648 research outputs found
Precise measurements of radio-frequency magnetic susceptibility in (anti)ferromagnetic materials
Dynamic magnetic susceptibility, , was studied in several intermetallic
materials exhibiting ferromagnetic, antiferromagnetic and metamagnetic
transitions. Precise measurements by using a 14 MHz tunnel diode oscillator
(TDO) allow detailed insight into the field and temperature dependence of
. In particular, local moment ferromagnets show a sharp peak in
near the Curie temperature, . The peak amplitude decreases and shifts to
higher temperatures with very small applied dc fields. Anisotropic measurements
of CeVSb show that this peak is present provided the magnetic easy axis is
aligned with the excitation field. In a striking contrast, small moment,
itinerant ferromagnets (i.e., ZrZn) show a broad maximum in that
responds differently to applied field. We believe that TDO measurements provide
a very sensitive way to distinguish between local and itinerant moment magnetic
orders. Local moment antiferromagnets do not show a peak at the N\'eel
temperature, , but only a sharp decrease of below due to the
loss of spin-disorder scattering changing the penetration depth of the ac
excitation field. Furthermore, we show that the TDO is capable of detecting
changes in spin order as well as metamagnetic transitions. Finally, critical
scaling of in the vicinity of is discussed in CeVSb and
CeAgSb
New supersymmetric solutions of N=2, D=5 gauged supergravity with hyperscalars
We construct new supersymmetric solutions, including AdS bubbles, in an N=2
truncation of five-dimensional N=8 gauged supergravity. This particular
truncation is given by N=2 gauged supergravity coupled to two vector multiples
and three incomplete hypermultiplets, and was originally investigated in the
context of obtaining regular AdS bubble geometries with multiple active
R-charges. We focus on cohomogeneity-one solutions corresponding to objects
with two equal angular momenta and up to three independent R-charges.
Curiously, we find a new set of zero and negative mass solitons asymptotic to
AdS_5/Z_k, for k \ge 3, which are everywhere regular without closed timelike
curves.Comment: Latex 3 times, 42 page
Domain walls between gauge theories
Noncommutative U(N) gauge theories at different N may be often thought of as
different sectors of a single theory: the U(1) theory possesses a sequence of
vacua labeled by an integer parameter N, and the theory in the vicinity of the
N-th vacuum coincides with the U(N) noncommutative gauge theory. We construct
noncommutative domain walls on fuzzy cylinder, separating vacua with different
gauge theories. These domain walls are solutions of BPS equations in gauge
theory with an extra term stabilizing the radius of the cylinder. We study
properties of the domain walls using adjoint scalar and fundamental fermion
fields as probes. We show that the regions on different sides of the wall are
not disjoint even in the low energy regime -- there are modes penetrating from
one region to the other. We find that the wall supports a chiral fermion zero
mode. Also, we study non-BPS solution representing a wall and an antiwall, and
show that this solution is unstable. We suggest that the domain walls emerge as
solutions of matrix model in large class of pp-wave backgrounds with
inhomogeneous field strength. In the M-theory language, the domain walls have
an interpretation of a stack of branes of fingerstall shape inserted into a
stack of cylindrical branes.Comment: Final version; minor corrections; to appear in Nucl.Phys.
Warped Phenomenology of Higher-Derivative Gravity
We examine the phenomenological implications at colliders for the existence
of higher-derivative gravity terms as extensions to the Randall-Sundrum model.
