The magnetism of the universe hidden

In nature, known four fundamental interactions that allow us to explain most of the physical phenomena observed: the strong, the weak interaction, electromagnetism and gravity. The first two are very short range so that, although they are essential to understand nuclear physics and elementary particles are practically irrelevant from atomic or molecular scale, why were the last to be discovered.

Magnetic field lines within the spiral galaxy M51. MPIfR Bonn. Image: UCM.

At these scales, the dominant force is electromagnetism, which allows us to understand the interactions between atoms and molecules. The reason this is so is that, unlike what happens with weak and strong interactions, its action is far-reaching. When considering an even larger scale, the positive and negative charges tend to compensate by making the bodies are electrically neutral, so that its electromagnetic interaction ceases.

Thus, while gravity is the weakest of all known interactions, because it also is a long-range force as there is no negative gravitational sources to compensate for the attraction of the masses, which governs dynamics of galaxies, clusters and, ultimately, the universe.

That electromagnetism and gravity are long-range interactions implies that its action is felt by far that we place ourselves from the source. However, the validity of both general relativity (our theory of gravity) and of electromagnetism has been seen only at the solar system, which is laughable when compared to the overwhelming size of the universe.

While we might assume that the behavior of these two interactions will be the same regardless of the distances involved, in fact there is no experimental evidence that this is so and, in fact, galactic and larger scales are phenomena that have not could be explained satisfactorily within the framework of these two theories.

Theories with dark areas

On the one hand, general relativity is unable to explain galactic dynamics without including the so-called dark matter , and much larger scales, it requires the presence of an exotic type of energy called dark energy , to account for the current phase accelerated expansion of the universe.

As for dark matter, most of the community accepts the existence of some type of particle that has not yet been detected, but expected to be observed with direct and indirect detectors currently operating or begin to operate in coming years.

However, in relation to the other dark component, has not yet reached a consensus on the true cause that is driving the accelerated expansion of the universe, if it is accepted an explanation that, because of its simplicity, turns out to be the most favored by the principle of Occam's razor: the cosmological constant .

The problem is that, although able to explain most of the high precision cosmological observations, the value of this constant is so extremely small that from a purely theoretical point of view, is not very natural , and this disturbs cosmology theoretical. This is the reason that we explore alternatives that allow us to elucidate the true nature of this constant.

On the other hand, is well known that galaxies and clusters of galaxies contain relatively intense magnetic fields that extend in a consistent manner throughout the entire structure. Moreover, in recent years has begun to see that these fields are also outside the galaxies themselves and could permeate the entire visible universe.

While known mechanisms that could amplify these fields from primordial seeds (tiny magnetic fields generated in the early universe, for cooling and due to a dynamo effect, grew to the values ​​observed today), the origin of these primordial fields not explained satisfactorily in the electromagnetic theory of Maxwell.

The low naturalness of the cosmological constant

Recently, researchers at the Department of Theoretical Physics I of the Faculty of Physical Sciences of the UCM have shown that both problems (the accelerated expansion of the universe and the existence of cosmological magnetic fields) could find a simple solution when taking into account the effects of the universe's expansion on the electromagnetic interaction.

Indeed, it has known for more than 50 years that the electromagnetic field contains components that are not physically manifest in ordinary situations and, in fact, are ignored in standard treatments. However, precisely what has been found in these studies is that these components can have physical effects when considered in a cosmological context.

In the early universe, it is believed that there was a phase of accelerated expansion, similar to what is happening now, called inflation . During this period inflation can not produce the usual physical components of the electromagnetic field, but are generated components that are usually ignored. In addition, at the end of the inflationary epoch, these components survive on large scales in the form of an effective cosmological constant whose value is determined by the temperature of the universe at the end of inflation.

What is striking about this mechanism is that, if the temperature of the universe at the end of inflation corresponds to the electroweak scale, the value of the cosmological constant agrees with that required to explain the current phase of accelerated expansion. This would solve the problem of naturalness of the cosmological constant, its value obtained from physics at a scale that is precisely what we intend to study in the Large Hadron Collider LHC in Geneva.

On the other hand, the components generated during inflation also produce magnetic fields that could not only act as seeds primordial galactic magnetic fields, but that would explain his presence outside of galaxies.

As so often happens in physics, two phenomena that appear unrelated, such as the presence of cosmological magnetic fields and cosmic acceleration could find a simple explanation and simultaneous when viewed from a different perspective. Surely the time will determine if this is correct.

References:
J. Jimenez Beltran and AL Maroto. "Cosmological electromagnetic fields and dark energy." JCAP 0903:016 (2009).
J. Jimenez Beltran and AL Maroto . "Dark energy: the absolute electric Potential of the Universe" . Int J. Mod Phys D18 :2243-2248 (2009).
J. Jimenez Beltran, TS Koivisto, AL Maroto and DF Mota. "Electromagnetic perturbations in dark energy." JCAP 0910:029 (2009).

Source: SINC