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Jean-Marc Schlenker
Works at University of Luxembourg
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Jean-Marc Schlenker

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Fascinating story.
 
Walter Pitts was used to being bullied. He’d been born into a tough family in Prohibition-era Detroit, where his father, a boiler-maker,…
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Jean-Marc Schlenker

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Open position: PhD candidate

We expect to have one open position for a PhD candidate starting on Sept 1, 2015 or possibly Oct 1, 2015.
This is a 3-year contract, with one additional year possible, for a total of 4 years.
The research work will be conducted in one of the following areas:
3-dimensional hyperbolic geometry, including open questions on the geometry of quasifuchsian or convex co-compact hyperbolic 3-manifolds,
3-dimensional anti-de Sitter (AdS) geometry and its relations to Teichmüller theory,
discrete or polyhedral geometry, including rigidity questions for non-convex polyhedra or hyperbolic manifolds with polyhedral boundary.

This is a relatively priviledged position, with several attractive features:
excellent working conditions in a young, active and dynamic department,
good support for travel to workshops, summer schools, etc,
low teaching load (45 to 60 hours/year)
a competitive salary.
For more informations contact me (by email): jean-marc.schlenker@uni.lu.
Open position: PhD candidate. We expect to have one open position for a PhD candidate starting on Sept 1, 2015 or possibly Oct 1, 2015. This is a 3-year contract, with one additional year possible, for a total of 4 years. The research work will be conducted in one of the following areas: ...
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Jean-Marc Schlenker

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"Prior to Edison [...], sleep had been divided into two distinct segments, separated by a period of night-waking that lasted between one and several hours. The pattern was called segmented sleep."
This night-waking is for many of us a good time to think.
People once woke up halfway through the night to think, write or make love. What have we lost by sleeping straight through?
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Jean-Marc Schlenker

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So, no big bang after all? Too bad...
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An interesting opinion piece on the evolution of British universities.
This meaningless pursuit of 'quality' is transforming academics into part-time administrators
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I didn't and my students did not like it, at first. Then they soared.
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An interesting point of view on a very big challenge: understanding the genome. Includes an analogy with translating languages.
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"Over their lifetimes, graduates with majors in [STEM] can expect to earn far more than high school graduates with no college attendance, with an earnings premium of $1.5 million over and above the $1.73 million that high school graduates with no college attendance can expect to earn. Business majors do slightly worse than STEM majors, with a lifetime earnings premium of $1.4 million. Social scientists stake out the middle ground, earning $1.05 million more than noncollege high school graduates over a lifetime. Arts and humanities majors can expect to earn about $700,000 more, on average, than high school graduates with no college attendance."
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Jean-Marc Schlenker

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Another false positive -- in physics.
"the BICEP2 measurements of B-mode polarization in the cosmic microwave background (CMB) was caused not by the presence of primordial gravitational waves, but by obscuring dust inside our own galaxy"
Physicists have announced that last year's much-publicized 'discovery' of gravitational waves embedded in the 'echo' of the Big Bang was a misstep.
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Why 2015 will be a key year for physics, in particular because experiments at the LHC should either prove or (almost) disprove Susy (super-symmetry). In non-technical terms, for non-experts.
IN MARCH, after a two-year shut down for an upgrade, the world’s biggest particle accelerator, the Large Hadron Collider (LHC), will reopen for business. The rest...
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+Alexis Naveros I agree but what to do with all the seemingly arbitrary constants that are built into our theories?
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Interesting news on the genetic aspects of autism spectrum disorders.
For years scientists searched fruitlessly for the causes of autism by looking for genes shared by families prone to the disorder. Now researchers taking a new approach have begun to unlock its secrets.
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Social media could well be making you unhappy... Quick, close this window!
A study of 50,000 people in Italy concludes that online social networks have a significant negative impact on individual welfare.
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and with great irony I'll share that
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24, the Monster, and quantum gravity

Think of a prime number other than 2 or 3. Multiply the number by itself and then subtract 1. The result is a multiple of 24. This observation might appear to be a curiosity, but it turns out to be the tip of an iceberg, with far-reaching connections to other areas of mathematics and physics.

This result works for more than just prime numbers. It works for any number that is relatively prime to 24. For example, 25 is relatively prime to 24, because the only positive number that is a factor of both of them is 1. (An easy way to check this is to notice that 25 is not a multiple of 2, or 3, or both.) Squaring 25 gives 625, and 624=(24x26)+1.

A mathematician might state this property of the number 24 as follows:
If m is relatively prime to 24, then m^2 is congruent to 1 modulo 24.
One might ask if any numbers other than 24 have this property. The answer is “yes”, but the only other numbers that exhibit this property are 12, 8, 6, 4, 3, 2 and 1; in other words, the factors of 24.

The mathematicians John H. Conway and Simon P. Norton used this property of 24 in their seminal 1979 paper entitled Monstrous Moonshine. In the paper, they refer to this property as “the defining property of 24”. The word “monstrous” in the title is a reference to the Monster group, which can be thought of as a collection of more than 8x10^53 symmetries; that is, 8 followed by 53 other digits. The word “moonshine” refers to the perceived craziness of the intricate relationship between the Monster group and the theory of modular functions.

The existence of the Monster group, M, was not proved until shortly after Conway and Norton wrote their paper. It turns out that the easiest way to think of M in terms of symmetries of a vector space over the complex numbers is to use a vector space of dimension 196883. This number is close to another number that is related to the Leech lattice. The Leech lattice can be thought of as a stunningly efficient way to pack unit spheres together in 24 dimensional space. In this arrangement, each sphere will touch 196560 others. The closeness of the numbers 196560 and 196883 is not a coincidence and can be explained using the theory of monstrous moonshine.

It is now known that lying behind monstrous moonshine is a certain conformal field theory having the Monster group as symmetries. In 2007, the physicist Edward Witten proposed a connection between monstrous moonshine and quantum gravity. Witten concluded that pure gravity with maximally negative cosmological constant is dual to the Monster conformal field theory. This theory predicts a value for the semiclassical entropy estimate for a given black hole mass, in the large mass limit. Witten's theory estimates the value of this quantity as the natural logarithm of 196883, which works out at about 12.19. As a comparison, the work of Jacob Bekenstein and Stephen Hawking gives an estimate of 4π, which is about 12.57.

Relevant links
Wikipedia on the Monster group: http://en.wikipedia.org/wiki/Monster_group
Wikipedia on the Leech lattice: http://en.wikipedia.org/wiki/Leech_lattice
Wikipedia on Monstrous Moonshine: http://en.wikipedia.org/wiki/Monstrous_moonshine
A 2004 survey paper about Monstrous Moonshine by Terry Gannon: http://arxiv.org/abs/math/0402345

#mathematics #physics #sciencesunday  
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Mathematics, mostly.
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  • University of Luxembourg
    prof, 2013 - present
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Mathematician, with interests in science, in education, and in how the research/higher education system works.
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Professor at the University of Luxembourg. My professional homepage is here.
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