The antimatter tag has no wiki summary.
15
votes
8answers
9k views
Is anti-matter matter going backwards in time?
Or: can it be proved that anti-matter definitely is nót matter going backwards in time?
From wikipedia:
[There is considerable speculation as to why the observable universe is apparently almost ...
14
votes
4answers
610 views
What is anti-matter?
Matter-- I guess I know what it is ;) somehow, at least intuitively. So, I can feel it in terms of the weight when picking something up. It may be explained by gravity which is itself is defined by ...
14
votes
1answer
422 views
In general what will holding an anti-hydrogen atom for more than a 1/10th of second allow scientists to discover?
In general what will holding an anti-hydrogen atom for more than a 1/10th of second allow scientists to discover?
Specifically, given that they can hold one for <1/10th of a second, what would ...
12
votes
3answers
703 views
No hair theorem for black holes and the baryon number
The no hair theorem says that a black hole can be characterized by a small number of parameters that are visible from distance - mass, angular momentum and electric charge.
For me it is puzzling why ...
10
votes
2answers
742 views
How Did Paul Dirac Predict The Existence of Antiproton?
The existence of the antiproton with -1 electric charge, opposite to the +1 electric charge of the proton, was predicted by Paul Dirac in his 1933 Nobel Prize lecture.
Quotation by Wikipedia.
...
10
votes
5answers
677 views
Anti-Matter Black Holes
Assuming for a second that there were a pocket of anti matter somewhere sufficiently large to form all the type of object we can see forming from normal matter - then one of these objects would be a ...
9
votes
2answers
1k views
Do anti-photons exist?
I know what anti-matter is and how when it collides with matter both are annihilated. However, what about anti-photons? Are there such things as anti-photons?
I initially thought the idea ...
9
votes
1answer
724 views
How would we tell antimatter galaxies apart?
Given that antimatter galaxies are theoretically possible,
how would they be distinguishable from regular matter galaxies?
That is, antimatter is equal in atomic weight and all properties, except for ...
9
votes
3answers
637 views
Why do or don't neutrinos have antiparticles?
This was inspired by this question. According to Wikipedia, a Majorana neutrino must be its own antiparticle, while a Dirac neutrino cannot be its own antiparticle. Why is this true?
7
votes
3answers
843 views
Does a particle annihilate only with its antiparticle? If yes, why?
Or to put the question another way - what is the result of a proton-positron collision, or an up quark-charm antiquark collision, etc.? As far as I know, annihilation happens only between particles of ...
7
votes
2answers
331 views
Practical uses of antimatter in the present
I recently found out that a PET scan stands for a positron emission tomography. Are there any other practical uses of antimatter in the present?
7
votes
3answers
449 views
What was missing in Dirac's argument to come up with the modern interpretation of the positron?
When Dirac found his equation for the electron $(-i\gamma^\mu\partial_\mu+m)\psi=0$ he famously discovered that it had negative energy solutions. In order to solve the problem of the stability of the ...
7
votes
3answers
608 views
What actually happens when an anti-matter projectile collides with matter?
I'm trying to understand what would really happen when large quantities (e.g., 10g) of anti-matter collide with matter. The normal response is that they'd annihilate each other and generate an ...
7
votes
1answer
841 views
Electric charge in string theory
The mass of an elementary particle in string theory is related with the way the string vibrates. The more frantically a string vibrates the more energy it posses and hence the more massive it is. My ...
7
votes
5answers
856 views
Why Negative Energy States are Bad
The argument is often given that the early attempts of constructing a relativistic theory of quantum mechanics must not have gotten everything right because they led to the necessity of negative ...
6
votes
4answers
352 views
Matter-Antimatter Asymmetry in Experiments?
As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
6
votes
4answers
1k views
Spontaneous pair production?
So I've been looking into particle-antiparticle pair production from a gamma ray and don't understand one thing.
Let's say I have a 1,1 MeV photon and it hits a nucleus - electron-positron pair with ...
