4,815 research outputs found
The effect of dark strings on semilocal strings
Dark strings have recently been suggested to exist in new models of dark
matter that explain the excessive electronic production in the galaxy. We study
the interaction of these dark strings with semilocal strings which are
solutions of the bosonic sector of the Standard Model in the limit
, where is the Weinberg angle. While
embedded Abelian-Higgs strings exist for generic values of the coupling
constants, we show that semilocal solutions with non-vanishing condensate
inside the string core exist only above a critical value of the Higgs to gauge
boson mass ratio when interacting with dark strings. Above this critical value,
which is greater than unity, the energy per unit length of the semilocal-dark
string solutions is always smaller than that of the embedded Abelian-Higgs-dark
string solutions and we show that Abelian-Higgs-dark strings become unstable
above this critical value. Different from the non-interacting case, we would
thus expect semilocal strings to be stable for values of the Higgs to gauge
boson mass ratio larger than unity. Moreover, the one-parameter family of
solutions present in the non-interacting case ceases to exist when semilocal
strings interact with dark strings.Comment: 16 pages including 6 figures; stability analysis adde
Peningkatan Kemampuan Berhitung Melalui Permainan Keranjang Tempurung Dan Biji Salak Di Taman Kanak-kanak Pk3a Taeh Baruah Kecamatan Payakumbuh
Kurangnya pengenalan anak terhadap berhitung hal ini disebabkan karena masih banyak anak yang belum mampu berhitung dengan benar. Tujuan penelitian untuk meningkatkan kemampuan berhitung anak. Jenis penelitian ini adalah penelitian tindakan kelas dengan subjek penelitian anak kelompok B1 berjumlah 15 orang. Penelitian ini dilakukan dalam dua siklus, setiap siklus tiga kali pertemuan. Data dikumpulkan melalui observasi, wawancara dan dokumentasi. Manfaat penelitian ini salah satu sarana untuk mengembangkan kemampuan berhitung anak untuk persiapan melanjutkan pedidikan berikutnya. Hasil permainan keranjang tempurung dan biji salak dapat meningkatkan kemampuan berhitung anak
Gravitating superconducting strings with timelike or spacelike currents
We construct gravitating superconducting string solutions of the U(1)_{local}
x U(1)_{global} model solving the coupled system of Einstein and matter field
equations numerically. We study the properties of these solutions in dependence
on the ratio between the symmetry breaking scale and the Planck mass. Using the
macroscopic stability conditions formulated by Carter, we observe that the
coupling to gravity allows for a new stable region that is not present in the
flat space-time limit. We match the asymptotic metric to the Kasner metric and
show that the relations between the Kasner coefficients and the energy per unit
length and tension suggested previously are well fulfilled for symmetry
breaking scale much smaller than the Planck mass. We also study the solutions
to the geodesic equation in this space-time. While geodesics in the exterior
space-time of standard cosmic strings are just straight lines, test particles
experience a force in a general Kasner space-time and as such bound orbits are
possible.Comment: 16 pages including 14 figure
Geodesic motion in the space-time of cosmic strings interacting via magnetic fields
We study the geodesic motion of test particles in the space-time of two
Abelian-Higgs strings interacting via their magnetic fields. These bound states
of cosmic strings constitute a field theoretical realization of p-q-strings
which are predicted by inflationary models rooted in String Theory, e.g. brane
inflation. In contrast to previously studied models describing p-q-strings our
model possesses a Bogomolnyi-Prasad-Sommerfield (BPS) limit. If cosmic strings
exist it would be exciting to detect them by direct observation. We propose
that this can be done by the observation of test particle motion in the
space-time of these objects. In order to be able to make predictions we have to
solve the field equations describing the configuration as well as the geodesic
equation numerically. The geodesics can then be classified according to the
test particle's energy, angular momentum and momentum along the string axis. We
find that the interaction of two Abelian-Higgs strings can lead to the
existence of bound orbits that would be absent without the interaction. We also
discuss the minimal and maximal radius of orbits and comment on possible
applications in the context of gravitational wave emission.Comment: v1: 22 pages including 17 figures; v2: new figure added, section on
observables added; acccepted for publication in Phys. Rev.
Remarks on the interaction between Born-Infeld solitons
We consider the Abelian Higgs model as well as the SU(2) Georgi-Glashow model
in which the gauge field action is replaced by a non linear Born-Infeld action.
