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Books > Science & Mathematics > Astronomy, space & time > Cosmology & the universe
Prior to the 1920s it was generally thought, with a few exceptions,
that our galaxy, the Milky Way, was the entire Universe. Based on
the work of Henrietta Leavitt with Cepheid variables, astronomer
Edwin Hubble was able to determine that the Andromeda Galaxy and
others had to lie outside our own. Moreover, based on the work of
Vesto Slipher, involving the redshifts of these galaxies, Hubble
was able to determine that the Universe was not static, as had been
previously thought, but expanding. The number of galaxies has also
been expanding, with estimates varying from 100 billion to 2
trillion. While every galaxy in the Universe is interesting just by
its very fact of being, the author has selected 60 of those that
possess some unusual qualities that make them of some particular
interest. These galaxies have complex evolutionary histories, with
some having supermassive black holes at their core, others are
powerful radio sources, a very few are relatively nearby and even
visible to the naked eye, whereas the light from one recent
discovery has been travelling for the past 13.4 billion years to
show us its infancy, and from a time when the Universe was in its
infancy. And in spite of the vastness of the Universe, some
galaxies are colliding with others, embraced in a graceful
gravitational dance. Indeed, as the Andromeda Galaxy is heading
towards us, a similar fate awaits our Milky Way. When looking at a
modern image of a galaxy, one is in awe at the shear wondrous
nature of such a magnificent creation, with its boundless secrets
that it is keeping from us, its endless possibilities for harboring
alien civilizations, and we remain left with the ultimate knowledge
that we are connected to its glory.
The meaning of "quark matter" is twofold: 1) It refers to compound
states known as "subquarks" (the most fundamental constituents of
matter), with quarks consisting of nuclear matter or "nucleons"
(the constituents of the nucleus), and 2) compound states of quarks
that consist of roughly equal numbers of up, down, and strange
quarks, and which may be absolutely stable. Recently, both types of
quark matter have become very intriguing subjects in physics and
astronomy since the recently discovered Higgs boson, which may be
taken as a composite object (possibly, a bound state of
subquark-antisubquark pairs). Additionally, many recently observed
compact stars have been considered "strange stars" (stars
consisting of quark matter). In this book, these subjects in
physics and astronomy are discussed without requiring readers to
comprehend mathematical details. This book consists of three
chapters: Chapter One: "Quark Matter and Strange Stars", Chapter
Two: "Composites of Subquarks as Quark Matter", and Chapter Three:
"Dark Energy, Dark Matter, and Strange Stars". Their contents
include the following: In Chapter One, quark matter and strange
stars are discussed in detail. In Chapter Two, the unified subquark
model of all fundamental particles (quarks, leptons, and gauge and
Higgs bosons) and forces (strong, electromagnetic, weak, and
gravitational forces) is discussed in detail. In Chapter Three,
pregeometry, in which the general theory of relativity for gravity
can be derived as an approximate theory at long distances, is
briefly reviewed. Furthermore, special and general theories of
"inconstancy" in pregeometry in which fundamental physical
constants may vary are introduced. Finally, possible solutions to
the most puzzling problem in current cosmology of dark energy and
dark matter in the universe are presented. Between Chapters One and
Two, pictures of Dr. Abdus Salam added, as Dr. Salam was one of the
founders of subquark models. Also, between Chapters Two and Three,
pictures of Dr. Andrei Sakharov are added, as Dr. Sakharov was the
founder of pregeometry.
Recent cosmological observations have posed a challenge for
traditional theories of gravity: what is the force driving the
accelerated expansion of the universe? What if dark energy or dark
matter do not exist and what we observe is a modification of the
gravitational interaction that dominates the universe at large
scales? Various extensions to Einstein's General Theory of
Relativity have been proposed, and this book presents a detailed
theoretical and phenomenological analysis of several leading,
modified theories of gravity. Theories with generalised
curvature-matter couplings are first explored, followed by hybrid
metric-Palatini gravity. This timely book first discusses key
motivations behind the development of these modified gravitational
theories, before presenting a detailed overview of their subsequent
development, mathematical structure, and cosmological and
astrophysical implications. Covering recent developments and with
an emphasis on astrophysical and cosmological applications, this is
the perfect text for graduate students and researchers.
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