Cosmological Koans
By ANTHONY AGUIRRE • Jul. 11, 2019 @ 17:02 GMT

A couple of months ago my book Cosmological Koans was released. Since I started this book before Max and I started FQXi in 2006, FQXI and the foundational questions community has obviously played a huge role in my thinking and what in the book. So I thought it would be nice to blog about it here and create some conversation. If you’ve not read it, I (surprise!) strongly recommend it. Limited spoilers to follow ;-)

I would say there are three overall aims of the book:

- Convey a lot of solid physics in a way that is (a) somewhat unusual in approach, (b) “real” in the sense of being conceptually solid such that with effort even someone with pretty limited background can get a real understanding of many core issues, (c) in a way that is tied to vivid stories rather than just text, so as perhaps to make things more immediate and memorable, and (d) in a way that highlights personal experience and at some level philosophical foundations rather than straight-up conventional physics concepts.

- Attempt to convey some of the sense of mystery, wonder, confusion and clarity that studying foundational physics contains. Despite a huge amount physics now describes very well, I wanted to get across in a visceral way that there are still deep and perplexing mysteries.

- Assemble something resembling a world-view that is rigorous in its physics, and in which observers play a key role, by highlighting how — to varying degrees — our description of the universe is a co-creation of the universe and the minds describing it.

Along the way, there are a number of science (and other) arguments to be made, including:

- My take on free will, which is that first one should clearly define what it would actually mean to have it (or not), then decide if that is a property of the relevant systems. I, for example, take free will to be the absence of a sense of coercion, an inability, even in principle, to perfectly predict one’s decisions/actions, decisions being made for reasons that the decider endorses, and the decisions being unknown without (the decider or another agent) going through the deciding process. I think humans have all of these properties (though that’s a long discussion, and not something I’d say I can prove.). Note that this definition does not require any sort of a-corporeal decision-making stuff outside the realm of physics (which there almost certainly is not), nor does it preclude there being influences on our decisions of which we are not consciously aware (which there almost certainly are.)

- Relatedly, my take on determinism. It drives my nuts when people say that the physics governing macroscopic systems (including humans) is deterministic. It’s just not. Schrödinger’s equation is deterministic, but it maps one current macroscopic configuration to many different future macroscopic configurations — like any other statistical theory (which may or may not be time-reversible). Whether you consider all of those distinct macro-outcomes to be equally real or only one to be real, the fact is that many of them exist in the evolved state. (And as for the argument that human brains are based on neurons that are essentially classical objects, that’s just not right thinking either — signaling is clearly affected by thermal noise, which is ultimately quantum in nature, so I think it’s very clear that one current brain state (or density matrix) corresponds to many distinct future ones, though we don’t know what the timescale for that divergence is.)

- My take on entropy and information. I and collaborators have spent a lot of time sorting out what I (now) think is the right way to think about Boltzmann vs. Gibbs entropy, in classical and quantum systems, in and out of equilibrium. Using the same word “entropy” for tho rather distinct concepts, as well as often using it interchangeably with “information” makes a lot of literature on the topic really confusing. But it need not be! I’ll write a separate blog about this but for those interested check out this paper, which spells things out fairly clearly (on the entropy side).

- An argument that sorting things into those that are “objective” and “not objective” is too simple and is misleading — it’s a sliding scale. There’s essentially nothing, I’d argue, that is totally objective. Even the mathematics we use is based on a set of axioms that we have selected out of many possibilities, and in which we have selected a tiny subset of all possible consequences of these axioms as “mathematics” (even though all are “true”). This selection corresponds to the creation of mathematical information. And admitting that things are not totally objective is OK — liberating even!

- An anti-reductionist thread pointing out that when we talk about one description being more “fundamental” than another (and don’t get me wrong, I’m a big fan of those descriptions!), it’s pretty hard to put a finger on exactly what we mean. And relatedly there’s almost always a whole lot of stuff (coarse-grainings, boundary conditions, assumptions about the state, indexical information, etc.) that must be added to a “fundamental” description, which undermine any idea that everything is in principle derivable just from the Hamiltonian. It’s just not.

