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Inflation, separation of gravity from other forces, separation of strong from electroweak force, and electroweak symmetry breaking, are all different events. It's easiest to start by describing the different sorts of fields involved. Quantum fields get classified by their "spin", which describes the angular momentum states that field quanta (particles) can ...

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Single clock inflation simply means that a single field's value has a one to one relationship with the scale factor $a$. For this to happen you need the field to be undergoing slow roll otherwise the expansion will depend on the field value and its time derivative.

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Objects moving in an expanding universe experience an apparent drag force called the Hubble drag and given by: $$D = 2\frac{\dot{a}}{a}\mathbf{u}$$ where $\mathbf{u}$ is the comoving velocity and $a$ is the scale factor. This isn't a real force, it's the result of the universe expanding away from the moving object, but the end result is that in an ...

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Just some minor remarks: (i) An expanding universe filled with matter and a zero spatial curvature are not in contradiction. Please read up about the Friedmann equations and the Robertson-Walker metric. (Sorry, but I think that's the way to understand cosmology properly.) (ii) Flat geometries are not necessarily infinite (non-compact). Take for example a ...

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According to what I have read, we have measured the universe to be flat More or less. I'm happy enough with the WMAP results that indicate that the universe is flat. To be blunt I never thought it could be anything other than flat. the shape of the universe is directly related to the mass-energy density. That's what they say. But IMHO two out of three ...

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As the universe expands, isn't energy required for stuff to fill in? If you had a universe with a cosmological constant of the right size and magnitude and nothing else, it is possible to expand, in particular there might be no mass, no matter, no antimatter, no dark matter, no light, nothing except space, time, curvature, and a cosmological constant. You ...

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