1,356,356 research outputs found
Nd-doped polarization maintaining all-fiber laser with dissipative soliton resonance mode-locking at 905 nm
No full textFunding Information: Manuscript received February 15, 2021; revised May 14, 2021; accepted May 27, 2021. Date of publication June 1, 2021; date of current version September 13, 2021. This work was supported by RFBR under Grant 20-32-90233. (Corresponding author: Aram A. Mkrtchyan.) Aram A. Mkrtchyan, Yuriy G. Gladush, and Kirill A. Sitnik are with the Skolkovo Institute of Science and Technology, Moscow 121205, Russia (e-mail: [email protected]; [email protected]; [email protected]). Publisher Copyright: © 1983-2012 IEEE.Moving the fiber laser emission to the region below one micron may provide a cheaper, more compact and robust alternatives to the existing solid state lasers. Here, for the first time we report a neodymium mode-locked fiber laser emitting at 905 nm in the all-fiber polarization maintaining configuration. We obtain a self-starting pulse generation in nonlinear amplifying loop mirror (NALM) cavity configuration. To suppress a dominant emission at 1064 nm corresponding to a 4-level laser scheme, we use an active fiber - 920/1064 division multiplexer - active fiber sandwich-like sequence in the NALM loop. A rectangular shape dissipative soliton had nJ energy, 30 pm spectral width and 80 ÷ 430 ps width linearly depending on the pump power. Excellent agreement with numerical simulation allowed us to recover pulse shape and width for the pulses out of autocorrelation window.Peer reviewe
The European Union and the South Caucasus; Three Perspectives on the Future of the European Project from the Caucasus. Europe in Dialogue 2009/1
No full textTigran Mkrtchyan singles out three main factors that determine Armenia’s rather positive attitude to and interest in EU policies in the Caucasus region. Firstly, further cooperation with the EU could guarantee a democratically stable future for the country. Secondly, Armenia would benefit from increased economic cooperation with the EU. Thirdly, to a large extent the population feels that it belongs to Europe. However, some critics, mostly from the ranks of the intelligentsia, have expressed concern that too much Europeanization constitutes a threat to national identity.///// Tabib Huseynov agrees with Mkrtchyan in calling for a more active EU role in the region and most notably in the resolution of the Nagorno-Karabakh conflict. This would lay the foundations for the ongoing development of the region. Huseynov outlines factors contributing to or impeding regional cooperation in the South Caucasus and cooperation between the EU and Azerbaijan. Whereas Georgia and Armenia are seeking EU membership in the long term and financial assistance in some areas, Azerbaijan remains financially independent on account of its oil revenues and is not interested in EU membership in the near future. It is far more interested in increased economic and trade cooperation./// Kakha Gogolashvili, Director of EU Studies at the Georgian Foundation for Strategic and International Studies (GFSIS), describes the level of acceptance for EU policies in Georgia. To a large extent the general goals of Georgian policy-makers are aligned with those of the EU, and this facilitates cooperation in implementing reforms in the country
[The formation of communities as a social-spatial practice] : [peculiarities of the community enlargement reform in the Republic of Armenia]
No full text[Shushanik Harutyunyan, Arem Mkrtchyan]Text armenischArmenisc
Off-shell construction of some trilinear higher spin gauge field interactions
No full textSeveral trilinear interactions of higher spin fields involving two equal (s = s1 = s2) and one higher even (s3 ≥ 2 s) spin are presented. Interactions are constructed on the Lagrangian level using Noether's procedure together with the corresponding next to free level fields of the gauge transformations. In certain cases when the number of derivatives in the transformation is 2 s - 1 the interactions lead to the currents constructed from the generalization of the gravitational Bell-Robinson tensors. In other cases when the number of derivatives in the transformation is more than 2 s - 1 we obtain the finite tower of interactions with smaller even spins less than s3 in full agreement with our previous results for the interaction of the higher even spins field with a conformal scalar [R. Manvelyan, K. Mkrtchyan, Conformal invariant interaction of a scalar field with the higher spin field in AdSD, arXiv:0903.0058 [hep-th]; R. Manvelyan, W. Rühl, Conformal coupling of higher spin gauge fields to a scalar field in AdS4 and generalized Weyl invariance, Phys. Lett. B 593 (2004) 253 arXiv:hep-th/0403241]
