Dr. Glenn Starkman
Case Western Reserve University
Project Title:
Can Cosmology Survive Without Birkhoff's Law?
Summary:
General Relativity (GR) is one of the great intellectual triumphs of the 20th century. Einstein transformed space and time into a single dynamic entity, space-time, that affects the motion of the objects in it, yet is altered by them. But looking at galaxies and clusters we find matter in them moving too fast for gravity to hold them together. Dark matter is a possible explanation that we spend great effort searching for. GR also tells us that the cosmic expansion should be slowed by matter's gravity; yet it accelerates. Instead of abandoning GR, we invent dark energy. Perhaps GR is wrong on large scales. Alternative theories are emerging that are testable. But a fundamental problem is largely ignored: GR has special properties that enable us to calculate the behaviour of stars, galaxies, etc. Among these is Birkrhoff's Theorem. Loosely, it says the gravity inside a region is independent of the matter outside. Without this, the acceleration at one place could depend on all the masses in the universe. No GR alternative has a Birkhoff's Theorem. Can we compute reliably in these theories? If so, how? If not, what do we do?
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Case Western Reserve University
Project Title:
Can Cosmology Survive Without Birkhoff's Law?
Summary:
General Relativity (GR) is one of the great intellectual triumphs of the 20th century. Einstein transformed space and time into a single dynamic entity, space-time, that affects the motion of the objects in it, yet is altered by them. But looking at galaxies and clusters we find matter in them moving too fast for gravity to hold them together. Dark matter is a possible explanation that we spend great effort searching for. GR also tells us that the cosmic expansion should be slowed by matter's gravity; yet it accelerates. Instead of abandoning GR, we invent dark energy. Perhaps GR is wrong on large scales. Alternative theories are emerging that are testable. But a fundamental problem is largely ignored: GR has special properties that enable us to calculate the behaviour of stars, galaxies, etc. Among these is Birkrhoff's Theorem. Loosely, it says the gravity inside a region is independent of the matter outside. Without this, the acceleration at one place could depend on all the masses in the universe. No GR alternative has a Birkhoff's Theorem. Can we compute reliably in these theories? If so, how? If not, what do we do?
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