge certain seemingly-elementary rebuttals to his arguments, only to find such acknowledgments after several pages. Originally, I thought the translator's introduction about how to read the book were basically excuses meant to cover for bad writing, but as I read through more of the book, I came to appreciate it more.

There are a few comments that I have about the contents. The first is that it isn't clear to me how citizens, in the author's view, are supposed to resume the exercise of natural rights, which have been pooled into the sovereign & redistributed as civil rights, when the social contract is thought to be violated, especially as it also isn't clear to me how to distinguish a violation of the social contract from an individual's unhappiness with the general will going against that individual's private will. Related to this, it isn't clear to me how a citizen, acting to debate & make laws for the sovereign to further the general will, is supposed to act completely separately, as a sort of Jekyll/Hyde situation, from that person's thoughts as an individual, because the execution of laws furthering the general will may affect that individual and others perhaps not particularly naming those people but naming a certain group affiliation, and it becomes hard then to define the general will in that context. The second is that so many of the author's arguments regarding the formation of a new state seem to depend on their being a full vacuum of power beforehand, with only the barest acknowledgment that new societies & nations don't emerge from a vacuum; to be fair, many of the great upheavals that figure prominently in my imagination regarding this point came after the publication of this book, but enough had happened which the author mentioned that this sparing treatment of the issue seems odd. I also have some more minor comments, namely that I'm not sure if the author's specific claims about the intertwined nature of politics & religion in ancient societies would be validated by modern scholarship, and the author's claims about there being no "true" Christian soldiers seems to rely too much on a no-true-Scotsman fallacy.

I would certainly need to reread this book carefully to better appreciate it, and perhaps that could address at least some of my comments. In any case, I'd only recommend this book to people with a serious deeply-rooted interest in political philosophy, who can appreciate the book and the context of its time & place, as opposed to novices like myself.

2020-05-28

Reflection: My Graduate Experiences at Princeton University

Please note: there will be mentions of the current global public health crisis in this post. I have no background in medicine, public health, or closely-related fields. Please consult public health agencies and other governmental agencies for guidance regarding responses to this crisis, and please consult actual professionals as appropriate for individual problems in this context.

This post is the third in a series of three posts about the end of my time as a PhD student in Princeton University (in this post henceforth referred to simply as "the university" when there is no ambiguity). As a write this, I have successfully defended my PhD thesis! Furthermore, I will officially be graduating this coming weekend. This post follows the first, which was meant as a reflection of the events of this public health crisis that led to my premature physical departure from the university campus combined with a paean to the friends I made over the course of 6 years in the PhD program, and the second, which explained the experiences & thought processes that led to my decision to change careers from research in physics to transportation policy. This post is a broader reflection of my time and experiences at the university, with all of its ups and downs, and a message of gratitude toward the people in the university and elsewhere who meant so much to me during my time in the program; a lot of it is taken from the acknowledgments in my thesis, though for privacy reasons, I won't be giving explicit names. Additionally, there will undoubtedly be many comparisons over the course of this post to my undergraduate experiences at MIT, for which I wrote a post around the time of graduation 6 years ago. Follow the jump to see more.

2020-04-28

Reflection: Starting a Shift to a New Career in Transportation Policy

This post is the second in a series of three posts about the end of my time as a PhD student in Princeton University (in this post henceforth referred to simply as "the university"). As a write this, I am still technically a PhD student enrolled full-time in the university, working on topics in nanophotonics & fluctuational electromagnetics. Next fall (assuming the current public health crisis abates to an extent that it is safe for me to do so — please note that I am not a public health expert or epidemiologist, so I am not making predictions in this regard), however, I will start a postdoctoral research position in the University of California Davis analyzing transportation policy, with a particular eye toward the effects of such current & future policies on the mobility and resulting socioeconomic opportunities for those who have been marginalized by current transportation systems, including people who are poor or have disabilities (like myself). This is a fairly drastic, and arguably surprising, change of career; I have told many friends and relatives about this, but not all of them, so I'd like to use this space to explain my thought process over the years leading up to this decision. Follow the jump to see more.

