78 research outputs found
Holography and Defect Conformal Field Theories
We develop both the gravity and field theory sides of the Karch-Randall
conjecture that the near-horizon description of a certain D5-D3 brane
configuration in string theory, realized as AdS_5 x S^5 bisected by an AdS_4 x
S^2 "brane", is dual to N=4 Super Yang-Mills theory in R^4 coupled to an R^3
defect. We propose a complete Lagrangian for the field theory dual, a novel
"defect superconformal field theory" wherein a subset of the fields of N=4 SYM
interacts with a d=3 SU(N) fundamental hypermultiplet on the defect preserving
conformal invariance and 8 supercharges. The Kaluza-Klein reduction of wrapped
D5 modes on AdS_4 x S^2 leads to towers of short representations of OSp(4|4),
and we construct the map to a set of dual gauge-invariant defect operators O_3
possessing integer conformal dimensions. Gravity calculations of and
are given. Spacetime and N-dependence matches expectations from dCFT,
while the behavior as functions of lambda = g^2 N at strong and weak coupling
is generically different. We comment on a class of correlators for which a
non-renormalization theorem may still exist. Partial evidence for the
conformality of the quantum theory is given, including a complete argument for
the special case of a U(1) gauge group. Some weak coupling arguments which
illuminate the duality are presented.Comment: 47 pages, LaTeX, 2 figures, feynmf. v2: fixed minor errors, added
references. v3: fixed more typo
On the geometrization of matter by exotic smoothness
In this paper we discuss the question how matter may emerge from space. For
that purpose we consider the smoothness structure of spacetime as underlying
structure for a geometrical model of matter. For a large class of compact
4-manifolds, the elliptic surfaces, one is able to apply the knot surgery of
Fintushel and Stern to change the smoothness structure. The influence of this
surgery to the Einstein-Hilbert action is discussed. Using the Weierstrass
representation, we are able to show that the knotted torus used in knot surgery
is represented by a spinor fulfilling the Dirac equation and leading to a
mass-less Dirac term in the Einstein-Hilbert action. For sufficient complicated
links and knots, there are "connecting tubes" (graph manifolds, torus bundles)
which introduce an action term of a gauge field. Both terms are genuinely
geometrical and characterized by the mean curvature of the components. We also
discuss the gauge group of the theory to be U(1)xSU(2)xSU(3).Comment: 30 pages, 3 figures, svjour style, complete reworking now using
Fintushel-Stern knot surgery of elliptic surfaces, discussion of Lorentz
metric and global hyperbolicity for exotic 4-manifolds added, final version
for publication in Gen. Rel. Grav, small typos errors fixe
Output spectrum of a detector measuring quantum oscillations
We consider a two-level quantum system (qubit) which is continuously measured
by a detector and calculate the spectral density of the detector output. In the
weakly coupled case the spectrum exhibits a moderate peak at the frequency of
quantum oscillations and a Lorentzian-shape increase of the detector noise at
low frequency. With increasing coupling the spectrum transforms into a single
Lorentzian corresponding to random jumps between two states. We prove that the
Bayesian formalism for the selective evolution of the density matrix gives the
same spectrum as the conventional master equation approach, despite the
significant difference in interpretation. The effects of the detector
nonideality and the finite-temperature environment are also discussed.Comment: 8 pages, 6 figure
Probabilistic analysis of the upwind scheme for transport
We provide a probabilistic analysis of the upwind scheme for
multi-dimensional transport equations. We associate a Markov chain with the
numerical scheme and then obtain a backward representation formula of
Kolmogorov type for the numerical solution. We then understand that the error
induced by the scheme is governed by the fluctuations of the Markov chain
around the characteristics of the flow. We show, in various situations, that
the fluctuations are of diffusive type. As a by-product, we prove that the
scheme is of order 1/2 for an initial datum in BV and of order 1/2-a, for all
a>0, for a Lipschitz continuous initial datum. Our analysis provides a new
interpretation of the numerical diffusion phenomenon
Involving patients and their families in deciding to use next generation sequencing: Results from a nationally representative survey of U.S. oncologists
Objective: Next generation sequencing (NGS) may aid in tumor classification and treatment. Barriers to shared decision-making may influence use of NGS. We examined, from oncologistsâ perspectives, whether barriers to involving patients/families in decision-making were associated with NGS use. Methods: Using data from the first national survey of medical oncologistsâ perspectives on precision medicine (N = 1281), we approached our analyses in two phases. Bivariate analyses initially evaluated associations between barriers to involving patients/families in deciding to use NGS and provider- and organizational-level characteristics. Modified Poisson regressions then examined associations between patient/family barriers and NGS use. Results: Approximately 59 % of oncologists reported at least one barrier to involving patients/families in decision-making regarding NGS use. Those reporting patient/family barriers tended to have fewer genomic resources at their practices, to be in rural or suburban areas, and to have a higher proportion of Medicaid patients. However, these barriers were not associated with NGS use. Conclusions: Oncologists encounter barriers to involving patients/families in NGS testing decisions. Organizational barriers may also potentially play a role in testing decisions. Practice implications: To foster patient-centered care, strategies to support patient involvement in genomic testing decisions are needed, particularly among practices in low-resource settings
Resonant Photonic Quasicrystalline and Aperiodic Structures
We have theoretically studied propagation of exciton-polaritons in
deterministic aperiodic multiple-quantum-well structures, particularly, in the
Fibonacci and Thue-Morse chains. The attention is concentrated on the
structures tuned to the resonant Bragg condition with two-dimensional
quantum-well exciton. The superradiant or photonic-quasicrystal regimes are
realized in these structures depending on the number of the wells. The
developed theory based on the two-wave approximation allows one to describe
analytically the exact transfer-matrix computations for transmittance and
reflectance spectra in the whole frequency range except for a narrow region
near the exciton resonance. In this region the optical spectra and the
exciton-polariton dispersion demonstrate scaling invariance and self-similarity
which can be interpreted in terms of the ``band-edge'' cycle of the trace map,
in the case of Fibonacci structures, and in terms of zero reflection
frequencies, in the case of Thue-Morse structures.Comment: 13 pages, 9 figures, submitted to Phys. Rev.
