Re: Physics Discussion Thread
Posted: 02 Oct 2019 19:24
..yes.. i agree with you on that....but i would want college kids and researches to think on these out of carton box too...esp in desh...to challenge/question...
Consortium of Indian Defence Websites
https://forums.bharat-rakshak.com/
what i found interesting in the article wasQuantum physics has shown time and again that it contradicts our intuition, which is also true in this case. Under certain conditions, negative energies are allowed, at least in a certain range of space and time. An international research team at the TU Vienna, the Université libre de Bruxelles (Belgium) and the IIT Kanpur (India) have now investigated the extent to which negative energy is possible. It turns out that no matter which quantum theories are considered, no matter what symmetries are assumed to hold in the universe, there are always certain limits to "borrowing" energy. Locally, the energy can be less than zero, but like money borrowed from a bank, this energy must be "paid back" in the end.
Repulsive Gravity
"In the theory of General Relativity, we usually assume that the energy is greater than zero, at all times and everywhere in the universe," says Prof. Daniel Grumiller from the Institute for Theoretical Physics at the TU Wien (Vienna). This has a very important consequence for gravity: Energy is linked to mass via the formula E=mc². Negative energy would therefore also mean negative mass. Positive masses attract each other, but with a negative mass, gravity could suddenly become a repulsive force.
Quantum theory, however, allows negative energy. "According to quantum physics, it is possible to borrow energy from a vacuum at a certain location, like money from a bank," says Daniel Grumiller. "For a long time, we did not now about the maximum amount of this kind of energy credit and about possible interest rates that have to be paid. Various assumptions about this "interest" (known in the literature as "Quantum Interest") have been published, but no comprehensive result has been agreed upon.
The so-called "quantum null energy condition" (QNEC), which was proven in 2017, prescribes certain limits for the "borrowing" of energy by linking relativity theory and quantum physics: An energy smaller than zero is thus permitted, but only in a certain range and only for a certain time. How much energy can be borrowed from a vacuum before the energetic credit limit has been exhausted depends on a quantum physical quantity, the so-called entanglement entropy.
"In a certain sense, entanglement entropy is a measure of how strongly the behavior of a system is governed by quantum physics," says Daniel Grumiller. "If quantum entanglement plays a crucial role at some point in space, for example close to the edge of a black hole, then a negative energy flow can occur for a certain time, and negative energies become possible in that region."
Grumiller was now able to generalize these special calculations together with Max Riegler and Pulastya Parekh. Max Riegler completed his dissertation in the research group of Daniel Grumiller at the TU Wien and is now working as a postdoc in Harvard. Pulastya Parekh from the IIT in Kanpur (India) was a guest at the Erwin Schrödinger Institute and at the TU Wien.
"All previous considerations have always referred to quantum theories that follow the symmetries of Special Relativity. But we have now been able to show that this connection between negative energy and quantum entanglement is a much more general phenomenon," says Grumiller. The energy conditions that clearly prohibit the extraction of infinite amounts of energy from a vacuum are valid for very different quantum theories, regardless of symmetries.
The law of energy conservation cannot be outwitted
Of course, this has nothing to do with mystical "over unity machines" that allegedly generate energy out of nothing, as they are repeatedly presented in esoteric circles. "The fact that nature allows an energy smaller than zero for a certain period of time at a certain place does not mean that the law of conservation of energy is violated," stresses Daniel Grumiller. "In order to enable negative energy flows at a certain location, there must be compensating positive energy flows in the immediate vicinity."
Even if the matter is somewhat more complicated than previously thought, energy cannot be obtained from nothing, even though it can become negative. The new research results now place tight bounds on negative energy, thereby connecting it with quintessential properties of quantum mechanics.
Quantum physics is difficult and explaining it even more so. Associate Professor Holger F. Hofmann from Hiroshima University and Kartik Patekar from the Indian Institute of Technology Bombay have tried to solve one of the biggest puzzles in quantum physics: how to measure the quantum system without changing it?
