Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [fine-tuning]

"Fine-tuning" is a situation in which the fundamental parameters in a theory must be "fine-tuned", i.e. precisely chosen, in order for a theory's predictions to agree with experimental data.

-1
votes
0answers
21 views

What is hierachy problem in Higgs mass? [duplicate]

What is actually the hierarchy Problem in Higgs mass? And whether we expect the Higgs mass to be huge experimentally or theoretically?
1
vote
0answers
22 views

What happens to the massive gauge bosons in a simple Little Higgs model?

I'm trying to understand a simple Little Higgs (toy) model where the Higgs doublet is made of pseudo Nambu-Goldstone Bosons generated by breaking the symmetry from $SU(3)_L\times U(1)_Y$ to $SU(2)_L\...
1
vote
0answers
41 views

Bound on large extra dimensions using gravitational waves

Are there proposed observations using gravitational waves which put a bound on the size of large extra dimensions (say in the context of ADD model)? The claim in the ADD paper is that you cannot ...
0
votes
1answer
56 views

Estimate of neutrino masses from the values of $\Delta m_{21}^2$ and $\Delta m_{13}^2$ only!

The blog here says that The measured mass differences between the eigenstates are $\Delta m_{21}^2=7.5\times 10^{-5} {\rm eV}^2$ and $\Delta m_{13}^2=2.5\times 10^{-3} {\rm eV}^2$, suggesting that ...
1
vote
0answers
36 views

Hierarchy problem and loop quantum gravity

According to https://en.wikipedia.org/wiki/Hierarchy_problem#Finite_Groups. Hierarchy problem can be theoretically solved using symmetry of certain bosonic string theory on the Leech lattice (though ...
2
votes
2answers
140 views

Why naturalness is an issue in particle physics? It is not in fluid dynamics

I have often heard that naturalness is a strong argument in favor of Supersymmetry. They say that there must be energy scales not too far away the EW-energy so that the quantum corrections of the ...
0
votes
1answer
77 views

Why universe is so perfectly made for us? [duplicate]

I am very eager to learn that, "Why universe is so perfectly made for us?" Or our universe is just stable by chance?
9
votes
1answer
199 views

Why is technical naturalness enough?

There are two notions of "naturalness" used in particle physics today. Dirac naturalness: all dimensionless parameters $g$ in a theory should be order $1$. Technical naturalness: an observed coupling ...
3
votes
0answers
42 views

Are trans-Planckian field values a problem for the relaxion?

The relaxion is a new model-building gadget that solves the hierarchy problem by allowing the Higgs mass term to dynamically relax to zero. To describe it as simply as possible, leaving a lot out: we ...
10
votes
0answers
248 views

What motivates clockwork theory?

Clockwork is a new model-building gadget that produces very small couplings starting from a theory with no small numbers at all, in an attempt to solve the hierarchy problem. To describe it as ...
1
vote
2answers
314 views

Is the universe really “fine-tuned for life”?

I understand what is meant when we say the universe is "fine tuned", but I've seen it claimed it's is fine tuned "for life". Is it? When I look at known or even speculated life in our universe, I see ...
7
votes
1answer
236 views

Why does standard model lose predictivity if it has unstable vacuum?

In String Theory In A Nutshell by Elias Kiritsis, Standard Model is unstable as we increase the energy (hierarchy problem of mass scales) and the theory loses predictivity as one starts moving far ...
0
votes
0answers
73 views

How fine-tuned is the expansion rate and the density of the universe?

I read somewhere that If the expansion rate of the universe were larger or the density of the universe were less , no galaxies would form. If the expansion rate of the universe were smaller or the ...
0
votes
0answers
90 views

The theoretical calculation underlying the cosmological constant problem

The electroweak vacuum energy density is $10^{120}$ times larger than the currently observed value of the dark energy. I have two questions in regard to this statement. $\bullet$ Firstly, what are ...
0
votes
0answers
28 views

Would the existence of leptoquarks solve the hierarchy problem of the Higgs-boson?

Would the existence of leptoquarks solve the hierarchy problem of the Higgs-boson ? According to wikipedia these are assumed to be bosons which could contribute to the cancellation of the vacuum ...
7
votes
3answers
163 views

In BSM model building, what counts as fine tuned?

The Standard Model contains an extreme fine-tuning: the Higgs mass is very small compared to what it would naturally be, by a factor of around $10^{15}$. Lots of theories extending the Standard Model ...
0
votes
2answers
101 views

Is Flatness Problem still a problem since the observable universe is flat but the whole universe can be curved on much larger scale?

