Stringy AdS3 from the worldsheet Gaberdiel, Matthias R.; Gopakumar, Rajesh; Hull, Chris
The journal of high energy physics,
07/2017, Letnik:
2017, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
We investigate the behaviour of the bosonic string on AdS
3
with H-flux at stringy scales, looking in particular for a ‘tensionless’ limit in which there are massless higher spin gauge ...fields. We do this by revisiting the physical spectrum of the
s
l
2
,
ℝ
k
WZW model and considering the limit in which
k
becomes small. At
k
= 3 we find that there is an infinite stringy tower of massless higher spin fields which are part of a continuum of light states. This can be viewed as a novel tensionless limit, which appears to be distinct from that inferred from the symmetric orbifold description of superstring AdS
3
vacua.
A
bstract
The symmetric orbifold of 𝕋
4
is exactly dual to string theory on AdS
3
× S
3
× 𝕋
4
with minimal (
k
= 1) NS-NS flux. In this paper we study the perturbation of the symmetric orbifold ...that is dual to switching on R-R flux, and hence to deforming the theory away from the tensionless point. More specifically, we determine systematically the action of a centrally extended supersymmetry algebra on the CFT states, and deduce from it the anomalous conformal dimensions. In the
w
-twisted sector with large
w
the structure is similar to what was found for
N
= 4 SYM: the basic excitations are multi-magnons whose individual dispersion relation is fixed by symmetry, and the comparison with the BMN answer suggests that the result is true to all orders in perturbation theory. Finally we show that the multi-magnon states interact via an integrable
S
-matrix and possess a natural family of bound states.
Higher spins & strings Gaberdiel, Matthias R.; Gopakumar, Rajesh
The journal of high energy physics,
11/2014, Letnik:
2014, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
It is natural to believe that the free symmetric product orbifold CFT is dual to the tensionless limit of string theory on AdS
3
× S
3
×
T
4
. At this point in moduli space, string theory ...is expected to contain a Vasiliev higher spin theory as a subsector. We confirm this picture explicitly by showing that the large level limit of the
N
=4 cosets of arXiv:1305.4181, that are dual to a higher spin theory on AdS
3
, indeed describe a closed subsector of the symmetric product orbifold. Furthermore, we reorganise the full partition function of the symmetric product orbifold in terms of representations of the higher spin algebra (or rather its
W
∞
extension). In particular, the unbroken stringy symmetries of the tensionless limit are captured by a large chiral algebra which we can describe explicitly in terms of an infinite sum of
W
∞
representations, thereby exhibiting a vast extension of the conventional higher spin symmetry.
Display omitted
•Judd-Ofelt intensity parameters of phosphors are evaluated from absorption spectra.•The radiative parameters are determined using emission spectra and exhibits high σe, σe × Δλeff, ...σe × τR and β.•The CIE, CCT and CRI values manifest the efficient application of phosphor in LEDs and indoor lighting.•The sensitivity values estimated using different spectral modes demonstrate the thermo-sensor application of phosphor.•The thermochromic study displays the safety sign marking application of phosphor.
LiCa2Mg2V3O12:Sm3+ phosphors have been prepared by solid state method and analysed by X-ray diffraction, EDX-elemental mapping, UV–VIS-NIR spectroscopy, photoluminescence (PL) and temperature dependent photoluminescence (TDPL). The absorption spectra analysis using Judd-Ofelt theory provides the intensity parameters and manifest the covalent nature of Sm-O bond. The PL spectra monitored at 338 nm excitation exhibits emission peaks of Sm3+ at 567, 617 and 651 nm in addition to the broad band emission of LiCa2Mg2V3O12 host. The Commision Internationale deL’Eclairage (CIE) coordinates, correlated color temperature (CCT) and color rendering index (CRI) values elucidate the efficient yellow emission of phosphors. The radiative parameters are evaluated and have outrageous branching ratio and cross section that aids in visible laser applications. The optical thermometry of phosphor is carried out by utilizing FIR method through selecting spectral modes 6H5/2/VO43-, 6H7/2/VO43- and 6H9/2/ VO43-. The mode 6H9/2/ VO43- have higher absolute sensitivity (Sa) and relative sensitivity (Sr) values of 0.4418 K−1 and 1.6079% K−1. The temperature resolution of modes are 0.1633, 0.1677 and 0.1563 K respectively. The thermochromic study reveals the high chromaticity shift (Δs = 0.1869) of phosphor and the Sa(x) and Sr(x) values evaluated based on CIE coordinates are 0.0011 K−1 and 0.2407% K−1 respectively. The PL and TDPL characteristics of prepared phosphor suggest that it have multifunctional application in the fields of lasers, thermo-sensors, thermochromic displays and LEDs.
