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62 views

Could anti matter collisions be or make dark matter?

I've recently seen that space is or could be a quantum vacuum full of particles like matter and anti matter appearing and possibly colliding causing in theory the same effects that dark energy has. My ...
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0answers
33 views

If there turns out to be matter with negative mass, would there also be antimatter with negative mass?

I just heard of the concept of negative mass. Googling led me to see that the concept of negative mass is often contrasted with antimatter. This made me to wonder whether there would then also be a ...
5
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1answer
366 views

Physical reason for annihilation? [duplicate]

What is the fundamental reason as to why matter and antimatter annihilate? Is it because both particles and antiparticles are excitations of quantum fields, and the annihilation process corresponds ...
2
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2answers
30 views

Big Bang Question

In the early Universe it it's believed that matter and anti-matter annihilated one another till there was but a remaining 1% left. In a matter/anti-matter collision, is there not an explosion of ...
7
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1answer
79 views

Is the pH of antimatter the reverse of the pH for matter?

If it does have a pH, I mean. Though I don't see why it shouldn't have it. Both the Brønsted-Lowry and Lewis definitions of acid have to do with the ability of a substance to accept, or provide ...
2
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1answer
52 views

What would happen in a collision of an antimatter singularty and a matter singularity? [duplicate]

Would energy be released if a black hole made out of antimatter and another of matter were to collide?
2
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1answer
116 views

Do particles travel backward in time in a particle interpretation of field theory?

In this Phys.SE answer Ron Maimon stats: there is no relativistic particle formalism in which the particles have postive energies and casual propagation. You can either deal with fields in which ...
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3answers
111 views

Is there a giant cloud of antimatter at centre of the Milky Way

Among others, this page says there is a giant cloud of antimatter at centre of the Milky Way, which was discovered in the 1970s. My brother doesn't believe there is any such cloud. I'm prepared to ...
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3answers
1k views

What exactly is an anti-neutrino?

According to the the definition of anti-particles, they are particles with same mass but opposite charge. Neutrinos by definition have no charge. So, how can it have an anti-particle?
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1answer
332 views

Does Fermi-Dirac Statistics explain anti-particles?

I wondered whether the Fermi-Dirac Statistics describes the anti-fermion particles. Does it include the anti-particles?
0
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1answer
58 views

Equality of masses of particle and antiparticle

Usually we say that equality of masses of particle and antiparticle follows from CPT-theorem. But do we need it for showing this equality? The first method to show that is following. The equation ...
0
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1answer
46 views

Why does Hawking Radiation not add up to zero? [duplicate]

First off: I am not familiar with the details of quantum mechanics or relativity. My understanding of Hawking radiation is as follows: Pairs of particles and anti-particles can and will spontaneously ...
3
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1answer
92 views

Why are neutrino and antineutrino cross sections different?

Particularly in the case of Majorana neutrinos, it seems a little odd that the particle and antiparticle would have differing cross sections. Perhaps the answer is in here, but I've missed it: ...
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0answers
25 views

How can a pion with neutral charge exist? [duplicate]

A $\pi^0$ consists of an up and anti-up quark. However, I also learned that when a particle and its anti-particle meet, energy is produced. So, my question is that how can $\pi^0$ exist? Won't it ...
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1answer
104 views

Does it matter if we are made of matter or antimatter?

Is there any difference between matter and antimatter other than the charge? Could we (theoretically of course) find in space a civilization made of antimatter?
1
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1answer
43 views

Will an anti-neutron annihilate a regular neutron even though they have no charge

Since neutrons have no electric charge will an anti-neutron annihilate when it comes into contact with a regular neutron as protons and anti-protons do? if so what causes it to annihilate?
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2answers
112 views

Matter vs. Antimatter shortly after Big Bang

I am not a physicist or astronomer in training at all, so this might be a dumb question with an obvious answer, but as I watched something the other day on matter & anti-matter, and the discussion ...
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1answer
39 views

Can Antimatter undergo nuclear fission/fusion?

