1,843 research outputs found
E10 and SO(9,9) invariant supergravity
We show that (massive) D=10 type IIA supergravity possesses a hidden rigid
SO(9,9) symmetry and a hidden local SO(9) x SO(9) symmetry upon dimensional
reduction to one (time-like) dimension. We explicitly construct the associated
locally supersymmetric Lagrangian in one dimension, and show that its bosonic
sector, including the mass term, can be equivalently described by a truncation
of an E10/K(E10) non-linear sigma-model to the level \ell<=2 sector in a
decomposition of E10 under its so(9,9) subalgebra. This decomposition is
presented up to level 10, and the even and odd level sectors are identified
tentatively with the Neveu--Schwarz and Ramond sectors, respectively. Further
truncation to the level \ell=0 sector yields a model related to the reduction
of D=10 type I supergravity. The hyperbolic Kac--Moody algebra DE10, associated
to the latter, is shown to be a proper subalgebra of E10, in accord with the
embedding of type I into type IIA supergravity. The corresponding decomposition
of DE10 under so(9,9) is presented up to level 5.Comment: 1+39 pages LaTeX2e, 2 figures, 2 tables, extended tables obtainable
by downloading sourc
Gradient Representations and Affine Structures in AE(n)
We study the indefinite Kac-Moody algebras AE(n), arising in the reduction of
Einstein's theory from (n+1) space-time dimensions to one (time) dimension, and
their distinguished maximal regular subalgebras sl(n) and affine A_{n-2}^{(1)}.
The interplay between these two subalgebras is used, for n=3, to determine the
commutation relations of the `gradient generators' within AE(3). The low level
truncation of the geodesic sigma-model over the coset space AE(n)/K(AE(n)) is
shown to map to a suitably truncated version of the SL(n)/SO(n) non-linear
sigma-model resulting from the reduction Einstein's equations in (n+1)
dimensions to (1+1) dimensions. A further truncation to diagonal solutions can
be exploited to define a one-to-one correspondence between such solutions, and
null geodesic trajectories on the infinite-dimensional coset space H/K(H),
where H is the (extended) Heisenberg group, and K(H) its maximal compact
subgroup. We clarify the relation between H and the corresponding subgroup of
the Geroch group.Comment: 43 page
K(E10), Supergravity and Fermions
We study the fermionic extension of the E10/K(E10) coset model and its
relation to eleven-dimensional supergravity. Finite-dimensional spinor
representations of the compact subgroup K(E10) of E(10,R) are studied and the
supergravity equations are rewritten using the resulting algebraic variables.
The canonical bosonic and fermionic constraints are also analysed in this way,
and the compatibility of supersymmetry with local K(E10) is investigated. We
find that all structures involving A9 levels 0,1 and 2 nicely agree with
expectations, and provide many non-trivial consistency checks of the existence
of a supersymmetric extension of the E10/K(E10) coset model, as well as a new
derivation of the `bosonic dictionary' between supergravity and coset
variables. However, there are also definite discrepancies in some terms
involving level 3, which suggest the need for an extension of the model to
infinite-dimensional faithful representations of the fermionic degrees of
freedom.Comment: 50 page
Vacua of N=10 three dimensional gauged supergravity
We study scalar potentials and the corresponding vacua of N=10 three
dimensional gauged supergravity. The theory contains 32 scalar fields
parametrizing the exceptional coset space . The admissible gauge groups considered in this work involve both
compact and non-compact gauge groups which are maximal subgroups of
and , respectively. These gauge groups are
given by for , , , and . We
find many AdS critical points with various unbroken gauge symmetries. The
relevant background isometries associated to the maximally supersymmetric
critical points at which all scalars vanish are also given. These correspond to
the superconformal symmetries of the dual conformal field theories in two
dimensions.Comment: 37 pages no figures, typos corrected and a little change in the
forma
An E9 multiplet of BPS states
We construct an infinite E9 multiplet of BPS states for 11D supergravity. For
each positive real root of E9 we obtain a BPS solution of 11D supergravity, or
of its exotic counterparts, depending on two non-compact transverse space
variables. All these solutions are related by U-dualities realised via E9 Weyl
transformations in the regular embedding of E9 in E10, E10 in E11. In this way
we recover the basic BPS solutions, namely the KK-wave, the M2 brane, the M5
brane and the KK6-monopole, as well as other solutions admitting eight
longitudinal space dimensions. A novel technique of combining Weyl reflexions
with compensating transformations allows the construction of many new BPS
solutions, each of which can be mapped to a solution of a dual effective action
of gravity coupled to a certain higher rank tensor field. For real roots of E10
which are not roots of E9, we obtain additional BPS solutions transcending 11D
supergravity (as exemplified by the lowest level solution corresponding to the
M9 brane). The relation between the dual formulation and the one in terms of
the original 11D supergravity fields has significance beyond the realm of BPS
solutions. We establish the link with the Geroch group of general relativity,
and explain how the E9 duality transformations generalize the standard Hodge
dualities to an infinite set of `non-closing dualities'.Comment: 76 pages, 6 figure
Kaluza-Klein supergravity on AdS_3 x S^3
We construct a Chern-Simons type gauged N=8 supergravity in three spacetime
dimensions with gauge group SO(4) x T_\infty over the infinite dimensional
coset space SO(8,\infty)/(SO(8) x SO(\infty)), where T_\infty is an infinite
