arXiv subjects

Chiu Man Ho

Publications and source records attributed to Chiu Man Ho.

51 records · Page 3Linked to original sources

arXiv2012

On Neutrino Flavor States

We review the issues associated with the construction of neutrino flavor states. We then provide a consistent proof that the flavor states are approximately well-defined only if neutrinos are ultra-relativistic or the mass differences are negligible compared to energy. However, we show that weak interactions can be consistently described by only neutrino mass eigenstates. Meanwhile, the second quantization of neutrino flavor fields generally has no physical relevance as their masses are indefinite. Therefore, the flavor states are not physical quantum states and they should simply be interpreted as definitions to denote specific linear combinations of mass eigenstates involved in weak interactions. We also briefly discuss the implication of this work for the mixing between active and heavy sterile neutrinos.

hep-ph↗

arXiv2012

Cosmic Neutrino Flavor Ratios with Broken $ν_μ-ν_τ$ Symmetry

Reactor neutrino experiments have now observed a nonzero value for $θ_{13}$ at $5σ$, and global fits to data imply a nonzero value above $10σ$. Nonzero values for $θ_{13}$ and/or $θ_{32}-π/4$ break a $ν_μ-ν_τ$ symmetry, which has qualitative as well as quantitative implications for the time-evolution of neutrino flavors. In particular, the large-distance flavor evolution matrix, non-invertible with $ν_μ-ν_τ$ symmetry, is now invertible. This means that measurements of neutrino flavor ratios at Earth can now be inverted to directly reveal the flavor ratios injected at cosmically distant sources. With the updated values of the three neutrino mixing angles, we obtain the inverted large-distance evolution matrix and use it to derive several phenomenological relations between the injection flavor ratios and the observable ratios at Earth. Taking the three popular injection models as examples, we also exhibit the shift of Earthly observed flavor ratios from the corresponding values in the case with $ν_μ-ν_τ$ symmetry.

hep-ph↗

arXiv2012

Inflatonless Inflation

We consider a 4+N dimensional Einstein gravity coupled to a non-linear sigma model. This theory admits a solution in which the N extra dimensions contract exponentially while the ordinary space expand exponentially. Physically, the non-linear sigma fields induce the dynamical compactification of the extra dimensions, which in turn drives inflation. No inflatons are required.

hep-ph↗

arXiv2012

Three Generations in Minimally Extended Standard Models

We present a class of minimally extended standard models with the gauge group $SU(3)_C \times SU(N)_L \times U(1)_X$ where for all $N \geq 3$, anomaly cancelation requires three generations. At low energy, we recover the Standard Model (SM), while at higher energies, there must exist quarks, leptons and gauge bosons with electric charges shifted from their SM values by integer multiples of the electron charge up to $ \pm [N/2] e$. Since the value N=5 is the highest $N$ consistent with QCD asymptotic freedom, we elaborate on the 3-5-1 model.

hep-ph↗

arXiv2012

Conformal Completion of the Standard Model with a Fourth Generation

We study dynamical electroweak symmetry breaking with a fourth generation within the $Z_n$ orbifolded $AdS_5\otimes S^5$ framework. A realistic $Z_7$ example is discussed. The initial theory reduces dynamically, due to the induced condensates, to a four-family trinification near a TeV-scale conformal fixed point where the gauge hierarchy problem does not exist. We predict new gauge bosons and bifundamental fermions and scalars accessible by the LHC.

hep-ph↗

arXiv2012

Dark Matter, Infinite Statistics and Quantum Gravity

We elaborate on our proposal regarding a connection between global physics and local galactic dynamics via quantum gravity. This proposal calls for the concept of MONDian dark matter which behaves like cold dark matter at cluster and cosmological scales but emulates modified Newtonian dynamics (MOND) at the galactic scale. In the present paper, we first point out a surprising connection between the MONDian dark matter and an effective gravitational Born-Infeld theory. We then argue that these unconventional quanta of MONDian dark matter must obey infinite statistics, and the theory must be fundamentally non-local. Finally, we provide a possible top-down approach to our proposal from the Matrix theory point of view.

hep-th↗

arXiv2011

Leptogenesis and CPT Violation

We construct a model in which neutrinos and anti-neutrinos acquire the same mass but slightly different energy dispersion relations.Despite CPT violation, spin-statistics is preserved. We find that leptogenesis can be easily explained within this model, without upsetting the solar, atmospheric and reactor neutrino data. Leptogenesis occurs without lepton number violation and the non-equilibrium condition. We consider only three active Dirac neutrinos, and no new particles or symmetries are introduced.