6
votes
1answer
329 views
Anti particles: What exactly is inverted?
http://en.wikipedia.org/wiki/Antiparticle says "Corresponding to most kinds of particles, there is an associated antiparticle with the same mass and opposite electric charge."
and
What is anti-matter?
...
6
votes
4answers
864 views
If an anti-matter singularity and a normal matter singularity, of equal masses, collided would we (outside the event horizon) see an explosion?
If an anti-matter singularity and a normal matter singularity, of equal masses, collided would we (outside the event horizon) see an explosion?
6
votes
3answers
175 views
supressing certain decay paths and enhancing others with interference
In a scattering reaction, there are many possible final states for the products, each with different production rates.
Question: Is there a way in which we could in general supress certain rates ...
5
votes
2answers
228 views
How does Annihilation work?
I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different charges? Then what about ...
5
votes
1answer
142 views
Why is the decay of neutral kaons (violates CP invariance) seemingly not sufficient enough for certain people to describe matter-antimatter imbalance?
The Nobel Prize in Physics in 1980 was awarded to James Cronin and Val Fitch for their discovery of a violation of Charge and Parity Invariance, in which the neutral kaon's quarks change into their ...
5
votes
1answer
124 views
How fast is the matter and antimatter reaction compared to nuclear chain reaction?
What I mean is, the nuclear chain reactions take microseconds for every generation and that is the reason that nuclear weapons exist. Because in nuclear reactors the reaction rate is much slower thus ...
4
votes
2answers
513 views
Do particles and anti-particles attract each other?
Do particles and anti-particles attract each other?
From the very basic understanding that they are created out of nothing mutually and collide to annihilate each other seems to indicate this happens ...
4
votes
2answers
390 views
Is nature symmetric between particles and antiparticles?
Is nature symmetric with respect to presence of particles? Do we have an antiparticle for every particle thought of? Are there any proven examples where we don't have an antiparticle? And what about ...
4
votes
2answers
217 views
Baryon asymmetry
Baryon asymmetry refers to the observation that apparently there is matter in the Universe but not much antimatter. We don't see galaxies made of antimatter or observe gamma rays that would be ...
4
votes
2answers
337 views
the causality and the anti-particles
How can I quantitatively and qualitatively understand the fact that there is a relevence between the existence of anti-particles and the causality?
3
votes
3answers
661 views
Why would Antimatter behave differently via Gravity?
Confinement of antihydrogen might help provide a future answer. http://arxiv.org/abs/1104.4982
3
votes
3answers
148 views
What barriers exist to prevent us from turning a baryon into a anti-baryon?
At present the only way we can produce anti-matter is through high powered collisions. New matter is created from the energy produced in these collisions and some of them are anti-matter particles ...
3
votes
1answer
192 views
Anti-Matter for Neutrons
The anti-particle corresponding to a proton or an electron is a particle with an equal mass, but an opposite charge. So what is the anti-particle corresponding to a neutron (which does not possess a ...
3
votes
2answers
164 views
Are there any differences between photons emited /absorbed by antimatter atoms to photon in usual atoms?
(Theoretically)
Are there any differences between photons emited /absorbed by antimatter atoms to photon in usual atoms?
for example, is it impossible to tell the difference between a photon emmited ...
3
votes
2answers
315 views
Creation of particle anti-particle pairs
I was reading some QFT notes and there is one point that I don't understand, they are justifying why we need QFT saying that the number of particles is not preserved once we consider special ...
3
votes
2answers
207 views
Can different species of particles annihilate with other species
Obviously electrons annihilate with positrons, but can a muon annihilate with an positron, or can an anti-taon cancel with a muon? similarly for quarks of different species, e.g. u and anti-strange.
...
3
votes
2answers
199 views
Can a neutron be created from pure energy
Is it possible to create a neutron out of pure energy, i.e. not by bringing a bunch of already-existing quarks together? (A quick calculation using E = mc2 shows the energy required would be about 1.5 ...
