Multiple copies of the Standard Model could solve the hierarchy problem

January 4, 2017 by Lisa Zyga feature
In the proposed model, the universe contains multiple sectors, each of which is governed by its own version of the Standard Model with its own Higgs vacuum expectation value. The sector with the smallest non-zero vacuum expectation value contains our copy of the Standard Model. Credit: Arkani-Hamed et al. ©2016 American Physical Society

(Phys.org)—One of the unanswered questions in particle physics is the hierarchy problem, which has implications for understanding why some of the fundamental forces are so much stronger than others. The strengths of the forces are determined by the masses of their corresponding force-carrying particles (bosons), and these masses in turn are determined by the Higgs field, as measured by the Higgs vacuum expectation value.

So the hierarchy problem is often stated as a problem with the Higgs field: specifically, why is the Higgs vacuum expectation value so much smaller than the largest energy scales in the universe, in particular the scale at which gravity (by far the weakest of the forces) becomes strong? Reconciling this apparent discrepancy would impact physicists' understanding of at the most fundamental level.

"The hierarchy problem is one of the deepest questions in particle physics, and almost every one of its known solutions corresponds to a different vision of the universe," Raffaele Tito D'Agnolo, a physicist at Princeton, told Phys.org. "Identifying the correct answer will not just solve a conceptual puzzle, but will change the way we think about particle physics."

In a new paper published in Physical Review Letters, D'Agnolo and his coauthors have proposed a solution to the hierarchy problem that involves multiple (up to 1016) copies of the Standard Model, each with a different Higgs vacuum expectation value. In this model, the universe consists of many sectors, each of which is governed by its own version of the Standard Model with its own Higgs vacuum expectation value. Our sector is the one with the smallest nonzero value.

If, in the very early universe, all sectors had comparable temperatures and seemingly equal chances of dominating, why did our sector, with the smallest nonzero Higgs vacuum expectation value, come to dominate? The physicists introduce a new mechanism called a "reheaton field" that explains this by reheating the universe as it decays. The physicists show that there are several ways in which the reheaton field could have preferentially decayed into and deposited the majority of its energy into the sector with the smallest Higgs vacuum expectation value, causing this sector to eventually dominate and become our observable universe.

Compared to other proposed solutions to the hierarchy problem, such as supersymmetry and extra dimensions, the new proposal—which the physicists call "N-naturalness"—is different in that the solution does not rely solely on new particles. Although the new proposal shares some features with both supersymmetry and extra dimensions, one of its unique characteristics is that it is not only new particles, but more importantly cosmological dynamics, that is central to the solution.

"N-naturalness is qualitatively different from the solutions to the hierarchy problem proposed in the past, and it predicts signals in cosmic microwave background (CMB) experiments and large-scale structure surveys, two probes of nature that were thought to be unrelated to the problem," D'Agnolo said.

As the physicists explain, it should be possible to detect signatures of N-naturalness by searching for signs of the existence of other sectors. For instance, future CMB experiments might detect extra radiation and changes in neutrino cosmology, since neutrinos in nearby sectors are expected to be slightly heavier and less abundant than those in our sector. This approach is interesting for another reason: the neutrinos in the other sectors are also a viable dark matter candidate, which the researchers plan to study in more detail. Future experiments might also find signatures of N-naturalness in the form of a larger-than-expected mass of axion particles, as well as supersymmetric signatures due to possible connections to supersymmetry.

"If new relativistic species are not detected by the next generation of CMB experiments (Stage 4), then I will stop thinking of N-naturalness as a possible solution to the hierarchy problem," D'Agnolo said. "According to the current timeline, these experiments should start taking data around 2020 and reach their physics goals in approximately five years."

Explore further: Dark matter may be hiding in a hidden sector

More information: Nima Arkani-Hamed et al. "Solving the Hierarchy Problem at Reheating with a Large Number of Degrees of Freedom." Physical Review Letters. DOI: 10.1103/PhysRevLett.117.251801. Also at arXiv:1607.06821 [hep-ph]

Related Stories

Dark matter may be hiding in a hidden sector

November 11, 2016

(Phys.org)—Currently, one of the strongest candidates for dark matter is weakly interacting massive particles, or WIMPS, although so far this hypothetical particle has not yet been directly detected. Now in a new study, ...