Their new paper published this month has found that by reading the information observed from a quantum system away from the system itself researchers can determine its state, depending on the method of analysis. Although the analysis is completely removed from the quantum system, it is possible to restore the initial superposition of possible outcomes by a careful reading of the quantum data.
"Normally we would search for something by looking. But in this case looking changes the object, this is the problem with quantum mechanics. We can use complicated maths to describe it, but how can we be sure that the mathematics describes what is really there? When we measure something there is a trade-off and the other possibilities of what it could be are lost. You cannot find out about anything without an interaction, you pay a price in advance." explains Hofmann.
During Patekar's month-long stay at Hiroshima University when he was an undergraduate student, the two physicists tried to imagine ways of measuring the system without "paying the price" i.e. keeping the system's superposition or meaning that the system can exist in all states. In order to understand their results Hofmann describes their findings using the well-known physics story of Schrödinger's cat:
Schrödinger's cat is in a box and the scientists don't know whether it is dead or alive. A camera is set up looking into the box that takes a photo from a position outside of the box. The photo taken of the cat comes out blurry; we can see there is a cat but not whether it is dead or alive. The flash from the camera has also removed a "quantum tag" marking the superposition of the cat. This photo is now entangled with the fate of the cat—i.e. we can decide what happened to the cat by processing this photo in a certain way.
The photo could then be taken away from the box and processed on a computer or in a darkroom. Depending on what method is used to process the photo, we can find out either if the cat is alive or dead, or what the flash did to the cat, restoring the quantum tag. The choice of the reader determines what we know about the cat. We can find out if it's dead/alive or restore the quantum tag that was removed when the picture was taken, but not both.
This is only a step forward in our understanding of quantum mechanics. Today its full application remains confined to expert-level systems like quantum computers, although some of its aspects can also be used in precise measurements, and for secure communication using quantum cryptography.
"This is a key part of my research. I really wanted to understand why this quantum weirdness is there. I focused on measurements because that's where the weirdness comes from!" says Hofmann.
Yes. Last I heard was that their patent is in the public domain. (http://www.physics.iisc.ernet.in/~arind ... nt/]<link> As far as publication in reputable journal (by the IISc Scientists - none.. but their tweeter accounts have "More update soon" for a long time.tandav wrote:https://theprint.in/science/why-the-phy ... ry/116838/
Interest in the IISC breakthrough claims in Room Temp SuperConductivity seems to be have ebbed... Anyone closer to the IISC research team can update us further.
One quick point is that Van Allen Radiation belt radiation is well studied so that is not of a lot of interest for current missions beyond LEO.Highlights
•A new application simulated radiation through full-sized spacecraft.
•Application implemented new computational detectors including human phantom.
•Simulations of dose for ISS and Apollo 11 matched well experimental measurements.
• Greatest contributor to radiation dose for Apollo missions was from GCR.
•Simulations of Apollo 14 showed higher measured dose most likely due to SPE.
Abstract
A significant challenge to current and future manned and/or unmanned space missions is due to deep space radiation. An improvement in more realistic (more accurate) simulation models in predicting the effects of radiation within the spacecraft is required, especially to better predict dose to astronauts, energy deposition within sensitive electronics, and effectiveness of radiation shielding for long-term space missions. The International Space Station provides an invaluable resource for long-term measurements of the radiation environment in Low Earth Orbit (LEO); however, the only manned missions with dosimetry data available beyond LEO are the Apollo missions. Thus the physiological effects and dosimetry for deep space missions are not well understood in planning extended missions.
<snipping how they used HPC with MPI to do Montecarlo etc.>
Thanks for the article - Okay got curious.. where in BRF someone talked about this fluid dynamics aspect and found that there were posts about solar wind in CY2 thread.Vayutuvan wrote:Since there was some talk on Kelvin-Helmholtz Instability, this paper - as per the abstract - seems to be of interest...<snip>
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This is not surprising - actually what everyone thought all the time. (Most "radiation" from SPE will be stopped by hull of the space-craft). GCR has much higher energy than solar wind particles. (GeV vs KeV).Greatest contributor to radiation dose for Apollo missions was from GCR.
