Matter Definition and 1000 Threads

Not sure who this is he may be a mondian but it is an alternative view. arXiv:1903.11217 [pdf, other] Is dark matter fact or fantasy? -- clues from the data Philip D. Mannheim Comments: Essay written for the Gravity Research Foundation 2019 Awards for Essays on Gravitation Subjects...

From what I have read gravitational waves are caused by the acceleration of massive object causing ripples in space time. What specifically causes this, and how does general relativity predict these. Does it have to be a high density of matter, or a large amount of it. How do these waves affect...

If the distribution of elements in the universe is also the distribution of elements in the solar system for regular matter, and being dark matter so overwhelmingly prevalent in the universe, why can't we see it overwhelmingly in the solar system?

I'm a physics and math major, going into my 3rd year. Suppose I want to do research in theoretical aspects of condensed matter. What would be the mathematics I should be learning as an undergraduate? Here is a rundown of courses I'm considering taking next year: Abstract Algebra: it seems a...

Homework Statement This is not a direct homework problem. Rather, I modified several that I saw that had different slopes but with the same initial velocity, and the same height answer: An icy, frictionless road slopes upward with angle Θ ° above the horizontal. A snowboarder of mass m...

The pressure of a scalar field is: Φ˙2−V(Φ) so to have zero or negligeable pressure it needs to have equipartition of its energy in potential and kinetic form ==> the potential must be positive. In particular a mass term m2Φ2 ... could be all right: the field should tend to roll down this...

For a Majorana neutrino in matter we have the equation $$(i\gamma^{\mu}\partial_{\mu}-A\gamma_{0})\nu_{L} = m\overline{\nu_{L}}.$$ A is to be considered constant. Squaring, in the ultra-relativistic limit one obtains the dispersion relation $$(E-A)^{2}-p^{2} \simeq mm^{\dagger}$$ i.e. $$p...

We all know that the state of matter can be changed by increasing temperature or by applying pressure. And, all of these, in some way lead to a change in the particles' speed. The speed of the particle decides the state of matter. So, if we were to throw an object at very high speeds, like 50%...

{Moderator's note: Moved to Cosmology forum.] Dark matter and the fabric of space time, Can someone with a real knowledge base of physics and the current accepted theories, please explain why the fabric of space is not the candidate for the elusive dark matter? Having read extensively about...

Hello, I am currently struggling to understand how one can write a Hamiltonian using group theory and change its form according to the symmetry of the system that is considered. The main issue is of course that I have no real experience in using group theory. So to make my question a bit less...

I read a physics book, it says here that... " Matter appears in three different phases that we call solid, liquid, and gas" How about plasma?

Wikipedia describes the distribution of Dark Matter as a halo around our galaxy. Are there any laws or equations on the distribution of dark matter? From what I have read, dark matter does not clump into stars, since it cannot radiate energy. It cannot be seen or directly observed. Does it repel...

Say that I define a set of pairs called ℂ, such that [a,b] ∈ ℂ iff a ∈ ℝ, b ∈ ℝ, [a,b]+[c,d] = [a+c,b+d] [a,b]*[c,d] = [ac-bd, ad+bc] Then this has exactly the same properties of a+bi, does it not? You can write any equation that uses i exactly the same way with those pairs, so all interesting...

From the energy equation E=m0c2/√(1-v2/c2) for non-relativistic gas molecules (v<<c) ,E reduces to m0c2...(1) From ideal gas law PV=nRT P=nRT/V P=nkBNAT/V P=(nNA)kBT/V P=(nNAm0)kBT/v P=mtotalkBT/vm0 P=(mtotal/V)kBT/m0 P=ρkBT/m0 (If n moles of a gas is taken in volume V at temp T and volume V,m0...

What happens to matter after it falls into a black hole? Are electrons pushed closer to the nucleus? Do electrons combine with protons to form neutrons? Are there nuclear reactions occurring in the process? Since no light can escape from a black hole and cool it, then how can a black hole...

The question arises in which procedure to follow, a balance by element or by compound? The excersise is this: A mineral of a process contains contains 90% FeS2 and 10% inerts by weight. This materialit is calcined with 25% excess air, according to the reaction: FeS2 + 02 ► Fe203 + S02 The...

Everyone knows that matter and antimatter annihilate upon contact. But exactly WHY this should happen is not at all obvious, at least to me. So what exactly happens when two such particles encounter one another that leads them to disappear in a large release of photons? And for that matter...

New observations of Compact Elliptical Galaxy Mrk 1216 show a very high apparently dark matter fraction based upon the intragalaxy dynamics of stars in the galaxy, relative to the baryonic mass of the galaxy inferred from typical mass to light ratios for galaxies of that type. The inferred...

From the rotation curve of spiral galaxy it is found that the entire mass is not concentrated at the centre but for large distance from the central core it varies linearly with r for which the velocities(rotational) of the objects far from the central core remains nearly constt. and near to the...

I'm wondering if the galactic rotation curves could be attributed to a deviation of the metric of spacetime from the ideal Schwarzschild metric. The Schwarzschild-metric is a well tested good approximation for the regions near the central mass - but at the outer space, far away from the...

If matter and antimatter are placed next to each other, will they attract each other and annihilate ? Do we have strong evidence regarding the existence of anti-matter ?

I am studying the modes of operation of the Atomic Force Microscopy (AFM). I know there are three: contact, tapping and non-contact. Are they really used in both hard and soft matter physics? If so, how are the difficulties/limitations that they present overcome?

https://arxiv.org/abs/1901.05973 It seems like there is some thing unexplained here, what is going on?

https://arxiv.org/pdf/1901.03711.pdf I wonder if this is an observational problem or if many other galaxies will be found to have no dark matter?

