5,113 research outputs found
Topological phase transition and two dimensional topological insulators in Ge-based thin films
We discuss possible topological phase transitions in Ge-based thin films of
Ge(BiSb)Te as a function of layer thickness and Bi
concentration using the first principles density functional theory
framework. The bulk material is a topological insulator at = 1.0 with a
single Dirac cone surface state at the surface Brillouin zone center, whereas
it is a trivial insulator at = 0. Through a systematic examination of the
band topologies we predict that thin films of Ge(BiSb)Te
with = 0.6, 0.8 and 1.0 are candidates for two-dimensional (2D) topological
insulators, which would undergo a 2D topological phase transition as a function
of . A topological phase diagram for Ge(BiSb)Te thin
films is presented to help guide their experimental exploration.Comment: 7 pages, 5 figures, Accepted for publication in Physical Review B
(2012
Higgs mass from compositeness at a multi-TeV scale
Within composite Higgs models based on the top seesaw mechanism, we show that
the Higgs field can arise as the pseudo Nambu-Goldstone boson of the broken
U(3)_L chiral symmetry associated with a vector-like quark and the t-b doublet.
As a result, the lightest CP-even neutral state of the composite scalar sector
is lighter than the top quark, and can be identified as the newly discovered
Higgs boson. Constraints on weak isospin violation push the chiral symmetry
breaking scale above a few TeV, implying that other composite scalars are
probably too heavy to be probed at the LHC, but may be within reach at a future
hadron collider with center-of-mass energy of about 100 TeV.Comment: 30 pages. v2: discussion of T parameter expanded; references added.
To be published in JHE
Electroweak symmetry breaking by extra dimensions
Electroweak symmetry breaking may be naturally induced by the observed quark
and gauge fields in extra dimensions without a fundamental Higgs field. We show
that a composite Higgs doublet can arise as a bound state of and a
linear combination of the Kaluza-Klein states of , due to QCD in extra
dimensions. The top quark mass depends on the number of active
Kaluza-Klein modes, and is consistent with the experimental value.Comment: 4 pages, LaTeX, talk presented at PASCOS99, Lake Tahoe, Californi
Visual attributes of subliminal priming images impact conscious perception of facial expressions
We investigated, in young healthy participants, how the affective content of subliminally presented priming images and their specific visual attributes impacted conscious perception of facial expressions. The priming images were broadly categorized as aggressive, pleasant, or neutral and further subcategorized by the presence of a face and by the centricity (egocentric or allocentric vantage-point) of the image content. Participants responded to the emotion portrayed in a pixelated target-face by indicating via key-press if the expression was angry or neutral. Response time to the neutral target face was significantly slower when preceded by face primes, compared to non-face primes (p < 0.05, Bonferroni corrected). In contrast, faster RTs were observed when angry target faces were preceded by face compared to non-face primes. In addition, participants’ performance was worse when a priming image contained an egocentric face compared to when it contained either an allocentric face or an egocentric non-face. The results suggest a significant impact of the visual features of the priming image on conscious perception of face expression.Published versio
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