or, by (11):
This equation determines the characteristic speeds
V, whose maximal value
is the pulse speed. In the case of moments and for a
non-degenerate gas at rest and in equilibrium this equation
reads, by (42
),
is the Maxwellian phase density, so that all integrals in (47
) are Gaussian integrals, easy to calculate. Weiss [49] has calculated the speeds
V
for different degrees
n
of extended thermodynamics. Recall that
,
range over the values 1 through
n
. He has made a list of
which is represented here in Table
1
.
is normalized in Table
1
by
, the ordinary speed of sound, sometimes called the adiabatic
sound speed.
Inspection of Table 1 shows that the pulse speed increases monotonically with the number of moments and there is clearly a suspicion that it may tend to infinity as n goes to infinity. This suspicion will presently be confirmed.
![]() |
Speeds of Propagation in Classical and Relativistic
Extended Thermodynamics
Ingo Müller http://www.livingreviews.org/lrr-1999-1 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |