Matter Definition and 1000 Threads

If we consider a perfect relativistic fluid it has energy momentum tensor $$T^{\mu \nu} = (\rho + p) U^\mu U^\nu + p\eta^{\mu \nu} $$ where ##U^\mu## is the four-velocity field of the fluid. ##\partial_\mu T^{\mu \nu} = 0## then implies the relativistic continuity equation...

Hi all. Can anyone please recommend me a good undergraduate level Condensed Matter Physics book that has a number of examples and concise explanations rather than walls of texts? It should cover typical topics such as scattering, magnetism etc. I apologize if this may strike a nerve with...

Hello, I'm having trouble understanding why if there are dark matter particles and other such particles (neutrinos) streaming through the Earth at all times, why don't they just collide with the atoms in our body or the desk or what have you? I understand that they're probably "weakly...

Matter can not be created nor destroyed..."in a closed system" ...and except where "energy transfers" are present. So, in a fusion reaction, energy is released; but mass is also lost. ? Can someone/s just square this more a layman (me) so I can understand exactly what's going on? Thanks! Max

Anyone knows about a good review of dark matter candidates? I want to learn about that but I would like to have a good review to start, any suggestion? Perhaps at an introductory level but if you have something advanced is more than welcomed. Books, papers, anything. Thanks

These papers, http://arxiv.org/abs/1402.4119 and http://arxiv.org/abs/1402.2301, make a case for direct detection of dark matter. The evidence takes the form of an unidentified emission line in the x ray spectrum of galactic clusters. The line is at a frequency and intensity consistent with...

I found an interesting paper... Dark Energy and Dark Matter as Inertial Effects A globally rotating model of the universe is postulated. It is shown that dark energy and dark matter are cosmic inertial effects resulting from such a cosmic rotation, corresponding to centrifugal and a...

What proof do we have that dark matter exists.

Homework Statement Use a graphing calculator to find \delta when 0<|x - \pi/2|<\delta and |sin(x) - 1|<0.2 Homework Equations I don't think there are any other than the format of the previous information: 0<|x-a|<\delta and |f(x)-L|<\epsilon The Attempt at a Solution Okay...

I've been reading reading an older article on ISW (integrated Sache-wolfe effect). One line struck me as odd in the paper. http://arxiv.org/abs/0801.4380v2 on page two the line " In particular, we know that during the matter dominated era the gravitational potential stays constant " I...

What is left if all matter and energy is removed from a particular region in space? For example, say I completely remove all of the matter and energy from a region of the air in front of me (also assuming no matter or energy moves in and out of this space once I do this), then what is left?

I'm in year 3 currently. I'll be applying for grad school in the US in the fall, and based on what I've seen on the internet and heard from others, most applications are due in December, some early January. My school is on a semester system, and our fall term grades aren't made official until...

Hi, I'm a sophomore undergrad and recently I've been wondering how much weight grad schools in the sciences actually put into your "course load." I've read some conflicting views on the internet, books on grad school admissions, and faculty. The websites for some grad/professional schools list...

Hello! :) I have a question.. Suppose that we have a finite automaton $A$(deterministic or not) and $L(A)$ the language that it accepts.It interest us to recognize the complement language $L'=(\Sigma^{*}-L(A))$.So,we reverse the states of A as followed:we make the accepting state non-accepting...

Hi, I keep reading about that the universe is supposed to be composed of only matter. And that this matter was an excess amount compared to anti-matter after the big bang. So most of the matter and anti-matter annihilated each other and some matter was left over. My question is: What is...

Hi, I'm new both to this forum and to physics in general. Here's hoping I've posted in the right place... I'm basically trying to understand the difference between energy and matter and how one can become the other. Please bear with me, I'm a total layman and can't seem to get a definitive...

A beta particle consists of a fast moving electron emitted from the nucleus of an atom. Beta particles can pass through the palm of a human hand. My question is .. Being a particle how can it pass through the palm of a hand? I still haven't done quantum Physics but I suspect that it has...

If equal amount of matter and anti-matter was created during the Big Bang, what is existing now? Matter? Thanks.

The Lagrangian for a point particle is just L=-m\sqrt{1-v^2}. If instead we had a continuous distribution of matter, what would its Lagrangian density be? I feel that this should be very easy to figure out, but I can't get a scalar Lagrangian density that reduces to the particle Lagrangian in...

I'm looking for an REU program to do over the summer in hard condensed matter. Some connection with quantum information/ quantum computing would be awesome, but not necessary. Does anyone have any recommendations?

Simple logical observation dictates that our sun (for example) would gravitationally attract Dark Matter to the sun's center of gravity because DM is "gravitationally attractive". What is the value of the gravitational component of dark matter between the center of gravity of the sun and earth...

I am hoping for a name change soon, but I am considering the career implications for changing my name. The name I am planning on doesn't match my race, but California (where I live) is a melting pot and there are white Lopez and Martinez and Asian Masons. People will know that I changed my name...

Hi I am a 20 year old college student currently studying at my local community college. I am getting the itch to transfer sooner than expected. This coming spring will be my second college semester and I should have 26 credit hours done by the end of May. If I continue with my grades I don't see...

I'm writing a sci-fi novel ("You don't say?") and I've decided that the only method of interstellar travel that will exist is wormholes. I've debated a warp drive that doesn't reach the speed of light, but I'll save that for another time. Basically, I need to know what properties matter would...

Since we can observe gravitational lensing and conclude that mass can affect the path of EM radiation it seems logical to me to assume that EM radiation will exert a slight gravitational attraction of it's own on a mass,- although I do not recall ever reading about this. Presumably the...