Hybrid AC/DC urban microgrids (HUMG) have emerged as a candidate solution to reliably, efficiently, and economically meet the increasing consumer electric demand and to ensure the quality of ...delivered power. Smart buildings (SB) are prevalent prosumers in HUMGs. To effectively utilise renewable resources in SBs, it is imperative to have assistance from battery energy storage systems (BESSs). Also, uncertainty in generation and demand necessitates real-time ancillary power support for SBs. Smart building interconnection forming SB clusters is an emerging solution for providing ancillary power support. Existing SB interconnection topologies require multiple power conversion stages, additional infrastructure, and underutilise the existing AC grid infrastructure. Most of these SB interconnections are not sustainable due to higher losses from more power conversion stages, increased cost, and excessive dependence on BESSs. A composite transmission system-based ancillary power dispatching architecture (CTS-APDA) for the sustainable operation of SB clusters is proposed in this paper. A multi-agent system based hierarchical control and decision logic in the CTS-APDA ensures the optimal ustilisation of battery resources. The operation of the proposed CTS-APDA and its efficacy as a fast-acting ancillary support is validated through extensive case studies. The proposed CTS-APDA will foster participation of electric vehicles in the transactive energy market of emerging SBs.
•Demonstrated the necessity for fast-acting ancillary power support for a Smart Building with renewable energy sources.•Proposed a composite transmission system-based ancillary power dispatching architecture for providing fast-acting ancillary power support.•The proposed architecture improves operational efficiency, transmission line utilisation, and usable life of battery energy storage systems.•Demonstrated the sustainable nature of the proposed ancillary power dispatching architecture.
Cytogenetics plays significant role in the diagnosis, prognosis and treatment evaluation of genetic disorders through chromosome image analysis technique called karyotyping. Karyotyping is the way by ...which chromosomes are classified into 24 classes. Digital image processing techniques and machine learning algorithms found its scope in automated karyotyping since they ease or eliminate manual efforts in chromosome classification and its analysis. Even though, researchers were putting great efforts in the design of Automated Karyotyping System (AKS), for the last three decades, a fully automated system is not yet routinely accepted in practice. These days, deepnets exhibit improved performance in computer vision tasks, they are progressively utilized for automating classification tasks as well. Here, two variants of deep Convolutional Neural Networks (CNNs) for chromosome classification are modelled. A preliminary study on the hyperparameters of these models has been conducted. Other state-of-the-art CNN models are experimented and analyzed for chromosome classification. Performance measures of all these CNN deep models are compared to formulate hypotheses on hyperparameters to classify chromosomes efficiently.
A series of Dy3+ doped LiCa2Mg2V3O12 phosphors have been synthesized by solid state method. The phase composition of the phosphor has been analyzed by X-ray powder diffraction and confirms a cubic ...phase with Ia-3d space group. The scanning electron microscope images of LiCa2Mg2V3O12:xDy3+ phosphor reveals the surface morphology and is further investigated by its energy dispersive X-ray spectrum. The elemental mapping analysis displays the uniform composition of the elements present in the phosphor. The band gap energy of the phosphors has been determined from the diffuse reflectance spectra. The Judd-Ofelt intensity parameters are determined from the absorption spectra and follows the trend Ω2 > Ω6 > Ω4. The photoluminescence spectra of phosphors excited at 338 nm have intense emission at 494 and 576 nm corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transition and is ascribed to the magnetic and electric dipole allowed transition respectively. The radiative parameters for the optimum dopant concentration x = 0.08 has been calculated. Temperature dependent PL spectra of phosphor displays the diverse thermal response of VO43− group and Dy3+ ion and this can be utilized for the development of thermosensor based on fluorescence intensity ratio (FIR). The phosphor have maximum absloute and relative sensitivity values of 0.0063 K−1 and 0.41% K−1 in the temperature range of 80–400 K. The optical properties of the phosphor suggest that it find applications in the fields of solid-state lighting, temperature sensing, optoelectronic devices and W-LEDs.
•Dy3+ activated LiCa2Mg2V3O12 phosphors have been synthesized by solid state method.•Judd-Ofelt intensity parameters of the phosphor are estimated.•4F9/2. → 6H13/2 transition in phosphor has higher σe × Δλeff and σe × τR that aid in optical amplifier applications.•CIE coordinates and CCT values of phosphor shows that it can be used in white light emitting diodes.•Temperature dependent PL studies demonstrate the efficient application of phosphor in thermo sensing.
String theory as a higher spin theory Gaberdiel, Matthias R.; Gopakumar, Rajesh
The journal of high energy physics,
09/2016, Letnik:
2016, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A
bstract
The symmetries of string theory on
AdS
3
×
S
3
×
T
4
at the dual of the symmetric product orbifold point are described by a so-called Higher Spin Square (HSS). We show that the massive ...string spectrum in this background organises itself in terms of representations of this HSS, just as the matter in a conventional higher spin theory does so in terms of representations of the higher spin algebra. In particular, the entire untwisted sector of the orbifold can be viewed as the Fock space built out of the multiparticle states of a
single
representation of the HSS, the so-called ‘minimal’ representation. The states in the twisted sector can be described in terms of tensor products of a novel family of representations that are somewhat larger than the minimal one.
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