449 research outputs found
Asynchronous Co-eating Through Video Message Exchange: Support for Making Video Messages
[HCII 2020]12th International Conference, CCD 2020, Held as Part of the 22nd HCI International Conference, HCII 2020, Copenhagen, Denmark, July 19–24, 2020, Proceedings, Part IIPart of the Lecture Notes in Computer Science book series (LNCS, volume 12193)Co-Eating, i.e., eating meals in the company of other people, has been widely recognized as good for both physical and mental health. However, the chances of co-eating have drastically decreased for families living separately and for older people living alone. To cope with this problem, we propose a framework of “asynchronous co-eating” that enables virtual co-eating through video message exchanges, which does not necessarily require people to eat simultaneously. This framework is aimed to maintain frequent communication between family members and promote ordinary types of co-eating when possible. To make this process easy for both older people and their distant family members, we designed a video message exchange scheme with an omnidirectional camera and a topic recommendation mechanism. With preliminary experiments, we obtained results that suggest our framework has the potential to be beneficial
On duality symmetries of supergravity invariants
The role of duality symmetries in the construction of counterterms for
maximal supergravity theories is discussed in a field-theoretic context from
different points of view. These are: dimensional reduction, the question of
whether appropriate superspace measures exist and information about non-linear
invariants that can be gleaned from linearised ones. The former allows us to
prove that F-term counterterms cannot be E7(7)-invariant in D=4, N=8
supergravity or E6(6)-invariant in D=5 maximal supergravity. This is confirmed
by the two other methods which can also be applied to D=4 theories with fewer
supersymmetries and allow us to prove that N=6 supergravity is finite at three
and four loops and that N=5 supergravity is three-loop finite.Comment: Clarification of arguments and their consistency with higher
dimensional divergences added, e.g. we prove the 5D 4L non-renormalisation
theorem. The 4L N=6 divergence is also ruled out. References adde
Maximally Supersymmetric Yang-Mills in five dimensions in light-cone superspace
We formulate maximally supersymmetric Yang-Mills theory in five dimensions in
light-cone superspace. The light-cone Hamiltonian is of the quadratic form and
the theory can be understood as an oxidation of the N=4 Super Yang-Mills Theory
in four dimensions. We specifically study three-point counterterms and show how
these counterterms vanish on-shell. This study is a preliminary to set up the
technique in order to study possible four-point counterterms.Comment: 25 pages, typos corrected, references adde
String Theory, Unification and Quantum Gravity
An overview is given of the way in which the unification program of particle
physics has evolved into the proposal of superstring theory as a prime
candidate for unifying quantum gravity with the other forces and particles of
nature. A key concern with quantum gravity has been the problem of ultraviolet
divergences, which is naturally solved in string theory by replacing particles
with spatially extended states as the fundamental excitations. String theory
turns out, however, to contain many more extended-object states than just
strings. Combining all this into an integrated picture, called M-theory,
requires recognition of the r\^ole played by a web of nonperturbative duality
symmetries suggested by the nonlinear structures of the field-theoretic
supergravity limits of string theory.Comment: 29 pages, 13 figures, 3 tables; Lectures given at the 6th Aegean
Summer School "Quantum Gravity and Quantum Cosmology", Chora, Naxos Island,
Greece, 12-17 September 201
Family routines and next-generation engagement in family firms
By focusing on the impact of different types of family routines and how they change, this commentary builds on concepts regarding the influence of perceived parental support and psychological control on next-generation engagement in family firms. Drawing on the organizational routines literature and the family studies literature, I propose that attention to family routines, and how these routines change (or not) over time can reveal additional insights regarding next-generation engagement in the family business
Massive amplitudes on the Coulomb branch of N=4 SYM
We initiate a systematic study of amplitudes with massive external particles
on the Coulomb-branch of N=4 super Yang Mills theory: 1) We propose that
(multi-)soft-scalar limits of massless amplitudes at the origin of moduli space
can be used to determine Coulomb-branch amplitudes to leading order in the
mass. This is demonstrated in numerous examples. 2) We find compact explicit
expressions for several towers of tree-level amplitudes, including scattering
of two massive W-bosons with any number of positive helicity gluons, valid for
all values of the mass. 3) We present the general structure of superamplitudes
on the Coulomb branch. For example, the n-point "MHV-band" superamplitude is
proportional to a Grassmann polynomial of mixed degree 4 to 12, which is
uniquely determined by supersymmetry. We find explicit tree-level
superamplitudes for this MHV band and for other simple sectors of the theory.
