549 research outputs found
SU(3) monopoles and their fields
Some aspects of the fields of charge two SU(3) monopoles with minimal
symmetry breaking are discussed. A certain class of solutions look like SU(2)
monopoles embedded in SU(3) with a transition region or ``cloud'' surrounding
the monopoles. For large cloud size the relative moduli space metric splits as
a direct product AH\times R^4 where AH is the Atiyah-Hitchin metric for SU(2)
monopoles and R^4 has the flat metric. Thus the cloud is parametrised by R^4
which corresponds to its radius and SO(3) orientation. We solve for the
long-range fields in this region, and examine the energy density and rotational
moments of inertia. The moduli space metric for these monopoles, given by
Dancer, is also expressed in a more explicit form.Comment: 17 pages, 3 figures, latex, version appearing in Phys. Rev.
A Classical Instability of Reissner-Nordstrom Solutions and the Fate of Magnetically Charged Black Holes
Working in the context of spontaneously broken gauge theories, we show that
the magnetically charged Reissner-Nordstrom solution develops a classical
instability if the horizon is sufficiently small. This instability has
significant implications for the evolution of a magnetically charged black
hole. In particular, it leads to the possibility that such a hole could
evaporate completely, leaving in its place a nonsingular magnetic monopole.Comment: (10 pages
Black Holes in Magnetic Monopoles
We study magnetically charged classical solutions of a spontaneously broken
gauge theory interacting with gravity. We show that nonsingular monopole
solutions exist only if the Higgs vacuum expectation value is less than or
equal to a critical value , which is of the order of the Planck mass.
In the limiting case the monopole becomes a black hole, with the region outside
the horizon described by the critical Reissner-Nordstrom solution. For
, we find additional solutions which are singular at , but which
have this singularity hidden within a horizon. These have nontrivial matter
fields outside the horizon, and may be interpreted as small black holes lying
within a magnetic monopole. The nature of these solutions as a function of
and of the total mass and their relation to the Reissner-Nordstrom
solutions is discussed.Comment: (28 pages
The Kazhdan-Lusztig conjecture for finite W-algebras
We study the representation theory of finite W-algebras. After introducing
parabolic subalgebras to describe the structure of W-algebras, we define the
Verma modules and give a conjecture for the Kac determinant. This allows us to
find the completely degenerate representations of the finite W-algebras. To
extract the irreducible representations we analyse the structure of singular
and subsingular vectors, and find that for W-algebras, in general the maximal
submodule of a Verma module is not generated by singular vectors only.
Surprisingly, the role of the (sub)singular vectors can be encapsulated in
terms of a `dual' analogue of the Kazhdan-Lusztig theorem for simple Lie
algebras. These involve dual relative Kazhdan-Lusztig polynomials. We support
our conjectures with some examples, and briefly discuss applications and the
generalisation to infinite W-algebras.Comment: 11 page
Supersymmetry and discrete transformations of the Dirac operators in Taub-NUT geometry
It is shown that the N=4 superalgebra of the Dirac theory in Taub-NUT space
has different unitary representations related among themselves through unitary
U(2) transformations. In particular the SU(2) transformations are generated by
the spin-like operators constructed with the help of the same covariantly
constant Killing-Yano tensors which generate Dirac-type operators. A parity
operator is defined and some explicit transformations which connect the
Dirac-type operators among themselves are given. These transformations form a
discrete group which is a realization of the quaternion discrete group. The
fifth Dirac operator constructed using the non-covariant Killing-Yano tensor of
the Taub-NUT space is quite special. This non-standard Dirac operator is
connected with the hidden symmetry and is not equivalent to the Dirac-type
operators of the standard N=4 supersymmetry.Comment: 14 pages, latex, no figure
SO(10) Cosmic Strings and SU(3) Color Cheshire Charge
Certain cosmic strings that occur in GUT models such as can carry a
magnetic flux which acts nontrivially on objects carrying
quantum numbers. We show that such strings are non-Abelian Alice strings
carrying nonlocalizable colored ``Cheshire" charge. We examine claims made in
the literature that strings can have a long-range, topological
Aharonov-Bohm interaction that turns quarks into leptons, and observe that such
a process is impossible. We also discuss flux-flux scattering using a
multi-sheeted formalism.Comment: 37 Pages, 8 Figures (available upon request) phyzzx, iassns-hep-93-6,
itp-sb-93-6
Pair Creation of Black Holes by Domain Walls
In this paper we study the production of pairs of neutral and charged black
holes by domain walls, finding classical solutions and calculating their
classical actions. We find that neutral black holes whose creation is mediated
by Euclidean instantons must be produced mutually at rest with respect to one
another, but for charged black holes a new type of instanton is possible in
which after formation the two black holes accelerate away from one another.
