-
Notifications
You must be signed in to change notification settings - Fork 98
/
NullPotential.py
165 lines (145 loc) · 4.29 KB
/
NullPotential.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
###############################################################################
# NullPotential.py: class that implements a constant potential
###############################################################################
from .Potential import Potential
class NullPotential(Potential):
"""Class that implements a constant potential with, thus, zero forces. Can be used, for example, for integrating orbits in the absence of forces or for adjusting the value of the total gravitational potential, say, at infinity"""
normalize= property() # turn off normalize
def __init__(self,amp=1.,ro=None,vo=None):
"""
NAME:
__init__
PURPOSE:
initialize a null potential: a constant potential with, thus, zero forces
INPUT:
amp - constant value of the potential (default: 1); can be a Quantity with units of velocity-squared
ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)
OUTPUT:
(none)
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
Potential.__init__(self,amp=amp,ro=ro,vo=vo,amp_units='velocity2')
self.hasC= True
self.hasC_dxdv= True
self.hasC_dens= True
return None
def _evaluate(self,R,z,phi=0.,t=0.):
"""
NAME:
_evaluate
PURPOSE:
evaluate the potential at R,z
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
Phi(R,z)
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 1.
def _Rforce(self,R,z,phi=0.,t=0.):
"""
NAME:
_Rforce
PURPOSE:
evaluate the radial force for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
the radial force
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.
def _zforce(self,R,z,phi=0.,t=0.):
"""
NAME:
_zforce
PURPOSE:
evaluate the vertical force for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
the vertical force
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.
def _dens(self,R,z,phi=0.,t=0.):
"""
NAME:
_dens
PURPOSE:
evaluate the density for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
the density
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.
def _R2deriv(self,R,z,phi=0.,t=0.):
"""
NAME:
_R2deriv
PURPOSE:
evaluate the second radial derivative for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
the second radial derivative
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.
def _z2deriv(self,R,z,phi=0.,t=0.):
"""
NAME:
_z2deriv
PURPOSE:
evaluate the second vertical derivative for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
the second vertical derivative
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.
def _Rzderiv(self,R,z,phi=0.,t=0.):
"""
NAME:
_Rzderiv
PURPOSE:
evaluate the mixed R,z derivative for this potential
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
phi - azimuth
t - time
OUTPUT:
d2Phi/dR/dz
HISTORY:
2022-03-18 - Written - Bovy (UofT)
"""
return 0.