From the Universe to the Elementary Particles: A First Introduction to Cosmology and the Fundamental Interactions (Undergraduate Lecture Notes in Physics)
Ulrich Ellwanger
Language: English
Pages: 192
ISBN: 3642243746
Format: PDF / Kindle (mobi) / ePub
In this book, the author leads the reader, step by step and without any advanced mathematics, to a clear understanding of the foundations of modern elementary particle physics and cosmology. He also addresses current and controversial questions on topics such as string theory. The book contains gentle introductions to the theories of special and general relativity, and also classical and quantum field theory. The essential aspects of these concepts are understood with the help of simple calculations; for example, the force of gravity as a consequence of the curvature of the space-time.
Also treated are the Big Bang, dark matter and dark energy, as well as the presently known interactions of elementary particles: electrodynamics, the strong and the weak interactions including the Higgs boson. Finally, the book sketches as yet speculative theories: Grand Unification theories, supersymmetry, string theory and the idea of additional dimensions of space-time. Since no higher mathematical or physics expertise is required, the book is also suitable for college and university students at the beginning of their studies. Hobby astronomers and other science enthusiasts seeking a deeper insight than can be found in popular treatments will also appreciate this unique book.
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exerts a force. The presence of an electric field is measurable only with the help of charged objects, which allow the force exerted by the field to be measured. The components gμν (r , t) of the metric, discussed in the previous chapter on general relativity, are fields as well. These fields play two roles: on the one hand they determine the curvature of space-time, and on the other hand the field g00 (r , t) is U. Ellwanger, From the Universe to the Elementary Particles, Undergraduate Lecture
the electromagnetic interaction. Equation (12.18) differs from (11.4) in that (a) the θ dependences of A(1) (θ ) and A(2) (θ ) are no longer the same, and (b) the energy dependence of the contribution of the loop diagram in Fig. 12.6 differs from that in the diagram in Fig. 12.5. However, the contribution of the loop diagram in Fig. 12.6 is numerically relevant c3 /κ ∼ 2.4 × 1018 GeV, for which the second term in only for energies E ∼ (12.18) becomes of the same order as the first term. In fact,
of the probability of a given process. The Feynman diagrams without loops reproduce the results of classical physics, as we saw in Sect. 5.3 in the example of the calculation of the probability P(θ ). Feynman diagrams with loops lead to additional contributions, which are, however, always proportional to higher powers of Planck’s constant (the power of is equal to the number of loops). For this reason the contributions from loop diagrams are denoted as quantum effects; the results of classical
Orbifold, 167 P Parity transformation, 87–88, 94 Parity violation, 86–87 Pauli, W., 8 Penzias, A.A., 21 Perl, M.L., 83 Perlmutter, S., 23 Photino, 156–157 Photon, 9, 37, 60–71, 129–133, 138 Photon–photon scattering, 67 Pierre Auger observatories, 119 Planck mass, 161, 163 Planck satellite, 26 Planck’s constant, 49, 62, 68 Planck, Max, 49 Plasma, 20 Polarization vector, 69, 86–87 Politzer, H.D., 148 188 P (cont.) Positron, 10, 12 Propagator, 63, 70 Proper time, 32–34 Proportional chamber, 107
pressure p(t) ∼ 13 r c2 . Then, (2.6) and (2.7) imply—under the assumption Λ ∼ 0— √ that a(t) ∼ a0 t instead of (2.10) during this early stage.) This Universe sort of exploded: it expanded very rapidly, whereupon its temperature and density decreased. This process is known as the “Big Bang”. In the course of time, the baryons, nuclei, atoms, molecules, and ultimately the stars and galaxies formed. Using (2.6) and (2.7), the laws of thermodynamics (which allow the temperature to be determined as a
