# Gravity and the standard model

1. Aug 3, 2004

### kurious

gravity and the standard model and Higgs theory

Massless particles always exist in a gravitational field, in the real universe.The standard model does not reflect this,so how can the standard model of particle physics be correct.And how can the Higgs theory of mass generation which is linked to the standard model,be correct?
Have we now reached the point in physics where to proceed further all
physical phenomena must be accounted for simultaneously?

Last edited: Aug 3, 2004
2. Aug 3, 2004

### Atheist

>> Massless particles always exist in a gravitational field, in the real universe.The
>> standard model does not reflect this,...

Care to explain this a bit more? Do you mean that photons are not explained by the standard model or do you think that gravity has a considerable influence on the subatomic level or did you mean something completely different?

>> Have we now reached the point in physics where to proceed further all
>> physical phenomena must be accounted for simulataneously?

No. I´d be very surprised if a theory for type 2 superconductors or the first quantum computers would take gravity into account, for example.

EDIT: Cut out my comments on unified theories because they were not really important and people might feel offended by them.

Last edited: Aug 3, 2004
3. Aug 3, 2004

### Antonio Lao

The reason, I think, is that gravity is the weakest force among the 4 fundamental forces. The case for standard model is not yet closed until graviton and Higgs boson are all detected. The breakthroughs for standard model were the detections of W+, W-, and Z0 vector gauge bosons. The Higgs particle is a scalar boson which causes complication in the model.

4. Aug 3, 2004

### Antonio Lao

In term of particle detection it's 3 against 2 for the standard model, not counting the 8 gluons which, to me, are not particles but mainly properties for a principle of directional invariance. Along the same line of thinking, I can also say that graviton and Higgs particle are not really particles but dimensional jumps of other known particles already in existence.

5. Aug 3, 2004

### kurious

The standard model should incorporate gravity - gravity may be weak but it's impact on the overall substance of the theory could be large.I think that the fact that the mass of the Higgs particle and the masses of quarks and leptons can't be predicted
accurately (i.e to several decimal places) by the standard model suggests that the Higgs theory - which is linked to it - must be wrong.How can a theory about the generation of mass
be accurate when the mass of the particle associated with the Higgs field is so uncertain?

6. Aug 3, 2004

### Antonio Lao

These are all detected and agreed with theory predictions (at low energy).

The predicted mass of the Higgs boson can only be confirmed when it is found. But the energy needed for its discovery is beyond current accelerator technologies. If a low energy effect of the Higgs boson can be theorized then it is considered as found.

Last edited: Aug 3, 2004
7. Aug 3, 2004

### Antonio Lao

It does. The vector boson of gravity is the graviton. Graviton is a by product of standard model which is the quantization of different fields called quantum field theories (QFT). To close the case, graviton must be found. I think, superstring theories have more to say about the graviton and also the concept of supersymmetry. Once the graviton is found everything will be as clear as crystal is clear.

But the Higgs boson is a scalar boson and it is the mass that leads to the gravity force. So it must also be related to the graviton. But there is no theory of this relationship. The question is how to quantized a scalar field without a fundamental force?

Last edited: Aug 3, 2004
8. Aug 3, 2004

### kurious

Antonio Lao:
It does. The vector boson of gravity is the graviton. Graviton is a by product of standard model which is the quantization of different fields called quantum field theories (QFT).

Kurious:
What I meant was not that the standard model should predict a graviton but rather that the fact that every particle in the standard model exists in a gravitational field which fills the universe should be taken into consideration - theoretical models seem to take place in gravitational vacuums and they should not because this does not reflect the existence of particles in real life.Gravity and the standard model have not been reconciled because gravity and electromagnetism have not,and EM is part of the standard model.
How can quantizing the Higgs filed lead to gravitons - the Higgs is not space-time itself,is it?

