618 research outputs found
Sensitivity bounds on heavy neutrino mixing and from LHCb upgrade
Decays of heavy pseudoscalar mesons , , and at LHCb
upgrade are considered, which produce either two equal sign muons or taus. In
addition, we consider the analogous decays with opposite sign muons or taus.
All these decays are considered to be mediated by a heavy on-shell neutrino
. Such decays of mesons, if not detected, will give in general stringent
upper bounds on the heavy-light mixing parameter as a function
of the neutrino mass GeV, principally due to the large expected
number of produced mesons . While some of the decays of the other mentioned
mesons are attractive due to a weaker CKM-suppression, the expected produced
number of such mesons is significantly smaller that that of 's; therefore,
the sensitivity bounds from such decays are in general comparable or less
restrictive. When pairs are produced, only two types of such decays are
significant: (and
), giving us stringent upper bounds on
; the other decays with a pair of , such as (and ), are
prohibited or very suppressed by kinematics.Comment: 13 pages, 4 figures; the paper is a continuation of our work
arXiv:1705.09403; v4: improved legends in Fig.
Non-Abelian Black Holes in D=5 Maximal Gauged Supergravity
We investigate static non-abelian black hole solutions of anti-de Sitter
Einstein-Yang-Mills-Dilaton gravity, which is obtained as a consistent
truncation of five-dimensional maximal gauged supergravity. If the dilaton is
(consistently) set to zero, the remaining equations of motion, with a
spherically-symmetric ansatz, may be derived from a superpotential. The
associated first-order equations admit an explicit solution supported by a
non-abelian SU(2) gauge potential, which has a logarithmically growing mass
term. In an extremal limit the horizon geometry becomes AdS. If
the dilaton is also excited, the equations of motion cannot easily be solved
explicitly, but we obtain the asymptotic form of the more general non-abelian
black holes in this case. An alternative consistent truncation, in which the
Yang-Mills fields are set to zero, also admits a description in terms of a
superpotential. This allows us to construct explicit wormhole solutions
(neutral spherically-symmetric domain walls). These solutions may be
generalised to dimensions other than five.Comment: Author's address, and a reference, adde
Domain Walls and Massive Gauged Supergravity Potentials
We point out that massive gauged supergravity potentials, for example those
arising due to the massive breathing mode of sphere reductions in M-theory or
string theory, allow for supersymmetric (static) domain wall solutions which
are a hybrid of a Randall-Sundrum domain wall on one side, and a dilatonic
domain wall with a run-away dilaton on the other side. On the anti-de Sitter
(AdS) side, these walls have a repulsive gravity with an asymptotic region
corresponding to the Cauchy horizon, while on the other side the runaway
dilaton approaches the weak coupling regime and a non-singular attractive
gravity, with the asymptotic region corresponding to the boundary of spacetime.
We contrast these results with the situation for gauged supergravity potentials
for massless scalar modes, whose supersymmetric AdS extrema are generically
maxima, and there the asymptotic regime transverse to the wall corresponds to
the boundary of the AdS spacetime. We also comment on the possibility that the
massive breathing mode may, in the case of fundamental domain-wall sources,
stabilize such walls via a Goldberger-Wise mechanism.Comment: latex file, 11 pages, 3 figure
Decoupling Limit, Lens Spaces and Taub-NUT: D=4 Black Hole Microscopics from D=5 Black Holes
We study the space-times of non-extremal intersecting p-brane configurations
in M-theory, where one of the components in the intersection is a ``NUT,'' i.e.
