Modern and Theoretical Physics

I know there are modems that can support up to 2 external antennas, but I was wondering if I use a combiner essentially having 2 antennas each port, which is 4. Does this have any up or down sides? Can I simply scale it to as much combining as I want? also, i dunno what branch of science this is so I just put it in physics...

More fusion reactions exist, yes. But D-T is the only accessible to tokamaks presently. It's far less difficult than any other one because only one proton in D repels one proton in T. D-D reacts too but produces little heat as it releases the less stable 3He or T, and the reaction rate is 100 times less than D-T. Other fuels like Li or 3He are hugely more difficult. They work in hydrogen bombs, in some inertial confinement setups, but as a means of controlled net energy production they are out of reach. ========== After ITER got >10 years late because of Covid-19, some sort of assembly was celebrated recently (2020, who cares about the month meanwhile). …

Hi all, Consider the Bargmann-Wigner equation, which is the relativistic wave equation for particles of arbitrary spin (i.e. valid for both bosons and fermions). This is a set of coupled differential equations for the components of the wave function, which is an object the type of which is in turn a representation of the Lorentz group. So for example, this would be a bispinor for the Dirac field, or a Rarita-Schwinger spinor for spin-3/2 particles, and so on. This equation can be generalised to curved spacetime backgrounds. I’ve struggled for a long time with the attempt to come up with some kind of geometric interpretation for this equation (or even just for th…

Hi guys, this is my very first message at this forum. i have a dental x ray head machine, to use in my experiments. I would like to perform fluoroscopy and developping x ray films to study x ray diffraction of my minerals, according to the Laue methode. im engaged in build a effective lead shielding, wich is compound of 4mm sheets directly on the head. I would like to know if it is enough for a effective shieldeing. I have made many researchs eand calculations but i would like to get your opinions. Thanks a lot.

How is it isolated for nuclear fusion?

I can’t post more than one page. Bad forums. Contact for al 26 pages.

There is an unusual term called "QCD axion dark matter". Do you have any idea what "QCD axion dark matter" is? Here are among others the most recent documents on this subject: https://arxiv.org/abs/1910.04163 QCD Axion Dark Matter from a Late Time Phase Transition https://arxiv.org/abs/1905.04686 A Unique Multi-Messenger Signal of QCD Axion Dark Matter https://arxiv.org/abs/1901.07401 A new experimental approach to probe QCD axion dark matter in the mass range above 40μμeV https://arxiv.org/abs/1711.10486 QCD Axion Dark Matter with a Small Decay Constant

If the Universe started approximately 13.75 billion years ago as theorized by the 'Big Bang' and TIME itself only came into existence at the moment of the Big Bang, then surely this must be 'Universal Time'. Yet Einstein and special relativity shows us that TIME is relative. There is no such thing as universal TIME. This has been experimentally proven. So then how could TIME only have come into existence with the Big Bang, as accepted by many supporters of the Big Bang. If TIME only came into existence with the Big Bang then that time would be universal. The universe would be 13.75 billion years old for us. And if there are aliens living in another galaxy…

Deuteron is p-n, so naively should have zero electric quadrupole moment. However, experimentally it turns out quite large: 0.2859 e⋅fm2 from https://en.wikipedia.org/wiki/Deuterium#Magnetic_and_electric_multipoles This Wikipedia article explains it by adding l=2 angular momentum states - should we imagine it as a hidden dynamics? Maybe as oscillations between 'pn' and 'np' by some pi+ exchange? (but shouldn't it make it a linear antenna producing EM waves?) To describe e.g. deuteron-proton scatterings they neglect quark structure, but require three-body force ( https://en.wikipedia.org/wiki/Three-body_force) - would including quarks into considerations allo…

If the anti-matter theoretically created during the "big bang" exists, would the neutrino "field" created by stars in the universe be capable of preventing matter and anti-matter from merging?

As seen in the attached image, the paper "Supersymmetric Nonlinear Sigma Models, (June 4, 2000)", on page 9 describes a manifold/projective space in terms of gauge group relations, including SU(n) , U(n) etc. How can one represent a \[C ^\infty (M) \] sheaf/supermanifold from supersymmetry (See Wikipedia/Supermanifold), as relations of simpler gauge groups? The gauge groups are such an elegant way to understand physics, and this could help me to better understand physics.The world reasonably needs more physicists, and maybe less soccer players.

