Kochen-Specker Theorem explained

I previously explained Bell’s Theorem, which is a “no go” theorem of quantum mechanics. In brief, Bell’s Theorem proved in 1964 that any hidden variable interpretation of quantum mechanics must be nonlocal.

Of course, you may be thinking, maybe the world just is nonlocal, and that hidden information is being passed around faster than light. Unfortunately, there’s another major theorem which makes hidden variable theories even more unpalatable. In 1966-1967, the Kochen-Specker Theorem proved that any hidden variable interpretation must be contextual.

To understand the meaning of “contextual”, suppose we have a quantum cat, and the cat has many possible states. It could be awake or asleep. It could be happy or unhappy. Or the cat could be none of those things because it is dead. Now suppose there are two possible measurements, which answer the following questions:

(1) Is the cat awake, asleep, or dead?
(2) Is the cat happy, unhappy, or dead?

This is a quantum cat, so you can only choose one of the two measurements. However, even if you can’t make both measurements experimentally, you might reasonably expect that the outcomes of the two measurements are related to each other.  Specifically, if measurement (1) would find a dead cat, then so would measurement (2), and vice versa. This assumption is called non-contextuality. This cannot be true of hidden variable interpretations of quantum mechanics! Such theories must be contextual.

Figure 1: ambiguous catFig. 1: Cat of ambiguous state.  Credit: Visentico / Sento

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Made in Criticalland

This is a repost of an article I wrote in 2014.  Relevant to my recent review of the Sokal paper.  Note that the blog Scientia Salon is now defunct.

Massimo Pigliucci started a new blog Scientia Salon, which is already bearing fruits.  I enjoyed this essay by Alan Sokal (yes, that Sokal) about academic postmodernists and extreme social constructivists.  In the 80s and 90s there were many such academics claiming that science was entirely based on prejudices.  Interestingly, Sokal claims that they have now backed off from the most extreme views, particularly because they were upset at the way the Bush regime used postmodernism to justify its anti-science policies.

Sokal’s primary citation for this is “Why has critique run out of steam? From matters of fact to matters of concern” by sociologist of science Bruno Latour in 2004.  I thought it was worth a read. [Read more…]

Why isn’t homosexuality (or religion) a mental disorder?

In a comment discussion last month, we touched on the question of whether religion could ever be considered a mental disorder. This is a common idea among atheists, sometimes expressed as a joke, or sometimes claimed seriously. I am not mentally ill, so I would defer to other people to explain why it is wrong to compare religion and mental illness even as a joke. Here I will ignore the jokes and consider only the serious question: Why isn’t religion a mental disorder?

According to the DSM-5,

A mental disorder is a syndrome characterized by clinically significant disturbance in an individual’ s cognition, emotion regulation, or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning. Mental disorders are usually associated with significant distress or disability in social, occupational or other important activities. An expectable or culturally approved response to a common stressor or loss, such as the death of a loved one, is not a mental disorder. Socially deviant behavior (e.g., political, religious, or sexual) and conflicts that are primarily between the individual and society are not mental disorders unless the deviance or conflict results from a dysfunction in the individual, as described above. [emphasis mine]

There you go. Religious behavior isn’t a mental disorder because the DSM-5, an authoritative document, says so. However, you could be forgiven for not taking the DSM’s word for it. Let’s dig deeper.

Look at what else has been excluded from mental disorders: socially deviant sexual behavior. This exclusion arises from a famous controversy, which led to the declassification of homosexuality as a mental disorder in the DSM in 1973. And until 1987, homosexuality remained as a mental disorder (“Sexual Orientation Disturbance” and later “Ego-dystonic Homosexuality”) as long as the patient was distressed about their orientation. The architect of these decisions was psychiatrist Robert Spitzer. I believe that Spitzer himself offers the best insight into the definition of mental disorders.

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Paper: The Sokal Hoax

In 1996, physicist Alan Sokal was unhappy with the tendency in academic postmodernism to dismiss scientific work. So he submitted a bogus paper called “Transgressing the Boundaries: Towards a Transformative Hermeneutics of Quantum Gravity” to Social Text, a journal in cultural studies. After it was published, he revealed it as a hoax. And now, it is one of the best known shots fired at academic anti-science.

While the hoax is a good conversation-starter, I would caution against thinking it’s a total slam-dunk. Journals are there to filter out shoddy work, rather than bad faith actors. Secondly, AFAICT Social Text is a journal of mediocre impact. Finally, Sokal himself said that academic postmodernism has now backed off from many of its previous excesses. (Sokal credits the Bush administration, which was more effective at satirizing academic postmodernism than he ever was.)

In any case, this is a paper report. To humorous ends, I will review Sokal’s paper as if it were a serious work.
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Some PTSD statistics

This is a repost of an article I wrote in 2015.

I occasionally read social science papers, and I think it’s worth sharing what I find, even though in principle you could read about it yourself. This time I read about statistics on Post-traumatic stress disorder (PTSD) in the US, and my particular interest is in PTSD from sexual assault and rape.

A good basic overview of PTSD can be found from the US Department of Veteran’s Affairs:

Diagnostic criteria for PTSD include a history of exposure to a traumatic event that meets specific stipulations and symptoms from each of four symptom clusters: intrusion, avoidance, negative alterations in cognitions and mood, and alterations in arousal and reactivity.[1]

According to the National Comorbidity Survey (NCS), about 7.8% of people in the US have experienced PTSD in their lifetime. This is reinforced by the NCS-R (a replication of the original study) which found 6.8% prevalence. However, just because someone has suffered from PTSD doesn’t necessarily mean they’re still suffering; Only 3.5% have had PTSD in the past year.[2] Here’s a timeline of PTSD recovery:

A graph showing how long it takes for people to recover from PTSD. There are separate curves for people who get treatment and people who don't get treatment. The study extends for 10 years, with about a third never recovering.
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Paper: The Chaos within Sudoku

“The Chaos within Sudoku” is a paper about solving Sudoku puzzles with physics. They simulate an imaginary physical system, let it run, and when it stops the puzzle is solved. See the video below:

The thing about Sudoku is that Sudoku is hard. More specifically, when Sudoku is generalized to grids of arbitrary size, it’s NP-complete. What happens when you translate an NP-complete problem to a physical simulation? The authors find chaotic dynamics.  And in the process, they identify the hardest Sudoku puzzle…
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Paper: First observation of gravitational waves

This is a repost from February, when LIGO reported its first observation of gravitational waves.  This is relevant because last month LIGO reported its second observation, also resulting from inspiraling black holes.

Today, the Laser Interferometry Gravitational-Wave Observatory (LIGO) reported the first observation of gravitational waves. You can read about it in The New York Times (warning: autoplay), on Sean Carroll’s blog, or in comic form. I went straight to Physical Review Letters.

As an undergrad, I did some work on LIGO. Specifically, I was a data analyst looking for exactly the kinds of gravitational waves here observed. Anyway, I’m happy to play the role of your local expert, providing some context and answering any questions.

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