dimensional translation subgroup of SO(8,\infty). This theory describes the
effective interactions of the (infinitely many) supermultiplets contained in
the two spin-1 Kaluza-Klein towers arising in the compactification of N=(2,0)
supergravity in six dimensions on AdS_3 x S^3 with the massless supergravity
multiplet. After the elimination of the gauge fields associated with T_\infty,
one is left with a Yang Mills type gauged supergravity with gauge group SO(4),
and in the vacuum the symmetry is broken to the (super-)isometry group of AdS_3
x S^3, with infinitely many fields acquiring masses by a variant of the
Brout-Englert-Higgs effect.Comment: LaTeX2e, 24 pages; v2: references update
Time-like T-duality algebra
When compactifying M- or type II string-theories on tori of indefinite
space-time signature, their low energy theories involve sigma models on
E_{n(n)}/H_n, where H_n is a not necessarily compact subgroup of E_{n(n)} whose
complexification is identical to the complexification of the maximal compact
subgroup of E_{n(n)}. We discuss how to compute the group H_n. For finite
dimensional E_{n(n)}, a formula derived from the theory of real forms of E_n
algebra's gives the possible groups immediately. A few groups that have not
appeared in the literature are found. For n=9,10,11 we compute and describe the
relevant real forms of E_n and H_n. A given H_n can correspond to multiple
signatures for the compact torus. We compute the groups H_n for all
compactifications of M-, M*-, and M'-theories, and type II-, II*- and
II'-theories on tori of arbitrary signature, and collect them in tables that
outline the dualities between them. In an appendix we list cosets G/H, with G
split and H a subgroup of G, that are relevant to timelike toroidal
compactifications and oxidation of theories with enhanced symmetries.Comment: LaTeX, 37 pages, 1 eps-figure, uses JHEP.cls; v2. corrected typo's in
tables 16 and 17, minor changes to tex
Quantitative analysis of videokymography in normal and pathological vocal folds: a preliminari study.
Videokymography (VKG) captures high-speed
images of the vocal folds independently of the periodicity
of the acoustic signal. The aim of this study was to preliminarily
assess a software package that can objectively
measure specific parameters of vocal fold vibration. From
August 2009 until December 2010, we prospectively
evaluated 40 subjects (Group A, 18 normal subjects;
Group B, 14 patients with benign lesions of the middle
third of the vocal fold, such as polyps and cysts; Group C, 8
patients treated by endoscopic excision of vocal fold
benign lesions) by videoendoscopy, videolaryngostroboscopy,
and VKG. A VKG camera was coupled to a 70
telescope and video was recorded during phonation. Images
were objectively analyzed by a post-processing software
tool (VKG-Analyser) with a user-friendly interface
developed by our group. Different parameters were considered,
including the ratio between the amplitude of the
vibration of one vocal fold with respect to the contralateral
(Ramp), the ratio between the period of one vocal fold
vibration and the opposite one (Rper), and the ratio between
the duration of the open and closed phase within a glottal
cycle (Roc). Mean values for Ramp, Rper, and Roc in Group A
were 1.05, 1.04, and 1.35, respectively; in Group B were
1.63, 0.92, and 0.97, respectively; and in Group C were
1.13, 0.91, and 1.85, respectively. Quantitative analysis of
videokymograms by the herein presented tool, named VKG-Analyser, is useful for objective evaluation of the
vibratory pattern in normal and pathologic vocal folds.
Important future developments of this tool for the study of
both physiologic and pathologic patterns of vocal fold
vibration can be expected
Narrow Band Imaging and High Definition Television in endoscopic evaluation of upper aero-digestive tract cancer.
Narrow band imaging and high definition television are recent innovations in upper aero-digestive tract endoscopy. Aim of this prospective,
non-randomized, unblinded study was to establish the diagnostic advantage of these procedures in the evaluation of squamous cell cancer
arising from various upper aero-digestive tract sites. Between April 2007 and January 2010, 444 patients affected by upper aero-digestive
tract squamous cell cancer, or previously treated for it, were evaluated by white light and narrow band imaging ± high definition television
endoscopy, both in the pre-/intra-operative setting and during follow-up. Tumour resection was performed taking into account narrow band
imaging and high definition television information to obtain histopathologic confirmation of their validity. Endoscopic and pathologic data
were subsequently matched to obtain sensitivity, specificity, positive, negative predictive values, and accuracy. Overall, 110 (25%) patients
showed adjunctive findings by narrow band imaging ± high definition television when compared to standard white light endoscopy. Of
these patients, 98 (89%) received histopatological confirmation. The sensitivity, specificity, positive, negative predictive values, and accuracy
for white light-high definition television were 41%, 92%, 87%, 82%, and 67%, for narrow band imaging alone 75%, 87%, 87%,
74%, and 80%, and for narrow band imaging-high definition television 97%, 84%, 88%, 96%, and 92%. The highest diagnostic gain was
observed in the oral cavity and oropharynx (25%). Narrow band imaging and high definition television were of value in the definition of
superficial tumour extension, and in the detection of synchronous lesions in the pre-/intra-operative settings. These technologies also played
an important role during post-treatment surveillance for early detection of persistences, recurrences, and metachronous tumours
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