Last edited: Aug 3, 2004
9. Aug 4, 2004

### Antonio Lao

In brane theory (offshoot of superstring), vector force models took place in just one brane while graviton connects two separated branes. All our reality can only be located in one brane. In a sense, a graviton is capable of transcending our physical reality into a separate reality of another brane universe.

The Higgs field is a scalar field with no inherent directional property. A vector field such as gravity field has a force to serve as its directional attribute. The problem is how do we quantize a scalar field? A field can easily be quantized iff there is a force.

The EM field has the EM force.
The Gluon field has the color force.
The weak field has the weak force.
The meson field has the pion force.

The forces are the exchange particles or carriers of the forces. The electroweak force share common carriers from EM and weak field.

10. Aug 4, 2004

### Antonio Lao

The Higgs field was invented in order to explain why some of the carriers of the electroweak force have mass (W+, W- and Z0 bosons). As can be noted all the other field particles have zero mass (photon, graviton, gluon, excluding pion which is really outdated concept superceded by the existence of quarks and the color force).

11. Aug 4, 2004

### Antonio Lao

The complication arising from having a force for vector fields is that gravity is known only to be attractive while the other forces can attract and also repel. So gravity field is a class of vector field all by itself and needed more ideas for its complete description.

12. Aug 4, 2004

### kurious

What if gravity is repulsive too but the repulsive particles have only a very short range field because something odd has happened to them.
Something has happened to the missing antimatter in the universe or
else we have to believe in some pretty fine tuning of the antimatter-matter ratio.Perhaps antimatter particles were fragmented in the early universe,
and this has removed the normal gravitational force from them.
It would be improbable that enough fragments would come together
at any point in space to collide with matter and annihilate.This is why we
don't witness such annihilations.

13. Aug 4, 2004

### Antonio Lao

This is easier said than done. Going off topic a bit, why does cold air sinks and hot air rises? Is it because cold air is denser? Why does supercool helium gas defies gravity? Why is it easier to lift a heavy object under water than on solid ground? Is gravity responsible for any of these cases? Or all of them?

The quantum vacuum fluctuations happen very fast. Although it is not possible to witness these events by the naked eye, the virtual fermions of matter and antimatter do interact with virtual photons in creations and destructions back and forth ceaselessly for all eternity.

14. Aug 4, 2004

### kurious

Kurious:
What if gravity is repulsive too

Antonio Lao:
This is easier said than done

Kurious:
Easily done if negative mass repels positive mass.Negative mass could have a short range gravitational field and might only be associated with fragmented antimatter.

15. Aug 5, 2004

### Antonio Lao

Because of the observed nature of the fundamental forces, both gravity and EM are considered long range forces while weak and strong nuclear forces are considered short range forces. The balancing acts between these forces were responsible for the creation of nuclei in the early universe and subsequently the formations of neutral atomic configurations. The birth of hydrogen atoms. The thermonuclear fusions of hydrogen nuclei (single proton state - 2 up quarks 1 down quark) created helium nuclei then lithium nuclei then the rest of the chemical elements follow in the same processes of fusion reaction between succeeding heavier and heavier nuclei configurations. The binding energy (also in term of temperature) needed can be plotted against the mass number (number of proton in the nuclei) into a graph showing stability around iron nuclei and probable fusion reaction at lower mass number and probable fission reaction at higher mass number.

The binding energy curve shows clearly that at low mass number nuclei tend to come together but at higher mass number nuclei tend to break apart.

16. Aug 5, 2004

### kurious

Antonio Lao:
Because of the observed nature of the fundamental forces

Kurious:
It would be hard to observe a short range gravitational repulsion because a large accumulation of repulsive mass would not have a cumulative effect over a big distance unlike like a large accumulation of attractive mass .

17. Aug 5, 2004

### Antonio Lao

Actually, the gravitational potential energy given by

$$U = - \frac{GMm}{r}$$

does allow either $M$ or $m$ to be both negative and the result is still acceptable. If just one mass is negative then the potential energy is positive which needs a new interpretation because it can appear that gauge symmetry is broken.