Dark matter Definition and 935 Threads

Consider a three dimensional representation of ##U(1)\times SU(2)## with zero hypercharge ##Y=0##: $$ L= \begin{pmatrix} L^+ \\ L^0 \\ L^- \end{pmatrix} $$ Then the mass term is given by [1]: $$ \mathcal{L} \supset -\frac m 2 \left( 2 L^+ L^- +L^0 L^0 \right) $$ I am wondering where the...

If for any given segment of the sky there are twice as many elliptical galaxies as there are spiral galaxies and if light to mass ratio of these elliptical galaxies (M/LH ratio is about 1.8, independent of RE/R1/2). https://arxiv.org/pdf/1303.6896.pdf It would seem that 2/3 of the universe...

I just had the thought that atoms emit light at quantized levels but that would seem to imply that only certain energy levels could possibly exist instead of a complete spectrum. But, if light is traveling down or away from a gravitational field the frequency gets shifted. Would this make it...

I'm trying to figure out how to arrive at the final expression, as given in the lecture notes. I tried to work this out by myself but getting different figure and units. I've considered the followings, normalize the equation from its values e.g. spins and x parameter, as g~100, x~10(m/t~10)...

So I have a question regarding the Alcubierre metric and the phenomena of stars on outer edges of galaxies moving at higher velocities than their orbital calculations state they should. When taking the accelerating expansion of space into account due to dark energy, could a sub-luminal...

How certain are scientists that the solution to the dark matter problem is a new, unknown particle (or more)? Theories that eliminate the need for new particle(s) and suggest modifications to the current understanding of gravity seem to get less attention. Why is that?

I apologize for the fact that this information is 2nd hand but a very intelligent and reliable friend tells me that in “Dark Matter and the Dinosaurs” by Lisa Randall she hypothesizes a disk of dark matter, which she calls “Double-Disk Dark Matter (DDDM)” that is superimposed over the center of...

I understand that the evidence for dark matter, although indirect, is quite strong. Yet there are a few things that puzzle me about the dark matter idea. If dark matter is the predominant form of matter in the universe, why does it have no effect on solar system dynamics? The solar system is...

The bulge of the milky way is 40 parsecs in radius. There is 288.218 stars per cubic light-year in the milky way bulge. At the density, spacetime for the entire 40 parsec radius should be severely distorted. The total stellar mass of the bulge is about 25 billion Solar masses. The Milky Way has...

Has the ratio of normal to dark matter remained the same since the beginning?

This is a theoretical question that may not be rooted in reality. I hope this was the right section. Please clear up all misunderstandings. Since dark matter can’t emit light, could it be possible that dark matter is ionized matter? I always thought you needed electrons to emit light. Then that...

Regarding dark matter, is it possible that at the quantum level there is some unknown property to gravity that is making it appear that there is this dark matter attracting normal mass but it's actually just that on a galactic scale gravity acts different than GR predicts? Or is that completely...

I'm wondering what properties of Dark Matter are known for certain. Such as: How much does it collide with itself, and with ordinary matter? What does ##\sigma/m\le 7cm^2/g## mean (and why is the estimate rising in more recent studies)? How does it compare with ordinary matter, e.g. liquid...

I would like to hear what the opinions are. Could sterile neutrino's be dark matter? I'm sure this has been discussed if not here then somewhere.

Are strongly interacting dark matter quarks displaced by visible matter? Chiral Gravitational Waves and Baryon Superfluid Dark Matter We develop a unified model of darkgenesis and baryogenesis involving strongly interacting dark quarks

Does anyone know the speed of light in dark matter?

If dark matter is a supersolid that fills 'empty' space and is displaced by visible matter, then is this the same notion as the spacetime fabric having mass and being curved by visible matter?

Can massless particles form some kind of nanotube that can trap other particles giving the nanotube mass? Is this dark matter?

According to the article in Astronomy Magazine June 2018, the satellite galaxies of Centaurus A are rotating in the same direction in a relatively thin plane, vs randomly distributed if there is a dark matter halo/sphere surrounding large galaxies. Any thoughts on this new finding? I've only...

From an outsiders view, it appears that the old shell theorem is relevant to the dark matter issue: If one views a spherical cluster of galaxies as an interconnected structure, gravity would increase linearly with distance from the center and be greatest at the edge of the cluster. For a spiral...

No I'm not a particularly big person with a weight issue. Somebody asked me this question and I don't know the answer, but somebody here will. OK, it's now accepted that dark matter is everywhere in the Universe, it tends to clump with regular matter because all matter is subject to gravity...

@vanhees71 reminds us that which suggests something I've wondered about for a while, whether dark matter might be adequately modeled by generalized free fields, which do not have asymptotic free states. Ray Streater, in Rep. Prog. Phys. 1975 38 771-846, "Outline of axiomatic relativistic...

Scientists Thought All Galaxies Had Dark Matter, but They Just Found One Without It Could dark matter fill 'empty' space, strongly interact with visible matter and be displaced by visible matter? Could the reason for the mistaken notion the galaxy is missing dark matter is that the galaxy is...

Just noticed this article. Wonder if anyone here has further info. Sounds very interesting. http://www.bbc.com/news/science-environment-43543195

Why do we need the theory of dark energy? I know the it is claimed that dark-matter has no affect on the electromagnetic spectrum. How do we know the affects attributed to dark-energy aren't affects caused by dark-matter? Dark-energy is claimed to be causing the universe to expand at an...

