35 research outputs found
Dynamical Electroweak Symmetry Breaking from Extra Dimensions
We study the dynamical electroweak symmetry breaking (DEWSB) in the -dimensional bulk with compactified extra dimensions. We identify
the critical binding strength for triggering the DEWSB, based on the ladder
Schwinger-Dyson equation. In the top mode standard model with extra dimensions,
where the standard model gauge bosons and the third generation of quarks and
leptons are put in the bulk, we analyze the most attractive channel (MAC) by
using renormalization group equations (RGEs) of (dimensionless) bulk gauge
couplings and determine the effective cutoff where the MAC coupling exceeds the
critical value. We then find that the top-condensation can take place for D=8.
Combining RGEs of top-Yukawa and Higgs-quartic couplings with compositeness
conditions, we predict the top mass, GeV, and the Higgs mass,
GeV, for D=8, where we took the universal compactification scale
TeV.Comment: 8 pages, Talk given at the 2002 International Workshop On "Strong
Coupling Gauge Theories and Effective Field Theories" (SCGT 02), Nagoya,
Japan, 10-13 December 200
Techni-dilaton at Conformal Edge
Techni-dilaton (TD) was proposed long ago in the technicolor (TC) near
criticality/conformality. To reveal the critical behavior of TD, we explicitly
compute the nonperturbative contributions to the scale anomaly
, which
are generated by the dynamical mass m of the techni-fermions. Our computation
is based on the (improved) ladder Schwinger-Dyson equation, with the gauge
coupling replaced by the two-loop running one having the
Caswell-Banks-Zaks IR fixed point : for the IR region , where is
the intrinsic scale (analogue of of QCD) relevant to the
perturbative scale anomaly. We find that
and in the
criticality limit () ("conformal edge"). Our result precisely
reproduces the formal identity , where is the nonperturbative beta function
corresponding to the above essential singularity scaling of .
Accordingly, the PCDC implies at criticality limit, where is the mass of TD and
the decay constant of TD. We thus conclude that at criticality limit
the TD could become a "true (massless) Nambu-Goldstone boson" ,
only when , namely getting decoupled, as was the case of
"holographic TD" of Haba-Matsuzaki-Yamawaki. The decoupled TD can be a
candidate of dark matter.Comment: 17 pages, 14 figures; discussions clarified, references added, to
appear in Phys.Rev.
New Ternary Hydride Formation in U-Ti-H System
Hydrogen absorption properties of two titanium-rich uranium alloys, UTi_2 and UTi_4, were studied in order to prepare and identify the recently found ternary hydride. They slowly reacted with hydrogen of the initial pressure of 10^5Pa at 873K to form the ternary hydride. The hydrogenated specimen mainly consisted of the pursued ternary hydride but contained also U(or UO_2), TiH_x, and some transient phases. X-ray powder diffraction and Electron Probe Micro Analysis proved that it was the UTi_2H_x with the expected MgCu_2 structure, though all the X-ray peaks were broad probably because of inhomogeneity. This compound had extremely high resistance to powdering on its formation, which showed high potential utilities for a non-powdering tritium storage system or for other purposes
Gauged Nambu-Jona-Lasinio model with extra dimensions
We investigate phase structure of the D (> 4)-dimensional gauged
Nambu-Jona-Lasinio (NJL) model with extra dimensions
compactified on TeV scale, based on the improved ladder Schwinger-Dyson (SD)
equation in the bulk. We assume that the bulk running gauge coupling in the SD
equation for the SU(N_c) gauge theory with N_f massless flavors is given by the
truncated Kaluza-Klein effective theory and hence has a nontrivial ultraviolet
fixed point (UVFP). We find the critical line in the parameter space of two
couplings, the gauge coupling and the four-fermion coupling, which is similar
to that of the gauged NJL model with fixed (walking) gauge coupling in four
dimensions. It is shown that in the presence of such walking gauge interactions
the four-fermion interactions become ``nontrivial'' even in higher dimensions,
similarly to the four-dimensional gauged NJL model. Such a nontriviality holds
only in the restricted region of the critical line (``nontrivial window'') with
the gauge coupling larger than a non-vanishing value (``marginal triviality
(MT)'' point), in contrast to the four-dimensional case where such a
nontriviality holds for all regions of the critical line except for the pure
NJL point. In the nontrivial window the renormalized effective potential yields
a nontrivial interaction which is conformal invariant. The exisitence of the
nontrivial window implies ``cutoff insensitivity'' of the physics prediction in
spite of the ultraviolet dominance of the dynamics. In the formal limit D -> 4,
the nontrivial window coincides with the known condition of the nontriviality