When we say the universe is flat, we mean just the observable universe. So that doesn’t mean the shape of the whole universe is also flat (ie. it can be curved on much larger scale) Is Flatness ...
2
votes
1answer
117 views

What deficiencies of the Standard Model does supersymmetry address?

I have been reading up on supersymmetry and how it was developed to fill the supposed gaps presented left by the Standard Model of Particle Physics. What is one main example of this gap?
-1
votes
1answer
65 views

A super-positioned boson-fermion particle

Is it possible to extend the standard model with super positioned particles: bosons+fermions at the same time. Instead of 2 dual particles as SUSY suggests, a particle collapses to its supercharge ...
5
votes
1answer
157 views

Does string theory give any values for the predicted “leakage” of gravity into extra spatial dimensions?

Sorry if this is a duplicate. I have read that string theory has a good explanation for the "hierarchy" problem of the force strength disparity between the fundamental forces because as gravity ...
5
votes
2answers
161 views

Understanding the fine-tuning problem related to baryon asymmetry as an initial condition

The reason for not assuming the Baryon asymmetry of the universe as an initial condition is often attributed to the following fine-tuning problem: If the baryon asymmetry had been an initial condition,...
2
votes
1answer
94 views

Naturalness in Physics and fundamental constants

From the "flatness problem" in Cosmology to the "strong CP problem" and "hierarchy problem" in the Model standard, a lot of problems in physics deal with Naturalness: a certain parameter in our theory ...
0
votes
0answers
254 views

How does the naturalness problem of the Higgs mass changes depending on the cut off scale of the Standard Model (SM)?

In this year's paper (check introduction) James D. Wells brings Susskind's 1979 argument that the SM is valid to a very high energy scale, say the Planck scale, $\Lambda \approx M_{Pl} \approx 10^{18} ...
12
votes
3answers
296 views

Why is imposing a symmetry on a theory considered more “natural” than fine-tuning its couplings?

Theories whose behavior would qualitatively change if their couplings were not fine-tuned to particular values are often dismissed as "unnatural" (in high-energy physics) or "unrealistic" (in ...
1
vote
1answer
393 views

Bare Cosmological Constant and Fine-Tuning Problem

Whenever anyone talks about the cosmological constant, they usually cite the difference of $\approx 120$ orders of magnitude between the observed and calculated values for the vacuum energy ($\rho_\...
1
vote
0answers
86 views

Examples of other hierarchy problems

The commonly quoted version of the hierarchy problem (at least, the one that I have heard), is concerned with the surprisingly low mass of the Higgs. We would expect the Higgs mass squared to have ...
0
votes
1answer
104 views

Before Dark Energy was discovered

I'm really confused on this topic. Pardon my French if my questions seem really stupid. Before Dark Energy was discovered in 1998 did scientists know that the cosmological constant calculated, I ...
2
votes
1answer
405 views

Why does the flatness problem (of the universe) present a fine tuning problem?

The Friedmann equation can be written $$|\Omega-1|=\frac{|k|}{a^2H^2}$$ In a period where the universe is decelerated $a^2H^2$ becomes bigger as we extrapolate into the past. We know $|\Omega-1|$ ...
5
votes
1answer
309 views

Does the Peccei-Quinn (PQ) mechanism require fine-tuning?

The strong CP problem: the QCD theta parameter can not be arbitrarily small due to 't Hooft's doctrine of naturalness (a parameter can be arbitrarily small only when putting it to zero provides an ...
1
vote
1answer
133 views

Precision of the Gravitational Constant [closed]

I went to a theological talk where the speaker, while answering a question on intelligent design, claimed that, if $G$ was different by one part in $10^{120}$,then the universe would either collapse ...
4
votes
1answer
266 views

Hierarchy problem and quadratic corrections in the Standard Model

In this paper, the third paragraph of the “Introduction” says that the Standard Model by itself is a natural theory. As I understand, they say there is no quadratic divergence in the Standard Model ...
3
votes
1answer
369 views

Supersymmetry as a solution of hierarchy problem

Hierarchy problem is the statement of why the weak force is much stronger than gravity. In terms of coupling constant, weak force (Fermi coupling) is much larger than gravity (Newton's constant). I ...
4
votes
0answers
89 views

Why do we need any model beyond SM to fine-tune the Higgs mass?

