Energy non-conservation at the very beginning

[savchenkoyana]

I want to use Nbody6 to simulate evolution of cluster in point-mass field KZ(14)=2 with GMG=4.3e10 Msun and RG=34 kpc. The energy is not conserved from the very beginning.

Could you please help me out? Is there some intuition why this could happen? This is a rather strong potential, but isn't the cluster supposed to survive at least a couple of Myr?

What I did:

I took input from the original Nbody6 example as a baseline (with slight modifications to reach the end of simulation) and it works fine. Then I modified it for my custom field:

1 10000.0
2000 1 25 10000 90 1
0.001 0.001 0.35 2.0 10.0 1000.0 4.0E-05 2.0 0.5
2 2 2 0 1 0 1 0 0 0
0 0 0 2 2 1 1 1 0 3
1 0 3 0 0 2 0 1 0 1
1 1 0 0 1 0 0 1 0 3
0 0 0 0 0 0 0 0 0 0
1.0E-04 0.001 0.1 1.0 1.0E-06 0.001
2.3 10.0 0.2 0 0 0.002 0.0 0.0
0.5 0.0 0.0 0.0 0.125
4.37E+10 34.0
20000.0 2 0
20000.0 2 0

What I see in my log is the following:

               N  NFIX  NCRIT  NRAND  NNBMAX  NRUN

            2000     1     25  10000      90     1


            ETAI      ETAR      RS0       DTADJ     DELTAT    TCRIT     QE        RBAR      ZMBAR

            1.0E-03   1.0E-03   3.5E-01   2.0E+00   1.0E+01   1.0E+03   4.0E-05   2.0E+00   5.0E-01


            OPTIONS

           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

           2  2  2  0  1  0  1  0  0  0  0  0  0  2  2  1  1  1  0  3  1  0  3  0  0  2  0  1  0  1  1  1  0  0  1  0  0  1  0  3  0  0  0  0  0  0  0  0  0  0


            DTMIN     RMIN      ETAU      ECLOSE    GMIN      GMAX

            1.0E-04   1.0E-03   1.0E-01   1.0E+00   1.0E-06   1.0E-03

            SINGLE STAR IMF:    NS =  2000  RANGE =  9.77E+00  2.00E-01  <MS> = 7.26E-01

            SCALING:    SX =  0.96  E = -2.60E-01  M(1) = 6.73E-03  M(N) = 1.38E-04  <M> = 5.00E-04

            TIME SCALES:   TRH = 5.1E+01  TCR =  2.83  2<R>/<V> =  2.83  SMAX =  0.125

            PHYSICAL SCALING:    R* = 2.00  M* =  1451.3  V* = 1.767  T* = 1.107  <M> = 0.73  SU = 8.9E+07

            GR SCALING:    V* =  1.77E+00  C =  1.70E+05  RZ =  1.04E-13

            POINT-MASS MODEL:    GMG =  3.0E+07  RG =  3.4E+01  OMEGA =  2.5E-03  RT = 37.91  RBAR =  2.00

            TIDAL PARAMETERS:    1.84E-05  0.00E+00 -6.13E-06  4.95E-03  TSCALE = 1.11E+00  RTIDE = 37.87


 ADJUST:  TIME =    0.00  Q = 0.50  DE =  0.0E+00  E = -0.250000  RMIN = 1.1E-03  DTMIN = 1.4E-05  TC =    0  DELTA =  0.0E+00  E(3) = -0.250000  DETOT =  0.000000


 T =     0.  N =  2000  <NB> = 58  KS =    0  NM =  0  MM = 0  NS =  2000  NSTEPS =          0         0          0          0  DE =  0.0E+00  E = -0.250000  M = 1.0000

 NRUN =  1  M# =  1  CPU =     0.0  TRC =  7.6  DMIN = 1.0E+02 1.0E+02 1.0E+02 1.0E+02  AMIN = 1.0E+02  RMAX = 0.0E+00  RSMIN = 0.350  NEFF =   886

    <R>  RTIDE  RDENS   RC    NC   MC   RHOD   RHOM  CMAX   <Cn>   Ir/R   UN    NP   RCM    VCM      AZ      EB/E   EM/E   TCR     T6  NESC  VRMS
 #1 0.78  37.9  0.03 0.3222  219  0.113    3.    14.    5.  75.8  0.264    0     0   0.000  0.0000   0.0040 -0.000 -0.000  2.83     0     0   1.2

       NNPRED    NBCORR  NBFULL  NBVOID    NICONV  NBSMIN  NBDIS  NBDIS2  NCMDER  NBDER  NFAST  NBFAST    NBLOCK    NBLCKR     NBPRED     NBFLUX  NIRECT  NRRECT  NURECT  NBRECT
 #2         0         0    1351        7        0       0      0       0       0      0      0       0         0         0          0          0       0       0       0       0

     NKSTRY  NKSREG  NKSHYP     NKSPER  NPRECT  NEWKS   NKSMOD    NTTRY  NTRIP  NQUAD  NCHAIN  NMERG  NEWHI  NSTEPT  NSTEPQ  NSTEPC
 #3        0      0       0          0       0      0        0        0      0      0       0      0      0       0       0       0

 ADJUST:  TIME =    2.00  Q =*****  DE =  1.0E+00  E =**********  RMIN = 7.8E-04  DTMIN = 8.7E-06  TC =*****  DELTA =  1.1E+05  E(3) =**********  DETOT =**********

         RESTART * * *   TIME =    0.00  ETAI =  0.001  ETAR =  0.001  ETAU =  0.100

 ADJUST:  TIME =    2.00  Q =-0.00  DE = -1.0E+00  E =**********  RMIN = 7.8E-04  DTMIN = 6.2E-06  TC =*****  DELTA = -2.3E+08  E(3) =**********  DETOT =**********

         RESTART * * *   TIME =    0.00  ETAI =  0.000  ETAR =  0.000  ETAU =  0.100

 ADJUST:  TIME =    2.00  Q =31.75  DE =  9.8E-01  E = 13.370483  RMIN = 7.8E-04  DTMIN = 4.3E-06  TC =   34  DELTA =  1.4E+01  E(3) = 13.370483  DETOT = 13.620483

         CALCULATIONS HALTED * * *