2,734 research outputs found
Two loop Kahler potential in beta-deformed N=4 SYM theory
In N=2 superconformal field theories the Kahler potential is known to be tree
level exact. The beta-deformation of N=4 SU(N) SYM reduces the amount of
supersymmetry to N=1, allowing for non-trivial, superconformal loop corrections
to the Kahler potential. We analyse the two-loop corrections on the Coulomb
branch for a complex deformation. For an arbitrary chiral field in the Cartan
subalgebra we reduce the problem of computing the two-loop Kahler potential to
that of diagonalising the mass matrix, we then present the result in a
manifestly superconformal form. The mass matrix diagonalisation is performed
for the case of the chiral background that induces the breaking pattern SU(N)
-> SU(N-2)*U(1)^2. Then, for the gauge group SU(3), the Kahler potential is
explicitly computed to the two-loop order.Comment: 24 pages, 1 figure, version published in JHE
The one-loop effective potential of the Wess-Zumino model revisited
The full one-loop supersymmetric effective potential for the Wess-Zumino
model is calculated using superfield techniques. This includes the K\"ahler
potential and the auxiliary field potential, of which the former was originally
computed in 1993 while the latter is derived for the first time. In the purely
bosonic sector our results match those of older component field calculations.
In light of prior contradictory results found in the literature, the
calculation of the leading term in the auxiliary field potential is approached
in a variety of ways. Issues related to conditional convergence that occur
during these calculations and their possible consequences are discussed.Comment: 32 page
Preliminary evidence of increased striatal dopamine in a nonhuman primate model of maternal immune activation.
Women exposed to a variety of viral and bacterial infections during pregnancy have an increased risk of giving birth to a child with autism, schizophrenia or other neurodevelopmental disorders. Preclinical maternal immune activation (MIA) models are powerful translational tools to investigate mechanisms underlying epidemiological links between infection during pregnancy and offspring neurodevelopmental disorders. Our previous studies documenting the emergence of aberrant behavior in rhesus monkey offspring born to MIA-treated dams extends the rodent MIA model into a species more closely related to humans. Here we present novel neuroimaging data from these animals to further explore the translational potential of the nonhuman primate MIA model. Nine male MIA-treated offspring and 4 controls from our original cohort underwent in vivo positron emission tomography (PET) scanning at approximately 3.5-years of age using [18F] fluoro-l-m-tyrosine (FMT) to measure presynaptic dopamine levels in the striatum, which are consistently elevated in individuals with schizophrenia. Analysis of [18F]FMT signal in the striatum of these nonhuman primates showed that MIA animals had significantly higher [18F]FMT index of influx compared to control animals. In spite of the modest sample size, this group difference reflects a large effect size (Cohen's d = 0.998). Nonhuman primates born to MIA-treated dams exhibited increased striatal dopamine in late adolescence-a hallmark molecular biomarker of schizophrenia. These results validate the MIA model in a species more closely related to humans and open up new avenues for understanding the neurodevelopmental biology of schizophrenia and other neurodevelopmental disorders associated with prenatal immune challenge
Relating the Komargodski-Seiberg and Akulov-Volkov actions: Exact nonlinear field redefinition
This paper constructs an exact field redefinition that maps the Akulov-Volkov
action to that recently studied by Komargodski and Seiberg in arXiv:0907.2441.
It is also shown that the approach advocated in arXiv:1003.4143v2 and
arXiv:1009.2166 for deriving such a relationship is inconsistent.Comment: 8 pages; V2: a reference added, minor changes mad
Facial grimace testing as an assay of neuropathic pain-related behavior in a mouse model of cervical spinal cord injury.
A major portion of individuals affected by traumatic spinal cord injury (SCI) experience one or more types of chronic neuropathic pain (NP), which is often intractable to currently available treatments. The availability of reliable behavioral assays in pre-clinical models of SCI-induced NP is therefore critical to assess the efficacy of new potential therapies. Commonly used assays to evaluate NP-related behavior in rodents, such as Hargreaves thermal and von Frey mechanical testing, rely on the withdrawal response to an evoked stimulus. However, other assays that test spontaneous/non-evoked NP-related behavior or supraspinal aspects of NP would be highly useful for a more comprehensive assessment of NP following SCI. The Mouse Grimace Scale (MGS) is a tool to assess spontaneous, supraspinal pain-like behaviors in mice; however, the assay has not been characterized in a mouse model of SCI-induced chronic NP, despite the critical importance of mouse genetics as an experimental tool. We found that beginning 2 weeks after cervical contusion, SCI mice exhibited increased facial grimace features compared to laminectomy-only control mice, and this grimace phenotype persisted to the chronic time point of 5 weeks post-injury. We also found a significant relationship between facial grimace score and the evoked forepaw withdrawal response in both the Hargreaves and von Frey tests at 5 weeks post-injury when both laminectomy-only and SCI mice were included in the analysis. However, within only the SCI group, there was no correlation between grimace score and Hargreaves or von Frey responses. These results indicate both that facial grimace analysis can be used as an assay of spontaneous NP-related behavior in the mouse model of SCI and that the information provided by the MGS may be different than that provided by evoked tests of sensory function
Supersymmetric Euler-Heisenberg effective action: Two-loop results
The two-loop Euler-Heisenberg-type effective action for N = 1 supersymmetric
QED is computed within the background field approach. The background vector
multiplet is chosen to obey the constraints D_\a W_\b = D_{(\a} W_{\b)} =
const, but is otherwise completely arbitrary. Technically, this calculation
proves to be much more laborious as compared with that carried out in
hep-th/0308136 for N = 2 supersymmetric QED, due to a lesser amount of
supersymmetry. Similarly to Ritus' analysis for spinor and scalar QED, the
two-loop renormalisation is carried out using proper-time cut-off
regularisation. A closed-form expression is obtained for the holomorphic sector
of the two-loop effective action, which is singled out by imposing a relaxed
super self-duality condition.Comment: 27 pages, 2 eps figures, LaTeX; V2: typos corrected, comments and
reference adde
Link between supercurrent diode and anomalous Josephson effect revealed by gate-controlled interferometry
In Josephson diodes the asymmetry between positive and negative current
branch of the current-phase relation leads to a polarity-dependent critical
current and Josephson inductance. The supercurrent nonreciprocity can be
described as a consequence of the anomalous Josephson effect -- a
-shift of the current-phase relation -- in multichannel ballistic
junctions with strong spin-orbit interaction. In this work, we simultaneously
investigate -shift and supercurrent diode efficiency on the same
Josephson junction by means of a superconducting quantum interferometer. By
electrostatic gating, we reveal a direct link between -shift and
diode effect. Our findings show that the supercurrent diode effect mainly
results from magnetochiral anisotropy induced by spin-orbit interaction in
combination with a Zeeman field.Comment: 15 pages, 8 figure
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