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Physics Forums Featured Threads

Gaia parallaxes might reduce tension for Hubble constant
In the last years a discrepancy between two methods to measure the Hubble constant appeared. Measurements based on redshift and the cosmic distance ladder produced results of about 73 km/(s*Mpc) while measurements based on the cosmic microwave background lead to results of about 68 km/(s*Mpc). While not completely outside the uncertainties the difference was still curious... 
Structure of Matter in Quantum Field Theory
This is a topic I've mentioned a few times before. Essentially the structure of matter in quantum gauge field theories is unclear to me. I have no clear question here, just some initial discussion points. So at the first level, it seems a particle based view of quantum field theory is difficult to maintain. In brief on the Hilbert Spaces of interacting field theories there is no welldefined number operator ##N##... 
Soyuz launch failure with crew on board (crew is fine)
A Soyuz flight that was supposed to launch two astronauts to the ISS had a booster failure (half an hour before this post). The Soyuz capsule separated from the rocket and landed, the crew is fine. Rescue teams got to them quickly. While they had to endure higher gforces than usual they seem to be in a good condition. 
Can anyone learn advanced math?
I often ask myself if anyone can learn math to an advanced level? I think that every healthy person can get very good at math. The only condition is that the person is interested in math. Of course, to get on the level of a FieldMedal winner you have to be blessed a little bit. But I think you can reach and understand a lot just by working out hard. What do you guys think? Can anyone learn math to a high level? 
Black holes squishing Earth
Scares of the CERN accelerator creating a black hole that swallows Earth are in the news once again. I know it is not possible for an accelerator to produce such a black hole in practice. But surely it's impossible even in principle. Surely, a particle accelerator creating a tiny black hole that could grow to swallow the Earth would violate the law of conservation of energy... 
Math Challenge  October 2018
Summer is coming and brings .... Oops, time for a change! Fall (Spring) is here and what's better than to solve some tricky problems on a long dark evening (with the power of returning vitality all around). 
LHCb Discovers Two New Particles
"The LHCb collaboration has found two neverbeforeseen particles, as well as hints of another new particle, in highenergy proton collisions at the Large Hadron Collider (LHC). Future studies of the properties of these new particles will shed light on the strong force that binds subatomic particles called quarks together."  LHC 
Has the Riemann hypothesis been proven?
I have heard through the grapevine that the Riemann hypothesis has been proven. What I read was this is a claim made by none other than Sir Atiyah himself and that he is planning to give a talk next week. So *if* the statement is true that it is a claim made by Atiyah, then it is of course an extremely serious and probably correct solution... 
Nobel Prize 2018 Announcements
The Nobel Prize winners of 2018 will be announced during the first week of October, starting with the Nobel Prize in Physiology or Medicine on Monday October 1. As most of us are biased towards physics: The physics prize will be announced Tuesday October 2 @ 11.45 (Stockholm time  CEST) at the earliest. 
Hardy's approach to quantum gravity and QM interpretation
Work in quantum foundations is partly considered important because of the hope that the way we think about QM may point to a road to quantum gravity. Lucien Hardy, who is wellknown in quantum foundations for his reformulation of QM in terms of five "reasonable" axioms, is one of the people who try to make this really tangible... 
The Rise of Incentivized Competitions for Humanity
The recent rise of incentivized competitions for humanity has prompted me to create this thread, to tell PFers what's out there and to share my meager experienced in "almost" entering one. The largest and arguably most influential one has been the XPRIZE organization which finds sponsors and puts out many competitions to solve some of our worst problems. Its a competitive game with many teams worldwide... 
Is a trip Alpha Centuri system feasible?
Can the journey be completed within the lifetime of a human adult? Assuming we have got around little problems like having an adequate form of propulsion, shielding from radiation, and avoiding deadly collisions with milligram sized dust particles. Let's say our engines can provide constant acceleration then deceleration at 1g. 
Does the Principle of Least Action Have a Physical Meaning?
I have found that some people say “yes, definitely”, and other days “no, definitely not”. Those who say “no” seem to regard PLA as merely a neat way of packaging the equations. Those who say “yes” seem to regard PLA as somehow fundamental. Is there a consensus among physicists that I am unaware of? If not, why not? What could the physical meaning of PLA even be? 
Swampland conjecture
The swampland conjecture is currently a very hot topic. Can someone explain, in simple terms, what exactly the swampland idea is? In particular, the conjecture states that the string landscape is surrounded by an even larger swampland of consistentlooking semiclassical effective field theories, which are actually inconsistent. What exactly does it mean that an effective theory is inconsistent? 
Intermediate Math Challenge  September 2018
Summer is coming and brings a new basic math challenge! Enjoy! For more advanced problems you can check our other basic level math challenge thread!
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