2020-03-17

Reflection: A Week of Downward-Spiraling Public Health News Culminating in Unexpected Adjustments

Please note: this is about the current widespread disease outbreak that is dominating the news. I will not mention the name of this disease or other common words used to describe its spread, because for good reason, popular search engines are cracking down on articles and videos other than those from official public health agencies and related well-established organizations to stop the spread of misinformation. I have no background in epidemiology or public health. This post is merely my musings about the last week, and the implications for my near-future plans. Please consult public health agencies and other governmental agencies for guidance regarding responses to this crisis.

This post is the first in a series of three posts about the end of my time as a PhD student in Princeton University (in this post henceforth referred to simply as "the university"). As a write this, I am still technically a PhD student enrolled full-time in the university. The second and third posts will be somewhat more traditional reflections for the end of my time, but this first one has been precipitated by the current public health crisis. Follow the jump to see more; it is effectively a chronological history of the developments of this crisis from my very narrow perspective, and my own (in hindsight, arguably delusional) reactions to these developments.

2020-02-03

Book Review: "Michael Polanyi" by Mark T. Mitchell

I've recently read the book Michael Polanyi by Mark T. Mitchell. (As an aside, it may be worth noting that some listings of this book carry the subtitle The Art of Knowing, but the usage of this subtitle within the copy of the book I got was inconsistent.) The book gives a relatively brief summary of the life and times of the physical chemist-turned-economist/philosopher Michael Polanyi in the first chapter, and then goes into a little more detail about his philosophies on economics, politics, science, morality, knowledge, religion, and other things in the second through fourth chapters, concluding in the fifth chapter with a comparison of his philosophical views to those of his contemporaries along with a little discussion about the implications of Polanyi's views for the present day.

The book is fairly short, well-written, and engaging even for a layperson like myself. The overview of Polanyi's life is quite interesting, and as I am considering the next steps for my own career (more on that in a future post), I was particularly taken by the story of Polanyi's career change so late in life. The discussion of his philosophy avoids unexplained jargon and very heavy technical arguments, instead clearly laying things out in simple terms & examples, and I was surprised (mainly as I was previously unacquainted with Polanyi's work per se, even though I have already read works about some of the people who influenced him and whom he may have influenced) to see myself having come to similar conclusions as Polanyi even before reading this book. With respect to the latter point, though, I do have a few criticisms, which are attributable in parts to Polanyi or to the author of this book. For one, the appeals to common sense & simple examples lead to the situation where the defense of Polanyi's theory of tacit knowledge against charges of subjectivism or circularity (i.e. begging the question) isn't necessarily as tightly constructed or satisfying as possible; some of this comes from Polanyi's own quotes, while the remainder comes from the author (who seems to agree with and follow Polanyi's philosophy). For another, some of Polanyi's defenses of Christianity and critiques of evolutionary theory, with respect to their implications for constructing meaning out of human existence, aren't clear as to how broadly they should be applied in his more general framework, and it isn't clear whether this very opacity is in itself the fault of Polanyi versus the author of this book. Overall, I really enjoyed reading this book, and would recommend it to anyone looking for a nontechnical clear read about a sometimes-overlooked figure in Western philosophy of the 20th century. Follow the jump to read more detailed summaries per chapter and about my thoughts regarding the book as well as Polanyi's philosophy (warning: it may be quite roughly organized).

