1,436 research outputs found
Hawking Radiation from Non-Extremal D1-D5 Black Hole via Anomalies
We take the method of anomaly cancellation for the derivation of Hawking
radiation initiated by Robinson and Wilczek, and apply it to the non-extremal
five-dimensional D1-D5 black hole in string theory. The fluxes of the electric
charge flow and the energy-momentum tensor from the black hole are obtained.
They are shown to match exactly with those of the two-dimensional black body
radiation at the Hawking temperature.Comment: 14 page
Hawking Radiation as Quantum Tunneling in Rindler Coordinate
We substantiate the Hawking radiation as quantum tunneling of fields or
particles crossing the horizon by using the Rindler coordinate. The thermal
spectrum detected by an accelerated particle is interpreted as quantum
tunneling in the Rindler spacetime. Representing the spacetime near the horizon
locally as a Rindler spacetime, we find the emission rate by tunneling, which
is expressed as a contour integral and gives the correct Boltzmann factor. We
apply the method to non-extremal black holes such as a Schwarzschild black
hole, a non-extremal Reissner-Nordstr\"{o}m black hole, a charged Kerr black
hole, de Sitter space, and a Schwarzschild-anti de Sitter black hole.Comment: LaTex 19 pages, no figure; references added and replaced by the
version accepted in JHE
High Superconductivity, Skyrmions and the Berry Phase
It is here pointed out that the antiferromagnetic spin fluctuation may be
associated with a gauge field which gives rise to the antiferromagnetic ground
state chirality. This is associated with the chiral anomaly and Berry phase
when we consider the two dimensional spin system on the surface of a 3D sphere
with a monopole at the centre. This realizes the RVB state where spinons and
holons can be understood as chargeless spins and spinless holes attached with
magnetic flux. The attachment of the magnetic flux of the charge carrier
suggest, that this may be viewed as a skyrmion. The interaction of a massless
fermion representing a neutral spin with a gauge field along with the
interaction of a spinless hole with the gauge field enhances the
antiferromagnetic correlation along with the pseudogap at the underdoped
region. As the doping increases the antiferromagnetic long range order
disappears for the critical doping parameter . In this framework,
the superconducting pairing may be viewed as caused by skyrmion-skyrmion bound
states.Comment: 10 pages, accepted in Phys. Rev.
Hawking radiation, W-infinity algebra and trace anomalies
We apply the "trace anomaly method" to the calculation of moments of the
Hawking radiation of a Schwarzschild black hole. We show that they can be
explained as the fluxes of chiral currents forming a W-infinity algebra. Then
we construct the covariant version of these currents and verify that up to
order 6 they are not affected by any trace anomaly. Using cohomological methods
we show that actually, for the fourth order current, no trace anomalies can
exist. The results reported here are strictly valid in two dimensions.Comment: 22 pages, typos correcte
Initial Commissioning of a Water-to-Water GHP System in KIER
GHP(Geothermal Heat Pump) system has been extensively disseminated due to the recent increasing demand of the new and renewable energy in Korea. However, the system reliability issues have been key barriers to ensure system performance as initially designed. This paper introduces a systematic method to verify its actually operating performance of a water to water GHP system. The main idea is to compare the actual performance with the manufacture data and then to reduce the gap between the actual and the manufacture data. The key result of this study is the development of a simplified GHP performance verification technique using the ISO standard based manufacture data. The manufacture performance data includes the information of EWT(entering water temperature), LWT(leaving water temperature), capacity, flow rate, power and COP. This technique has been verified to a w to w GHP system designed and installed at KIER site. The verification study showed that actual performance was lower than Manufacture data. And then the refrigerant was recharged and the compressor and the expansion valve were replaced. As a result, we can easily identify the GHP system problems and heating and cooling COP has been increased 25.26%,
18.24%
Doping dependent Irreversible Magnetic Properties of Ba(Fe1-xCox)2As2 Single Crystals
We discuss the irreversible magnetic properties of self-flux grown
Ba(Fe1-xCox)2As2 single crystals for a wide range of concentrations covering
the whole phase diagram from the underdoped to the overdoped regime, x=0.038,
0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized
by a magneto-optical method and show excellent spatial uniformity of the
superconducting state. The overall behavior closely follows classical Bean
model of the critical state. The field-dependent magnetization exhibits second
peak at a temperature and doping - dependent magnetic field, Hp. The evolution
of this fishtail feature with doping is discussed. Magnetic relaxation is
time-logarithmic and unusually fast. Similar to cuprates, there is an apparent
crossover from collective elastic to plastic flux creep above Hp. At high
fields, the field dependence of the relaxation rate becomes doping independent.
