A question for a cosmologist about brane death

English: An alternate version of :Image:Calabi...
Image via Wikipedia

The “string theory revolution” began in 1984 and I graduated with my astrophysics degree in 1987, perhaps unsurprisingly, having been taught nothing about it at all.

But now, reading The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, (a good book) I discover that we may all be living on a brane – a three dimensional slab of reality “floating” inside ten dimensional space. And indeed there may be many of these branes perhaps just milimetres away from all of us, each of which might appear to its inhabitants (if its physical laws allow for any inhabitants, of course), as a fully dressed universe in its own right.

Now, so the theory goes, photons and indeed all particles of the electroweak or grand unified force (assuming it exists) cannot move between the branes, but gravitons, the theoretical (and undetected so far) quantum messengers of the gravitational force can. Indeed this ability of gravitons to stray into other dimensions is what is believed to make the gravitational force seem so weak to us.

But what if a highly massive object in another brane were to pass close by us. Such an object could have a very strong gravitational field that we would feel in this universe/brane and which could have drastic effects, perhaps putting us all at risk of “brane death”. Couldn’t it?

Well, I suspect I have misunderstood the mathematics of this. The fact we don’t see galaxies ripped to pieces by the super massive black holes at the centres of galaxies in other branes is rather more likely to lead me to believe that I have missed a point about how this works than to conclude the theory is that easily disproved.

Perhaps a reader might enlighten me?


More delays for VMUFAT

Seagate Barracuda HDD
Seagate Barracuda HDD (Photo credit: Andres Rueda)

Obviously the whole world is waiting for VMUFAT to hit the streets, but it looks as though it will have to hold its collective breath a little longer, as I have hit more delays.

Working with big volumes (several megabytes) reveals the code eats a lot of memory in ways I don’t yet fully understand. But that will need to be fixed, even if no one is ever really likely to want a 32MB VMUFAT volume.

Spoke too soon (of course)

Image via Wikipedia

It’s like the curse of the software demonstration: it doesn’t break until then.

I discovered as soon as I posted that I was ready to (try to) push the VMUFAT stuff up to main line that there was a bug in the software.

Very large VMUFAT volumes were not being properly handled. But I think I have fixed that now. Some more testing is due, though, before I proclaim victory a second time!

VMUFAT: almost done (I hope)

A Sega Dreamcast Visual Memory Unit
Image via Wikipedia

About a decade ago I first wrote some Linux kernel code that would handle the filesystem on the little slab of flash storage that came with a SEGA Dreamcast Visual Memory Unit (VMU).

A few attempts to get this in the kernel mainline then followed. It was a bruising experience and unsuccessful. But I am about to try again.

I am a bit more confident this time – not least because I have written some userland code which will allow anyone to test the filesystem out, whether they have a VMU or not: mkfs.vmufat is now available at GitHubhttps://github.com/mcmenaminadrian/mkfs.vmufat/blob/master/mkfs.vmufat.c

Secondly I do think I am a better coder thanks to the MSc and have put some effort into fixing the filesystem code itself.

But we’ll see, hopefully tomorrow, how it goes down.

GitHub message confirmed genuine

Image representing GitHub as depicted in Crunc...
Image via CrunchBase

It seems the GitHub message is genuine, though looking through Twitter suggests there is a lot of unhappiness about the way the message was spread, its timing and its content.

Not sending such a message from your own mailservers also looks very foolish to me – checking the headers of a dodgy looking email is, I am sure, the first thing many of us do when we are not sure.

Anyway, as GitHub don’t tell you – here is how to do what they are asking (approve as valid your SSH keys):

ssh-keygen -lf ~/.ssh/id_rsa.pub

And check the output against GitHub’s public key.

“Github” message a scam?

About an hour ago I received an email message claiming to be from Github stating:

A security vulnerability was recently discovered that made it possible for an attacker to add new SSH keys to arbitrary GitHub user accounts. This would have provided an attacker with clone/pull access to repositories with read permissions, and clone/pull/push access to repositories with write permissions. As of 5:53 PM UTC on Sunday, March 4th the vulnerability no longer exists.

While no known malicious activity has been reported, we are taking additional precautions by forcing an audit of all existing SSH keys.

Thunderbird has flagged it as a scam, though it looks very credible, but the email header is a bit flaky as the email has not come from a GitHub server:

X-Original-To: adrian@newgolddream.dyndns.info
Delivered-To: adrian@newgolddream.dyndns.info
Received: from o3.newslettergrid.com (o3.newslettergrid.com [])
	by webmail.thecentreground.com (Postfix) with SMTP id 90FE4BAC449
	for <adrian@newgolddream.dyndns.info>; Wed,  7 Mar 2012 18:21:49 +0000 (GMT)

The worrying thing is that there is nothing on the github site itself to say if it is genuine or indeed a scam.

Right now I am not acting on the message.

Comrades, let’s optimise!

Cover of US edition of Red PlentyOne thing has occupied my free time more than anything else these last few days – Francis Spufford‘s marvellous work of history and imagination, Red Plenty.

The book is a marvel in joining linear programming, economics, mathematics, cybernetics, computing, chemistry, textiles, politics, sociology, popular music, genetics and history all in one long fabric. The book is not quite a novel but nor is it history, the author himself calls it a “fairy tale”.

The ground on which it works is the Soviet Union between Stalin’s death in 1953 and what might be considered as the cementing in of what was later called the “era of stagnation” in 1970. The main characters are the scientists and engineers who saw, in that time, a new hope for the USSR in Khrushchev‘s claims that “this generation will know communism” – with a 1980 deadline – and who was willing to indulge their hopes of a rational, mathematical reshaping of the Soviet system.

Novelisations of actual events and the actions of real and fictional people are interwoven with passages of historical and scientific commentary and the effect is that we can sympathise with the hopes and dreams of the scientists but also know that they are destined for heart-breaking (for many at least) failure as the essential gangsterised and cynical nature of the state created by Stalin crushes their hopes which, in any case, were always naive at best.

But along the way we get to understand why the Soviet Union excelled at maths (and to a lesser extent computing science) – as it was both free of the pollutant of Marxism-Leninism but also valued by the Marxist-Leninists – scared the west with epic economic growth in the 1950s and so failed its citizens economically – nobody lost their job or reputation by failing the consumer, but if you failed to deliver a capital good you risked both.

We also get a portrait of a society that is much more granulated than the simple riffs of anti-communism would let us believe.

At the top we see Khrushchev was a fool who had done many evil things but he also hoped to make amends, Brezhnev and Kosygin the champions of a new wave of repression and stultification but also men frightened by how earlier reforms led to massacres and desperate not to see that return.

But most of all we see the scientists and their hopes get ground down. They all begin as believers and have only three choices in the end: to rebel and lose every physical thing, to compromise and lose hope or to opt out of the real world and chose only science.

The bitterness of their defeat, and that of all those who hoped for a better world after Stalin, is summed up in the words of a (real) song, sung in the book by Alexander Galich, a writer of popular songs turned underground critic and, after the shock of the public performance, recounted here, of his satirical works, exile.

We’ve called ourselves adults for ages

We don’t try to pretend we’re still young

We’ve given up digging for treasure

Far away in the storybook sun.

(As a companion work I’d also recommend Khrushchev: The Man and His Era)