These new types of instantons are not possible in Einstein-Maxwell theory with
a cosmological constant. We also find that the creation of non-orientable black
hole solutions can be mediated by Euclidean instantons and that in addition if
one is prepared to consider entirely Lorentzian no-boundary type contributions
to the path integral then mutually accelerating pairs may be created even in
the neutral case. Finally we consider the production of Kaluza-Klein monopoles
both by a standard cosmological term and in the presence of a domain wall. We
find that compactification is accompanied by the production of pairs of
Kaluza-Klein monopoles.Comment: 22 pages (REVTeX with AMS Symbols) with 5 postscript figures attached
in a single uuencoded, g-zipped, tar file at end of tex fil
Current preconception care practice in the Netherlands — An evaluation study among birth care professionals
Objective: To evaluate the current practice of preconception care in the Netherlands and the perceptions of birth care professionals concerning preconception care. Methods: We have developed a digital questionnaire and conducted a cross-sectional study by distributing the questionnaire among 102 organisations: 90 primary care midwifery practices and obstetric departments of 12 hospitals in the Southwest region of the Netherlands between December 2020 and March 2021. One birth care professional per organization was asked to complete the questionnaire. Descriptive statistics were used to present the results. Findings: Respondents of eighty-three organisations (81.4 %) filled in the questionnaire, of whom 74 respondents were independent primary care midwives and 9 respondents were obstetricians. Preconception care mostly consisted of an individual consultation in which personalized health and lifestyle advice was given. Among the respondents, 44.4 % reported that the organization had a preconception care protocol. The way in which the consultation was carried out, as well as the health and lifestyle related questions asked, differed between respondents. More than 85 % of the respondents inquire about the following possible risk factors for complications: maternal illnesses, obstetric history, folic acid supplement intake, alcohol intake, smoking, substance abuse, hereditary disease, prescription medication, dietary habits, overweight, and birth defects in the family. The respondents acknowledged that preconception care should be offered to all couples who wish to become pregnant, as opposed to offering preconception care only to those with an increased risk of complications. Still, respondents do not receive many questions regarding the preconception period or requests for preconception care consultations. Key conclusion: Birth care professionals acknowledge the need for preconception care for all couples. In the Netherlands, preconception care consists mostly of an individual consultation with recommendations for health and lifestyle advice. However, the identification of risk factors varies between birth care professionals and less than half of the respondents indicate that they have a protocol available in their practice. Furthermore, the demand of parents-to-be for preconception care is low. More research, that includes more obstetricians, is necessary to investigate if there is a difference between the care provided by primary care midwives and obstetricians. Implications for practice:To increase the awareness and uptake of preconception care, it would be prudent to emphasize its importance to parents-to-be and professionals, and actively promote the use of widespread, standardized protocols for birth care professionals.</p
p53-mediated neurodegeneration in the absence of the nuclear protein Akirin2.
Proper gene regulation is critical for both neuronal development and maintenance as the brain matures. We previously demonstrated that Akirin2, an essential nuclear protein that interacts with transcription factors and chromatin remodeling complexes, is required for the embryonic formation of the cerebral cortex. Here we show that Akirin2 plays a mechanistically distinct role in maintaining healthy neurons during cortical maturation. Restricting Akirin2 loss to excitatory cortical neurons resulted in progressive neurodegeneration via necroptosis and severe cortical atrophy with age. Comparing transcriptomes from Akirin2-null postnatal neurons and cortical progenitors revealed that targets of the tumor suppressor p53, a regulator of both proliferation and cell death encoded b
Anyons from nonsolvable finite groups are sufficient for universal quantum computation
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