2021 Fiscal Year Research-status Report
The Hubble parameter experimental puzzle in the context of Modfied Gravity models
| Project/Area Number |
20K03969
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2025-03-31
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| Keywords | Cosmology / Modified gravity models |
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| Outline of Annual Research Achievements |
In this last year of my research, I have been working on modifications of gravity in the light of new experimental data which seem to set strong constraints on General Relativity.
Either the experiment are wrong or the theory is wrong. In this situation I tend to be open-minded and try whether by modifying gravity I can solve this dilemma.
Since no modifications seem to appearing at astrophysical scales, I have been proposing/exploring theories of gravity which do not introduce new gravity degrees of freedom, but do modify, on the other hand, observables in cosmology.
This is possible by allowing Lorentz breaking terms to modify only the gravity sector, leaving the matter Lagrangians fulfill four dimensional diffeomorphism invariance. I have then been setting constraints on these models by using both early and late times experiments. I have proposed new models as to explain all the tensions which seem to be present in the data. I have been trying to explain the meaning and properties of shadowy modes, non-propagating modes which are often present in these modified theories of gravity.
The possibilities for this kind of modifications are very large, however, I tend to have an approach as to introduce/study the simplest possible examples which are still able to give non-trivial contributions in the field of cosmology.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The understanding of the theories and the implementation of the constraints on them have been developing smoothly.
In fact, I have reached a much deeper knowledge of the nature of the theories, as well as of the shadowy modes, which these theories seem to incorporate.
Also the implementation of the planned constraints from observations went smoothly.
I now feel comfortable with these theories and hope they can be used as to explain the issues of today's cosmology.
Also I feel I have got the means (both analytical and numerical) in order to discuss and understand several classes of modified gravity models.
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| Strategy for Future Research Activity |
In the future, I would like to better understand how serious and strong the cosmological issues are. To understand exactly what modification is required as to resolve all the tensions.
So I want to pursue the path taken so far, by extending my theoretical knowledge of modified gravity models, and at the same time to further develop numerical methods as to constrain them.
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| Causes of Carryover |
Because of the Corona virus, I did not go oversea for any collaboration and/or conference. Therefore, I was not able to use all the funding I planned to.
Hopefully the situation will get better and I will be able to use this funding to visit some oversea collaborator.
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