hep-ph↗

arXiv2011

Quantum Gravity and Dark Matter

We propose a connection between global physics and local galactic dynamics via quantum gravity. The salient features of cold dark matter (CDM) and modified Newtonian dynamics (MOND) are combined into a unified scheme by introducing the concept of MONDian dark matter which behaves like CDM at cluster and cosmological scales but emulates MOND at the galactic scale.

gr-qc↗

arXiv2010

LHC Higgs Production and Decay in the T' Model

At $\sqrt{s} = 7$ TeV, the standard model needs at least $10\, (fb)^{-1}$ integrated luminosity at LHC to make a definitive discovery of the Higgs boson. Using binary tetrahedral ($T^{'}$) discrete flavor symmetry, we discuss how the decay of the lightest $T'$ Higgs into $γ\,γ$ can be effectively enhanced and dominate over its decay into $b \, \bar{b}$. Since the two-photon final state allows for a clean reconstruction, a decisive Higgs discovery may be possible at 7 TeV with the integrated luminosity only of $\sim 1\, (fb)^{-1}$.

hep-ph↗

arXiv2010

Modulated pair condensate of p-orbital ultracold fermions

We show that an interesting of pairing occurs for spin-imbalanced Fermi gases under a specific experimental condition---the spin up and spin down Fermi levels lying within the $p_x$ and $s$ orbital bands of an optical lattice, respectively. The pairs condense at a finite momentum equal to the sum of the two Fermi momenta of spin up and spin down fermions and form a $p$-orbital pair condensate. This $2k_F$ momentum dependence has been seen before in the spin- and charge- density waves, but it differs from the usual $p$-wave superfluids such as $^3$He, where the orbital symmetry refers to the relative motion within each pair. Our conclusion is based on the density matrix renormalization group analysis for the one-dimensional (1D) system and mean-field theory for the quasi-1D system. The phase diagram of the quasi-1D system is calculated, showing that the $p$-orbital pair condensate occurs in a wide range of fillings. In the strongly attractive limit, the system realizes an unconventional BEC beyond Feynman's no-node theorem. The possible experimental signatures of this phase in molecule projection experiment are discussed.

cond-mat.quant-gas↗

arXiv2010

Cold Dark Matter with MOND Scaling

We provide a holographic dual description of Milgrom's scaling associated with galactic rotation curves. Our argument is based on the recent entropic reinterpretation of Newton's laws of motion. We propose a duality between cold dark matter and modified Newtonian dynamics (MOND). We introduce the concept of MONDian dark matter, and discuss some of its phenomenological implications. At cluster as well as cosmological scales, the MONDian dark matter would behave as cold dark matter, but at the galactic scale, the MONDian dark matter would act as MOND.

hep-th↗

arXiv2010

Electron and Muon $g-2$ Contributions from the $T'$ Higgs Sector

We study the experimental constraints from electron and muon $g-2$ factors on the Higgs masses and Yukawa couplings in the $T'$ model, and thereby show that the discrepancy between the standard model prediction and experimental value of muon anomalous $g-2$ factor can be easily accommodated.

hep-ph↗

arXiv2009

Nonequilibrium Dynamics in Noncommutative Spacetime

We study the effects of spacetime noncommutativity on the nonequilibrium dynamics of particles in a thermal bath. We show that the noncommutative thermal bath does not suffer from any further IR/UV mixing problem in the sense that all the finite-temperature non-planar quantities are free from infrared singularities. We also point out that the combined effect of finite temperature and noncommutative geometry has a distinct effect on the nonequilibrium dynamics of particles propagating in a thermal bath: depending on the momentum of the mode of concern, noncommutative geometry may switch on or switch off their decay and thermalization. This momentum dependent alternation of the decay and thermalization rates could have significant impacts on the nonequilibrium phenomena in the early universe at which spacetime noncommutativity may be present. Our results suggest a re-examination of some of the important processes in the early universe such as reheating after inflation, baryogenesis and the freeze-out of superheavy dark matter candidates.

hep-th↗

arXiv2009

Unparticles and Holographic Renormalization Group

We revisit the unparticle interactions and propagators from the AdS-CFT point of view, and we show how the contact terms and their renormalization group flow appear in the context of the holographic renormalization. We study both vector unparticles and unfermions, uncovering the relevant boundary conditions and renormalization group flows.

hep-th↗

arXiv2008

Dangerous Liouville Wave -- exactly marginal but non-conformal deformation

We give a non-trivially interacting field theory example of scale invariant but non-conformal field theory. The model is based on the exactly solvable Liouville field theory coupled with free scalars deformed by an exactly marginal operator. We show non-vanishing of the trace of the energy-momentum tensor by using the quantum Schwinger-Dyson equation for the Liouville field theory, which is a sophistication of the quantum higher equations of motion for the Liouville field theory introduced by Alyosha Zamolodchikov. Possibly dangerous implications for the super-critical string theory will be discussed.

hep-th↗