Such terms are expected to arise on rather general grounds, e.g., from string
theory. In 5-d, if we demand that the theory be unitary and ghost free, these
new contributions to the bulk action are uniquely of the Gauss-Bonnet form. We
demonstrate that the usual expectations for the production cross section and
detailed properties of graviton Kaluza-Klein resonances and TeV-scale black
holes can be substantially altered by existence of these additional
contributions. It is shown that measurements at future colliders will be highly
sensitive to the presence of such terms.Comment: 29 pages, 8 figure
An Improved Brane Anti-Brane Action from Boundary Superstring Field Theory and Multi-Vortex Solutions
We present an improved effective action for the D-brane-anti-D-brane system
obtained from boundary superstring field theory. Although the action looks
highly non-trivial, it has simple explicit multi-vortex (i.e. codimension-2
multi-BPS D-brane) multi-anti-vortex solutions. The solutions have a curious
degeneracy corresponding to different ``magnetic'' fluxes at the core of each
vortex. We also generalize the brane anti-brane effective action that is
suitable for the study of the inflationary scenario and the production of
defects in the early universe. We show that when a brane and anti-brane are
distantly separated, although the system is classically stable it can decay via
quantum tunneling through the barrier.Comment: 24 pages, 1 figure, JHEP3.cls; v2: references added, tunneling rate
discussion expande
Noncommutativity and Tachyon Condensation
We study the fuzzy or noncommutative Dp-branes in terms of infinitely many
unstable D0-branes, from which we can construct any Dp-branes. We show that the
tachyon condensation of the unstable D0-branes induces the noncommutativity. In
the infinite tachyon condensation limit, most of the unstable D0-branes
disappear and remaining D0-branes are actually the BPS D0-branes with the
correct noncommutative coordinates. For the fuzzy S^2 case, we explicitly show
only the D0-branes corresponding to the lowest Landau level survive in the
limit. We also show that a boundary state for a Dp-brane satisfying the
Dirichlet boundary condition on a curved submanifold embedded in the flat space
is not localized on the submanifold. This implies that the Dp-brane on it is
ambiguous at the string scale and solves the problem for a spherical D2-brane
with a unit flux on the world volume which should be equivalent to one
D0-brane. We also discuss the diffeomorphism in the D0-brane picture.Comment: 30 pages, references added, minor corrections and clarifications,
version to appear in JHE
Nariai, Bertotti-Robinson and anti-Nariai solutions in higher dimensions
We find all the higher dimensional solutions of the Einstein-Maxwell theory
that are the topological product of two manifolds of constant curvature. These
solutions include the higher dimensional Nariai, Bertotti-Robinson and
anti-Nariai solutions, and the anti-de Sitter Bertotti-Robinson solutions with
toroidal and hyperbolic topology (Plebanski-Hacyan solutions). We give explicit
results for any dimension D>3. These solutions are generated from the
appropriate extremal limits of the higher dimensional near-extreme black holes
in a de Sitter, and anti-de Sitter backgrounds. Thus, we also find the mass and
the charge parameters of the higher dimensional extreme black holes as a
function of the radius of the degenerate horizon.Comment: 10 pages, 11 figures, RevTeX4. References added. Published versio
Organizational and Leadership Implications for Transformational Development
Transformational development is a concept of change that originated in the Christian context but has now become generally used in the work of both secular and faith-based organizations. The growing use of the concept by organizations that are fundamentally different has naturally led to some confusion about what the concept means and what it takes to effectively implement it. In this article, we describe the key features of the concept and how they are important in determining the organizational requirements for its effective implementation. Drawing on a few cases, the paper highlights the centrality of faith in transformational development work
CANELC: constructing an e-language corpus
This paper reports on the construction of CANELC: the Cambridge and Nottingham e-language Corpus.3 CANELC is a one million word corpus of digital communication in English, taken from online discussion boards, blogs, tweets, emails and SMS messages. The paper outlines the approaches used when planning the corpus: obtaining consent; collecting the data and compiling the corpus database.
This is followed by a detailed analysis of some of the patterns of language used in the corpus. The analysis includes a discussion of the key words and phrases used as well as the common themes and semantic associations connected with the data. These discussions form the basis of an investigation of how e-language operates in both similar and different ways to spoken and written records of communication (as evidenced by the BNC - British National Corpus).
3 CANELC stands for Cambridge and Nottingham e-language Corpus. This corpus has been built as part of a collaborative project between The University of Nottingham and Cambridge University Press with whom sole copyright of the annotated corpus resides. CANELC comprises one-million words of digital English taken from SMS messages, blogs, tweets, discussion board content and private/business emails. Plans to extend the corpus are under discussion. The legal dimension to corpus âownershipâ of some forms of unannotated data is a complex one and is under constant review. At the present time the annotated corpus is only available to authors and researchers working for CUP and is not more generally available
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