2020-01-13

Fifth, Sixth, and Seventh Papers

My fifth, sixth, and seventh papers have been published! These require subscriptions to read, so here are alternate links to older preprints for the fifth, sixth, and seventh papers, respectively (which have most of the same content, with some minor changes to explanations, citations, and figures relative to the published versions). As with my previous papers, in the interest of explaining these ideas in a way that is easy to understand, I am using the ten hundred most used words in English (except for the two lines that came before this one), as put together from the XKCD Simple Writer. I will use numbers sometimes without completely writing them out, use words for certain names of things without explaining further, and explain less used words when they come up. Keep reading to see what comes next. I'm putting these three papers together in a single post because they form a trilogy of sorts, all having to do with finding the biggest number for how much heat, through light, can go from one body to another when they are really close together, or can go from one body into outer space. These papers need a lot more math (note: "math" isn't one of the ten hundred words) than the papers before, and because they need a lot of thinking to get, I actually won't say as much about them.

The fifth paper is called "T Operator Bounds on Angle-Integrated Absorption and Thermal Radiation for Arbitrary Objects", and is in volume 123, issue 5 of Physical Review Letters. This is the one that has to do with how much heat, through light, can go from one body to outer space. People knew before that the number for how much heat really big bodies can put through light into outer space grows like the surface area of the body, but for really small bodies it grows like the space of the whole body (volume), and they were not sure how these two things join in between. This paper lets people figure out what the most heat is that can go from a body through light into outer space no matter what the largest shape the body can sit in, and shows how to join the things that people knew before for middle-size bodies of different shapes. (Another press release from my department can be found here.)

The sixth paper is called "Fundamental limits to radiative heat transfer: Theory", and is in volume 101, issue 3 of Physical Review B, while the seventh paper is called "Fundamental Limits to Radiative Heat Transfer: The Limited Role of Nanostructuring in the Near-Field", and is in volume 124, issue 1 of Physical Review Letters. Those two papers go together, so I'll write about them together. The sixth paper is about the math behind figuring out the biggest number for heat, through light, to go between two bodies. The seventh paper shows that heat, through light, going between two big flat bodies that are close together can be pretty close to the biggest number possible, so making the shapes of the bodies less simple than just flat surfaces is of no use.

2019-12-20

My Time at the STEPS+ 2019 Fall Symposium

Last week, I attended the STEPS+ 2019 Fall Symposium, hosted at UC Davis. (I'll have more details about the broader reasons for the trip in an upcoming post). It was a nice set of talks and open discussions about energy issues in transportation, as well as a good opportunity for professional networking. Much of the discussion was focused on California because its large geographic & demographic size, the fact that its own metropolitan areas have minimal spillover into other states and vice versa, and the clear separation of powers between the state and local governments means that it can effectively operate like an autonomous country in miniature (evidenced also by its own large population and economic output). That said, the diverse range of political interests, geographic features, and climates in the state make it to some extent a microcosm of what would need to happen at the national level too with respect to combating climate change, decarbonizing the economy, and making transportation generally more sustainable. Thus, although my interests tend more toward the direct relationship between transportation and issues of socioeconomic equity, there are strong indirect relationships through energy and climate issues too, so it was really interesting to learn about these, to learn more about communication between researchers and policymakers, and to see what models exist for working toward greater sustainability in transportation.

2019-11-05

Fourth Paper: "Impact of nuclear vibrations on van der Waals and Casimir interactions at zero and finite temperature"

My fourth paper has been published! It is in volume 5, issue 11 of Science Advances, which is an open-access journal, so anyone can read it. As with my previous papers, in the interest of explaining these ideas in a way that is easy to understand, I am using the ten hundred most used words in English (except for the two lines that came before this one), as put together from the XKCD Simple Writer. I will use numbers sometimes without completely writing them out, use words for certain names of things without explaining further, and explain less used words when they come up. Keep reading to see what comes next.