We study soliton solutions arising in these models, namely the vortex and
monopole solutions, respectively. We construct formulas which provide good
approximations for the mass of the Born-Infeld deformed solitons using only the
data of the undeformed solutions. The results obtained indicate that in the
self-dual limit, the Born-Infeld interaction leads to bound vortices, while for
monopoles it gives rise to repulsion.Comment: 11 Revtex pages; some typos corrected, formular adde
Analisis Lama Waktu Pelayanan Laboratorium di Rumah Sakit Umum Daerah Pasaman Barat
Hospital laboratory services is one of the activities in hospitals that support quality health services. One indicator of the success of health services in the field of clinical pathology laboratory services is the waiting time for laboratory services. The standard set for laboratory service outcome waiting time is ≤ 140 minutes for blood chemistry and routine blood. This research analyzed the service time of outpatient laboratory that conducted hematology and clinical chemistry examination in the laboratory of Pasaman Barat Hospital. This research is a type of descriptive analytic research that is quantitative and supported by qualitative using cross sectional approach. The result of the research showed that laboratory service time at RSUD Pasaman Barat fulfilled the standard (≤ 140 minutes) for hematology examination 33.94 minutes, clinical chemistry 83.92 minutes, hematology and clinical chemistry 98 minutes. Based on the results of this study, the stages that contribute to the length of time laboratory services for hematological examination lies in the pre analytical stage, for clinical chemistry examination is located at the analytical stage, as well as for hematology and clinical chemistry examination lies in the analytic stage as well as the factors that affect the length of time laboratory services are human resources that is in the ability of officers and infrastructure facilitie
Deformed vortices in (4+1)-dimensional Einstein-Yang-Mills theory
We study vortex-type solutions in a (4+1)-dimensional
Einstein-Yang-Mills-SU(2) model. Assuming all fields to be independent on the
extra coordinate, these solutions correspond in a four dimensional picture to
axially symmetric multimonopoles, respectively monopole-antimonopole solutions.
By boosting the five dimensional purely magnetic solutions we find new
configurations which in four dimensions represents rotating regular nonabelian
solutions with an additional electric charge.Comment: 11 pages, including 5 eps files; reference added, discussion
extended; typos correcte
Stability of superconducting strings coupled to cosmic strings
We study the stability of superconducting strings in a U(1)_{local} x
U(1)_{global} model coupled via a gauge field interaction term to U(1)
Abelian-Higgs strings. The effect of the interaction on current stability is
numerically investigated by varying the relevant parameters within the physical
limits of our model. We find that the propagation speed of transverse (resp.
longitudinal) perturbations increases (decreases) with increasing binding
between the superconducting and Abelian-Higgs string. Moreover, we observe that
for small enough width of the flux tube of the superconducting string and/or
large enough interaction between the superconducting and the Abelian-Higgs
string superconducting strings cannot carry space-like, i.e. magnetic currents.
Our model can be seen as a field theoretical realization of bound states of p
F-strings and q superconducting D-strings and has important implications to
vorton formation during the evolution of networks of such strings.Comment: 18 pages including 17 figures: v2: figures change
The worldwide physical height datum project
AbstractThe definition of a common global vertical coordinate system is nowadays one of the key points in Geodesy. With the advent of GNSS, a coherent global height has been made available to users. The ellipsoidal height can be obtained with respect to a given geocentric ellipsoid in a fast and precise way using GNSS techniques. On the other hand, the traditional orthometric height is not coherent at global scale. Spirit levelling allows the estimation of height increments so that orthometric heights of surveyed points can be obtained starting from a benchmark of known orthometric heights. As it is well known, this vertical coordinate refers to the geoid, which is assumed to be coincident to the mean sea level. By means of a tide gauge, the mean sea level is estimated and thus a point of known orthometric height is defined. This assumption, which was acceptable in the past, became obsolete given the level of precision which is now required. Based on the altimetry observation, one can precisely quantify the existing discrepancy between geoid and mean sea level that can amount to 1 ÷ 2 m at global scale. Therefore, different tide gauges provide biased estimates of the geoid, given the discrepancy between this equipotential surface and the mean sea level. Also, in the last years, another vertical coordinate was used, the normal height that was introduced in the context of the Molodensky theory. In this paper, a review of the existing different height systems is given and the relationships among them are revised. Furthermore, an approach for unifying normal height referring to different tide gauges is presented and applied to the Italian test case. Finally, a method for defining a physical height system that is globally coherent is discussed in the context of the definition of the International Height Reference System/Frame, a project supported by the Global Geodetic Observing System of the International Association of Geodesy (IAG). This project was established in 2015 during the XXVI IAG General Assembly in Prague as described in IAG Resolution no. 1 that was presented and adopted there
Spherically symmetric Yang-Mills solutions in a (4+n)- dimensional space-time
We consider the Einstein-Yang-Mills Lagrangian in a (4+n)-dimensional
space-time. Assuming the matter and metric fields to be independent of the n
extra coordinates, a spherical symmetric Ansatz for the fields leads to a set
of coupled ordinary differential equations. We find that for n > 1 only
solutions with either one non-zero Higgs field or with all Higgs fields
constant exist. We construct the analytic solutions which fulfill this
conditions for arbitrary n, namely the Einstein-Maxwell-dilaton solutions. We
also present generic solutions of the effective 4-dimensional
Einstein-Yang-Mills-Higgs-dilaton model, which possesses n Higgs triplets
coupled in a specific way to n independent dilaton fields. These solutions are
the abelian Einstein-Maxwell- dilaton solutions and analytic non-abelian
solutions, which have diverging Higgs fields. In addition, we construct
numerically asymptotically flat and finite energy solutions for n=2.Comment: 15 Latex pages, 4 eps figures; v2: discussion of results revisite
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