1. Tev particle astrophysics at IHEP
Natural Phantom Dark Energy, Wiggling Hubble Parameter H(z) and Direct H(z) Data
张宏升（KASI）
Principle reference: Zhang,Hongsheng and Zhu, Zong-Hong, JCAP03(2008)007
2019/2/25
Tev particle astrophysics at IHEP

2. Tev particle astrophysics at IHEP
Outline
A quick glance at DE models
New features of H(z) data
NP DE model
Summary
2019/2/25
Tev particle astrophysics at IHEP

3. Tev particle astrophysics at IHEP
Acceleration
Really accelerating?
1. Problem of the standard candles
2. Nebulae and interstellar matters
Alternative gravity theory
1. f(R) gravity
2. Braneworld gravity
Exotic matters (or called dark energy)
1. Cosmological constant (w=-1)
2. Dynamical ones
a. Quintessence (w>-1)
b. Phantom (w<-1)
c. Quintom (crossing w=-1)
D. The EoS of the total fluid (not only the dark energy) crosses
w=-1, which is the topic of my report.
In the 3rd scheme, we do not change the frame of general relativity, but add some exotic matter, which generates negative pressure.
F® gravity, for example, Dr Miao’s report
Other theories, for example, Dr Blanchet’ report on gravity polarization.b
However, although fundamental for our understanding of the universe, its nature remains as a completely open question nowadays.
2019/2/25
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Wiggles on H(z)
The deficiency of luminosity distances
Hence, direct H(z) data can break the degeneration.
(J. Simon, L. Verde and R. Jimenez, Phys. Rev. D 71, (2005))
2019/2/25
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5. Wiggles on H(z): parameterizations
We can directly parameterize the H(z) data with oscillation behavior, for examples,
(H. Wei and S. N. Zhang, Phys. Lett. B 644, 7 (2007))
The oscillating parameterizations work well.
2019/2/25
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6. Pseudo Nambu-Goldstone Boson (PNGB)
The H(z) data in table I implies the EOS of total fluid in the universe crosses −1, not only the dark energy sector.
PNGB is an important idea in particle physics. It emerges whenever a global symmetry is spontaneously broken. There are two key scales of PNGB generation.
One is the scale at which the global symmetry breaks, denoted by f, and the other is the scale at which the soft explicit symmetry breaks, denoted by C.
The property of oscillation appears naturally in the present natural dark energy model.
2019/2/25
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Construction
We work in a frame of standard general relativity and spatially flat
FRW universe
2019/2/25
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Fitting result
The fitting result of the parameters and p. (a) The 68.3% confidence contour plot by using the direct H(z) data.
(b) The 68.3% confidence contour plot by using the SNLS data.
2019/2/25
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Some discussions
Comparing the two figures, it is evident that the resolution of supernavae data is less inefficiency than direct H(z) data to the oscillating behaviour of H(z).
The 68.3% confidence contour of H(z) data is disconnect. The physical explanation is that the data set of direct H(z) is too small, that is, the data do not distinctly illuminate how many “wiggles” inhabit on H(z). New wiggles may hide in the gaps of the data set, which leads that a much bigger p lies in the same confidence region as a smaller p.
2019/2/25
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10. Deceleration parameter
The universe oscillates between deceleration phase and acceleration phase.
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Quantum stability
A severe problem of any phantom field is quantum stability. In practice, we do not require that the phantom is fundamentally stable, but quasi-stable, which means, its lifetime is larger than the age of the universe.
We consider both the ordinary coupling and derivative coupling, and we find that We find it is a viable model if we treat it as an effective theory truncated by an upperbound.
Every time when phantom is discussed, quantum stability must be involved.
2019/2/25
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12. Tev particle astrophysics at IHEP
Summary
To summarize, this research illuminates that direct H(z) data is much more efficient than the supernovae for the fine structures of Hubble diagram.
We first put forward a model based on the previous studies on the PNGB. In this model the total fluid in the universe may evolve as phantom in some stages, which contents the direct H(z) data. We fit our model by using H(z) data and supernovae data, respectively. The results are quite different, as we expected.
We investigate the stability of the present model. Our treatise is to treat the phantom model as an effective model truncated at some energy scale. We find that the couplings between phantom and graviton are viable for the special potential of the present model.
2019/2/25
Tev particle astrophysics at IHEP

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Thanks
2019/2/25
Tev particle astrophysics at IHEP