Hello, I often read that hot dark matter is constrained by structure formation issues. But I'm now wondering why it is not constrained by the CMB data itself because such hot dark matter should belong to radiation (with density evolving as 1/a^4 rather than 1/a^3) so for instance when we...

what are the good books on advanced condensed matter physics with detail notation explained?

Dr James Farnes of Oxford's e-Research Centre recently proposed a new model which unifies dark energy and dark matter into a single phenomenon - a fluid which possesses "negative mass". https://news.sky.com/story/mystery-of-dark-matter-may-have-been-solved-by-oxford-scientists-11572089 The paper...

How could we detect negative mass matter? The only proposal I've ever heard of is that we could detect there's a cutoff frequency in the gravitational waves we receive, due to attenuation of those lower frequency waves by negative matter. Are there more experiments that could be conducted...

I have read that postdocs are extremely hard to come by in Astrophysics, and is likely a dead end at the end of the PHD and that Condensed Matter is less competitive in academia. Would a Condensed Matter PhD also provide more opportunities in UK science industry - in particular the life sciences...

Hi! I'm currently applying for a masters program in theoretical physics, more specifically in String and Quantum Field theory. I will apply for Oxford, Kings college, Imperial college and Perimeter Institute among other universities and institutions. However, I also want to go to Uppsala...

Homework Statement Show that the temperature of non-relativistic matter scales as ##a^{-2}## in the absence of interactions. Start from the zero-order part of Eq. (4.68) and assume a form ##f_{dm} \propto e^{-E/T}=e^{-p^2/2mT}##. Note that his argument does not apply to electrons and protons...

Usually, if I understand this correctly, matter will have either a positive charge from the nucleus "sticking out' or a negative charge from the electrons. What would happen if I had a chunk of matter that had no charge and I tried to touch it and interact with it? I guess there are neutrons...

Hello everyone, By considering the effects of the gravitational time dilation the speed of the inner stars must be higher for the local observer than for the external one. So why the gravitational time dilation can not potentially explain the galaxy rotation curve? I already read that the...

I'm writing a thesis for my high school research paper on dark matter. It's difficult to come up with a claim that is argumentative, engaging, and related to the research I've done on the scientific process in relation to theories about dark matter. Do you think I could reasonably argue that...

What is the easiest way to calculate dark energy and matter density at any given age of the universe?

Hello! In most papers that present exclusion plots as cross section versus mass, the plot has a specific shape in which mostly the cross section decreases with mass. I am a bit confused why. If you assume that the density and speed of DM is constant, shouldn't a higher mass (and hence a higher...

Hi everyone, On Page 72 of S. Weinberg's Cosmology book, it's mentioned, just after Equation 1.9.16, that, for the universe matter density ρ(r) to be an analytic function near the origin (spherical symmetry), it has to be given near r = 0 by a power series of r2. I'm not a math wizard, so can...

I read that 1. dark matter has to be concentrated in galaxies; 2. McGaugh & Co discovered a precise relationship between visible-ordinary matter and the calculated sum of ordinary + dark matter from thorough observation of actual acceleration of more than 150 galaxies. 3. First experiments to...

I would like to discuss the topic of light (photons) being emitted from stars potentially being the source of dark energy and dark matter. Photons have mass and velocity; therefore they will affect space time, and their impact could have an effect on objects causing acceleration. Would love to...

Any thoughts on this paper? https://arxiv.org/abs/1712.07962

Both of these webpages show snippets comparing the HSC map of dark matter to the Planck map of dark matter, as well as a graphic showing the time evolution of the dark matter over time: https://www.livescience.com/63711-3d-dark-matter-map.html...

Hi, I'm an undergrad materials engineering student. I am thinking of studying all the way to a PhD as I'm interested on working in research. Right now I work with Semiconductors and I like the field a lot. However, considering what I'm studying, I want to know if it's a good Idea to look for a...

I mean on a deeper more fundamental level. In my mind I've always had the idea that the universe is like a set of strings. Matter being knots and entanglements in those strings, and energy being vibrations on it. Thoughts on this? Thanks in advance

This paper says they do. but I have been lead to believe that DM only interacts with gravity https://arxiv.org/abs/1811.08843 What is the standard view?

Quantum field theory is a powerful tool to calculate observables given the amplitude of some process. I only know the application to high energy physics: you have a Lagrangian with an interaction term between some fields, and you can calculate the amplitude of some process. Once you have this...

Hello. I have a very small antenna and I was wondering if it can receive and/or transmit low frequency signals (or if it can only receive/transmit high frequencies). Likewise, do I need a very large antenna to receive/transmit low frequencies? I've read somewhere on the internet that the...

A lot of popular level explanations introduce the idea of tunneling by saying that "in principle" a person in one room can "find themselves" in the next room, i.e. one can tunnel through a wall Of course, the presenter then hastens to clarify that this is so unlikely that we would have to wait...

Hello! I read several papers about different model of DM beyond basic WIMPs and axions but haven't found a lot about DM effects on baryon asymmetry. I was wondering, is it possible to have a type of DM that decays (or at least it did a lot in the past) preferably more to matter than antimatter...

Hello! I am currently applying for graduate schools in the USA and during my undergraduate career I was mainly involved in Dark Matter research. However, my research focused on testing different models (experimentally or using numerical simulations) and doing some basic calculations, basically...

A new experiment (it's true a small scale one with the possibility of being brought to a much larger scale) has failed to find any sign of Dark Matter (DM), like all the other experiments before (at least the ground based one). AMS seems to have found some important extra anti-protons and...