On Covariant Actions for Chiral p-Forms
No full textWe construct a Lorentz covariant, polynomial action for free chiral forms, classically equivalent to the Pasti-Sorokin-Tonin (PST) formulation. The minimal set up requires introducing an auxiliary form on top of the physical gauge form and the PST scalar. The action enjoys duality symmetries which exchange the roles of physical and auxiliary form fields. Same type of actions are available for duality-symmetric formulations, which is demonstrated on the example of electromagnetic field in four dimensions. There, the degrees of freedom of a single Maxwell field are described employing four distinct vector gauge fields and a scalar field. Similarly to PST, our models are available only in spaces of Minkowski signature
Linearized interactions of scalar and vector fields with the higher spin field in AdSD
No full textThe explicit form of linearized gauge arid generalized "Weyl invariant" interactions of scalar and general higher even spin fields in the AdSD space constructed in [1] is reviewed. Also a linearized interaction of vector field with general higher even spin, gauge field is obtained. It is shown that the gauge invariant action of linearized vector field interacting with the higher spin field also includes the whole tower of invariant actions for couplings of the same vector field with the gauge fields of smaller even spin. © 2011 Pleiades Publishing, Ltd
Conformal invariant interaction of a scalar field with higher spin field in AdSD
No full textThe explicit form of linearized gauge invariant interactions of scalar and general higher even spin fields in the AdSD space is obtained. In the case of general spin-l a generalized "Weyl" transformation is proposed and the corresponding "Weyl" invariant action is constructed. In both cases the invariant actions of the interacting higher even spin gauge field and the scalar field include the whole tower of invariant actions for couplings of the same scalar with all gauge fields of smaller even spin. For the particular value of l = 4, all results are in exact agreement with Ref. 1. © 2010 World Scientific Publishing Company
ARDD 2020: from aging mechanisms to interventions
No full textAging is emerging as a druggable target with growing interest from academia, industry and investors. New technologies such as artificial intelligence and advanced screening techniques, as well as a strong influence from the industry sector may lead to novel discoveries to treat age-related diseases. The present review summarizes presentations from the 7th Annual Aging Research and Drug Discovery (ARDD) meeting, held online on the 1st to 4th of September 2020. The meeting covered topics related to new methodologies to study aging, knowledge about basic mechanisms of longevity, latest interventional strategies to target the aging process as well as discussions about the impact of aging research on society and economy. More than 2000 participants and 65 speakers joined the meeting and we already look forward to an even larger meeting next year. Please mark your calendars for the 8th ARDD meeting that is scheduled for the 31st of August to 3rd of September, 2021, at Columbia University, USA. © 2020. Mkrtchyan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. All Rights Reserved
Conformal invariant powers of the Laplacian, Fefferman–Graham ambient metric and Ricci gauging
No full textAbstractThe hierarchy of conformally invariant kth powers of the Laplacian acting on a scalar field with scaling dimensions Δ(k)=k−d/2, k=1,2,3, as obtained in the recent work [R. Manvelyan, D.H. Tchrakian, Phys. Lett. B 644 (2007) 370, hep-th/0611077] is rederived using the Fefferman–Graham (d+2)-dimensional ambient space approach. The corresponding mysterious “holographic” structure of these operators is clarified. We explore also the (d+2)-dimensional ambient space origin of the Ricci gauging procedure proposed by A. Iorio, L. O'Raifeartaigh, I. Sachs and C. Wiesendanger as another method of constructing the Weyl invariant Lagrangians. The corresponding gauged ambient metric, Fefferman–Graham expansion and extended Penrose–Brown–Henneaux transformations are proposed and analyzed
Algorithmic bias in social research: A meta-analysis
No full textReplication material for Thiem, A., L. Mkrtchyan, T. Haesebrouck and D. Sanchez. 2020. "Algorithmic bias in social research: A meta-analysis." PLoS ONE 15(6): e0233625. DOI: 10.1371/journal.pone.023362
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