ATLAS and CMS combined their results recently and it shows that higgs mass is ~125 GeV. Theoretical physicists try to figure out the "low mass" of the Higgs which causes hierarchy problem at high ...
2
votes
1answer
215 views

Doubts in understanding the role if quantum corrections in the Hierarchy Problem

Trying to understand the Hierarchy problem many questions come to my mind that I am unable to answer due probably to my poor understanding of renormalization. The basic set up of the hierarchy ...
0
votes
0answers
34 views

If neutron would be lighter by 1 MeV, how stability of Hydrogen could be changed?

In current Universe proton is stable and the following reaction does not go $ p + e \rightarrow n + \overline{\nu_e}$ Currently proton is lighter than neutron by 1.293 MeV. If neutron would be ...
8
votes
0answers
286 views

$d=2$ pole argument of quadratic divergences in Peskin & Schroeder's book

Q1: My question is, in the context of dimensional regularisation(DREG, in dimension $d$), why do they mention the absence of $d=2$ pole in the gauge theory cases[1], whereas the $d=2$ pole is not ...
13
votes
4answers
1k views

Why is the relative weakness of gravity a problem?

In my physics classes, I remember it being repeated a few times that gravity is a much weaker force than the other three fundamental forces, and being told this is an open problem in physics. However, ...
-1
votes
1answer
219 views

Leonard Susskind said that the small value of the cosmological constant could mean that the universe is much bigger than we thought. Why?

He said that near the beginning of this Youtube video that it could mean that the universe is much bigger than he had thought that it was, and that the cosmological constant wasn't even a constant. I ...
2
votes
2answers
294 views

How “unnatural” is the universe? [closed]

Looking to read up on the impact the discovery of Higgs boson has on the String Theory I came upon these two paragraphs in an article about the Higgs boson Nobel Prize: One possibility has been ...
7
votes
0answers
139 views

Finite corrections to the Higgs mass in SUSY

I am worried here about specific supersymmetric scenarios in which an energy scale above the TeV is introduces. An example would be the Seesaw extension of the Minimal Supersymmetric Standard Model. ...
3
votes
2answers
251 views

Smolin on Cosmological selection and neutron stars

Regarding the cosmological selection hypothesis and testable predictions, Lee Smolin asserted the following: "Smolin: I did make two predictions which were eminently checkable by astrophysical ...
11
votes
2answers
662 views

Scalar field divergent mass correction interpretation question (hierarchy problem)

Simple power counting tells you that a scalar field coupled to some fermions at one-loop picks up a correction to the mass of the order $\Lambda^2$. Based on this people say things like "it's natural ...
5
votes
1answer
728 views

Renormalization and the Hierarchy Problem

The hierarchy problem is roughly: A scalar particle such as the Higgs receives quadratically divergent corrections, that have to cancel out delicately with the bare mass to give the observed Higgs ...
18
votes
2answers
1k views

Can dimensional regularization solve the fine-tuning problem?

I have recently read that the dimensional regularization scheme is "special" because power law divergences are absent. It was argued that power law divergences were unphysical and that there was no ...
1
vote
1answer
102 views

Multiverse explanation of fine tuning of cosmic constants

Physicists proposed the idea of multiverses to explain extraordinary fine tuning of the cosmic constant and physical laws which is essential for rise of life on earth. Is there any experiment that ...
1
vote
1answer
591 views

Fine tuning: why is multiverse with anthropic principle considered a better explanation than anthropic principle alone?

I got the impression from several public lectures that, when it comes to the fine tuning problem, physicists tend to give multiverse together with anthropic principle as a plausible solution, but ...
2
votes
0answers
530 views

Dimensional analysis to estimate order of magnitude of quantities

In the Coursera course From the Big Bang to Dark Energy on several occasions dimensional analysis was used to estimate the scale of quantities. This almost seems like a contradiction in terms to me, ...
4
votes
2answers
3k views

What are the implications of the Holographic principle?

What are the implications for the Holographic principle? I understand the basics of the principle, the relationship with black holes and string theory but what this is going to tell us? Does it help ...
2
votes
0answers
184 views

Sharp cut-off, quadratic corrections and naturalness

When introducing the fine-tuning problem, a sharp cut-off as a regulator in the calculation of the Higgs mass corrections is used. Since this regulator breaks translational and gauge invariance, up to ...
2
votes
1answer
562 views

Fine-Tuning, the Hiearchy Problem, and Mass in the Standard Model

In Chapter 1 of his book String Theory in a Nutshell, Kiritsis states the following. The [Standard M]odel is unstable as we increase the energy (hierarchy problem of mass scales) and the theory ...