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Weakless Universe
 
 
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The Weakless Universe is a hypothetical universe
Universe

The universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and physical constants that govern them....
 that contains no weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
s, but is otherwise very similar to our own universe. In particular, the Weakless Universe is constructed to have nuclear physics
Nuclear physics

Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.The most commonly known applications of nuclear physics are nuclear power and nuclear weapons, but the research field is also the basis for a far wider range of applications, including in the medical sector , in materials engineering...
 and chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
 identical to standard nuclear physics and chemistry. The dynamics of the Weakless Universe includes a period of big bang
Big Bang

The Big Bang is the physical cosmology model of the initial conditions and subsequent development of the universe supported by the most comprehensive and accurate explanations from current scientific method and observation....
 nuclear synthesis
Nucleosynthesis

Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons . It is thought that the primordial nucleons themselves were formed from the quark-gluon plasma from the Big Bang as it cooled below ten million degrees....
, star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 formation, stars that burn for billions of years, stellar nuclear synthesis of heavy elements and also supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
e that distribute the heavy elements into the interstellar medium.

strength of the weak interaction is an outstanding problem in modern particle physics
Particle physics

Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them....
.






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The Weakless Universe is a hypothetical universe
Universe

The universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and physical constants that govern them....
 that contains no weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
s, but is otherwise very similar to our own universe. In particular, the Weakless Universe is constructed to have nuclear physics
Nuclear physics

Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.The most commonly known applications of nuclear physics are nuclear power and nuclear weapons, but the research field is also the basis for a far wider range of applications, including in the medical sector , in materials engineering...
 and chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
 identical to standard nuclear physics and chemistry. The dynamics of the Weakless Universe includes a period of big bang
Big Bang

The Big Bang is the physical cosmology model of the initial conditions and subsequent development of the universe supported by the most comprehensive and accurate explanations from current scientific method and observation....
 nuclear synthesis
Nucleosynthesis

Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons . It is thought that the primordial nucleons themselves were formed from the quark-gluon plasma from the Big Bang as it cooled below ten million degrees....
, star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 formation, stars that burn for billions of years, stellar nuclear synthesis of heavy elements and also supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
e that distribute the heavy elements into the interstellar medium.

Motivation and Anthropics

The strength of the weak interaction is an outstanding problem in modern particle physics
Particle physics

Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them....
. A theory should ideally explain why the weak interaction is 32 orders of magnitude stronger than gravity; this is known as the hierarchy problem
Hierarchy problem

In theoretical physics, a hierarchy problem occurs when the fundamental parameters of some Lagrangian mechanics are vastly different from the parameters measured by experiment....
.

There are various models that address the hierarchy problem in a dynamical and natural way, for example, supersymmetry
Supersymmetry

In particle physics, supersymmetry is a symmetry that relates elementary particles of one Spin to another particle that differs by half a unit of spin and are known as superpartners....
, technicolor
Technicolor (physics)

In physics, technicolor models are theories beyond the Standard Model which do not have a scalar field Higgs field. Instead, they have a larger number of fermion fields than the Standard Model and involve a larger gauge group....
, warped extra dimensions
Randall-Sundrum model

In physics, Randall-Sundrum models imagine that the real world is a higher-dimensional Universe described by warped geometry. More concretely, our Universe is a five-dimensional anti de Sitter space and the elementary particles except for the graviton are localized on a -dimensional brane or branes....
, etc. An alternative approach to explaining the hierarchy problem is to invoke the anthropic principle
Anthropic principle

In physics and cosmology, the anthropic principle is the collective name for several ways of asserting that physical and chemistry theories, especially astrophysics and cosmology, need to take into account that there is life on Earth, and that one form of that life, Homo sapiens, has attained sapience....
. Within this approach one assumes that there are many other patches of the Universe (or Multiverse
Multiverse (science)

The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality. The different universes within the multiverse are sometimes called parallel universes....
) in which physics is very different. In particular one can assume that the "landscape" of universes contains ones where the weak force has a different strength compared to our own. In such a scenario observers would presumably evolve wherever they can. If the observed strength of the weak force is then vital for the emergence of observers, this would explain why the weak force is indeed observed with this strength. It was indeed argued by Barr and others that if one only allows the electroweak symmetry breaking scale to vary between universes, keeping all other parameters fixed, atomic physics would change in ways that would not allow life as we know it. Anthropic arguments have recently been boosted by the realization that string theory has many solutions, or vacua, dubbed the string landscape, and by Weinberg
Steven Weinberg

Steven Weinberg is an United States physicist and Nobel Prize in Physics for his contributions with Abdus Salam and Sheldon Lee Glashow to the Electroweak interaction of the weak force and electromagnetism interaction between elementary particles....
's prediction of the cosmological constant by anthropic reasoning.

The hypothetical weak interaction-less universe is meant to serve as a counter example to the anthropic approach to the hierarchy problem. In the weakless universe other parameters are varied as the electroweak breaking scale is changed. Indeed, string theory implies that the landscape is very big and diverse. The seeming habitability of the Weakless Universe implies that one cannot explain the hierarchy problem by anthropic reasoning alone, and that one must make strong assumptions about the available vacua in the landscape.

Weakless stars

Perhaps the biggest obstacle for a habitable Weakless Universe is the necessary existence of stars. Our sun works through burning two protons to deuterium, which proceeds through weak interactions. In the Weakless Universe of Harnik, et al. (see below) this is overcome by ensuring a high primordial deuterium/hydrogen ratio during Big Bang Nucleosynthesis (BBN). This permits long lived stars fueled by direct deuterium-proton burning to helium, which proceeds through strong interactions. The high initial deuterium/hydrogen ratio (~1/3 by mass) is arranged by simply reducing the overall baryon/photon ratio, which allows the BBN deuterium to be produced at a lower temperature, where the Coulomb barrier then protects it from immediate fusion into 4He.

Another potential problem for a Weakless Universe is that supernova explosions are necessarily neutrinoless. The resulting efficiency of production and dispersion of heavy elements (in particular, oxygen) into the interstellar medium for subsequent incorporation into habitable planets has been questioned by Clavelli and White (see below).