I was curious if antimatter could undergo nuclear fission/fusion with other antimatter. It makes sense, I was wondering if it would work?
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3answers
462 views

How are anti-matter atoms created?

What is the reaction, or reactions that make anti-matter? I don't understand how anti-matter is created by CERN if interaction with normal matter causes annihilation.
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3answers
622 views

What happens to gravity after matter-antimatter annihilation?

Both matter and antimatter have mass and thus gravity, but since energy from annihilation has no mass what happens to the force of gravity that was previously present? What about conservation of ...
0
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1answer
129 views

Gravity and antimatter

If we put earth like planet made up of antimatter (same mass of earth, same diameter etc..) with same distance from moon as current distance between earth and moon then center of gravity of moon and ...
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1answer
91 views

Matter-antimatter asymmetry problem

As we know that matter-antimatter asymmetry is one of unsolved problems in physics. One possible solution to this problem is given as baryogenesis which produce asymmetry in rate of creation between ...
0
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1answer
71 views

Neutron-Antineutron creation/annihilation data

What is the most precise data for neutron-antineutron production by one photon (hitting a target in the laboratory system)? and/or What is the most precise data for neutron-antineutron annihilation ...
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0answers
42 views

anti-matter activation energy

In chemical reactions, there are usually energy barriers that must be overcome before a reaction can take place. It seems that such a phenomena also exists at the atomic level as well. For instance, ...
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0answers
32 views

antimatter moving back in time [duplicate]

This just blew my mind away! I was watching a video about imagining the fourth dimension and the narrator said that little line. Can some people elaborate on this. Also please keep it simple not ...
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0answers
23 views

It's commonly said that the existence of antiparticles “saves causality”. How? [duplicate]

The way I've always thought about is something like this: If measurements of space and time are essentially indeterminate (indeterminacy principle), then an entity "traveling at less than the speed of ...
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2answers
73 views

Could Gamma ray bursts be caused by matter-antimatter annihilation?

As far as I know a collisions of matter and antimatter leads to the complete annihilation of both, whereby 100% of the rest mass of the particles is converted into gamma rays. Could this mechanism be ...
3
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2answers
99 views

Neutrinos and anti-neutrinos in the Standard Model

In standard model neutrinos and the left handed electron forms SU(2) doublet. What about the anti-neutrinos in the standard model? Do they also form some doublet? If neutrinos have tiny masses will ...
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6answers
2k views

Is there any way to annihilate matter without the use of anti-matter?

Is there any way to annihilate matter without the use of anti-matter? And vice versa? I mean, for example is it possible to totally convert the mass of a proton into "pure energy" without use an ...
4
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1answer
66 views

What is the difference between the process in which energy converts to matter and that in which it converts to antimatter?

What is the difference between the process in which energy converts to matter and the process in which it converts to antimatter? In colliders, for instance, is the product (either being the matter or ...
0
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1answer
101 views

Little confusion in drawing Feynmam diagram

If the arrows of both the outgoing solid lines of the Feynman diagram corresponding to the bhabha scattering of $e^+$ and $e^-$, are just reversed, will it not describe same thing? Doesn't both imply ...
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1answer
94 views

Is there there is another universe which is made up of antimatter, in large amounts like ours is made up of matter?

Can it be possible that in the big bang, not one, but two universes were formed, one formed of matter, and the other formed of antimatter? It seems logical to me that since our universe is formed of ...
3
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1answer
159 views

How to think about antiparticles in KG equation?

I am a beginner to study QFT and have a problem. I know, in Dirac equation, thanking to the Pauli exclusion principle and believing that the vacuume is the state that all the negative energy states ...
0
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0answers
31 views

Why is it more likely that the particle with negative mass falls into a black hole? [duplicate]

If particle-antiparticle pairs pop into existence at the event horizon, and presumably their orientation to the black hole is random, why is it the particle with negative mass is more often (always?) ...
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2answers
244 views

How come the universe is made of matter and not antimatter?