And lots more! I had a great time writing and thinking it all through; for those who read it I hope you enjoy it and get provoked in various ways; and to everyone in the FQXi community thanks again for the support and inspiration!


Black Hole Photographed for the First Time: EHT Announcement
By ZEEYA MERALI • Apr. 9, 2019 @ 19:33 GMT

Updated:

Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity. Credit: Event Horizon Telescope Collaboration

Official press announcement.

On 10 April, astronomers revealed the first ever image of a black hole event horizon -- the surface beyond which light cannot escape from the hole's grasp -- taken by the Event Horizon Telescope (actually a network of telescopes around the world).

You can watch the English language press conference from Brussels live:




Information as Fuel — A New FQXi Research Program
By ANTHONY AGUIRRE • Feb. 13, 2019 @ 19:03 GMT

We're proud to announce one of our latest ventures: a research program investigating the theme of "Information as Fuel." We intend to award up to US$8million in this program, which has been sponsored by the Templeton World Charity Foundation. We are currently accepting initial applications for experimental projects on the topic, until March 31, 2019.

What do we mean by "information as fuel"? Since at least the nineteenth century, when people sought to understand how steam engines work and what limits their efficiency, it has been known that there is an intimate link between information and thermodynamics. Analysis of the physical limits of information acquisition and erasure has established a fundamental connection between information and the second law of thermodynamics. Inverting this relationship leads to the intriguing possibility that (ordered) information may serve as a resource—in effect, a type of fuel.

Expressed in the starkest terms, cutting-edge theoretical work implies that one could run an engine using information either as the fuel or as the way to dump entropy to satisfy the second law. Other conjectures have been accompanied by thought experiments that try to elucidate the implications of newly developed concepts. But while significant theoretical progress is being made, experimental study of the non-equilibrium thermodynamics of information generally has tended to trail some distance behind.

Fortunately, advances in experimental techniques are putting practical experiments with such systems within reach. Quantum information can be created and manipulated in a variety of implementations, ranging from trapped ions to solid state superconducting circuits to spin states of electrons. There is thus rich scope for applying concepts of quantum thermodynamics to quantum systems out of equilibrium.

With this in mind, FQXi has chosen to focus entirely on experiments in the Information as Fuel grant round. We intend to fund 4-8 research groups globally with three-year grants ranging from $500,000 to $2,500,000 per research group. Each group will design, perform, and report on one or more experiments, in which the group will incorporate a significant theoretical effort as part of the experiment’s motivation, design, and interpretation.

Both our large-grant and mini-grant programs are designed to particularly encourage new collaborations between experimentalists and theoreticians. The Information as Fuel theme will also be featured at a future FQXi international conference, and through essay contests. FQXi has always been committed to fostering a vibrant research community, and we envision that the Information as Fuel program will continue in this tradition.


Our Quantum Reality: A Physics-Art Project
By PAUL KNOTT • Feb. 4, 2019 @ 16:14 GMT

Paul Knott & Joseph Namara Hollis

In my day job, I am a quantum physicist, but I also recently completed a collaborative art-physics project, with award-winning artist Joseph Namara Hollis, to produce a short, illustrated book about the quantum mechanical reality in which we live.

From the start, this was an ambitious project. Our aim was to introduce quite challenging philosophical concepts deeply embedded in quantum mechanics. Our target audience was broad: we hoped that anyone from school science students to academic quantum physicists would both learn something, and be entertained, by the book. And finally, the book is short – only six double page spreads – and contains minimal text, with the intention that the illustrations play a central part in conveying the concepts we introduce. So, have we succeeded? You can find out by reading the book online here.

The seed of this project began when I undertook a short Postdoc, as part of FQXi’s physics of the observer program, at the University of Nottingham, with supervisors Prof Gerardo Adesso, Dr Tommaso Tufarelli, and Dr Marco Piani. The general question I was to dive into was: why does our everyday world look the way it does, despite being made of bizarre quantum mechanical particles? Quantum entities, such as electrons, atoms, and photons, perpetually exist in bizarre states: they can be in two places at the same time, be travelling in multiple directions simultaneously, and can even teleport. But if everyday objects – such as chairs, tables and cats – are made of such things, then why do they look so normal?

