8 research outputs found
Non-perturbative Thermodynamics in Matrix String Theory
A study of the thermodynamics in IIA Matrix String Theory is presented. The
free string limit is calculated and seen to exactly reproduce the usual result.
When energies are enough to excite non-perturbative objects like D-particles
and specially membranes, the situation changes because they add a large number
of degrees of freedom that do not appear at low energies. There seems to be a
negative specific heat (even in the Microcanonical Ensemble) that moves the
asymptotic temperature to zero. Besides, the mechanism of interaction and
attachment of open strings to D-particles and D-membranes is analyzed.Comment: 30 pages, 3 figures. Several points are clarified. Final version to
appear in Nucl. Phys. B. Also available at http://condmat1.ciencias.uniovi.e
Thermodynamic nonextensivity in a closed string gas
Well known results in string thermodynamics show that there is always a
negative specific heat phase in the microcanonical description of a gas of
closed free strings whenever there are no winding modes present. We will
carefully compute the number of strings in the gas to show how this negative
specific heat is related to the fact that the system does not have
thermodynamic extensivity. We will also discuss the consequences for a system
of having a microcanonical negative specific heat versus the exact result that
such a thing cannot happen in any canonical (fixed temperature) description.Comment: Title + 13 pages, more typos correcte
Finite Temperature Matrix Theory
We present the way the Lorentz invariant canonical partition function for
Matrix Theory as a light-cone formulation of M-theory can be computed. We
explicitly show how when the eleventh dimension is decompactified, the N = 1
eleven dimensional SUGRA partition function appears. We also provide a high
temperature expansion which captures some structure of the canonical partition
function when interactions amongst D-particles are on. The connection with the
semi-classical computations thermalizing the open superstrings attached to a
D-particle is also clarified through a Born-Oppenheimer approximation. Some
ideas about how Matrix Theory would describe the complementary degrees of
freedom of the massless content of eleven dimensional SUGRA are discussed.
Comments about possible connections to black hole physics are also made.Comment: 32 pages. LaTeX, 1 epsf figure. Corrections and changes made in
Section 4. One reference adde
The String Density of States from The Convolution Theorem
We study the microcanonical density of states and the thermal properties of a
bosonic string gas starting from a calculation of the Helmholtz free energy in
the S-representation. By adding more and more strings to the single string
system, we induce that, for infinite volume, there is no negative specific heat
region but a transition at a finite value of the energy per string from the low
energy regime to a region of infinite specific heat at the Hagedorn
temperature. Forcing the description of this phase in terms of strings gives a
picture in which there is a very fat string in a sea of low energetic ones. We
argue that the necessary changing of this description should not change the
fact that perturbatively is a maximum temperature of the system.Comment: 15 pages, LaTeX, epsf.sty and a4.sty, 5 figures in PostScrip