1,711 research outputs found
Bayesian multitask inverse reinforcement learning
We generalise the problem of inverse reinforcement learning to multiple
tasks, from multiple demonstrations. Each one may represent one expert trying
to solve a different task, or as different experts trying to solve the same
task. Our main contribution is to formalise the problem as statistical
preference elicitation, via a number of structured priors, whose form captures
our biases about the relatedness of different tasks or expert policies. In
doing so, we introduce a prior on policy optimality, which is more natural to
specify. We show that our framework allows us not only to learn to efficiently
from multiple experts but to also effectively differentiate between the goals
of each. Possible applications include analysing the intrinsic motivations of
subjects in behavioural experiments and learning from multiple teachers.Comment: Corrected version. 13 pages, 8 figure
Charge and Colour Breaking Constraints in the MSSM With Non-Universal SUSY Breaking
We examine charge/colour breaking along directions in supersymmetric field
space which are F and D-flat. We catalogue the dangerous directions and include
some new ones which have not previously been considered. Analytic expressions
for the resulting constraints are provided which are valid for all patterns of
supersymmetry breaking. As an example we consider a recently proposed pattern
of supersymmetry breaking derived in Horava-Witten M-theory, and show that
there is no choice of parameters for which the physical vacuum is a global
minimum.Comment: 12 Pages plain latex; includes 1 postscript figure. Final version to
appear in PL
Effective theoretical approach of Gauge-Higgs unification model and its phenomenological applications
We derive the low energy effective theory of Gauge-Higgs unification (GHU)
models in the usual four dimensional framework. We find that the theories are
described by only the zero-modes with a particular renormalization condition in
which essential informations about GHU models are included. We call this
condition ``Gauge-Higgs condition'' in this letter. In other wards, we can
describe the low energy theory as the SM with this condition if GHU is a model
as the UV completion of the Standard Model. This approach will be a powerful
tool to construct realistic models for GHU and to investigate their low energy
phenomena.Comment: 18 pages, 2 figures; Two paragraphs discussing the applicable scope
of this approach are adde
Supersymmetric codimension-two branes and U(1)_R mediation in 6D gauged supergravity
We construct a consistent supersymmetric action for brane chiral and vector
multiplets in a six-dimensional chiral gauged supergravity. A nonzero brane
tension can be accommodated by allowing for a brane-localized Fayet-Iliopoulos
term proportional to the brane tension. When the brane chiral multiplet is
charged under the bulk U(1)_R, we obtain a nontrivial coupling to the extra
component of the U(1)_R gauge field strength as well as a singular scalar
self-interaction term. Dimensionally reducing to 4D on a football
supersymmetric solution, we discuss the implication of such interactions for
obtaining the U(1)_R D-term in the 4D effective supergravity. By assuming the
bulk gaugino condensates and nonzero brane F- and/or D-term for the uplifting
potential, we have all the moduli stabilized with a vanishing cosmological
constant. The brane scalar with nonzero R charge then gets a soft mass of order
the gravitino mass. The overall sign of the soft mass squared depends on the
sign of the R charge as well as whether the brane F- or D-term dominates.Comment: 28 pages, no figures, version to appear in JHE
Heterotic SO(32) model building in four dimensions
Four dimensional heterotic SO(32) orbifold models are classified
systematically with model building applications in mind. We obtain all Z3, Z7
and Z2N models based on vectorial gauge shifts. The resulting gauge groups are
reminiscent of those of type-I model building, as they always take the form
SO(2n_0)xU(n_1)x...xU(n_{N-1})xSO(2n_N). The complete twisted spectrum is
determined simultaneously for all orbifold models in a parametric way depending
on n_0,...,n_N, rather than on a model by model basis. This reveals interesting
patterns in the twisted states: They are always built out of vectors and
anti--symmetric tensors of the U(n) groups, and either vectors or spinors of
the SO(2n) groups. Our results may shed additional light on the S-duality
between heterotic and type-I strings in four dimensions. As a spin-off we
obtain an SO(10) GUT model with four generations from the Z4 orbifold.Comment: 1+37 pages LaTeX, some typos in table 4 corrected, and we have
included some discussion on exceptional shift vectors which ignored in the
previous version
Probing the MSSM Higgs Boson Sector with Explicit CP Violation through Third Generation Fermion Pair Production at Muon Colliders
We perform a systematic study of the production of a third-generation
fermion-pair, for , and t in the minimal
supersymmetric standard model (MSSM) with explicit CP violation, which is
induced radiatively by soft trilinear interactions related to squarks of the
third generation. We classify all the observables for probing the CP property
of the Higgs bosons constructed by the initial muon beam polarization along
with the unpolarized final fermions and with the final-fermion polarization
configuration of equal helicity, respectively. The observables allow for
complete determination of CP property of the neutral Higgs bosons. The
interference between the Higgs boson and gauge boson contributions also could
provide a powerful method for the determination of the CP property of two heavy
Higgs bosons in the top-quark pair production near the energy region of the
Higgs-boson resonances. For the lightest Higgs-boson mass there is no sizable
interference between scalar and vector contributions for the determination of
the CP property of the lightest Higgs boson. We give a detailed numerical
analysis to show how the radiatively-induced CP violation in the Higgs sector
of the MSSM can be measured.Comment: 30 pages, 7 figures including 5 eps ones. Typos corrected and
references added. To appear in Phys. Rev.