The very first prize in medicine was awarded to Emil von Behring in 1901 for the discovery of antitoxins, but not to his close collaborator Shibasaburo Kitasato.
Yes! Satyen Nath Bose was nominated 4 times for Nobel Prize - according to recently made public report. Boson (like photons etc) are named after him. Bosons follow "Bose-Einstein Statistics". The other kind of particles are Fermions (like electrons, protons, neutrons etc) which follow "Fermi-Dirac Statics".Vayutuvan wrote:Jagadish Chandra Bose in the center - polymath.p, inventor of radio before Marconi.
SN Bose - second row second from the left.
Meghnad Saha, left of Sh JC Bose!.. That's at least three Nobels in there - in the same frame. Testament to the fact that Nobel missed the most prominent Indians, continues to do so, and deliberately.Vayutuvan wrote:Jagadish Chandra Bose in the center - polymath, invented the radio before Marconi did.
SN Bose - second row second from the left.
The list is public only up to 1966. Saha, SN Bose, Raman, Bhaba's work was in 20's 30's 40's etc..Vayutuvan wrote:What about ECG Sudarshan? Was he ever nominated? Kapany?
The people are:Rishi_Tri wrote:Meghnad Saha, left of Sh JC Bose!.. That's at least three Nobels in there - in the same frame. Testament to the fact that Nobel missed the most prominent Indians, continues to do so, and deliberately.Vayutuvan wrote:Jagadish Chandra Bose in the center - polymath, invented the radio before Marconi did.
SN Bose - second row second from the left.
Anyway, what a photograph. Truly For the Ages.
you know ecg sudarshan personally, IIRC. also cv Raman's family. you said this before in brf.Amber G. wrote:The list is public only up to 1966. Saha, SN Bose, Raman, Bhaba's work was in 20's 30's 40's etc..Vayutuvan wrote:What about ECG Sudarshan? Was he ever nominated? Kapany?
(Not secret that Sudarshan's name was nominated quite a few times as the people who nominates can sometimes let it know)
Three scientists have been awarded the 2019 Nobel prize in physics for groundbreaking discoveries about the evolution of the Universe and the Earth’s place within it.
The Canadian scientist James Peebles has been awarded half of the 9m Swedish kronor (£740,000) prize for his theoretical discoveries about the evolution of the universe. A Swiss duo of astronomers, Michel Mayor and Didier Queloz, will share the other half of the prize for their discovery of the first planet beyond our solar system.
James Peebles was rewarded for laying a foundation for modern cosmology, including his realisation that the faint microwave radiation that filled the cosmos just 400,000 years after the Big Bang contains crucial clues to what the universe looked like at this primitive stage and how it has evolved over the subsequent 13bn years.
Mayor and Queloz have been recognised for their joint discovery in 1995 of the first exoplanet 50 light years away in the constellation of Pegasus. The planet, 51 Pegasi b, is a gaseous ball about 150 times more massive than the Earth and with a scorching surface temperature of 1000C.
The discovery heralded a new era of astronomy, with astronomers having since found more than 4,000 exoplanets, with an incredible range of sizes, forms and orbits. Learning about these strange and varied world’s beyond our solar system has transformed our understanding of how planets formed and given new focus to the question of whether there could be alien life is out there somewhere.
Peebles is also credited with developing the theoretical tools that allowed scientists to perform a cosmic inventory of what the universe is made from, showing that ordinary matter makes up just 5% of its known contents, with the rest being dark matter and dark energy.
https://www.theguardian.com/science/201 ... anets-2019
“We still must admit that the dark matter and dark energy are mysterious,” Peebles told the Royal Swedish Academy of Sciences on Tuesday. “There are still many open questions...What in the world is this dark matter?”
Looking back over his career spanning half a century, Peebles, who is Albert Einstein professor emeritus of science at Princeton University, said that he never set out with a grand plan. “I could think of one or two things to do in cosmology. I just did them and kept going,” he said. “The prizes and awards, they are charming, much appreciated, but that’s not part of your plans. You should enter science because you are fascinated by it.”
