1,823 research outputs found
Lessons from T-mu(mu) on inflation models: Two-scalar theory and Yukawa theory
No full text© 2020 authors. Published by the American Physical Society. We demonstrate two properties of the trace of the energy-momentum tensor T-mu(mu) in the flat spacetime. One is the decoupling of heavy degrees of freedom; i.e., heavy degrees of freedom leave no effect for low-energy T-mu(mu)-inserted amplitudes. This is intuitively apparent from the effective field theory point of view, but one has to take into account the so-called trace anomaly to explicitly demonstrate the decoupling. As a result, for example, in the R-2 inflation model, scalaron decay is insensitive to heavy degrees of freedom when a matter sector minimally couples to gravity (up to a nonminimal coupling of a matter scalar field other than the scalaron). The other property is a quantum contribution to a nonminimal coupling of a scalar field. The nonminimal coupling disappears from the action in the flat spacetime, but leaves the so-called improvement term in T-mu(mu). We study the renormalization group equation of the nonminimal coupling to discuss its quantum-induced value and implications for inflation dynamics. We work it out in the two-scalar theory and Yukawa theory11Nsciescopu
Applying the Hirose-Kamada filter to Swiss data: Output gap and exchange rate pass-through estimates
No full textMultivariate filters based on the Hodrick-Prescott filter are appealing because they combine the advantages of the Hodrick-Prescott filter with economic relationships. Recently, a new multivariate filter has been put forward by Hirose and Kamada (2003). In this article we apply this new filter to Swiss data spanning the period from 1981 to 2005. We estimate both potential output and the associated output gap with quarterly data. Moreover, a model-consistent Phillips curve for an open economy is derived from simple economic relationships. Based on the estimated Phillips curve, we investigate exchange-rate pass through effects on consumer prices. We find only a weak transmission of exchange rate fluctuations into consumer prices.potential output, output gap, multivariate filter, Hirose and Kamada filter, exchange-rate pass through
Unification of the standard model and dark matter sectors in [SU(5) × U(1)]4
No full text© 2019, The Author(s).A simple model of dark matter contains a light Dirac field charged under a hidden U(1) gauge symmetry. When a chiral matter content in a strong dynamics satisfies the t’Hooft anomaly matching condition, a massless baryon is a natural candidate of the light Dirac field. One realization is the same matter content as the standard SU(5) × U(1)(B−L) grand unified theory. We propose a chiral [SU(5) × U(1)]4 gauge theory as a unified model of the SM and DM sectors. The low-energy dynamics, which was recently studied, is governed by the hidden U(1)4 gauge interaction and the third-family U(1)(B−L)3 gauge interaction. This model can realize self-interacting dark matter and alleviate the small-scale crisis of collisionless cold dark matter in the cosmological structure formation. The model can also address the semi-leptonic B-decay anomaly reported by the LHCb experiment11Nsciescopu
Strongly-interacting massive particle and dark photon in the era of the intensity frontier
No full text© 2020 author(s). Published by the American Physical Society. A strongly interacting massive particle (SIMP) is an interesting candidate for dark matter (DM) because its self-interaction cross section can be naturally strong enough to address the astrophysical problem of small-scale structure formation. A simple model was proposed by assuming a monopole condensation, where composite SIMP comes from a "strongly interacting" U(1)(d) gauge theory. In the original model, the DM relic abundance is determined by the 3 -> 2 annihilation process via the Wess-Zumino-Witten term. In this paper, we discuss that the DM relic abundance is naturally determined also by a semiannihilation process via a kinetic mixing between the hypercharge gauge boson and the dark U(1)(d) gauge boson (dark photon). The dark photon can be discovered by LDMX-style missing momentum experiments in the near future11Nsciescopu
Recommended from our members
Letter to Yasahiko Kamada from John T. Lonsdale on 1960-06-28
No full textJackson School of Geoscience
Visualizing the Marrow of Science
No full textThis study proposes a new methodology that allows for
the generation of scientograms of major scientific domains,
constructed on the basis of cocitation of Institute
of Scientific Information categories, and pruned using
PathfinderNetwork, with a layout determined by algorithms
of the spring-embedder type (Kamada–Kawai),
then corroborated structurally by factor analysis. We
present the complete scientogram of the world for the
Year 2002. It integrates the natural sciences, the social
sciences, and arts and humanities. Its basic structure
and the essential relationships therein are revealed,
allowing us to simultaneously analyze the macrostructure,
microstructure, and marrow of worldwide scientific
output
LHC lifetime frontier and visible decay searches in composite asymmetric dark matter models