Antimatter is like matter on opposite day: it has the same properties as the stuff that makes up planets, stars and galaxies, but one vital piece is different—its charge. The universe supposedly ...
3
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1answer
119 views

Quantum Field Theory and antiparticles vs particles

Does a particle and its antiparticle share the same field in QFT? If an electron is an energized spot in the electron field, is a positron a less energized spot or even a spot of negative energy (if ...
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2answers
169 views

Why does the spiral of a positron have a larger radius than that of an electron in this picture in a bubble chamber?

The smaller spiral is caused by an electron The bigger spiral is caused by a positron However, they have the same mass and magnitude of charge. So, during this pair production, why does the positron ...
3
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1answer
112 views

Sign of mass of an anti-particle

When deriving the Lagrangian for Spin $\frac{1}{2}$ particles we are naturally led to using $\Psi$ and $\bar{\Psi}$. The Euler-Lagrange equations lead us to two wave equations: \begin{equation} ...
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1answer
88 views

Can a positron beam cut through metal?

Can a positron beam be used to cut through metal?
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0answers
81 views

Dirac representation between matter and anti-matter

If $|\psi \rangle$ represents a wavefunction through a column matrix and $\langle \psi |$ represents the dual vector in a row matrix and $|\psi \rangle \langle \psi | = \rho $ is the probability ...
3
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2answers
155 views

Can path integral paths go backwards in time?

The paths can cross any coordinate at any time in the whole space (e.g. Universe space). Integration goes over all could-you-imagine paths. But time goes strictly forward. Can time variable resemble ...
5
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1answer
146 views

QED and Newton's 3rd law

According to some lecture notes on propagators (see bottom of page) the Feynman particle/anti-particle hypothesis states: The emission (absorption) of an antiparticle of 4-momentum $p^\mu$ is ...
0
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1answer
122 views

Need for acceleration in particle-antiparticle annihilation? [closed]

If an electron and positron are accelerated towards each other, at distances quite far away, there wouldn't be any significant electrostatic attraction, hence they need to be accelerated. But when ...
1
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1answer
41 views

Lifetime of Positron and its existence

Since we know in condensed matter the lifetime of positron is about 10^-10 seconds, how do we collide positrons with electrons? How many positrons were there during the LEP experiment? I know ...
0
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1answer
89 views

What happens when half of an orbiting object's matter is annihilated?

Suppose object A orbits object B, and that there are no outside gravitational influences non-Sun gravity influences, and that object A is completely spherical and its mass is evenly distributed. Now, ...
2
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2answers
104 views

What distinguishes the particles we chose as matter from their antimatter equivalent? [duplicate]

Back before we knew about antimatter we just called everything matter. Ignoring CP-violation for a moment, there is nothing special about matter versus antimatter. Once we knew about antimatter it ...
7
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2answers
309 views

Anti-matter as matter going backwards in time? (requesting further clarification upon a previous post)

I understand this question has already been asked here, however, I don't have enough reputation points to place a comment (I suppose that's the reason) on a specific answer to request a reference. A ...
0
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1answer
305 views

If time travel to the past is not possible why is this situation considered in Feynman diagrams?

I recently read R.P Feynman's QED:A Strange Theory of Light and Matter. It is believed that time travel to the past is not possible. Then why is particles going backward in time considered in the book ...
7
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1answer
135 views

Are there models/simulations of antigravitational antimatter-galaxies?

In the comments to another question's answer, I started wondering: Assuming antimatter possessed negative gravitational mass§ (which is not proven impossible to date, though deemed unlikely), ...
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5answers
1k views

Does antimatter curve spacetime in the opposite direction as matter?

According to the Dirac equation, antimatter is the negative energy solution to the following relation: $$E^2 = p^2 c^2 + m^2 c^4.$$ And according to general relativity, the Einstein tensor (which ...