Dark energy is here and it is very difficult to get rid of

Female researchers gave nearly 40% of public presentations at 17th International Conference on Astroparticles and Geophysics (TAUP 2021), organized virtually from Valencia by the Institute of Somatic Physics (CSIC-UV) between August 26 and September 3.

Including Italian astrophysics Lycia Green (Venice, 1971), ICREA Professor at the Institute of Cosmology (ICC) of the University of Barcelona and this year’s winner of King Jaume I Award in basic sciences. His intervention focused on the reality of cosmology.

Do you think there is only one world or that there could be more?

I cannot rule out the existence of other universes, but as it can be observed here and now, there can be no more than one: ours. With data from the Wilkinson Microwave Contrast Probe (WMAP), there are up to study Which sets a limit: There must be less than 1.6 visible universes, and there can be no more than that. And the data from the Planck mission will be better, with higher resolution and lower noise.

It is true that there are still some anomalies, such as fame cold spot [una región del cosmos inusualmente grande y fría] which has no clear explanation.

Among the many possible possibilities, there are those who have suggested that it is a sign from another universe, such as a ‘bruise’ from a collision with another universe, but this is highly speculative, just one of many other, less exotic possible explanations.

Did our universe begin with the Big Bang or is it just inflating and contracting in succession and now it’s expanding?

It either started with the Big Bang or something very similar and indistinguishable from the Big Bang. In addition, there are many indications that something like inflation was happening as well: a superfast accelerating expansion that lasted a fraction of a second and, upon completion, left the visible universe the size of a house or so. What had happened prior to that stage has been canceled by this expansion.

Deviations from inflation forecasts and information regarding possible pre-inflation or the “pre-Big Bang” phase were searched, but nothing was found.

Lack of evidence is not evidence of absence, but this will start to appear Russell teapot [una analogía planteada en los debates sobre la existencia de Dios por el filósofo Bertrand Russell sobre una supuesta tetera que orbita alrededor del Sol].

Can we continue to trust the solidity of the Standard Model of cosmology, or is it starting to crack?

It has so far survived a torrent of observations, tests and experiments. With a few parameters, this model well describes observations of the universe, from shortly after the Big Bang to the present, and on scales that travel from the horizon we observe to galaxy clusters.

Moreover, the value of these parameters is always the same within margins of error, for all observations, with different objects, from the light of the early universe to the statistical properties of galaxies, with one exception: the value of the expansion rate of the universe today, the Hubble constant.

some of your studies Focuses on that problem. What about the Hubble constant?

The value of this Standard Model parameter derived from observations of the older universe (for example, the cosmic microwave background) does not quite match what we get today by directly measuring distances and velocities, for example, with Cepheid stars.

The deviation is small, between 5 and 7%, but the error bars have become so small that the deviation is significant.

The scientific community has not yet reached a consensus on the origin of this contradiction. If an effective effect or an error in the measurements can be categorically ruled out, this may be a sign of cracks in the Standard Model, but as long as there is no such consensus, we still trust it.

Follow up discoveries gravitational waves with detectors lego And VirgoAnd Which What is the next challenge in this field?

Do you see the detection of primordial gravitational waves since the beginning of the big bang, like the ones you thought you spotted? BICEP2?

This would be interesting to understand what ignited the Big Bang, the energy scale of inflation and its physics. There is a huge experimental effort, but I don’t think it will be achieved very soon. It is a very difficult challenge! But for the impatient, it will also be interesting to discover the overall distribution of the sources of gravitational waves discovered through the LIGO-Virgo collaboration.

In theory, there should be a hiatus or mass gap, not finding objects with about 3 solar masses or much less the mass of the Sun… This would provide consistency between what we’ve learned about stars and gravitational waves. But of course… there may be surprises.

Neutrinos are those mysterious, ghostly particles that can help unlock some of the universe’s deepest mysteries.

We know that it has mass (although this discovery was unexpected), that it is dark matter although it cannot be all dark matter (since it is hot and works a lot!) and that there are three types or flavors, which also exchange with some Some when they travel through space.

But we don’t know their masses, we don’t know why and how they have them, or how they relate to other particles in the Standard Model, and how they rotate (spin) and morph into each other.

Also, a neutrino can be an antiparticle of its own, and understanding this can provide an answer to the question Why are we here? Because, in theory, the big bang generated as much matter as antimatter, and they should only have perished each other. Radiation: Neither stars, nor galaxies, nor planets…but it wasn’t.

Regarding dark matter search experiments,Which What are the main research methods?

The strongest evidence for its existence comes from cosmological and astronomical observations. We know that it is not made of “natural” (baryonic) matter, that there is a lot of it and it must be cold.

But this is indirect evidence, so if dark matter is a particle – very attractive to particle physics – it would be nice to be able to detect it and thus have direct evidence.

Direct searches for dark matter try to do just that. But this matter does not interact (or almost) with electromagnetism or with the strong nuclear force, only the weak nuclear force remains. This is why WIMP (Weakly interactive massive particlesIt was a common idea.

It is assumed that when a dark matter particle interacts with a detector (for example, a crystal as in the case of experiments SuperCDMSAnd Lady / Libra NS Anees, or a liquid noble gas as in luxAnd xenonAnd PandaX NS The dark side), the impact of the collision produces vibrations, photons, or electric charges.

Unfortunately, after decades of effort, no proof has yet been found. Of course, dark matter could also be another particle, such as an axon, but no evidence has been found for one of them that could be dark matter.

Is it true that the results of the Spanish ANAIS experiment, located in the underground laboratory of Canfranc (Huesca), contradict precedent?

The DAMA/LIBRA experiment (located in the Gran Sasso laboratory in Italy) detected and continued to see a signal with seasonal adjustment that could be interpreted as WIMP winds.

The Sun moves around the galactic center in the form of a cloud of dark matter, so it experiences winds of those particles, if there is a WIMP.

The Earth (which revolves around the Sun) also has these winds, but as in the summer (in the Northern Hemisphere) our planet moves with a component that goes in the same direction as the Sun and in winter it should receive these modified winds.

However, ANAIS does not see any modified signal. It is an independent experiment and leads us to the conclusion that the modification discovered by DAMA is not dark matter, but rather is probably environmental.

Regarding ANAIS, it must be remembered that it is an experience Made in SpainSpecifically from the University of Zaragoza. It’s also led by two researchers and their team has the highest ratio of women to men (about 50-50) I’ve seen in high-end physics experiments.

Any breakthrough in dark energy? How is DESI tool you collaborate with?

Dark energy is here and it is very difficult to get rid of. All experiments agree that they make up approximately 70% of the universe’s content, are indistinguishable from the cosmological constant, and have implications for the geometry and history of the expansion of the universe, as well as for the growth of structures. .

Regarding the spectroscopic instrument of dark energy (DESI), He is Data taken from last May.

On a good two nights it measures as many spectra of light as the entire 2dFGRS, a map that took me five years to do and made for my PhD thesis.

Currently, I am researching accurate analyzes of large 3D maps of galaxies, in particular to apply them to DESI data and make valid cosmological interpretations. With my group we are conducting a series of studies that spark ideas and methodologies, and now we just need to put them into practice!