ConceptChecks
ConceptCheck 26-1: Early expansion is different in the inflation model compared to the gradual Hubble expansion. As shown in Figure 26-2, the inflationary model predicts an even smaller universe at early times than that described by gradual expansion. In this more compact condition, much more material would be in contact and reach the same temperature. Then, during inflation, this matter would get spread out so much that today this matter is at opposite ends of our observable universe (such as points A and B).
ConceptCheck 26-2: Yes. Inflation expands the universe by about a factor of 1050. With the curved space of the universe represented on the surface of a sphere, after the radius of the sphere increases during inflation by a factor of 1050, the surface (and universe) would appear flat. Due to tremendous inflation, just about any initial curvature ends up nearly flat after inflation.
ConceptCheck 26-3: Yes. The up and down quarks are held together by the strong force. Since the strong force is transmitted by gluons, these gluons are also involved in holding a neutron together.
ConceptCheck 26-4: No. Photons are massless, whereas W and Z particles have mass. The particles of the Standard Model appear after spontaneous symmetry breaking has changed the electroweak force into two distinct forces (electromagnetic and weak), which are transmitted by distinct particles (photons and intermediate vector bosons).
ConceptCheck 26-5: As the universe expands, it cools down, and the average energy of colliding particles decreases. Therefore, as the universe expands, there is a spontaneous symmetry breaking when particles naturally begin to collide with energies below 100 GeV.
ConceptCheck 26-6: Shorter. The greater the mass of the virtual particles, the shorter they last. A virtual pair of protons lasts about 1/2000th as long as a virtual pair of electrons.
ConceptCheck 26-7: No. Electrically charged virtual pairs come with one positively charged particle and one negative particle, so the pair’s total charge is zero.
ConceptCheck 26-8: First, because the amount of antimatter would be equal to the amount of matter in our universe, this hypothesis would imply a lot of “hidden” antimatter. Second, near the boundary or boundaries of the hidden cache of antimatter, matter and antimatter would annihilate to produce gamma rays. And third, the gamma rays produced by these annihilations would be very easy to recognize because they all occur at the same energy determined by E = mc2. Taken together, these effects would make it very hard to hide so much antimatter.
ConceptCheck 26-9: The temperature of the universe steadily decreases with time as the universe expands. When the universe was less than 3 minutes old, hot radiation filling the universe was energetic enough to break apart protons and neutrons before they could begin to build atomic nuclei. However, the temperature also determines the average speed at which atomic nuclei collide into each other. After 15 minutes, the temperature was not high enough for colliding nuclei, with their charged protons, to overcome their electric repulsion and build larger nuclei.
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ConceptCheck 26-10: A clump of matter will not form. When the universe reaches T = 3000 K, the Jeans length is LJ = 100 light-years. Fluctuations shorter in length will not contract into clumps because there is not enough gravitational attraction to overwhelm the increased pressure that clumping would produce.
ConceptCheck 26-11: Cold dark matter particles (which are heavier and move at lower speeds) lead to “bottom up” formation, which is what we observe. Hot dark matter, such as neutrinos, leads to “top down” formation, which is not supported by observations.
ConceptCheck 26-12: We only notice four dimensions—three for space and one for time. That would leave seven hidden dimensions of space. If these dimensions are curled up tightly, as in Figure 26-24, we would not notice them until experiments could probe the tiny microscopic sizes scales in which they are curled.
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