Prenatal Metal Exposure Alters the Placental Proteome in a Sex-Dependent Manner in Extremely Low Gestational Age Newborns: Links to Gestational Age
Prenatal exposure to toxic metals is associated with altered placental function and adverse infant and child health outcomes. Adverse outcomes include those that are observed at the time of birth, such as low birthweight, as well as those that arise later in life, such as neurological impairment. It is often the case that these adverse outcomes show sex-specific responses in relation to toxicant exposures. While the precise molecular mechanisms linking in utero toxic metal exposures with later-in-life health are unknown, placental inflammation is posited to play a critical role. Here, we sought to understand whether in utero metal exposure is associated with alterations in the expression of the placental proteome by identifying metal associated proteins (MAPs). Within the Extremely Low Gestational Age Newborns (ELGAN) cohort (n = 230), placental and umbilical cord tissue samples were collected at birth. Arsenic (As), cadmium (Cd), lead (Pb), selenium (Se), and manganese (Mn) concentrations were measured in umbilical cord tissue samples via ICP-MS/MS. Protein expression was examined in placental samples using an LC-MS/MS-based, global, untargeted proteomics analysis measuring more than 3400 proteins. MAPs were then evaluated for associations with pregnancy and neonatal outcomes, including placental weight and gestational age. We hypothesized that metal levels would be positively associated with the altered expression of inflammation/immune-associated pathways and that sex-specific patterns of metal-associated placental protein expression would be observed. Sex-specific analyses identified 89 unique MAPs expressed in female placentas and 41 unique MAPs expressed in male placentas. Notably, many of the female-associated MAPs are known to be involved in immune-related processes, while the male-associated MAPs are associated with intracellular transport and cell localization. Further, several MAPs were significantly associated with gestational age in males and females and placental weight in males. These data highlight the linkage between prenatal metal exposure and an altered placental proteome, with implications for altering the trajectory of fetal development
Stringing Spins and Spinning Strings
We apply recently developed integrable spin chain and dilatation operator
techniques in order to compute the planar one-loop anomalous dimensions for
certain operators containing a large number of scalar fields in N =4 Super
Yang-Mills. The first set of operators, belonging to the SO(6) representations
[J,L-2J,J], interpolate smoothly between the BMN case of two impurities (J=2)
and the extreme case where the number of impurities equals half the total
number of fields (J=L/2). The result for this particular [J,0,J] operator is
smaller than the anomalous dimension derived by Frolov and Tseytlin
[hep-th/0304255] for a semiclassical string configuration which is the dual of
a gauge invariant operator in the same representation. We then identify a
second set of operators which also belong to [J,L-2J,J] representations, but
which do not have a BMN limit. In this case the anomalous dimension of the
[J,0,J] operator does match the Frolov-Tseytlin prediction. We also show that
the fluctuation spectra for this [J,0,J] operator is consistent with the string
prediction.Comment: 27 pages, 4 figures, LaTex; v2 reference added, typos fixe
Two-loop HTL Thermodynamics with Quarks
We calculate the quark contribution to the free energy of a hot quark-gluon
plasma to two-loop order using hard-thermal-loop (HTL) perturbation theory. All
ultraviolet divergences can be absorbed into renormalizations of the vacuum
energy and the HTL quark and gluon mass parameters. The quark and gluon HTL
mass parameters are determined self-consistently by a variational prescription.
Combining the quark contribution with the two-loop HTL perturbation theory free
energy for pure-glue we obtain the total two-loop QCD free energy. Comparisons
are made with lattice estimates of the free energy for N_f=2 and with exact
numerical results obtained in the large-N_f limit.Comment: 33 pages, 6 figure
Identifying the transcriptional response of cancer and inflammation-related genes in lung cells in relation to ambient air chemical mixtures in Houston, Texas
Atmospheric pollution represents a complex mixture of air chemicals that continually interact and transform, making it difficult to accurately evaluate associated toxicity responses representative of real-world exposure. This study leveraged data from a previously published article and reevaluated lung cell transcriptional response induced by outdoor atmospheric pollution mixtures using field-based exposure conditions in the industrialized Houston Ship Channel. The tested hypothesis was that individual and co-occurring chemicals in the atmosphere relate to altered expression of critical genes involved in inflammation and cancer-related processes in lung cells. Human lung cells were exposed at an airâliquid interface to ambient air mixtures for 4 h, with experiments replicated across 5 days. Real-time monitoring of primary and secondary gas-phase pollutants, as well as other atmospheric conditions, was simultaneously conducted. Transcriptional analysis of exposed cells identified critical genes showing differential expression associated with both individual and chemical mixtures. The individual pollutant identified with the largest amount of associated transcriptional response was benzene. Tumor necrosis factor (TNF) and interferon regulatory factor 1 (IRFN1) were identified as key upstream transcription factor regulators of the cellular response to benzene. This study is among the first to measure lung cell transcriptional responses in relation to real-world, gas-phase air mixtures
- âŠ