of the four-dimensional gauged NJL model, .Comment: 34 pages, 6 figures, references added, to appear in Phys.Rev.D. The
title is changed in PR
Towards global sustainability: Education on environmentally clean energy technologies
The recent climate change agreement in Paris highlights the imperative to aggressively decarbonize the energy economy and develop new technologies, especially for the generation of electrical energy that are environmentally clean. This challenge can only be addressed by a multi-pronged approach to research and education of the next generation of scientists and engineers as well as informed public discourse. Consequently this requires the introduction of new and comprehensive education programs on sustainable energy technologies for universities and, possibly, high schools. Among others, the new programs should provide in-depth knowledge in the development of new materials for more efficient energy conversion systems and devices. The enhanced level of education is also needed for properly assessing the competing technologies in terms of their economic and social benefits. The increasing recognition of the significance of clean and efficient energy conversion indicates the need for a comprehensive education program to be developed. The purpose of the present work is to consider the structure of both an education program and the related textbook where the energy-related fundamental and applied subjects are presented in a concentrated and uniform manner. Such a textbook could be an education aid for students of energy-related courses as well as the teachers involved in the formulation of the education programs. The textbook, which should be dedicated mainly for students at the undergraduate levels at universities, and possibly high schools, should include in-depth interdisciplinary sections dedicated to energy experts and graduate students. This paper considers the present international efforts in reducing the impact of climate change and the need to develop new technologies for clean energy generation. It is argued that progress in this area requires recognition of hydrogen as the main energy carrier of the future. This work also delineates the goals of the Sustainable Energy Network, SEN, involved in the UN program of Future Earth
Dynamical chiral symmetry breaking in gauge theories with extra dimensions
We investigate dynamical chiral symmetry breaking in vector-like gauge
theories in dimensions with () compactified extra dimensions, based on
the gap equation (Schwinger-Dyson equation) and the effective potential for the
bulk gauge theories within the improved ladder approximation. The non-local
gauge fixing method is adopted so as to keep the ladder approximation
consistent with the Ward-Takahashi identities.
Using the one-loop gauge coupling of the truncated KK
effective theory which has a nontrivial ultraviolet fixed point (UV-FP)
for the (dimensionless) bulk gauge coupling , we find that there
exists a critical number of flavors, ( for
for SU(3) gauge theory): For , the dynamical
chiral symmetry breaking takes place not only in the ``strong-coupling phase''
() but also in the ``weak-coupling phase'' ()
when the cutoff is large enough. For , on the other hand,
only the strong-coupling phase is a broken phase and we can formally define a
continuum (infinite cutoff) limit, so that the physics is insensitive to the
cutoff in this case.
We also perform a similar analysis using the one-loop ``effective gauge
coupling''. We find the turns out to be a value similar to
that of the case, notwithstanding the enhancement of the
coupling compared with that of the .Comment: REVTEX4, 38 pages, 18 figures. The abstract is shortened; version to
be published in Phys. Rev.
Topped MAC with extra dimensions?
We perform the most attractive channel (MAC) analysis in the top mode
standard model with TeV-scale extra dimensions, where the standard model gauge
bosons and the third generation of quarks and leptons are put in D(=6,8,10,...)
dimensions. In such a model, bulk gauge couplings rapidly grow in the
ultraviolet region. In order to make the scenario viable, only the attractive
force of the top condensate should exceed the critical coupling, while other
channels such as the bottom and tau condensates should not. We then find that
the top condensate can be the MAC for D=8, whereas the tau condensation is
favored for D=6. The analysis for D=10 strongly depends on the regularization
scheme. We predict masses of the top (m_t) and the Higgs (m_H), m_t=172-175 GeV
and m_H=176-188 GeV for D=8, based on the renormalization group for the top
Yukawa and Higgs quartic couplings with the compositeness conditions at the
scale where the bulk top condenses. The Higgs boson in such a characteristic
mass range will be immediately discovered in H -> WW^(*)/ZZ^(*) once the LHC
starts.Comment: REVTEX4, 24 pages, 21 figures, to appear in PRD. The title is changed
in PRD. One reference added, typos correcte