Prof Goran Hansson, secretary-general of the Royal Swedish Academy of Sciences that chooses the laureates, said the three had made “contributions to our understanding of the evolution of the universe, and Earth’s place in the cosmos.”
Prof Sir Martin Rees, the astronomer Royal, described Peebles as the world’s “most
influential and respected leader of empirical cosmology with a sustained
record of achievement spanning half a century”.
“The study of exoplanets is perhaps the most vibrant field of astronomy. We
now know that most stars are orbited by retinues of planets; there may be a
billion planets in our galaxy resembling the Earth (similar in size and at
a distance from their parent star where liquid water can exist),” Rees added. “This takes us a step towards the fascinating question of detecting evidence for life
on the nearest of these exoplanets.”
On Monday, Americans William Kaelin and Gregg Semenza and Britain’s Peter Ratcliffe won the Nobel prize for physiology or medicine for discovering details of how the body’s cells sense and react to low oxygen levels, providing a foothold for developing new treatments for anaemia, cancer and other diseases.
The Nobel prize for chemistry will be announced on Wednesday, two literature prizes will be awarded on Thursday, and the peace prize comes on Friday. This year will see two literature prizes handed out because the one last year was suspended after a scandal rocked the Swedish Academy.
So, not too bad a guess..This year’s #NobelPrize in Physics rewards new understanding of the universe’s structure and history, and the first discovery of a planet orbiting a solar-type star outside our solar system. The discoveries have forever changed our conceptions of the worldAmber G. wrote:Okay - The season is near.. here are predictions for 2019 Physics Nobel: (from those discussed in physics dhaga )
- Related to Blackhole - (viewtopic.php?p=2342065#p2342065 etc) This year or next year. For Nobel the cut-off data is February that post was in April. (But work was done for years by those scientists).
- Detecting Exoplanets - Lot of discussion in this dhaga.
- Structure of Neutron stars (Gravitational Waves)
- Superconductivity (new classes of super conductors containing Fe (Hideo Hosono) or Hydrogen (Mikhail Eremets ) - (Proven)
- Quantum Entanglement / Quantum computing / practical application. (People Aspect, Clauser ,Zeilinger) .. Theorist Bell has died so will not be eligible).
Meanwhile, happy to share that Prof Rajesh Gopakumar got Distinguished Alum award from IIT Kanpur this year.
Yes, this is still one of method used.ArjunPandit wrote:what i find interesting is the way first exoplanets were discovered by the wobbling of stars..very crudely said thats nothing but another application of newton's third law and the gravitational force..
For interested, there is lot of material out in libraries. (Check out their biographies).Prasad wrote:Tangential but have to ask. What did all these amazing people setup in their lifetimes to continue and expand study in their respective fields? CV Raman was involved with IISc afaik. Others?
Really! Apart from physics his contribution in mathematics (many well known papers in pure math) , chemistry, biology, mineralogy, philosophy, arts, literature, and music (he played esraj masterfully) are quite noteworthy. He was fluent in Bengali, English, French, German and Sanskrit a poet.ArjunPandit wrote:^^i was talking to an oxford grad in physics sometime back and he mentioned about SN bose and mentioned that he was beyond BEC his contribution was not much.
It is all measuring accuracy of the instrumentation dependent. Most of the research is in building measuring devices with the required accuracy. Lower the M_p/M_s ratio (masses of the planet and star) the smaller the wobble. Also there could be many planets of different masses orbiting the star (or rather center of mass of the multibody system). One has to solve an n-body problem (or rather an inverse problem).ArjunPandit wrote:what i find interesting is the way first exoplanets were discovered by the wobbling of stars..very crudely said thats nothing but another application of newton's third law and the gravitational force..
Vijayk g,vijayk wrote:http://blogs.discovermagazine.com/d-bri ... t-gravity/
The Case Against Dark Matter
What do BR experts think?