DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

maximal extension of a space-time
P(k) [h 3 Mpc 3 ]
10 6
10 5
10 4
10 3
10 2
10 1
k [h Mpc 1
]
ACOE
ACOR
APMT
APMgal.3D
APMgal.2D
CfA2
LCRS
IRASP
IRASTE
Observed power spectrum of galaxies and clusters of
galaxies: ACO-E and ACO-R are spectra for Abell-
ACO clusters as derived with two different techniques;
APM-T is the spectrum of APM clusters; APM-gal.3D
and APM-gal.2D are spectra of APM galaxies found
from 3-D and 2-D data; CfA2 is the spectrum of the
SSRS+CfA2 130 Mpc/h sample; LCRS is the spectrum
of the Las Campanas Redshift Survey; IRAS-P and
IRAS-TE are spectra of IRAS galaxies found by two
different groups. Notice the difference in amplitude
when the power spectrum corresponds to galaxies and
clusters. The difference is due to bias.
despite frequent and systematic attempts to observe
them, sunspots were detected only occasionally.
During this period, when sunspots
were detected, they were observed at relatively
low latitudes. The solar rotation was slower than
today, in addition, and the differential rotation
was more pronounced. This period of unusual
low solar activity is also documented indirectly
by an unusually small number of aurora observations
and unusual high counts in cosmogenic
nuclides such as 14 C and 10 Be. The 10 Be concentrations
in ice cores suggest that a solar cycle
still was existent but its duration was reduced to
9 years. The combination of these observations
with models of solar activity suggests that during
the Maunder Minimum the solar constant
might have been reduced by 0.2 to 0.5%. The
Maunder Minimum coincides with an unusual
cold time period, the Little Ice Age.
maximalextensionofaspace-time Aspacetime
is called extendible if it has an extension.
A maximal extension of a space-time is an extension
that is not extendible. See extensions of
space-times.
© 2001 by CRC Press LLC
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maximally rotating black hole A Kerr black
hole for which the angular momentum per unit
mass (which in geometrized units has dimensions
of [mass]) reaches a maximum value equal
to the mass of the black hole, in these units.
Thus, the maximum angular momentum expected
from the solution of Einstein’s field equation
for a rotating black hole is equal toGM 2 /c,
and corresponds to a black hole rotating at the
speed of light at a radius equal to GM/c 2 , i.e.,
at the event horizon for this maximally rotating
case. (In the nonrotating case the event horizon
is at r = 2GM/c 2 .) As shown by Thorne, a
rotating black hole interacting with its environment
can come close to, but cannot reach, this
limit.
maximally symmetric space A metric space
which admits the maximum number N of linearly
independent Killing vectors. If D is the
dimension of space, then N = D(D + 1)/2
and the space is isotropic with respect to each
point; therefore, it is also homogeneous and has
constant curvature.
For D= 3, one has N= 6 and the spacetime
is described by one of the Robertson–
Walker metrics. See homogeneity, isotropy,
Killing vector, Robertson–Walker cosmological
models.
Maximum Observable Frequency (MOF)
Defined as the highest frequency at which a
reflection from the ionosphere occurs during
oblique incidence sounding between two points.
The MOF is a measurement made on a real propagation
path using an oblique sounder capable
of exciting all possible paths for the circuit. It
may also refer to an identified mode, in which
case the mode would be shown with the MOF.
See ionospheric radio propagation path, oblique
ionogram.
maximum probable wave (or probable maximum
wave) A description of the largest wave
that is expected to exist in a particular sea condition.
Used for design purposes.
Maxwell–Boltzmann distribution An expression
for the fraction of molecules f(v)in a
gas that have velocity v within a small specified