36 research outputs found
Towards New Classes of Flux Compactifications
We derive novel solutions of flux compactification with D7-branes on the
resolved conifold in type IIB String Theory and later extend this solution to
allow for non-zero temperature. At zero temperature, we find that adding
D7-branes via the Ouyang embedding contributes to the supersymmetry-breaking
(1,2) imaginary-self-dual flux, without generating a bulk cosmological
constant. We further find that having D7-branes and a resolved conifold
together give rise to a non-trivial D-term on the D7-branes. This
supersymmetry-breaking term vanishes when we take the singular conifold limit,
although supersymmetry appears to remain broken. We also lift our construction
to F-theory where we show that the type IIB (1,2) flux goes to (2,2)
non-primitive flux on the fourfold.
In the second part of the thesis, we extend these results by taking the
non-extremal limit of our geometry to incorporate temperature. In this case,
the internal NS-NS and R-R fluxes are no longer expected to be self-dual, but
they should also naturally be extensions of the fluxes found above. From the
supergravity equations of motion, we compute how the new contributions to the
fluxes should enter, due to the squashing of the resolved metric and
non-extremality. This provides us with a compelling gravity dual of large N
thermal quantum chromodynamics with flavor.Comment: 111 pages, 7 figures, PhD thesi
Attractive Lagrangians for Noncanonical Inflation
Treating inflation as an effective theory, we expect the effective Lagrangian
to contain higher-dimensional kinetic operators suppressed by the scale of UV
physics. When these operators are powers of the inflaton kinetic energy, the
scalar field can support a period of noncanonical inflation which is smoothly
connected to the usual slow-roll inflation. We show how to construct
noncanonical inflationary solutions to the equations of motion for the first
time, and demonstrate that noncanonical inflation is an attractor in phase
space for all small- and large-field models. We identify some sufficient
conditions on the functional form of the Lagrangian that lead to successful
noncanonical inflation since not every Lagrangian with higher-dimensional
kinetic operators can support noncanonical inflation. This extends the class of
known viable Lagrangians and excludes many Lagrangians which do not work.Comment: 39 pages, 9 figures. v2. Fixed typos, added reference, small changes
to examples; v3. Added discussion of field redefinitions, added references,
matches published versio
Initial Conditions for Non-Canonical Inflation
We investigate the dynamics of homogeneous phase space for single-field
models of inflation. Inflationary trajectories are formally attractors in phase
space, but since in practice not all initial conditions lead to them, some
degree of fine tuning is required for successful inflation. We explore how the
dynamics of non-canonical inflation, which has additional kinetic terms that
are powers of the kinetic energy, can play a role in ameliorating the initial
conditions fine tuning problem. We present a qualitative analysis of
inflationary phase space based on the dynamical behavior of the scalar field.
This allows us to construct the flow of trajectories, finding that trajectories
generically decay towards the inflationary solution at a steeper angle for
non-canonical kinetic terms, in comparison to canonical kinetic terms, so that
a larger fraction of the initial-conditions space leads to inflation. Thus,
non-canonical kinetic terms can be important for removing the initial
conditions fine-tuning problem of some small-field inflation models.Comment: 15 pages, 9 figure
Toward the Gravity Dual of Heterotic Small Instantons
The question of what happens when the heterotic SO(32) instanton becomes
small was answered sometime back by Witten. The heterotic theory develops an
enhanced Sp(2k) gauge symmetry for k small instantons, besides the allowed
SO(32) gauge symmetry. An interesting question now is to ask what happens when
we take the large k limit. In this paper we argue that in some special cases,
where Gauss' law allows the large k limit, the dynamics of the large k small
instantons can be captured by a dual gravitational description. For the cases
that we elaborate in this paper, the gravity duals are non-Kahler manifolds
although in general they could be non-geometric. These small instantons are
heterotic five-branes and the duality allows us to study the strongly coupled
field theories on these five-branes. We review and elaborate on some of the
recent observations pointing towards this duality, and argue that in certain
cases the gauge/gravity duality may be understood as small instanton
transitions under which the instantons smoothen out and consequently lose the
Sp(2k) gauge symmetry. This may explain how branes disappear on the dual side
and are replaced by fluxes. We analyse the torsion classes before and after the
transitions, and discuss briefly how the ADHM sigma model and related vector
bundles could be studied for these scenarios.Comment: 47 pages, 3 eps figures, LaTex, JHEP3 file; v2: Another consistency
check added, typos corrected and a reference added; v3: Text expanded a bit,
minor typos corrected and a few references updated. Final version to appear
in Phys. Rev.