Retrodiction of Generalised Measurement Outcomes
If a generalised measurement is performed on a quantum system and we do not
know the outcome, are we able to retrodict it with a second measurement? We
obtain a necessary and sufficient condition for perfect retrodiction of the
outcome of a known generalised measurement, given the final state, for an
arbitrary initial state. From this, we deduce that, when the input and output
Hilbert spaces have equal (finite) dimension, it is impossible to perfectly
retrodict the outcome of any fine-grained measurement (where each POVM element
corresponds to a single Kraus operator) for all initial states unless the
measurement is unitarily equivalent to a projective measurement. It also
enables us to show that every POVM can be realised in such a way that perfect
outcome retrodiction is possible for an arbitrary initial state when the number
of outcomes does not exceed the output Hilbert space dimension. We then
consider the situation where the initial state is not arbitrary, though it may
be entangled, and describe the conditions under which unambiguous outcome
retrodiction is possible for a fine-grained generalised measurement. We find
that this is possible for some state if the Kraus operators are linearly
independent. This condition is also necessary when the Kraus operators are
non-singular. From this, we deduce that every trace-preserving quantum
operation is associated with a generalised measurement whose outcome is
unambiguously retrodictable for some initial state, and also that a set of
unitary operators can be unambiguously discriminated iff they are linearly
independent. We then examine the issue of unambiguous outcome retrodiction
without entanglement. This has important connections with the theory of locally
linearly dependent and locally linearly independent operators.Comment: To appear in Physical Review
Robustness of quantum Markov chains
If the conditional information of a classical probability distribution of
three random variables is zero, then it obeys a Markov chain condition. If the
conditional information is close to zero, then it is known that the distance
(minimum relative entropy) of the distribution to the nearest Markov chain
distribution is precisely the conditional information. We prove here that this
simple situation does not obtain for quantum conditional information. We show
that for tri-partite quantum states the quantum conditional information is
always a lower bound for the minimum relative entropy distance to a quantum
Markov chain state, but the distance can be much greater; indeed the two
quantities can be of different asymptotic order and may even differ by a
dimensional factor.Comment: 14 pages, no figures; not for the feeble-minde
Minimal gauge-Higgs unification with a flavour symmetry
We show that a flavour symmetry a la Froggatt-Nielsen can be naturally
incorporated in models with gauge-Higgs unification, by exploiting the heavy
fermions that are anyhow needed to realize realistic Yukawa couplings. The case
of the minimal five-dimensional model, in which the SU(2)_L x U(1)_Y
electroweak group is enlarged to an SU(3)_W group, and then broken to U(1)_em
by the combination of an orbifold projection and a Scherk-Schwarz twist, is
studied in detail. We show that the minimal way of incorporating a U(1)_F
flavour symmetry is to enlarge it to an SU(2)_F group, which is then completely
broken by the same orbifold projection and Scherk-Schwarz twist. The general
features of this construction, where ordinary fermions live on the branes
defined by the orbifold fixed-points and messenger fermions live in the bulk,
are compared to those of ordinary four-dimensional flavour models, and some
explicit examples are constructed.Comment: LaTex, 37 pages, 2 figures; some clarifying comments and a few
references adde
- …