The more specific question we hoped to answer related to the concept of objectivity. If two people look at the same object then they invariably agree on the details, such as the size, shape, and orientation, of the object. These properties are said to be objective. But, due to the bizarre quantum world discussed above, it is not clear at first sight why objects that are made of quantum mechanical particles should look objective. To cut a long story short, our work during this project, together with previous quantum physicists’ results, demonstrated that the mathematical structure of quantum mechanics itself implies that everyday objects should indeed have objective properties. As part of this project we collaborated with the same artist, Joseph Namara Hollis, to produce an illustration related to our work, which we were honoured to be selected for the front cover of Physical Review Letters.

But despite the success of this work, I wasn’t quite satisfied with the philosophical backdrop to our findings. Our results were mainly concerned with why we observe the world to be objective. But using the quantum mechanical formalism we can go beyond our mere observations, and ask questions about the whole of reality – the observed and the unobserved – in which we live. And when I plunged into such questions, I emerged with a strong view that the equations of quantum mechanics are really telling us that our universe is only one in an unimaginably large number of parallel universes! This is certainly not the only conclusion that can be drawn from the equations of quantum mechanics, but for reasons that I explain here, I personally find this the most convincing and compelling.

This brings us to the main motivation of creating the FQXi-sponsored illustrated book that this blog pertains to. When we use both philosophy and physics to dive into the question of what quantum physics really tells us about reality, it turns out that there are many possible answers (of which quantum parallel-universes is just one). Other answers include that quantum mechanics must be incorrect or incomplete, and a revised theory is necessary in order to make sense of reality; or that quantum mechanics is really telling us about our knowledge of the world, rather than directly relating to the objects in our surroundings themselves. But when scouring through the literature to try to understand this, I found that the introductions and explanations to the different theories were dense and complicated, and it seemed impossibly hard to form a simple, overarching picture of what quantum mechanics tells us about reality.

This, then, is the purpose of the book: to create a (relatively) straightforward overview of the various theories that quantum physicists use to explain reality; and to introduce the philosophical conundrum at the heart of quantum mechanics that requires such an array of theories to be introduced. And to do all this is an entertaining and intuitive way by using the beautiful and fantastical illustrations of Joseph Namara Hollis.

We invite you to take a look at the book, which is freely available, and let us know what you think!

—

Paul Knott is a quantum physicist at Nottingham University.


YouTube Video Lectures: Thinking about Quantum Gravity
By TEJINDER PAL SINGH • Jan. 21, 2019 @ 18:09 GMT

There is likely a deep connection between the study of quantum foundations on the one hand, and the much sought after quantum theory of gravity on the other. Despite the enormous success of quantum theory, there are issues in our understanding of the theory, which need addressing. These include: the nature of the quantum to classical transition, the peculiar nature of quantum non-locality, the problem of time in quantum theory, the extreme dependence of the theory on its own classical limit, and the physical meaning of the wave function. Could it be that addressing these issues requires us to reformulate / modify quantum theory, in such a way that we get rid of the theory's dependence on its own limit, and on classical space-time? If that is the case, then introducing non-classical space-time in quantum theory naturally leads us to a falsifiable quantum theory of gravity. This is the viewpoint developed in the ongoing video lecture series `Thinking about Quantum Gravity'. The lectures are addressed to those undergraduate and graduate students in physics who would like to research in quantum gravity. It is not expected that the viewer will agree with everything that is said in these lectures. Rather, it is hoped that you will find something to think about, as you develop your own thinking towards quantum gravity.



The first video is available on YouTube and every video gives the link to the next one. Your comments and criticisms will be greatly appreciated. Thank you.

--

Tejinder P. Singh

Tata Institute of Fundamental Research, Mumbai

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