We discuss our results in the framework of the weak collective pinning and show
that vortex physics in iron-based pnictide crystals is much closer to high-Tc
cuprates than to conventional s-wave (including MgB2) superconductors.Comment: for the special issue of Physica C on iron-based pnictide
superconductor
Regional Recurrence Risk Following a Negative Sentinel Node Procedure Does Not Approximate the False-Negative Rate of the Sentinel Node Procedure in Breast Cancer Patients Not Receiving Radiotherapy or Systemic Treatment
Background: Although the false-negative rate of the sentinel lymph node biopsy (SLNB) in breast cancer patients is 5–7%, reported regional recurrence (RR) rates after negative SLNB are much lower. Adjuvant treatment modalities probably contribute to this discrepancy. This study assessed the 5-year RR risk after a negative SLNB in the subset of patients who underwent breast amputation without radiotherapy or any adjuvant treatment.Methods: All patients operated for primary unilateral invasive breast cancer between 2005 and 2008 were identified in the Netherlands Cancer Registry. Patients with a negative SLNB who underwent breast amputation and who were not treated with axillary lymph node dissection, radiotherapy, or any adjuvant systemic treatment were selected. The cumulative 5-year RR rate was estimated by Kaplan–Meier analysis.Results: A total of 13,452 patients were surgically treated for primary breast cancer and had a negative SLNB, and 2012 patients fulfilled the selection criteria. Thirty-eight RRs occurred during follow-up. Multifocal disease was associated with a higher risk of developing RR (P = 0.04). The median time to RR was 27 months and was significantly shorter in patients with estrogen receptor-negative (ER−) breast cancer (9.5 months; P = 0.003). The 5-year RR rate was 2.4% in the study population compared with 1.1% in the remainder of 11,440 SLNB-negative patients (P = 0.0002).Conclusions: Excluding the effect of radiotherapy and systemic treatment resulted in a twofold 5-year RR risk in breast cancer patients with a tumor-free SLNB. This 5-year RR rate was still much lower than the reported false-negative rate of the SLNB procedure.</p
A reported 20-gene expression signature to predict lymph node-positive disease at radical cystectomy for muscle-invasive bladder cancer is clinically not applicable
Background Neoadjuvant chemotherapy (NAC) for muscle-invasive bladder cancer (MIBC) provides a small but significant survival benefit. Nevertheless, controversies on applying NAC remain because the limited benefit must be weight against chemotherapy-related toxicity and the delay of definitive local treatment. Therefore, there is a clear clinical need for tools to guide treatment decisions on NAC in MIBC. Here, we aimed to validate a previously reported 20-gene expression signature that predicted lymph node-positive disease at radical cystectomy in clinically node-negative MIBC patients, which would be a justification for upfront chemotherapy. Methods We studied diagnostic transurethral resection of bladder tumors (dTURBT) of 150 MIBC patients (urothelial carcinoma) who were subsequently treated by radical cystectomy and pelvic lymph node dissection. RNA was isolated and the expression level of the 20 genes was determined on a qRT-PCR platform. Normalized Ct values were used to calculate a risk score to predict the presence of node-positive disease. The Cancer Genome Atlas (TCGA) RNA expression data was analyzed to subsequently validate the results. Results In a univariate regression analysis, none of the 20 genes significantly correlated with nodepositive disease. The area under the curve of the risk score calculated by the 20-gene expression signature was 0.54 (95% Confidence Interval: 0.44-0.65) versus 0.67 for the model published by Smith et al. Node-negative patients had a significantly lower tumor grade at TURBT (p = 0.03), a lower pT stage (p<0.01) and less frequent lymphovascular invasion (13% versus 38%, p<0.01) at radical cystectomy than node-positive patients. In addition, in the TCGA data, none of the 20 genes was differentially expressed in node-negative versus node-positive patients. Conclusions We conclude that a 20-gene expression signature developed for nodal staging of MIBC at radical cystectomy could not be validated on a qRT-PCR platform in a large cohort of dTURBT specimens
Corrections to Hawking-like Radiation for a Friedmann-Robertson-Walker Universe
Recently, a Hamilton-Jacobi method beyond semiclassical approximation in
black hole physics was developed by \emph{Banerjee} and
\emph{Majhi}\cite{beyond0}. In this paper, we generalize their analysis of
black holes to the case of Friedmann-Robertson-Walker (FRW) universe. It is
shown that all the higher order quantum corrections in the single particle
action are proportional to the usual semiclassical contribution. The
corrections to the Hawking-like temperature and entropy of apparent horizon for
FRW universe are also obtained. In the corrected entropy, the area law involves
logarithmic area correction together with the standard inverse power of area
term.Comment: 10 pages, no figures, comments are welcome; v2: references added and
some typoes corrected, to appear in Euro.Phys.J.C; v3:a defect corrected. We
thank Dr.Elias Vagenas for pointing out a defect of our pape
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