- #1

marcus

Science Advisor

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Dearly Missed

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## Main Question or Discussion Point

The two that look most promising to me are Lorentzian DT and Loop.

To look at the raw numbers---sheer quantity of research papers written per year---you'd say LQG was growing rapidly and DT was flat.

Lorentzian DT was first proposed in 1998 (a paper by Ambjorn and Loll), here are some preprint numbers:

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/1998/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/1999/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2000/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2001/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2002/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2003/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2004/0/1

LORENTZIAN DT (etc.) PREPRINTS

Numberwise, DT doesn't look like much is happening.

Loop has been going longer, at least since the early 1990s. Here are output numbers for Loop and allied QG approaches.

Year 1994:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1994/0/1

Year 1995:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1995/0/1

Year 1996:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1996/0/1

Year 1997:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1997/0/1

Year 1998:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1998/0/1

Year 1999:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1999/0/1

Year 2000:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2000/0/1

Year 2001:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2001/0/1

Year 2002:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2002/0/1

Year 2003:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2003/0/1

Year 2004:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2004/0/1

LOOP (etc.) PREPRINTS

The 2004 figures are up through 19 December, which is close enough to yearend so one gets an idea.

I have been reading nothing but DT papers this morning. the approach has some unique and impressive advantages working in its favor. I would like to be able to compare these two quantum spacetime theories on an equal footing.

Their most noticeable disagreement is apt to concern the area and volume operators. As yet no indication that in DT these will have discrete spectra.

I would like to know why the research output in DT is essentially flat. Given its apparent promise and the recent (2004) success, why arent more people getting into DT?

To look at the raw numbers---sheer quantity of research papers written per year---you'd say LQG was growing rapidly and DT was flat.

Lorentzian DT was first proposed in 1998 (a paper by Ambjorn and Loll), here are some preprint numbers:

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/1998/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/1999/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2000/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2001/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2002/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2003/0/1

http://arxiv.org/find/grp_physics/1...gravity+AND+Lorentzian+quantum/0/1/0/2004/0/1

LORENTZIAN DT (etc.) PREPRINTS

Code:

```
1998 3
1999 3
2000 5
2001 4
2002 6
2003 4
2004 4
```

Loop has been going longer, at least since the early 1990s. Here are output numbers for Loop and allied QG approaches.

Year 1994:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1994/0/1

Year 1995:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1995/0/1

Year 1996:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1996/0/1

Year 1997:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1997/0/1

Year 1998:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1998/0/1

Year 1999:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/1999/0/1

Year 2000:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2000/0/1

Year 2001:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2001/0/1

Year 2002:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2002/0/1

Year 2003:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2003/0/1

Year 2004:

http://arXiv.org/find/nucl-ex,astro...m+AND+OR+triply+doubly+special/0/1/0/2004/0/1

LOOP (etc.) PREPRINTS

Code:

```
1994 61
1995 83
1996 72
1997 70
1998 67
1999 76
2000 89
2001 98
2002 121
2003 139
2004 178
```

I have been reading nothing but DT papers this morning. the approach has some unique and impressive advantages working in its favor. I would like to be able to compare these two quantum spacetime theories on an equal footing.

Their most noticeable disagreement is apt to concern the area and volume operators. As yet no indication that in DT these will have discrete spectra.

I would like to know why the research output in DT is essentially flat. Given its apparent promise and the recent (2004) success, why arent more people getting into DT?

Last edited: