It's of course good that you remember it (I read the book about 2 years ago, and I didn't really remember it), but I don't know why you mention the configuration space. Xeelee never had access to it, moreover, they are literally afraid of it, which is why the bacteria of the configuration space were eventually shot by the Night Fighter.
What? The
Transcendent humanity had nearly mastered configuration space, and the Xeelee were so superior to them that a single Nightfighter could wipe out the entire human history including the era of the Transcendants despite them having multiple layers of acausality.
Both time and space in the Xeelee sequence are nothing more than emerging properties, that have their origin in the presence of particles and the relations between said particles. The configuration space itself is the total map of all possible states matter can take in the universe. The mentioned here states, when arranged in a given order, create a possible history that the universe can undergo. This translates into every single possible version of the history of the main universe being represented in this space, as one of the possible arrangements of the "reality dust of nows".
The dimensionality of this map
d, which is understood here as the amount of measurements of the distances between particles that one needs to know in order to fully define a given space, increases with the number of particles in the system
n, as
d~n. Out of all of the states of matter represented in this space one of them is special, as it represents all particles in the universe being located in a single point. As we can deduce from this description, this state represents the initial singularity, as at that "moment" all particles in the universe were in fact separated by a zero distance.
Reth glared at him, eyes hard. 'You are beginning to understand. Now. Imagine a space of stupendously many dimensions. ' He held up a dust grain. 'Each grain represents one configuration of all the particles in our universe, frozen in time. This is reality dust, a dust of the Nows. And the dust fills configuration space, the realm of instants. Some of the dust grains may represent slices of our own history.' He snapped his fingers, once, twice, three times. 'There. There. There. Each moment, each juggling of the particles, a new grain, a new coordinate on the map. There is one unique grain that represents the coalescing of all the universe's particles into a single point. There are many more grains representing chaos - darkness - a random, structureless shuffling of the atoms.
'Configuration space contains all the arrangements of matter there could ever be. It is an image of eternity.' He waved a fingertip through the air. 'But if I trace out a path from point to point—'
'You are tracing out a history,' said Hama. 'A sequence of configurations, the universe evolving from point to point.'
'Yes. But we know that time is an illusion. In configuration space, all the moments that comprise our history exist simultaneously. And all the other configurations that are logically possible also exist, whether they lie along the track of that history or not.'
In a higher reality where universes are grains of sand, and the space of all possible universes and all possible timelines is a beach, the Xeelee are the
ocean. And later, in Exultant, when Pirius tries to enter this reality, a Xeelee kicks him out
It was, Gemo said, a vast, spreading landscape, under a towering sky; she had glimpsed a beach, a rising, oily sea, an immense mountain shrouded in mist . . .
Reth stalked back and forth, arms spread wide. 'We remain human, Hama Druz. I cannot apprehend a multi-dimensional continuum. So I sought a metaphor. A human interface. A beach of reality dust. A sea of entropy, chaos. The structures folded into the living things, the shape of the landscape, represent consistency - what we time-bound creatures apprehend as causality.'
'And the rising sea?'
'The cosmos-spanning threat of the Xeelee,' he said, smiling thinly. 'And the grander rise of entropy, across the universe, which will bring about the obliteration of all possibility.
And a reminder that the whole set of possible versions of the main universe is stated to be
uncountably infinite. Baxter is a theoretical physicist and everything we see in his works is based on modern scientific theories in one way or another including the configuration space and time-travel, so he knows exactly what he's talking about when making mentions of infinities.
"And so you believe," came the Ghost's simulated voice, "that this universe is essentially transient— all you sense, all you achieve, even your experiences of your inner self will pass away."
"Not transient, exactly," Burden called back. "Just one of an uncountably infinite number of possibilities which will, cumulatively, be resolved at timelike infinity, after the manner of a collapse of quantum functions."
"But in that case, what basis for morality can there be?"
"There is a moral basis for every decision," said Burden. "To show loyalty to one's fellows—to put oneself in harm's way for the sake of one's species. And while this is only one out of a myriad timelines, we believe that the, umm, the goodness in each timeline will sum at the decision point at timelike infinity to gather into Optimality..."
To further prove my point- a being that existed in configuration space once teleported a moon into a Nightfighter. The Nightfighter went to sleep right there because 5 million years later, the crew of the Great Northern would stumble upon that exact spot so that it could carry them through the Ring and thereby save them from the universe dying- configuration space and everything this entails is nothing new to the Xeelee.
Besides, it was not the magnetar itself that stopped the Nightfighter but rather the crystallization of space-time around its wings caused by the electromagnetic fields which prevented its drive from working and only because of how they work
Citation for the above claim which I made previously-
At its heart the magnetic field embracing the flare had been as strong as any field since the first moments of the universe itself. At such field strengths atoms themselves were distorted, forced into skinny cylindrical shapes; no ordinary molecular structure could survive. Photons were split and combined. Even the structure of spacetime was distorted: it became birefringent, Pirius learned, crystalline.
It was this last which had probably done for the Xeelee. Nobody knew for sure how a nightfighter's sublight drive worked. But the drive seemed to work by manipulating spacetime itself. In a place where spacetime crystallized, that manipulation could no longer work.
That being said, if you really wanna debate this then create a Xeelee Nightfighter vs Goetia thread. My point was that you are either downplaying the Xeelee or severely underestimating them if you think that a Nightfighter can be defeated by a solar flare or that the Xeelee has no control over the configuration space.