Could 'Higgsogenesis' explain dark matter?

October 22, 2013

(Phys.org) —The recently discovered Higgs boson is best known for its important role in explaining particle mass. But now some physicists are wondering if the Higgs could have played an equally significant role in generating ...

Is the Vacuum Empty? -- the Higgs Field and the Dark Energy

May 10, 2007

The problems in understanding the true nature of the “vacuum” of space were discussed by theoretical physicist Alvaro de Rújula from CERN (the European Council for Nuclear Research) in Geneva, Switzerland, and a professor ...

Recommended for you

Imaging technique unlocks the secrets of 17th century artists

November 21, 2017

The secrets of 17th century artists can now be revealed, thanks to 21st century signal processing. Using modern high-speed scanners and the advanced signal processing techniques, researchers at the Georgia Institute of Technology ...

Physicists design $100 handheld muon detector

November 20, 2017

At any given moment, the Earth's atmosphere is showered with high-energy cosmic rays that have been blasted from supernovae and other astrophysical phenomena far beyond the Solar System. When cosmic rays collide with the ...

A curious quirk brings organic diode lasers one step closer

November 20, 2017

Since their invention in 1962, semiconductor diode lasers have revolutionized communications and made possible information storage and retrieval in CDs, DVDs and Blu-ray devices. These diode lasers use inorganic semiconductors ...

8 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Spaced out Engineer
1 / 5 (2) Jan 04, 2017
Not my field, but this makes sense with metastability. The lingering questions are Platonic or Pythagorean, does it need multiple instantiation or is this just an aspect of infinite distant mathematical holons?
Much beauty...
richdiggins
1 / 5 (3) Jan 04, 2017
"According to the current timeline, these experiments should start taking data around 2020 and reach their physics goals in approximately five years."

"Just in time for me to retire, pay off my second mortgage, get the kids thru college " D'Agnolo said
Hyperfuzzy
not rated yet Jan 04, 2017
You are kidding, right? No one is this ill informed.
Gigel
5 / 5 (1) Jan 05, 2017
"Just in time for me to retire, pay off my second mortgage, get the kids thru college " D'Agnolo said

He is a bit too young for a retirement.
Hyperfuzzy
not rated yet Jan 05, 2017
Think, Maxwell does not define any particles, only charge. The field of the charge exist from it's center to infinity and is updated at the speed of light relative to its center. No particles, no mass, no gluons since what is required is to solve N equation with N unknowns when one realizes that a neutron is a supposition of an electron and a proton. I prefer diametrical spherical fields equals charge.

You may only imagine the standard model but never measure anything but the field.

Since superposition applies it's easy to see that these centers are invisible and indivisible. So let's realize the standard model is so last century.
Hyperfuzzy
not rated yet Jan 05, 2017
By the way, we only see the wrinkles in the field. Anything else will never be seen, so ...
xinhangshen
1 / 5 (1) Jan 14, 2017
Lisa Zyga, Please be aware that Einstein's relativity theory has already been disproved both theoretically and experimentally (see "Challenge to the special theory of relativity" March 1, 2016 Physics Essays). The most obvious and indisputable evidence disproving special relativity is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which are moving with huge velocities relative to each other (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks.) while special relativity claims that time is relative (i.e. different on different reference frame) and can never be synchronized on clocks with relative velocities. That is, the Standard Model itself is totally wrong.
Hyperfuzzy
not rated yet Jan 14, 2017
Lisa Zyga, Please be aware that Einstein's relativity theory has already been disproved both theoretically and experimentally (see "Challenge to the special theory of relativity" March 1, 2016 Physics Essays). The most obvious and indisputable evidence disproving special relativity is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which are moving with huge velocities relative to each other (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks.) while special relativity claims that time is relative (i.e. different on different reference frame) and can never be synchronized on clocks with relative velocities. That is, the Standard Model itself is totally wrong.

So this you accept?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.