Theoretical Astrophysics
and Dark Matter

In the last years, the quest concerning the nature of the dark matter in the Universe has received much attention and has become of great importance for understanding the structure formation in the Universe. Some candidates for dark matter have been discarded and some others have recently appeared. The standard candidates of the Cold Dark Matter (CDM) model are axions and WIMP'S (Weakly Interacting Massive Particles), which are themselves not free of problems. Axions are massive scalar particles with no self interaction. In order for axions to be an essential component of the dark matter content of the Universe, their mass should be m ~ 10^{-5}eV. With this axion mass, the scalar field collapses forming compact objects with masses of order of M_{crit} ~ 0.6 m_Pl^{2}/m ~ 10^{-6}Mo \cite{seidel91,seidel94}, which corresponds to objects with the mass of a planet. Since the dark matter mass in galaxies is ten times higher than the luminous matter, we would need tenths of millions of such objects around the solar system, which is clearly not the case. On the other hand, there are many viable particles with nice features in super-symmetric theories, such as WIMP'S, which behave just like standard CDM. However, a central debate nowadays is whether CDM can explain the observed scarcity of dwarf galaxies and the smoothness of the galactic-core matter densities, since high resolution numerical simulations with standard CDM predict an excess of dwarf galaxies and density profiles with cusps \cite{firmani}. Even when there are some intents to give a solution to these problems inside the CDM paradigm, \cite{dalal,primack}, the debate is still open because new obsevations in galaxie centers of dwarf galaxies do not show a real correspondence with CDM predictions \cite{binney,blok}. This is the reason why we need to look for alternative candidates that can explain both the structure formation at cosmological level, the observed amount of dwarf galaxies, and the dark matter density profile in the core of galaxies. However, since these candidates behave just like standard CDM, they can not explain the observed scarcity of dwarf galaxies and the smoothness of the galactic-core matter densities, since high resolution numerical simulations with standard CDM predict an excess of dwarf galaxies and density profiles with cusps \cite{firmani}.

This is the reason why we need to look for alternative candidates that can explain both the structure formation at cosmological level, the observed amount of dwarf galaxies, and the dark matter density profile in the core of galaxies.

References

{seidel91}E. Seidel and W. Suen, Phys. Rev. Lett. 66, 1659 (1991).

{seidel94}E. Seidel and W. Suen, Phys. Rev. Lett. 72, 2516 (1994).

{firmani} B. Moore, F. Governato, T. Quinn, J. Stadel and G. Lake,
ApJ {\bf 499}, L15 (1998). Y. P. Jing and Y. Suto, ApJ {\bf 529}, L69
(2000).

{dalal} N. Dalal and C. S. Kochanek, ApJ in press. E-print astro-ph/0111456.

Class. Quant. Grav.17 (2000)1455-1466

Rev. Mex. A.A 37(2001)63-72. Available at: astro-ph/9811143

Class. Quant. Grav.18,(2001)2015-2024.

Class. Quant. Grav18(2001)5055-5064. Available at: gr-qc/0108027.

Gen. Rel. Grav.34 (2002) 283-306. Available at: astro-ph/0005528

Class. Quant. Grav.19 (2002) 3603-3615. Available at: gr-qc/0112044

{QSDMCQG}TT. Matos and L. A. Ureña-López, Class. Quantum Grav. 17, L75 (2000).

{COSPRD}T. Matos and L. A. Ureña-López, Phys. Rev. D63, 63506 (2001).

{DMCQG}F. S. Guzmán and T. Matos, Class. Quantum Grav. 17, L9 (2000).
T. Matos and F. S. Guzmán, Ann. Phys. (Leipzig) 9, SI-133 (2000).

{SPHPRD}T. Matos, F. S. Guzmán and D. Núñez, Phys. Rev. D62, 061301 (2000).

{vladimir}V. Avila-Reese, C. Firmani, A. Klypin and A. V. Kravtsov, MNRAS 309, 507 (1999).

{CROSS}T. Matos and L. A. Ureña-López, Phys. Lett. B538, (2002), 246-250
. Preprint astro-ph/0010226.

{apj}L. Ferrarese and D. Merritt, ApJL, 539} L9 (2000). K. Gebhardt et al, Astrophys. J. Lett. 539 L13 (2000).

{diego}D. F. Torres, S. Capozziello and G. Lambiase, Phys. Rev. D 62, 104012 (2000).

{luis}L. A. Ureña-López. Class. Quantum Grav. 19, 2617 (2002)..

{tkachev}A. Riotto and I. Tkachev, Phys. Lett. B 484, 177 (2000).

{jeremy}J. Goodman, preprint astro-ph/0003018.

{peebles}P.J.E. Peebles, preprint astro-ph/0002495.

{salbur}Paolo Salucci and Andreas Burkert. Preprint astro-ph/0004397.

{seidel90}E. Seidel and W. Suen, Phys. Rev. D 42, 384 (1990).

{seidel98}J. Balakrishna, E. Seidel and W. Suen, Phys. Rev. D 58, 104004 (1998).

{choptuik}S.H. Hawley and M.W. Choptuik, Phys. Rev. D 62, 104024 (2000).

{futuro}
Miguel Alcubierre, F. Siddhartha Guzmán, Tonatiuh Matos,
Darío Núñez, Luis A. Ureña and Petra Wiederhold.

Galactic Collapse of Scalar Field Dark Matter. Class. Quant. Grav. 19, (2002), 5017-5024.
Available at: gr-qc /0110102.
Highlight paper at the period 2001-2002 nominated
by the Editorial Board of the Journal Classical and Quantum Gravity.

{ma}T. Matos, Ann. Phys. (Leipzig) 46, 462 (1989). T. Matos, J. Math. Phys. 35, 1302 (1994).
T. Matos, Math. Notes 58, 1178 (1995). Available here.

{halzen}F. Halzen and A. D. Matin, Quarks and Leptons:
an Introductory Course in Modern Particle Physics''. John Wiley & Sons, 1984.

{chale}M. Visser, Science 276, 88 (1997).