Matter and antimatter

In the quantum field theories that describe the physics of elementary particles, the vacuum becomes somewhat more complex than previously defined. Even in empty space, matter can appear spontaneously as a result of fluctuations of Ihe vacuum. It may be pointed, out, for example, that an electron and a positron, or antielectron, can be created out of the void, Particles created in this way have only a fleeting existence they are annihilated almost as soon as they appear, and their pressure can never be detected directly. They are called virtual particles in order to distinguish them from real particles. Thus, the traditional definition of vacuum (space with no real particles in it) holds. In their excellent paper, the aforementioned authors discuss how, near a superheavy atomic nucleus, empty space may become unstable, with the result that matter and antimatter can be created without any input of energy. The process may soon be observed experimentally. 

In this connection Alfven proposed the annihilation of matter and antimatter as a possible source of energy, but also other mechanisms, in particular, some form of release of gravitational energy were examined. 

Could that be so that the Universe was created with the preponderance of matter over antimatter We have no support for such hypothesis. Einstein remarked If that s the way God made the world then I don t want to have anything to do with Him [7]. Indeed, the contemporary Standard Model of Physics suggests that equal amounts of matter and antimatter were born during the Big-Bang. Where has the antimatter gone What causes the apparent asymmetry between matter and antimatter Obviously the antiparticles have been annihilated by particles - but apparently this process was not fully symmetric, since enough matter was left over for our Universe. We seem to be the result of an accident, caused by a a slight imperfection of Nature. 

The CPT theorem suffices to guarantee the equality of masses, lifetimes, spins, and exactly opposite charges and magnetic moments for particles and antiparticles. The following consequence is that the structure of bound species should be the same for both matter and antimatter in particular the fine, hyperfine structure, and Lamb shift of antiatoms should be the same as that of atoms. 

This differs from 0 when 77 1, i.e. when the gravitational accelerations of matter and antimatter are different. 

Abstract. The antiprotonic helium,pe He2+ (= pHe+), is a peculiar metastable atom, interfacing between matter and antimatter. A series of metastable states axe composed of the He nucleus, one electron in the ground Is configuration and one antiproton orbiting with large quantum numbers (n, l), where n l e 38. They possess... 

Unique interface between matter and antimatter Whereas particles and antiparticles cannot coexist stably, Antiprotonic Helium is an exceptional case, where an intruder antiparticle (p) coexists with the normal matter (helium medium) for microseconds. Here, the property of the orbiting p (charge, mass, magnetic moment and other QED characteristics) can be probed. It is an interesting irony that the property of the proton cannot always be studied so precisely, because there is no atomic system in which a proton is orbiting. 

Abstract. CPT invariance is a fundamental property of quantum field theories in flat space-time. Principal consequences include the predictions that particles and their antiparticles have equal masses and lifetimes, and equal and opposite electric charges and magnetic moments. It also follows that the fine structure, hyperfine structure, and Lamb shifts of matter and antimatter bound systems should be identical. 

Hence Eq. (3.6.15) is not merely an academic exercise Indeed, positron emission tomography (PET) is a known analytical technique used in medicine (the annihilation rate is subtly spindependent and varies, depending on the type of human body tissue traversed). When matter and antimatter collide in the universe, they annihilate each other in a cosmic version of Eq. (3.6.15). 

Color change is perhaps the simplest version of antisymmetry. The general definition of antisymmetry, at the beginning of this section, however, calls for a much broader interpretation and application. The relationship between matter and antimatter is a conspicuous example of antisymmetry. There is no limit to down-to-earth examples, as well as to abstract ones, especially if, again, symmetry is considered rather loosely. 

Not too many theories have been formulated from this point of view and some of the more interesting cases are at the speculative stage of development. Even so, it is remarkable how some of the most enigmatic of natural phenomena have no convincing explanation apart from broken-symmetry theories. Included are the initiation or nucleation of phase transitions, superconductivity (T4.5.1), the arrow of time (entropy) and the cosmic imbalance between matter and antimatter. The beauty of the world, indeed seems to lie in approximate symmetries. 

Like numbers and their conjugates, matter and antimatter would merge naturally if the two conjugate surfaces constituted the double cover of a... 

Mobius strip. In this way the antimatter mystery disappears matter and antimatter are one and the same thing, which merely appear to be different depending on their position in the double cover. In more dimensions the Mobius model is replaced by a projective plane, obtained from an open hemisphere on identifying points on opposite sides of the circular edge. Topologically equivalent constructs are known as a Roman surface or a Klein bottle. 

To understand why there is no mutual annihilation of matter and antimatter that come into contact at the interface, it is noted that these phases are separated in the direction of the fourth coordinate u. By construction, points separated by the interface have their world lines (u) in opposite directions and therefore with perceived time flow inverted. This time difference prevents contact and hence annihilation across the interface. 

For example, where is the antideuterium More generally, where is the antimatter At the microscopic level, that is, the level of fundamental particles that make up the Earth, Sun, and Milky Way, all evidence points to a clear symmetry between matter and antimatter yet, on the macroscopic level we observe an asymmetry—matter dominates the cosmos. Why should this be Did the... 

The absence of antimatter only spurs more questions. Why did the big bang elect to serve up matter rather than antimatter Or did the big bang create both matter and antimatter, but in slightly different amounts so that when particles and antiparticles annihilated each other, there was a residue of matter remaining that, after 15 billion years of expansion, makes up the current universe There are plausible answers to these questions, but the answers are laced with speculation and uncertainties. Speculation is not always unproductive, however. Today s provisional answers are likely to be present in tomorrow s facts. 

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