2
votes
4answers
3k views
What is pure energy in matter antimatter annihilation?
I used to read the term "pure energy" in the context of matter antimatter annihilation,
are them photons? is it other form of heat, are particles with mass ?
What does it refer to?
thanks
2
votes
2answers
455 views
What happens if we put together a proton and an antineutron?
A hydrogen nucleus consists of a single proton.
A 2-hydrogen (deuterium) nucleus consists of a proton and a neutron.
A tritium nucleus consists of a proton and two neutrons.
This makes me wonder how ...
2
votes
2answers
107 views
How much energy is carried away by neutrinos in matter-antimatter annihilation?
Some people say that neutrinos carry away most of the energy, some others say just a fraction. So what is the truth ? what is the percentage of energy lost due to neutrinos ?
2
votes
1answer
830 views
Anti-matter black hole and time
I have recently read some hard science-fiction story based on an assumption that if time stops (from external observer's perspective) on the event horizon of black hole, then in an anti-matter black ...
2
votes
2answers
106 views
Can the charge of particles spontaneously flip from positive to negative or vice versa?
I'm thinking of matter antimatter annihilation, are there reactions where normal matter converts to antimatter?
2
votes
2answers
537 views
What is the correct term for the “polarity” of matter (matter vs. antimatter)? Are fractional polarities allowed?
What is the correct term for the "polarity" of matter (matter vs. antimatter)?
Are neutral polarities allowed? (1,0,-1)
Are fractional polarities allowed?
2
votes
3answers
595 views
Particle antiparticle annihilation-do they have to be of the same type?
I read that a particle will meet its antiparticle and annihilate to generate a photon. Is it important for the pairs to be of the same type? What will happen when for example a neutron meets an ...
2
votes
4answers
435 views
Why do electron-positron pair annihilate upon contact?
I'll a appreciate a layman's explanation, if there exists one, to this question that arose when reading an popular-science level article on Einstein and the $E=MC^2$ equation.
What I mean is that, ...
2
votes
2answers
303 views
How does slow anti-hydrogen annihilate with normal matter in the lab?
In a recent article:
Physical Review A 83, 032903 (2011), A.Yu. Voronin, P.Froelich, V.V. Nesvizhevsky, Antihydrogen Gravitational Quantum States
the authors claim that anti-hydrogen has a lifetime ...
2
votes
1answer
100 views
On non-local physics
Recently I've encountered work by prof. B.V Alekseev, in which he claims that some physical problems can be easily solved if we consider non-local interactions in kinetic theory (interactions of ...
2
votes
0answers
62 views
positronium BEC stability
After reading this article regarding Positronium BEC formation (for lasing purposes), there is a mention in there regarding Ps "up" atoms not annihilating with "down" atoms, the article is pretty ...
2
votes
0answers
146 views
What makes *electric* charge special (wrt. CPT theorem)?
I'm wondering why the 'C' in CPT - charge conjugation - refers specifically to electric charge. Of course you could say that C is just defined as $e^+ \leftrightarrow e^-$... but there has to be ...
1
vote
3answers
154 views
mechanism of annihilation
Can the annihilation of matter and antimatter be explained by the electro-weak interaction?
Can pair-production be explained in the same way?
1
vote
2answers
545 views
When matter and anti-matter collide
Do they create energy? Or do they just disappear with zero energy?
If they create energy when disappearing, that means it takes energy to create them, right?
If they disappear into zero energy, ...
1
vote
3answers
143 views
Do particle pairs avoid each other? Please end my musings
Can you explain what happens when a particle and its antiparticle are created. Do they whiz away from each other at the speed of light or what? I suppose that they don't because otherwise they would ...
1
vote
2answers
116 views
Matter - Antimatter Reactory Practicality
With current technology, would the energy released by a matter-antimatter annihilation be more than the energy needed to created the antimatter in the first place? Would it be worth it? Just curious, ...