Why is it apparent that small things determine how big things work and not vice versa? Why is cause and effect noncommutative with respect to "size". In the sense that CAUSE is due to some physical laws: Quantum fluctuations CAUSE real and virtual particles. Real particles cause leptons, quarks, bosons. Leptons and quarks cause protons, neutrons and electrons. Protons neutrons electrons cause hydrogen helium and carbon atoms. Hydrogen, iron and oxygen cause stars, planets, and water. Stars, planets and water cause galaxies, solar systems, and oceans. Galaxies do not cause stars. Stars do not cause hydrogen. Hydrogen does not cause protons. Prot…

That is how compactification is understood in mathematics. It is a topological concept. Unfortunately it has little to do with the use of the same term in physics, where it is an analytical concept, that is, it talks about sizes. E.g. the default compactification of \(\mathbb{R}^4\) is gotten by adding a single new element, which is usually written with the \(\infty\) symbol. In the context of the thread, this is not apparently what is meant.

I am not a scientist. I'm a drop out ... but a creative , musician and thinker. Recently I have been thinking of the damage caused to the planet since the start of the industrial revolution and have been pondering on why in this day and age governments have not put a stop to it. Parallel to this I have always been interested by the thought of space, and in particular the mars rovers and the possibility of man one day being able to "venture where no man has before". These coinciding thoughts have previosly never gelled until I started looking into Mars atmosphere and rad (radiation) levels. We of course cannot survive in the conditions of another planet in our …

Hi everyone, Reading other threads in this forum, like https://www.scienceforums.net/topic/120772-please-tell-me-we-have-free-will/, it seems to be well-accepted that our universe is almost completely (except for quantum uncertainty) deterministic. My question is, what determined the inital state of the universe? I mean, where did all the initial information come from? Thank you for reading.

What is the wave function of an electron in a Hydrogen atom?

how would neutrinos interact with an encounter with a black hole? Are they capable of a closer orbit to the event horizon without falling in due to the negligible mass, or would that matter? thanks

Here is a study that looked at 1498 cases and 3530 controls in a case control study. Is this reliable? Should I be worried? Study: https://www.ncbi.nlm.nih.gov/pubmed/25466607/

Just wondered... If a train is moving alogn at 70mph, and you throw a ball off the back at 70mph...does the ball effectivly 'stop'? Dan

There are 2 points here: 1. If Relativity is used to describe the BB, how does it come that the result of the BBT is an absolute number (~13BY ago) and not a relative number (~13BY before us). The difference is subtle. The 2nd concept means that any observer, wherever he is, whenever he lives, will measure the time to the BB as~13 BY. It is NOT what is supposed to be. It is supposed that an ancient observer would have measured say 11BY, and another in the future will measured say 20 BY ago. Both of them using the same theory (Relativity) but applied to different measurements (because the Universe is changing over time). The 2nd concept above could only be feasible …

We are at wonderous times right now (yeah right, every generation before us said the same thing), we’ve managed to advance in physics and math tools an incredible amount since we’ve come into existence 160K years ago (or 2mln depending how we look at it) We’ve reached energies at LHC probing distances a million times smaller than the atomic nucleous, we’ve managed to build machines that land on other moons & planets thanks to physics, material and software advancements and various other branches of science. We can clone organisms, develop software that wins at „Go” with humans and we’ve managed to achieve thousands of other awesome things in science. Yet we have no id…

Can somebody share an a articles or something related with this topic. I want to understand well the main problem (the root and the details) and why it is so difficult. I've come across many videos and news that give you some kind of metaphorical picture (made for the public), which in some cases is quite misleading. I don't need the approaches (string theory, loop quantum gravity), i need just the problem! Thank you for your time!

I read somewhere that they do and I turn cause oxidative stress leading to cancer. Could this be possible? And if so how if the only effect of NIR is a minimal heating one? (I’m talking about non-ionising radiation at the frequency of cell phones)

I’m a bit concerned about phone radiation. I read a paper saying this: Is there any truth behind this? Here’s the link: https://www.ncbi.nlm.nih.gov/m/pubmed/27903411/

Hello and thank you for reading my first post on this forum. I'm not part of any research departments or colleges etc, I'm just reading books of interest but seem to generate more questions than answers. I'm currently reading about the atom and its components. What I think I have learned to date is this; The atom is made up of protons, neutrons in a nucleus with orbiting electrons in shells or rings. My interest at the moment is about the nucleus and valence ring in regards to electricity. What started all this off was that I read in a science book that voltage does not move through materials like steel etc, so that got me thinking well I've worked wit…