Non-Extremality, Chemical Potential and the Infrared limit of Large N Thermal QCD
Non-extremal solution with warped resolved-deformed conifold background is
important to study the infrared limit of large N thermal QCD. Earlier works in
this direction have not taken into account all the back-reactions on the
geometry, namely from the branes, fluxes, and black-hole carefully. In the
present work we make some progress in this direction by solving explicitly the
supergravity equations of motions in the presence of the backreaction from the
black-hole. The backreactions from the branes and the fluxes on the other hand
and to the order that we study, are comparatively suppressed. Our analysis
reveal, among other things, how the resolution parameter would depend on the
horizon radius and how the RG flows of the coupling constants should be
understood in these scenarios, including their effects on the background
three-form fluxes. We also study the effect of switching on a chemical
potential in the background and, in a particularly simplified scenario, compute
the actual value of the chemical potential for our case.Comment: 61 pages, LaTex, 3 eps figures; v2: Some corrections done in sec 2.1
to sharpen the regime of validity of our results. Text expanded, typos
corrected and minor corrections added to the other sections; v3: Text
expanded at various places, typos corrected and references added. Final
version to appear in Physical Review
Supersymmetric Configurations, Geometric Transitions and New Non-Kahler Manifolds
We give a detailed derivation of a supersymmetric configuration of wrapped
D5-branes on a two-cycle of a warped resolved conifold. Our analysis reveals
that the resolved conifold should support a non-Kahler metric with an SU(3)
structure. We use this as a starting point of the geometric transition in type
IIB theory. A mirror, and a subsequent flop transition using an intermediate
M-theory configuration with a G_2 structure, gives rise to the complete IR
geometric transition in type IIA theory. A further mirror transformation gives
the type IIB gravity dual of the IR gauge theory on the wrapped D5-branes.
Expectedly non-Kahler deformations of the resolved and the deformed conifolds
appear as the gravity duals of the confining gauge theories in type IIA and
type IIB theories respectively, although in more generic cases these manifolds
could also be non-geometric. In the local limit we reproduce precisely the
scenarios presented in our earlier works. Our present work should therefore be
viewed as providing a supergravity proof of geometric transitions in the full
global scenarios in type II theories.Comment: 45 pages plus appendices, 2 eps figures, LaTex JHEP3; v2: Typos
corrected, some comments and references added; v3: More typos corrected and
the text expanded in this final version. The version that appears in Nucl.
Phys. B do not have the appendices. All the appendices in the published
version are restored in this archive versio
Staying at work with back pain: patients' experiences of work-related help received from GPs and other clinicians. A qualitative study
<p>Abstract</p> <p>Background</p> <p>Low back pain commonly affects work ability, but little is known about the work-related help and advice that patients receive from GPs and other clinicians. The purpose of this study was to explore the experiences of employed people with back pain and their perceptions of how GPs and other clinicians have addressed their work difficulties.</p> <p>Methods</p> <p>A qualitative approach with thematic analysis was used. Individual interviews were carried out with twenty-five employed patients who had been referred for back pain rehabilitation. All had expressed concern about their ability to work due to low back pain.</p> <p>Results</p> <p>The perception of the participants was that GPs and other clinicians had provided little or no work-focused guidance and support and rarely communicated with employers. Sickness certification was the main method that GPs used to manage participants' work problems. Few had received assistance with temporary modifications and many participants had remained in work despite the advice they had received. There was little expectation of what GPs and other clinicians could offer to address work issues.</p> <p>Conclusions</p> <p>These findings question the ability of GPs and other clinicians to provide work-focused support and advice to patients with low back pain. Future research is recommended to explore how the workplace problems of patients can be best addressed by health professionals.</p