My Google searches are result in either something too complicated, or confusing non scientific journal articles. I always thought black holes were what people were referring to by dark matter. And I also was under the impression that small black holes should have all evaporated by now if they...

Hi, please could someone help as I have got myself desperately confused with how radiation interacts with matter largely because of conflicting sources on the internet. Apparently there are 2 main types of interaction of radiation with matter; atomic/molecular vibrations and electron...

I want to go into aerospace engineering and I have really messed up in high school (not going into details) long story short I am definitely not getting into some big name school I am trying to improve but I am beginning to realize how little of an impact I am having. I am not going to stop...

It could be useful to group some references for this: http://arxiv.org/pdf/1204.5379v1.pdf (Light Sterile Neutrinos: A White Paper) http://arxiv.org/abs/arXiv:1311.0282 (Sterile neutrino dark matter bounds from galaxies of the Local Group) I'd like some more references. Please share any good...

Hello, There is a problem like why universe end up with more matter than anti matter but is it not possible that matter and antimatter does not have enough time to meet and annihilate because of inflationary epoch because of exponential expansion of space time?

Homework Statement The andromeda galaxy has a velocity of 250 km/s as it rotates. The observed mass is 1 x 10^42 kg. If the galaxy is roughly a circle with a diameter of 66,00 light years how much mass is not accounted for visibly? Homework Equations Fc=mv^2/r and Fg=Gm1m2/r^2 The...

Homework Statement The andromeda galaxy has a velocity of 250 km/s as it rotates. The observed mass is 1 x 10^42 kg. If the galaxy is roughly a circle with a diameter of 66,00 light years how much mass is not accounted for visibly? Homework Equations Fc=mv^2/R Fg=Gm1m2/R^2 The...

I can undurstand that a dark matter halo is an area that surrounds galaxies and cluster of galaxies. dark matter haloes can be constructed using N-body simulations, but what is the relation between the haloes and the cluster which we observe. Running a simulation for a cosmology profile (...

If instead of evaluating the above line integral in counter-clockwise direction, I evaluate it via the clockwise direction, would that change the answer? What if I evaluate ##C_1## and ##C_3## in the counter-clockwise direction, but I evaluate ##C_2## in the clockwise direction?

What are the odds that there is a different event horizon for dark matter?

In Bessel's ODE x^{2}y''+xy''+(x^{2}-\nu^{2})y=0, why must \nu not be less than zero? I have looked it up, but I do not find a satisfying answer anywhere.

In other words, can dark matter be reconciled with GR without drastically changing the idea that force is due to space-time curvature? and in the case of the standard model is there any thoughts of how the force of dark matter is transmitted via the exchange of a particle? It seems that this...

To clarify, I'm not confused as to how massless strings can add up to make massive objects, I understand why that happens. My question has more to do with the speed at which strings move. If strings are massless, they must travel at the speed of light, correct? If so, then first off, what is the...

Homework Statement Consider the following statement: "The temperature of a gas is a measure of the speed of its particles (atoms and molecules). Now suppose that I mix two gases together, for example oxygen and carbon dioxide, which are initially at different temperatures; if I wait long...

Dark matter build up near or inside Black holes, thoughts ? I can see it making a real mess of the motions and energies of normal matter in and around a black hole or other very dense body that confines dark matter to a small adjacent region. Unslowed by frictional forces...think angry...

Hi, aside from nucleons is there any other stable (metastable doesn't count in this question) hadronic matter that could form 'exotic atoms' in a way? Thanks for any help.

I read recently, that by separating two quarks, once a high enough energy has been introduced, new quark pairs will form. This sounds to me like a meson, being turned into two mesons. I don't know how clear I am on this, but I was wondering... Is the same true for Baryons. If we magically...

Is it correct to define matter as a force moving primarily in time dimension, and energy as the same force moving primarily in space dimension of spacetime?

This paper, http://arxiv.org/abs/1311.1627, discusses the possibility of giant monopoles as a dark matter candidate. It is not a 'new' idea, it dates back to Dirac's giant monopole concept. In this case, the author suggests the 't Hooft-Polyakov monopole, which avoids the singularity problem of...

Just for some observation, is there any good "maps" of the universe? like nothing detailed but shows the hemispheres. Also is there any website which show totals of matter in the universe, and how it changes when you go to different parts of the universe?

Sorry - a very vague question: Could a superconductor be used to detect dark matter? The dark matter might interact with electrons in the superconductor giving them some momentum. These moving electrons would constitute a supercurrent which could be measured - maybe! Perhaps the...

Forgive me for being a lay person, I am a medical student and the only physics I've ever had was non-calculus based 200-level. Anyway, I was reading the "wormhole" faqs page from Dr. Rodrigo's webpage via UCal-Irvine: http://www.webfilesuci.org/WormholeFAQ.html I was wondering what your...

Forgive me as I have no formal secondary education so my actual knowledge of terms and what not is limited but I am working on a theory that has me wanting to explore the varying chemical states of matter and what defines them. For example, how Nitrogen can be both a gas and a liquid in room...

Homework Statement Suppose that a sprial galaxy has the mass profile: ##M_{disk}(r)=M_d[1-(1+\frac{r}{r_{rd}})e^{-\frac{r}{r_{rd}}}]## Where rrd=3Kpc. and Md is unknown. Like all galaxies, this galaxy also contains dark matter as well as its luminous matter. Using the rotational...

Hi all, I was wondering, could the dark matter just be the particles that actually pop in and out of existence inside the protons and neutrons and all other matter or anti-matter? Please enlighten me if my assumption is wrong somewhere.