a configuration of the Taub-NUT type. Such a Taub-NUT configuration
corresponds, upon compactification to D=4, to a Gross-Perry-Sorkin (GPS)
monopole. We show that in the decoupling limit of the CFT/AdS correspondence,
the 4-dimensional transverse space of the NUT configuration in D=5 is foliated
by surfaces that are cyclic lens spaces S^3/Z_N, where N is the quantised
monopole charge. By contrast, in D=4 the 3-dimensional transverse space of the
GPS monopole is foliated by 2-spheres. This observation provides a
straightforward interpretation of the microscopics of a D=4 string-theory black
hole, with a GPS monopole as one of its constituents, in terms of the
corresponding D=5 black hole with no monopole. Using the fact that the
near-horizon region of the NUT solution is a lens space, we show that if the
effect of the Kaluza-Klein massive modes is neglected, p-brane configurations
can be obtained from flat space-time by means of a sequence of dimensional
reductions and oxidations, and U-duality transformations.Comment: 22 pages, Late
Kaluza-Klein Consistency, Killing Vectors, and Kahler Spaces
We make a detailed investigation of all spaces Q_{n_1... n_N}^{q_1... q_N} of
the form of U(1) bundles over arbitrary products \prod_i CP^{n_i} of complex
projective spaces, with arbitrary winding numbers q_i over each factor in the
base. Special cases, including Q_{11}^{11} (sometimes known as T^{11}),
Q_{111}^{111} and Q_{21}^{32}, are relevant for compactifications of type IIB
and D=11 supergravity. Remarkable ``conspiracies'' allow consistent
Kaluza-Klein S^5, S^4 and S^7 sphere reductions of these theories that retain
all the Yang-Mills fields of the isometry group in a massless truncation. We
prove that such conspiracies do not occur for the reductions on the Q_{n_1...
n_N}^{q_1... q_N} spaces, and that it is inconsistent to make a massless
truncation in which the non-abelian SU(n_i+1) factors in their isometry groups
are retained. In the course of proving this we derive many properties of the
spaces Q_{n_1... n_N}^{q_1... q_N} of more general utility. In particular, we
show that they always admit Einstein metrics, and that the spaces where
q_i=(n_i+1)/\ell all admit two Killing spinors. We also obtain an iterative
construction for real metrics on CP^n, and construct the Killing vectors on
Q_{n_1... n_N}^{q_1... q_N} in terms of scalar eigenfunctions on CP^{n_i}. We
derive bounds that allow us to prove that certain Killing-vector identities on
spheres, necessary for consistent Kaluza-Klein reductions, are never satisfied
on Q_{n_1... n_N}^{q_1... q_N}.Comment: Latex, 43 pages, references added and typos correcte
Consistent Kaluza-Klein Sphere Reductions
We study the circumstances under which a Kaluza-Klein reduction on an
n-sphere, with a massless truncation that includes all the Yang-Mills fields of
SO(n+1), can be consistent at the full non-linear level. We take as the
starting point a theory comprising a p-form field strength and (possibly) a
dilaton, coupled to gravity in the higher dimension D. We show that aside from
the previously-studied cases with (D,p)=(11,4) and (10,5) (associated with the
S^4 and S^7 reductions of D=11 supergravity, and the S^5 reduction of type IIB
supergravity), the only other possibilities that allow consistent reductions
are for p=2, reduced on S^2, and for p=3, reduced on S^3 or S^{D-3}. We
construct the fully non-linear Kaluza-Klein Ansatze in all these cases. In
particular, we obtain D=3, N=8, SO(8) and D=7, N=2, SO(4) gauged supergravities
from S^7 and S^3 reductions of N=1 supergravity in D=10.Comment: 27 pages, Latex, typo correcte
Entropy-Product Rules for Charged Rotating Black Holes
We study the universal nature of the product of the entropies of all horizons
of charged rotating black holes. We argue, by examining further explicit
examples, that when the maximum number of rotations and/or charges are turned
on, the entropy product is expressed in terms of angular momentum and/or
charges only, which are quantized. (In the case of gauged supergravities, the
entropy product depends on the gauge-coupling constant also.) In two-derivative
gravities, the notion of the "maximum number" of charges can be defined as
being sufficiently many non-zero charges that the Reissner-Nordstrom black hole
arises under an appropriate specialisation of the charges. (The definition can
be relaxed somewhat in charged AdS black holes in .) In
higher-derivative gravity, we use the charged rotating black hole in
Weyl-Maxwell gravity as an example for which the entropy product is still
quantized, but it is expressed in terms of the angular momentum only, with no
dependence on the charge. This suggests that the notion of maximum charges in
higher-derivative gravities requires further understanding.Comment: References added. 24 page
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