4) Dual conformal generators are constructed, and we explore the dual conformal
properties of the simplest massive amplitudes. Our compact expressions for
amplitudes and superamplitudes should be of both theoretical and
phenomenological interest; in particular the tree-level results carry over to
truncations of the theory with less supersymmetry.Comment: 29 pages, 1 figur
On duality symmetry in perturbative quantum theory
Non-compact symmetries of extended 4d supergravities involve duality
rotations of vectors and thus are not manifest off-shell invariances in
standard "second-order" formulation. To study how such symmetries are realised
in the quantum theory we consider examples in 2 dimensions where vector-vector
duality is replaced by scalar-scalar one. Using a "doubled" formulation, where
fields and their momenta are treated on an equal footing and the duality
becomes a manifest symmetry of the action (at the expense of Lorentz symmetry),
we argue that the corresponding on-shell quantum effective action or S-matrix
are duality symmetric as well as Lorentz invariant. The simplest case of
discrete Z_2 duality corresponds to a symmetry of the S-matrix under flipping
the sign of the negative-chirality scalars in 2 dimensions or phase rotations
of chiral (definite-helicity) parts of vectors in 4 dimensions. We also briefly
discuss some 4d models and comment on implications of our analysis for extended
supergravities.Comment: 21 pages, Latex v2: comments and references added v3: references and
minor comments adde
Superconformal symmetry and maximal supergravity in various dimensions
In this paper we explore the relation between conformal superalgebras with 64
supercharges and maximal supergravity theories in three, four and six
dimensions using twistorial oscillator techniques. The massless fields of N=8
supergravity in four dimensions were shown to fit into a CPT-self-conjugate
doubleton supermultiplet of the conformal superalgebra SU(2,2|8) a long time
ago. We show that the fields of maximal supergravity in three dimensions can
similarly be fitted into the super singleton multiplet of the conformal
superalgebra OSp(16|4,R), which is related to the doubleton supermultiplet of
SU(2,2|8) by dimensional reduction. Moreover, we construct the ultra-short
supermultiplet of the six-dimensional conformal superalgebra OSp(8*|8) and show
that its component fields can be organized in an on-shell superfield. The
ultra-short OSp(8*|8) multiplet reduces to the doubleton supermultiplet of
SU(2,2|8) upon dimensional reduction. We discuss the possibility of a chiral
maximal (4,0) six-dimensional supergravity theory with USp(8) R-symmetry that
reduces to maximal supergravity in four dimensions and is different from
six-dimensional (2,2) maximal supergravity, whose fields cannot be fitted into
a unitary supermultiplet of a simple conformal superalgebra. Such an
interacting theory would be the gravitational analog of the (2,0) theory.Comment: 54 pages, PDFLaTeX, Section 5 and several references added. Version
accepted for publication in JHE
The D^{2k} R^4 Invariants of N=8 Supergravity
The existence of a linearized SUSY invariant for N=8 supergravity whose
gravitational components are usually called R^4 was established long ago by
on-shell superspace arguments. Superspace and string theory methods have also
established analogous higher dimensional D^{2k} R^4 invariants. However, very
little is known about the SUSY completions of these operators which involve
other fields of the theory. In this paper we find the detailed component
expansion of the linearized R^4 invariant starting from the corresponding
superamplitude which generates all component matrix elements of the operator.
It is then quite straightforward to extend results to the entire set of D^{2k}
R^4 operators.Comment: 17 page
Non-extremal black holes from the generalised r-map
We review the timelike dimensional reduction of a class of five-dimensional
theories that generalises 5D, N = 2 supergravity coupled to vector multiplets.
As an application we construct instanton solutions to the four-dimensional
Euclidean theory, and investigate the criteria for solutions to lift to static
non-extremal black holes in five dimensions.
We focus specifically on two classes of models: STU-like models, and models
with a block diagonal target space metric. For STU-like models the second order
equations of motion of the four-dimensional theory can be solved explicitly,
and we obtain the general solution. For block diagonal models we find a
restricted class of solutions, where the number of independent scalar fields
depends on the number of blocks. When lifting these solutions to five
dimensions we show, by explicit calculation, that one obtains static
non-extremal black holes with scalar fields that take finite values on the
horizon only if the number of integration constants reduces by exactly half.Comment: 22 pages. Based on talk by OV at "Black Objects in Supergravity
School" (BOSS2011), INFN, Frascati, Italy, 9-13 May, 201
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