Very interesting stuff
Direct evidence of dark matter would be great. Not quite there yet of course.
Astro-physicists remain cautiously (around media) excited (among themselves) about an unexpected X-ray signal discovered in a survey of galactic clusters. Having first put their findings in the public sphere in March, as reported by The Register at the time, the work has now passed peer review to hit the presses in the …
It would be more than interesting, it would be a whole new branch of physics wherein we can find ways to detect things that don't interact with anything else using known forces other than, obviously, the gravity we've already detected because it completely overwhelms our measurements of the movements of galaxies and galactic structures.
But that raises a puzzle. The lines they're talking about are absorbtion pits in the electromagnetic spectrum of blackbody radiation coming from the hot object. If these things can only interact by gravity, then there should be only overall doppler shifting, not electromagnetic filtering with a Q high and tight enough to create an absorption line. So this explanation for the line is either incomplete or balls. I'll vote incomplete, because this is the Register, not an actual source of information.
The lines they're talking about are absorbtion pits in the electromagnetic spectrum of blackbody radiation coming from the hot object.
Not at all. They are emissions possibly due to photons generated by the decay of the sterile neutrino (which thus unsterilizes when increasing system entropy). What are you getting at?
Given the success of the standard model using just three columns for matter with each of the three know types of neutrino being in a separate column along with its associated lepton and two quarks, it makes me wonder if there now need to be a fourth column of sterile particles (two quarks, a lepton and the sterile neutrino)?
Assuming the particles in this 'sterile' column were all non-interacting except via gravity they could well be the missing dark matter. Poses two other questions which end of the standard model should it go (lower or higher mass/energy end) and will there be any additional bosons needed or does the lack of bosons make them sterile? I would go for the low energy end (more stable) and no bosons (haven't seen anything).
Discuss at leisure. (Paris because she has no idea either)
"They're also one of the reasons we believe in dark matter ..."
Noooooooooooooooooooooooooooooooooooooooooooooooooooooooo
They're an observed phenomena which can be explained, using current scientific theories and understanding, by the presence of "dark matter". We no more 'believe in dark matter' than we believe that a duck-billed platypus called Arnold will score the next goal for Brazil.
People believe in God, Yogic Flying, Homeopathic medicines and luck ...
<... What was that? Arnold *is* in the starting 11? ...>
ANOTHER family of particles? Dear god, our universe seems to be massively overengineered, if the goal was just to generate conciousness. Doesn't look so hot for Bostrom's simulation argument... who would craft a simulation so inefficient that it spent most of its time simulating non-interacting particles, when all you really need for life is an up and down quark and an electron?
I wonder at what point the AI's we'll soon be creating (and placing in their own simulated universes in order to receive sensory input, socially interact, and learn) will take a look around their world, and think "Oh shit.. it's too neat and efficient and perfect. I'm just a simulation aren't I..."
Poor things.
I've often wondered what would be the result if you created a truly massive Minecraft world, gave the agents within it a neural network and the ability to breed, communicate, move and see, and then just let it run for a while...
If you're going to simulate a universe, you're most likely going to simulate one that has the same laws as yours.
All those climate scientists running their models to see what global warming is going to do, they're trying to get their models right, aren't they? If they simplified stuff, like "no one lives in Antarctica, let's just drop that from the simulation because it complicates matters" then the results would be worthless. I assume the same is true for our universe simulating overlords (in this case they really would be overlords!)
Via Peter Woit, this gem,
“Physical Mathematics and the Future”
accompanying a lecture at String 2014, cites Dirac:
The steady progress of physics requires for its theoretical formulation a mathematics that gets continually more advanced ... What however was not expected by the scientific workers of the last century (i.e. the 19th) was the particular form that the line of advancement of the mathematics would take, namely, it was expected that the mathematics would get more and more complicated, but would rest on a permanent basis of axioms and definitions, while actually the modern physical developments have required a mathematics that continually shifts its foundations and gets more abstract ... It seems likely that this process of increasing abstraction will continue in the future ...
and Einstein:
Our experience up to date justifies us in feeling sure that in Nature is actualized the ideal of mathematical simplicity. It is my conviction that pure mathematical construction enables us to discover the concepts and the laws connecting them which give us the key to the understanding of the phenomena of Nature. Experience can of course guide us in our choice of serviceable mathematical concepts; it cannot possibly be the source from which they are derived; experience of course remains the sole criterion of the serviceability of a mathematical construction for physics, but the truly creative principle resides in mathematics. In a certain sense, therefore, I hold it to be true that pure thought is competent to comprehend the real, as the ancients dreamed.
More from this paper (file under "WTF am I reading?")...
We can divide physicists into two types: Those who believe the world is special and inevitable, and those who believe it is random and accidental.
Steven Weinberg’s correct prediction of the cosmological constant certainly gives the latter camp a strong upper hand. If that latter camp is right it would seem that winning the next Nobel Prize in high energy theoretical physics is equivalent to winning the Lottery. It might well be this is just the way things are. On the other hand, it must be said that much of Physical Mathematics has a predilection for special, sporadic, and exceptional structures. Superconformal field theories and supergravity theories are closely related to magical properties of low-dimensional Clifford algebras, leading to startling connections with platonic solids, triality symmetries, division algebras (including the octonions), exceptional groups, Freudenthal-Tits magic squares, and so on. Moreover, certain conformal field theories have famously been closely related to the sporadic finite simple groups, especially the monster group.
Even if we live in a random world, it cannot be denied that it contains within it some exceptional gems of rare beauty which can only inspire a sense of awe. One could write an extensive essay on the numerous “coincidences” and “accidents” associated with exceptional structures appearing in Physical Mathematics which call for deeper understanding. I cannot forecast what stormy weather our field is destined to endure, but I can confidently forecast abundant moonshine in the years ahead.
Among the most notable recent examples of such structures is the Mathieu Moonshine phenomenon associated with K3 sigma models and mock modular forms. Four years after its discovery it remains largely mysterious, despite very intense efforts of first-rate scientists to find a natural explanation. Indeed, the mystery has only deepened with the extension to umbral moonshine. The state of the art is summarized in [SCGP workshop on Mock Modular Forms, Moonshine, and String Theory]. Here is a fairly concrete question in this general area:
"Is there an algebraic structure on the BPS states (spacetime or worldsheet) of string theory compactifications involving K3 surfaces whose automorphism group is naturally related to (the Mathieu Group) M_24?"
In the heady days after the invention of the heterotic string many of the exceptional “accidents” were adduced as evidence of deeper structure. Some of these “accidents”, such that the relation of surface singularities to Lie groups and the Kodaira classification of elliptic fibrations have been incorporated beautifully into enhanced gauge symmetries in string theory and F-theory compactification. But other “accidents” remain unexplained and unutilized. My favorite question in this class would be:
"Is there a physical interpretation of the fact that the group of 11-dimensional exotic spheres, {Z}_992, is cyclic with order four times the dimension of E8?"
Finally, we might ask whether there are applications of various Moonshine phenomena to laboratory experiments. There are claims that neutron scattering from cobalt niobate detects the first two Perron-Frobenius eigenvalues of the Cartan matrix of E8. If E8 appears, can the Monster be far behind?