In papers that came before this one, I looked at how to do a better job of figuring out the van der Waals (vdW) forces, which are the forces that let geckos (small animals with hard skin over which your finger can slip easily) stick to anything no matter what it is made of, between molecules, which are the little things that make up most of the stuff we see and are in turn made of smaller things called atoms; I also looked at how to do a better job of figuring out how heat (through light) goes between different molecules, especially when they are near larger bodies, and that needed me to do a better job of considering how molecules can make changes on each other through light, and that means that I need to better consider how the full atoms within molecules move toward and away from each other in a way that repeats itself. In this paper, I used the new way from the paper that came before of considering how molecules can make changes on each other through light to show what happens with vdW forces between molecules and larger bodies, especially when they aren't as cold as possible but are as hot as a room you might go into each day. It turns out that for small or long thin molecules made of carbon atoms, our work can do a pretty good job of showing how being as hot as a room can make vdW forces look very different. For some kinds of large thin sheets of atoms, like boron nitride in which every other atom is boron or nitrogen, our work still does a pretty good job because the electrons, which are the parts of the atoms that are the smallest, lightest, and move around the most, are still pretty close to the centers of the atoms. On the other hand, for other kinds of large thin sheets of atoms, like graphene in which every atom is carbon, our work has some more problems, because electrons in graphene can move around a lot more than our work might make you think, and the ways in which those electrons change how the rest of the atoms move around when they are as hot as a room (instead of as cold as possible) makes vdW forces harder to figure out than our work can say. This means we still need to do more work to better figure out how vdW forces look for those kinds of sheets.

2019-10-14

Book Review: "Bad Blood" by John Carreyrou

I've recently read the book Bad Blood by John Carreyrou, who is an investigative journalist with the Wall Street Journal. It is essentially a reworking of a series of investigative articles he did with that newspaper about the company Theranos and its founder Elizabeth Holmes, showing how that company's promise of a revolution in medical diagnosis and treatment by replacing expensive medical testing equipment and the need for large blood draws with small devices that can do hundreds of tests using only a few drops of blood was based on fraud, through fabricating and falsifying test results submitted to investors & regulators and even when demonstrating their devices to investors in person. While it does give some background about the early life & motivations of Elizabeth Holmes as well as some of the other key players in Theranos, and though it does give at least a little background on everyone introduced by name, the story makes clear that lies and falsification of data were occurring even within the first couple of years of the company's existence, and shows how as more people got involved, it became clear just how much more deceit was occurring. In this sense, I expected there to be a sharper transition period from reasonable activity to fraud but was surprised to see such fraud taking place so early on and so consistently throughout the story, though there certainly was a transition from fraudulent behavior being limited to occasional circumstances mixed with typical Silicon Valley hyperbole to fraudulent behavior being the modus operandi of the company at a systemic level especially as the company neared its product rollout through corporate partnerships, to the point where Holmes and her second-in-command/boyfriend Ramesh Balwani had basically turned the company culture into a religious cult that tolerated no dissent or raising of ethical concerns.

The book is quite well-written for the most part. The introduction of each character in the story is clear & relatable, and the progression of events is fairly easy to follow, making for a compelling & engaging story. There are two minor criticisms that I have of the book, and in some sense they may not really be addressable given the way the events themselves unfolded. One is that the last 6 (out of 24) chapters, in which the author suddenly introduces his own role in the story after describing how one of the people involved calls the Wall Street Journal, felt a bit disjointed. In particular, the chapters before seemed to tell a cohesive story from the points of view of those directly involved in the story, whereas those final chapters had rougher transitions between the author's own conflicting attachment to the story and detachment from the various players' personal lives versus those players' own attachment to the scandal as they directly observed it; this could have been made smoother, though I think the suspense built by reading about the extremes to which Theranos went to harass & intimidate its former employees (without having direct proof of their involvement with journalistic activities) made up for this deficiency. The other is that perhaps just because of how early fraudulent activity played a role in the operations of Theranos, there wasn't much room to really meditate on how Holmes and the others who really believed in Theranos could willingly resort to fraud (apart from a short statement about this in the epilogue), so in that sense, I felt a little let down as I simply read a straightforward story about corporate fraud without being prompted to think about broader ethical & moral implications. Overall, I enjoyed reading this book, and would recommend it to anyone who wishes to read a nonfiction thriller about corporate fraud involving medical technology.