How do astrophysicists accurately account for all of the energy and pressure within a galaxy? How is it tabulated? My understanding of general relativity predicts that space-time curvature is a consequence of mass, energy, and pressure as expressed in the Energy-Momentum tensor. The accepted...

Does space have its own density? i.e. a mass density distinct from the mass density of 'particles' in it? or may it have a uniform density of some kind of vast particle(s)? If so, would the effect on observable masses largely cancel out? One answer from...

https://www.space.com/39837-first-stars-universe-fingerprints-dark-matter.html...

Do dark matter and energy affect on red shift phenomena? If yes, what, and what is the consequence of it?

The talk, given at the Royal Institution in October 2016, will take us on a breath-taking journey from the origin of the Universe, through the evolution of life and consciousness, to the eternal question of what it all really means.

Dr Sean Carroll is an astrophysicist at the California Institute of Technology. He has written a variety of popular science books along with textbooks and has long been interested in the biggest questions in astronomy: Where does probability come from? How does time work? What is dark matter?

Hydrogen and Helium are pervasive throughout our universe so their interaction with light is universal too. Dark Matter has been theorized to not interact with light but couldn't that be masked by the Helium and Hydrogen we already see?

http://arxiv.org/abs/1801.04083 UV completion of a theory of Superfluid Dark Matter Andrea Addazi, Antonino Marciano (Submitted on 12 Jan 2018) We show that a model of superfluid dark matter, modifying the Newtonian potential and explaining galactic rotational curves, can be unitarized by the...

My query is really to find out what everybody thinks about 'empty space'. Does dark matter/energy exist and if so, it fills all voids in the universe? Where does it come from? Is it produced by some force? Without DM/DE, does space even exist? Say the supernovas, the collision of neutron stars...

Does the event horizon of a black hole really represents the surface of the "star" (or mass) itself? What I mean to say is: That the event horizon is the (let's say it this way) sphere surface where the scape velocity is => than the speed of light. So it is not necessary for event horizon to be...

Question 1: Do the calculations/models for galactic structure, the basis for the missing 6x mass problem that created the notion of "Dark Matter," include any factor/variable or set of variables that account for space-time dilation due to relativistic effects caused by the super-massive black...

On the podcast “Skeptics Guide to the Universe”, host, Steven Novella mentioned that astronomers can tell the difference between globular clusters orbiting the Milky Way Galaxy and satellite galaxies by looking to see if there is the gravitational effects of dark matter. Why would this be? That...

https://www.sciencedaily.com/releases/2017/11/171122113013.htm How plausible does this seem?

Hello everyone. I was watching this : and this question popped up in my mind ... could dark matter actually be visible, but it is so reflective on every electromagnetic spectrum that we cannot glimpse it from a distance .?. I would like to know if this question is in fact valid or totally...

I found an article https://arxiv.org/abs/1703.07365 and also it says that we should change current standart model about DM. Also I find this; "If this "wobbling" is not an unknown astrophysical phenomenon and in fact the result of the behaviour of dark matter, then it is inconsistent with...

Can someone explain why we are certain there is dark matter in our universe? I understood it like this. At some Point in our recent history we figured out, that according to our math galaxies (or sth like that) wouldn't have developed like they did or wouldn't even stay in 1 Piece since they do...

Today's APOD https://apod.nasa.gov/apod/ap171031.html shows a simulation picture of the developing universe involving galaxy formations and dark matter thin threads. I am wondering if any PF participant can answer the following questions: 1. Why does dark matter form thin thread structures...

https://www.sciencedaily.com/releases/2017/10/171026103110.htm Astronomers have discovered that the brightest galaxies within galaxy clusters 'wobble' relative to the cluster's center of mass. This unexpected result is inconsistent with predictions made by the current standard model of dark...

I have a curiosity. I saw recently how a team of researchers discovered two super massive black holes orbiting each other in a far off galaxy. (Google it if you didn’t hear, fascinating how they did it.). Anyway, I read a few things about unsolved mysteries of their formation and how SMBHs...

I just came across an August 2012 article that suggests possible first evidence for a disk of dark matter. https://phys.org/news/2012-08-plenty-dark-sun.html Here are some quotes. Astronomers at the University of Zürich, the ETH Zurich, the University of Leicester and NAOC Beijing have found...

Im doing a group presentation in one of my astrophysics papers this semester, and my part of the presentation is to research and outline the various theories for what dark matter could be. Does anyone on the pf know of any sites they may think will be helpful in my research, or any ideas on...

Hello, How much volume or mass of space does one need to see appreciable effects of dark matter where general relatively seems to break down? What is the critical volume of space at this time where people can see the effects of dark matter and where they cannot? Is there a spatial scale smaller...

Hello, My question is, how much dark matter (any of mass, volume, density, etc) would we have to have in our solar system for us to detect it? My guess is that we would detect the dark matter through gravitational lensing or the perturbation of planetary orbits. On previous posts about dark...

Wikipedia dixit: The standard model of cosmology indicates that the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy ******************************************************************************* According to this, dark matter must be...

Are there variations of dark matter concentration on Earth based on months or seasons of the year?