No full text© 2022, The Author(s).The LHC lifetime frontier will probe dark sector in near future, and the visible decay searches at fixed-target experiments have been exploring dark sector. Composite asymmetric dark matter with dark photon portal is a promising framework explaining the coincidence problem between dark matter and visible matter. Dark strong dynamics provides rich structure in the dark sector: the lightest dark nucleon is the dark matter, while strong annihilation into dark pions depletes the symmetric components of the dark matter. Dark photons alleviate cosmological problems. Meanwhile, dark photons make dark hadrons long-lived in terrestrial experiments. Moreover, the dark hadrons are produced through the very same dark photon. In this study, we discuss the visible decay searches for composite asymmetric dark matter models. For a few GeV dark nucleons, the LHC lifetime frontier, MATHUSLA and FASER, has a potential to discover their decay when kinetic mixing angle of dark photon is ϵ ≳ 10−4. On the other hand, fixed-target experiments, in particular SeaQuest, will have a great sensitivity to dark pions with a mass below GeV and with kinetic mixing ϵ ≳ 10−4 in addition to the LHC lifetime frontier. These projected sensitivities to dark hadrons in dark photon parameter space are comparable with the future sensitivities of dark photon searches, such as Belle-II and LHCb.11Nsciescopu
Unification for darkly charged dark matter
No full text© 2020 authors. Published by the American Physical Society. We provide a simple UV theory for Dirac dark matter with a massless Abelian gauge boson. We introduce a single fermion transforming as the 16 representation in the SO(10)' gauge group, which is assumed to be spontaneously broken to SU(5)' x U(1)'. The SU(5)' gauge interaction becomes strong at an intermediate scale, and then we obtain a light composite Dirac fermion with U(1)' gauge interaction at a low-energy scale. Its thermal relic can explain the observed amount of dark matter consistently with other cosmological and astrophysical constraints. The dark matter mass and U(1)' fine-structure constant are predicted to be 600-700 GeV and (2.5-2.9) x 10(-2), respectively. We discuss that a nonzero kinetic mixing between the U(1)' gauge boson and the hypercharge gauge boson is allowed and the temperature of the visible sector and the dark matter sector can be equal to each other11Nsciescopu
heating of strongly interacting massive particles
No full textIt was recently pointed out that semiannihilating dark matter (DM) may experience a novel temperature evolution dubbed as self-heating. Exothermic semiannihilation converts the DM mass to the kinetic energy. This yields a unique DM temperature evolution, T-chi alpha 1/a, in contrast to T-chi alpha 1/a(2) for free-streaming nonrelativistic particles. Self-heating continues as long as self-scattering sufficiently redistributes the energy of DM particles. In this paper, we study the evolution of cosmological perturbations in self-heating DM. We find that sub-GeV self-heating DM leaves a cutoff on the subgalactic scale of the matter power spectrum when the self-scattering cross section is sigma(self)/m(chi) similar to O(1) cm(2)/g. Then we present a particle physics realization of the self-heating DM scenario. The model is based on recently proposed strongly interacting massive particles with pionlike particles in a QCD-like sector. Pionlike particles semiannihilate into an axionlike particle, which is thermalized with dark radiation. The dark radiation temperature is smaller than the standard model temperature, evading the constraint from the effective number of neutrino degrees of freedom. It is easily realized when the dark sector is populated from the standard model sector through a small coupling11Nsciescopu
Self-interacting dark matter with a vector mediator: kinetic mixing with the U 1 B − L 3 gauge boson
No full textAbstract A spontaneously broken hidden U(1) h gauge symmetry can explain both the dark matter stability and the observed relic abundance. In this framework, the light gauge boson can mediate the strong dark matter self-interaction, which addresses astrophysical observations that are hard to explain in collisionless cold dark matter. Motivated by flavoured grand unified theories, we introduce right-handed neutrinos and a flavoured B − L gauge symmetry for the third family U 1 B − L 3 . The unwanted relic of the U(1) h gauge boson decays into neutrinos via the kinetic mixing with the U 1 B − L 3 gauge boson. Indirect detection bounds on dark matter are systematically weakened, since dark matter annihilation results in neutrinos. However, the kinetic mixing between U 1 B − L 3 and U(1) Y gauge bosons are induced by quantum corrections and leads to an observable signal in direct and indirect detection experiments of dark matter. This model can also explain the baryon asymmetry of the Universe via the thermal leptogenesis. In addition, we discuss the possibility of explaining the lepton flavour universality violation in semi-leptonic B meson decays that is recently found in the LHCb experiment
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