Earlier today, i had a coup doeil through the following article:(adsbygoogle = window.adsbygoogle || []).push({});

http://cerncourier.com/main/article/43/6/15/1

While most of it was clear as sun, certain issue did arise, and i'd like you guys to crystalise those to me.

I've been told by emeritus in particle physics, the following: A crucial role in these developments was played by the discovery of "p-branes", which are higher dimensional objects extended in p spatial dimensions, so generalizing the notion of a point particle (p = 0) or a string (p = 1). One of the main consequences of this discovery is that the string scale is, in general, a free parameter that can be dissociated from the Planck mass if the universe is localized on a p-brane and does not feel all the extra dimensions of string theory. The braneworld description of our universe separates the dimensions of space into two groups: those that extend along our p-braneworld, called parallel dimensions, and those transverse to it. Obviously the parallel ones must contain at least the three known dimensions of space, but they may contain more.

So my first question is conspicuously carnassial: does this definition hold true for all cases, or it could manifest itself elsewhere? Is it even correct to define the p-brane space in such a way? d-branes float in subspace orthogonal to 'our' classical 3 dimensions space. the direct sum of the classical 3-dimensions space with d-brane spaces give the p-brane space

My second question is more of a request for a better explanation and requires the following figure.

Could anyone here put it in a more familiar language? In the type I string framework, our universe contains (besides the three known spatial dimensions; denoted by a single blue line) some extra dimensions (dII = p-3) parallel to our world p-brane (green plane), along which the light described by open strings propagates, as well as some transverse dimensions (yellow space), where only gravity described by closed strings can propagate. The longitudinal extra dimensions have a string size of about 10-18 m, while the size of the transverse dimensions varies between 10-14 m and a fraction of a millimetre.

Thanks guys.

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# P-brane inquiry

Can you offer guidance or do you also need help?

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