8,390 research outputs found
Supersymmetric solutions to Euclidean Romans supergravity
We study Euclidean Romans supergravity in six dimensions with a non-trivial
Abelian R-symmetry gauge field. We show that supersymmetric solutions are in
one-to-one correspondence with solutions to a set of differential constraints
on an SU(2) structure. As an application of our results we (i) show that this
structure reduces at a conformal boundary to the five-dimensional rigid
supersymmetric geometry previously studied by the authors, (ii) find a general
expression for the holographic dual of the VEV of a BPS Wilson loop, matching
an exact field theory computation, (iii) construct holographic duals to
squashed Sasaki-Einstein backgrounds, again matching to a field theory
computation, and (iv) find new analytic solutions.Comment: 31 pages; v2: published version (with reference added
Supersymmetric gauge theories on squashed five-spheres and their gravity duals
We construct the gravity duals of large N supersymmetric gauge theories
defined on squashed five-spheres with SU(3) x U(1) symmetry. These five-sphere
backgrounds are continuously connected to the round sphere, and we find a
one-parameter family of 3/4 BPS deformations and a two-parameter family of
(generically) 1/4 BPS deformations. The gravity duals are constructed in
Euclidean Romans F(4) gauged supergravity in six dimensions, and uplift to
massive type IIA supergravity. We holographically renormalize the Romans
theory, and use our general result to compute the renormalized on-shell actions
for the solutions. The results agree perfectly with the large N limit of the
dual gauge theory partition function, which we compute using large N matrix
model techniques. In addition we compute BPS Wilson loops in these backgrounds,
both in supergravity and in the large N matrix model, again finding precise
agreement. Finally, we conjecture a general formula for the partition function
on any five-sphere background, which for fixed gauge theory depends only on a
certain supersymmetric Killing vector.Comment: 63 pages, no figures; v2: minor corrections and reference adde
Durable low surface-energy surfaces
A formulation for forming a low surface-energy surface on a substrate having (i) a fluoroalkyl silane having a low surface energy part, (ii) a liquid crystal silane operable for enhancing the orientation of the molecules of the fluoroalkyl silane and for crosslinking with the fluoroalkyl silane, and, (iii) a transport medium for applying the fluoroalkyl silane and the liquid crystal silane to the surface of a substrate. In one embodiment the formulation can includes a crosslinking agent for crosslinking the fluoroalkyl silane. In another embodiment the formulation has a condensation catalyst for enhancing chemical bonding of the fluoroalkyl silane to the substrate. The transport medium can be an alcohol such as methanol or ethanol
Symmetric Rotating Wave Approximation for the Generalized Single-Mode Spin-Boson System
The single-mode spin-boson model exhibits behavior not included in the
rotating wave approximation (RWA) in the ultra and deep-strong coupling
regimes, where counter-rotating contributions become important. We introduce a
symmetric rotating wave approximation that treats rotating and counter-rotating
terms equally, preserves the invariances of the Hamiltonian with respect to its
parameters, and reproduces several qualitative features of the spin-boson
spectrum not present in the original rotating wave approximation both
off-resonance and at deep strong coupling. The symmetric rotating wave
approximation allows for the treatment of certain ultra and deep-strong
coupling regimes with similar accuracy and mathematical simplicity as does the
RWA in the weak coupling regime. Additionally, we symmetrize the generalized
form of the rotating wave approximation to obtain the same qualitative
correspondence with the addition of improved quantitative agreement with the
exact numerical results. The method is readily extended to higher accuracy if
needed. Finally, we introduce the two-photon parity operator for the two-photon
Rabi Hamiltonian and obtain its generalized symmetric rotating wave
approximation. The existence of this operator reveals a parity symmetry similar
to that in the Rabi Hamiltonian as well as another symmetry that is unique to
the two-photon case, providing insight into the mathematical structure of the
two-photon spectrum, significantly simplifying the numerics, and revealing some
interesting dynamical properties.Comment: 11 pages, 5 figure
Predicting the effectiveness of farm planning at the Byenup Hill catchment using a groundwater model
A catchment model was constructed for the Byenup Hill catchment based on detailed hydrogeological mapping, information on land mapping units and land use collected from landholders. The aim of this work was to assess the likely impact of proposed land management changes to soil salinisation and recharge in the Byenup Hill Catchment
Dark-ages Reionization & Galaxy Formation Simulation VIII. Suppressed growth of dark matter halos during the Epoch of Reionization
We investigate how the hydrostatic suppression of baryonic accretion affects
the growth rate of dark matter halos during the Epoch of Reionization. By
comparing halo properties in a simplistic hydrodynamic simulation in which gas
only cools adiabatically, with its collisionless equivalent, we find that halo
growth is slowed as hydrostatic forces prevent gas from collapsing. In our
simulations, at the high redshifts relevant for reionization (between
and ), halos that host dwarf galaxies () can be reduced by up to a factor of 2 in mass due to the
hydrostatic pressure of baryons. Consequently, the inclusion of baryonic
effects reduces the amplitude of the low mass tail of the halo mass function by
factors of 2 to 4. In addition, we find that the fraction of baryons in dark
matter halos hosting dwarf galaxies at high redshift never exceeds
of the cosmic baryon fraction. When implementing baryonic processes, including
cooling, star formation, supernova feedback and reionization, the suppression
effects become more significant with further reductions of to
60\%. Although convergence tests suggest that the suppression may become weaker
in higher resolution simulations, this suppressed growth will be important for
semi-analytic models of galaxy formation, in which the halo mass inherited from
an underlying N-body simulation directly determines galaxy properties. Based on
the adiabatic simulation, we provide tables to account for these effects in
N-body simulations, and present a modification of the halo mass function along
with explanatory analytic calculations.Comment: 17 pages, 11 figures; Updated to match the published version. Two
changes in Figures 1 and 3 in order to 1) correct bin sizes of the 10^8 and
10^8.5 Msol bins for NOSN_NOZCOOL_NoRe (was 0.5, should be 0.25); 2) include
stellar mass in baryon fraction (was missed in Fig. 3). Quantitative
description of Fig. 3 changed slightly in Section 2.2. All other results and
conclusions remain unchange
Dark-ages reionization and galaxy formation simulation--VII. The sizes of high-redshift galaxies
We investigate high-redshift galaxy sizes using a semi-analytic model
constructed for the Dark-ages Reionization And Galaxy-formation Observables
from Numerical Simulation project. Our fiducial model, including strong
feedback from supernovae and photoionization background, accurately reproduces
the evolution of the stellar mass function and UV luminosity function. Using
this model, we study the size--luminosity relation of galaxies and find that
the effective radius scales with UV luminosity as at --. We show that recently discovered very luminous
galaxies at (Bowler et al. 2016) and (Oesch et al. 2016)
lie on our predicted size--luminosity relations. We find that a significant
fraction of galaxies at will not be resolved by JWST, but GMT will have
the ability to resolve all galaxies in haloes above the atomic cooling limit.
We show that our fiducial model successfully reproduces the redshift evolution
of average galaxy sizes at . We also explore galaxy sizes in models
without supernova feedback. The no-supernova feedback models produce galaxy
sizes that are smaller than observations. We therefore confirm that supernova
feedback plays an important role in determining the size--luminosity relation
of galaxies and its redshift evolution during reionization.Comment: 10 pages, 4 figures, Accepted for publication in MNRA
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