Many Worlds in One: The Search for Other Universes (28 page)

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Authors: Alex Vilenkin

BOOK: Many Worlds in One: The Search for Other Universes

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Polchinski is largely responsible for the realization that string theory must include branes of different dimensions.

Bubbles of
higher
energy density can also be formed, though with a much smaller probability.

Edward Witten, one of the leading string theorists, was awarded the 1990 Fields Medal—the mathematics equivalent of the Nobel Prize.

The minimum radius of the de Sitter sphere is roughly equal to the distance traveled by light during one doubling time of inflation.

The existence of such a class of observers can be taken as a definition of an expanding universe.

More precisely, the quantity called the
wave function
is found by adding up the contributions of different histories. The probability is given by the square of the wave function.

The error in my original paper was independently noticed and corrected by Andrei Linde, by Valery Rubakov, and by Yakov Zel’dovich and Alexei Starobinsky.

The following day Hawking had another important engagement: he went to Hollywood to have his electronic voice recorded for a special episode of the animated television show
The Simpsons
.

The quaternion is a generalization of the more familiar complex number. It has one real and three imaginary parts.

Hill and Wang
A division of Farrar, Straus and Giroux
19 Union Square West, New York 10003

www.fsgbooks.com

Drawings by Delia Schwartz-Perlov and the author

eISBN 9780374707149

First eBook Edition : June 2011

Published in 2006 by Hill and Wang
First paperback edition, 2007

The Library of Congress has cataloged the hardcover edition as follows: Vilenkin, A. (Alexander)

Many worlds in one : the search for other universes / Alex Vilenkin.—1st ed.

p. cm.

Includes bibliographical references and index.

ISBN-13: 978-0-8090-9523-0 (hardcover : alk. paper)