Journal Club

Seminar Room

Monday 11th of February, 2019

BasisGen: automatic generation of operator bases

Juan Carlos Criado
(Submitted on 11 Jan 2019)
BasisGen is a Python package for the automatic generation of bases of operators in effective field theories. It accepts any semisimple symmetry group and fields in any of its finite dimensional irreducible representations. It takes into account integration by parts redundancy and, optionally, the use of equations of motion. The implementation is based in well-known methods to generate and decompose representations using roots and weights, which allow for fast calculations, even with large numbers of fields and high-dimensional operators. BasisGen can also be used to do some representation-theoretic operations, such as finding the weight system of an irreducible representation from its highest weight or decomposing a tensor product of representations.
Comments: 12 pages
Subjects: High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:1901.03501 [hep-ph]
  (or arXiv:1901.03501v1 [hep-ph] for this version)

Presented by J.C. Criado

 

Large-scale inhomogeneity of dark energy produced in the ancestor vacuum

Yue Nan, Kazuhiro Yamamoto, Hajime Aoki, Satoshi Iso, Daisuke Yamauchi
(Submitted on 31 Jan 2019)
We investigate large-scale inhomogeneity of dark energy in the bubble nucleation scenario of the universe. In this scenario, the present universe was created by a bubble nucleation due to quantum tunneling from a metastable ancestor vacuum, followed by a primordial inflationary era. During the bubble nucleation, supercurvature modes of some kind of a scalar field are produced, and remain until present without decaying; thus they can play a role of the dark energy, if the mass of the scalar field is sufficiently light in the present universe. The supercurvature modes fluctuate at a very large spatial scale, much longer than the Hubble length in the present universe. Thus they create large-scale inhomogeneities of the dark energy, and generate large-scale anisotropies in the cosmic microwave background (CMB) fluctuations. This is a notable feature of this scenario, where quantum fluctuations of a scalar field are responsible for the dark energy. In this paper, we calculate imprints of the scenario on the CMB anisotropies through the integrated Sachs-Wolfe (ISW) effect, and give observational constraints on the curvature parameter $\Omega_K$ and on an additional parameter $\epsilon$ describing some properties of the ancestor vacuum.
Comments: 13 pages, 5 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
Report number: HUPD-1811, SAGA-HE-293, KEK-TH-2095
Cite as: arXiv:1901.11181 [astro-ph.CO]
  (or arXiv:1901.11181v1 [astro-ph.CO] for this version)

 

Presented by P. Kozow

 

Co-Scattering Dark Matter

Jia Liu, Xiao-Ping Wang, Wei Xue
(Submitted on 6 Feb 2019)
We propose a novel mechanism that, in two-component dark matter models, the subdominant one can thermalize the dominant one in galaxies, and leads to core density profiles. We take ultralight dark photons and $\mathrm{GeV}$-$\mathrm{TeV}$ Dirac fermions as an example, with a $U(1)$ coupling between the two dark matter candidates. This mechanism is significantly different from the self-interacting dark matter, due to three effects: 1) large occupation number enhancement, 2) forward-backward scattering cancellation, and 3) multiple scatterings required for the heavy dark matter. Unlike the fuzzy dark matter solution to the small structure problems having tension with Lyman-$\alpha$, the ultralight dark photons with mass $\gtrsim 10^{-21}$ eV can have a core profile through interactions with $\psi$ and are not constrained by other astrophysical observations.
Comments: 7 pages, 1 figure
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)
Report number: EFI-19-3, CERN-TH-2019-010
Cite as: arXiv:1902.02348 [hep-ph]
  (or arXiv:1902.02348v1 [hep-ph] for this version)

 

Presented by R. Vega-Morales

 


Constraining Rapidly Oscillating Scalar Dark Matter Using Dynamic Decoupling

Shahaf Aharony, Nitzan Akerman, Roee Ozeri, Gilad Perez, Inbar Savoray, Ravid Shaniv
(Submitted on 7 Feb 2019)
We propose and experimentally demonstrate a method for detection of light scalar Dark Matter (DM), through probing temporal oscillations of fundamental constants in an atomic optical transition. Utilizing the quantum information notion of Dynamic Decoupling (DD) in a table-top setting, we are able to obtain model-independent bounds on variations of $\alpha$ and $m_e$ at frequencies up to the MHz scale. We interpret our results to constrain the parameter space of light scalar DM field models. We consider the generic case, where the couplings of the DM field to the photon and to the electron are independent, as well as the case of a relaxion DM model, including the scenario of a DM boson star centered around Earth. Given the particular nature of DD, allowing to directly observe the oscillatory behaviour of coherent DM, and considering future experimental improvements, we conclude that our proposed method could be complimentary to, and possibly competitive with, gravitational probes of light scalar DM.
Comments: 11 pages, 3 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Atomic Physics (physics.atom-ph)
Cite as: arXiv:1902.02788 [hep-ph]
  (or arXiv:1902.02788v1 [hep-ph] for this version)

 

Presented by J. Santiago