## January 10, 2006

### Killing Horizons

You know what a black hole is, right?  Not so fast, these cul de sacs in space-time may not exist at all.

We’ve all read about the enormous black hole at the center of our galaxy, the Milky Way.  However, black holes by their nature can’t be seen since light doesn’t escape from them.  What is observed is matter falling towards what appears to be almost a black hole.  These observations would be the same whether or not actual black holes exist.

Son Jarah, a string theory post-doc at the Free University of Brussels, is more concerned over his latest paper than he’s been over the dozens that he’s written before.  The other papers have properly academic titles like “K-Theory and S-Duality: Starting Over from Square 3”, “IIB Soliton Spectra with All Fluxes Activated”, and “Nonabelian Superconductors: Vortices and Confinement in ${\cal N}=2$ SQCD”.  Despite intense curiosity, I have no idea what any of them are about.

His latest paper is simply “Killing Horizons”.  Even though I don’t understand the math, I do know what this paper is about.

It’s both a radical claim and one that is not, strictly speaking, in his field of string theory: two reasons why a young man who will someday be looking for tenure has cause to be concerned.

Jarah’s claim is that event horizons introduce anomalies into physics which both contradict the usual ways that we formulate physical principals and are unhelpful in proceeding towards a Grand Unified Field Theory (GUT).  If there are no event horizons, then there are essentially no black holes.  He puts his claim a little more cautiously: “…while the elimination of horizons is a possibility which may be a consequence of a hypothesized principle, we have presented no evidence that either this possibility or this principle is realized.”  He goes on to suggest observational data which may soon be available which would tend to validate (or contradict) his hypothesis.

Black holes have been getting grey for a while.  Hawking long ago suggested that they leak “Hawking radiation”.  Lately Hawking has agreed with others that information trapped inside a black hole can leak out.  The black holes of string theory aren’t really black

An implication of Jarah’s argument is that physics researchers have overlooked the anomalies introduced by the concepts of event horizons and black holes; their energy is better spent in speculating on a universe which contains neither.

If this argument is correct, for example, the strange concept of a period of “inflationary expansion” in the very early life of our universe is unnecessary and unhelpful.  According to Jarah, there is a simpler quantum explanation for the fact that the entire observed universe seems to have the same level of background radiation despite the observation that some parts of the universe would seem to be across the event horizon from other parts.

Jarah agonized over how strong a claim to make in the abstract for his paper.  “I rarely read papers with radical claims, myself,” he said.  On the other hand, the abstract should be interesting or no one will read the paper.  And it should describe what’s inside.

Not very long ago, the referees of a scientific journal would have decided whether or not this paper should be published.  Such gatekeepers have been notoriously conservative about papers which upset the conventional wisdom.  On the other hand, they’ve probably saved many hot-headed young scientists from career-damaging mistakes.  For better or worse (I think better), Jarah and his contemporaries publish their papers simply by posting them on a dedicated website.

That doesn’t mean you and I can self-publish our speculations there, however; it’s Jarah’s undergraduate degree from Caltech and doctorate from Berkeley which give him write privileges to this repository.  Jarah’s paper will only get whatever attention it gets because of his credentials, other papers he’s published, talks he’s given, and conferences he’s participated in.

Science like business advances in fits and starts.  A new theory fits all known facts.  Then new observations, usually first thought to be observational errors, fall outside the penumbra of the current theory.  The current theory is patched and patched like an old computer program to fit the new facts.  Finally someone takes the bold step of replacing the patched-up old theory with a new, cleaner one that explains the then known facts.  And the cycle starts again.

Just as most new businesses fail, most new ideas are wrong.  It is only with hindsight that it is clear what the breakthroughs are.  I’m proud of Jarah for this intellectual startup.  If I could, I would short black holes; they’re history.