Effects of Tensor + Scaler gravity

In summary, Bob Dicke and Carl Brans developed a S+T gravity model fifty years ago. Dicke also had a project to look for a small solar oblateness, and wanted to offset the precession of Mercury caused by the scaler part of gravity with the opposite precession caused by oblateness. In the last ten years, a scaler field has been suggested as a possible explanation for dark energy, but there has been no evidence of it causing a part of Mercury's precession. The effect of a scaler suggested today is much less than the effect caused by Dicke and Brans' scaler. A scalar field is a field defined by a single number at every point in space, while a tensor field is
  • #1
captn
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Fifty years ago (m/l), Bob Dicke and Carl Brans developed a S+T gravity model.

Concurrently, Dicke had a project to look for a small solar oblateness. He wanted the precession of Mercury caused by the scaler part of gravity to be offset by the opposite precession caused by oblateness.

In the last ten years, a scaler field has been suggested to the dark (matter? or energy?), but I have seen nothing about that field causing a part of Mercury's precesion.

Is the effect of a scaler suggested today much less than the effect caused by dicke/brans' scaler? Please help me to understand the effects of today's sacler.

Thanks, Neil
 
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  • #2
captn said:
Fifty years ago (m/l), Bob Dicke and Carl Brans developed a S+T gravity model.

Concurrently, Dicke had a project to look for a small solar oblateness. He wanted the precession of Mercury caused by the scaler part of gravity to be offset by the opposite precession caused by oblateness.

In the last ten years, a scaler field has been suggested to the dark (matter? or energy?), but I have seen nothing about that field causing a part of Mercury's precesion.

Is the effect of a scaler suggested today much less than the effect caused by dicke/brans' scaler? Please help me to understand the effects of today's sacler.

Thanks, Neil
Well, it is the case that any scalar field will necessarily also cause a gravity-like force. Typically the Quintessence models of dark energy that make use of such a scalar field having one whose interactions are such that they are undetectable.

And by the way, the way to distinguish between normal gravity and gravity induced by a scalar field is by looking at the deflection of light: the two deflect differently, and so a scalar field would cause the measurement of our Sun's mass by gravitational lensing to differ from its mass as measured through the orbits of the planets. So far the two agree to within experimental precision, so any scalar field that exists must necessarily have either very weak or very short-range interactions.
 
  • #3
Chalnoth said:
... models of dark energy that make use of such a scalar field having one whose interactions are such that they are undetectable.

Okay---Thanks,

Neil
 
  • #4
Can someone provide an analogy of scalar versus tensor (fields)? I've read through the wikipedia, but it's difficult to visualize. Some examples of each that could be used to differentiate the two would be great.

Thanks in advance.
 
  • #5
JinChang said:
Can someone provide an analogy of scalar versus tensor (fields)? I've read through the wikipedia, but it's difficult to visualize. Some examples of each that could be used to differentiate the two would be great.

Thanks in advance.
Well, a scalar field is a field that is fully defined by a single number at every point in space, whereas a tensor field is one that is fully defined by a tensor at every point in space (typically a second rank tensor).

Now, an example of a scalar field would be energy density: energy density is just a single number at every point in space. Note that this isn't a quantum field in and of itself, but rather a property of other fields. A quantum scalar field would be a fundamental particle that can be identified in such a way.

An example of a tensor field would be the stress tensor. The stress tensor is composed of pressure along the diagonal components, and anisotropic shears on the off-diagonal components. This type of tensor is required to fully define the forces in an extended object. If I have a rod, for example, I can give it pressure in one direction or another by squeezing/stretching it. I can give it an anisotropic shear by twisting the rod.

Depending upon what you mean by a tensor field, you can also add in the momentum and energy density of the rod (to make a stress-energy tensor). The difference would be whether you just want the spatial components of the tensor, or also the space-time components.
 
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Thanks, Chalnoth. While I need to study upon some of your explanation, it's certainly a great place to start.
 

1. What is Tensor + Scaler gravity?

Tensor + Scaler gravity is a theoretical model proposed by physicists to explain the effects of gravity. It combines the concepts of tensor gravity and scaler gravity, which are both theories of gravity that have been proposed in the past.

2. How does Tensor + Scaler gravity differ from other theories of gravity?

Tensor + Scaler gravity differs from other theories of gravity in that it attempts to reconcile the differences between general relativity and quantum mechanics. It also predicts different effects of gravity on a macroscopic scale compared to other theories, such as Newton's law of gravitation.

3. What are some potential implications of Tensor + Scaler gravity?

One potential implication of Tensor + Scaler gravity is that it could help us better understand the behavior of gravity in extreme conditions, such as near black holes or during the early stages of the universe. It could also potentially lead to the development of new technologies, such as improved methods for space travel.

4. Has Tensor + Scaler gravity been proven or tested?

At this time, Tensor + Scaler gravity is still a theoretical model and has not been proven or tested. However, scientists are conducting experiments and observations to gather evidence that could support or refute this theory.

5. What are the potential limitations or challenges of studying Tensor + Scaler gravity?

One limitation of studying Tensor + Scaler gravity is that it is a highly complex and mathematically challenging theory. It also involves concepts from both general relativity and quantum mechanics, which are notoriously difficult to reconcile. Additionally, it may be difficult to design experiments or make observations that can test the predictions of this theory.

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