arXiv subjects

E. Ivanov

Publications and source records attributed to E. Ivanov.

At least 19 recordsLinked to original sources

arXiv2020

${\cal N}{=}4$ Supersymmetric $d=1$ Sigma Models on Group Manifolds

We construct manifestly ${\cal N}=4$ supersymmetric off-shell superfield actions for the HKT $d=1$ sigma models on the group manifolds U(2) and SU(3), using the harmonic $d=1$ approach. The underlying $({\bf 4, 4, 0})$ and $({\bf 4, 4, 0})\oplus({\bf 4, 4, 0})$ multiplets are described, respectively, by one and two harmonic analytic superfields $q^+$ satisfying the appropriate nonlinear harmonic constraints. The invariant actions in both cases are bilinear in the superfields. We present the corresponding superfield realizations of the U(2) and SU(3) isometries and show that in fact they are enlarged to the products U(2)$\times$SU(2) and SU(3)$\times$U(2). We prove the corresponding invariances at both the superfield and component levels and present the bosonic $d=1$ sigma model actions, as integral over $t$ in the U(2) case and over $t$ and ${\rm SU}(2)$ harmonics in the SU(3) case. In the U(2) case we also give a detailed comparison with the general harmonic approach to HKT models and establish a correspondence with a particular action of the off-shell nonlinear multiplet $({\bf 3, 4, 1})$. A possible way of generalizing U(2) model to the matrix U($2n$) case is suggested.

hep-th↗

arXiv2020

Edge mode engineering for optimal ultracoherent silicon nitride membranes

Due to their high force sensitivity, mechanical resonators combining low mechanical dissipation with a small motional mass are highly demanded in fields as diverse as resonant force imaging, mass sensing, or cavity optomechanics. "Soft-clamping" is a phononic engineering technique by which mechanical modes of highly-stressed membranes or strings are localized away from lossy regions, thereby enabling ultrahigh-Q for ng-scale devices. Here, we report on parasitic modes arising from the finite size of the structure which can significantly degrade the performance of these membranes. Through interferometric measurements and finite-element simulations, we show that these parasitic modes can hybridize with the localized modes of our structures, reducing the quality factors by up to one order of magnitude. To circumvent this problem, we engineer the spectral profile of the parasitic modes in order to avoid their overlap with the high-Q defect mode. We verify via a statistical analysis that this modal engineering reproducibly yields higher quality factors in fabricated devices, consistent with theoretically predicted values.

physics.app-ph↗

arXiv2020

Supersymmetric Calogero models from superfield gauging

Using the superfield gauging procedure, we construct new ${\cal N}\,{=}\,2$ and ${\cal N}\,{=}\,4$ superfield systems that generalize Calogero models. In the bosonic limit, these systems yield rational Calogero models and hyperbolic Calogero-Sutherland models in the ${\cal N}\,{=}\,2$ case, and their ${\rm U}(2)$ spin generalization in the ${\cal N}\,{=}\,4$ case.

hep-th↗

arXiv2019

Testing of Generalized Uncertainty Principle With Macroscopic Mechanical Oscillators and Pendulums

Recent progress in observing and manipulating mechanical oscillators at quantum regime provides new opportunities of studying fundamental physics, for example, to search for low energy signatures of quantum gravity. For example, it was recently proposed that such devices can be used to test quantum gravity effects, by detecting the change in the [x,p] commutation relation that could result from quantum gravity corrections. We show that such a correction results in a dependence of a resonant frequency of a mechanical oscillator on its amplitude, which is known as amplitude-frequency effect. By implementing this new method we measure amplitude-frequency effect for 0.3 kg ultra high-Q sapphire split-bar mechanical resonator and for 10 mg quartz bulk acoustic wave resonator. Our experiments with sapphire resonator have established the upper limit on quantum gravity correction constant for $β_0<5 \times10^6$ which is a factor of 6 better than previously detected. The reasonable estimates of $β_0$ from experiments with quartz resonators yield an even more stringent limit of $4\times10^4$. The data sets of 1936 measurement of physical pendulum period by Atkinson results in significantly stronger limitations on $β_0 \ll 1$. Yet, due to the lack of proper pendulum frequency stability measurement in these experiments, the exact upper bound on $β_0$ can not be reliably established. Moreover, pendulum based systems only allow testing a specific form of the modified commutator that depends on the mean value of momentum. The electro-mechanical oscillators to the contrary enable testing of any form of generalized uncertainty principle directly due to much higher stability and a higher degree of control.

quant-ph↗

arXiv2018

Parametrically squeezed states of microwave magnons in yttrium iron garnet films

We demonstrate theoretically, and confirm experimentally, that nonlinear spin waves excited in thin yttrium iron garnet films are good candidates for squeezing vacuum quantum noise. The experimental demonstration is in the form of a measurement of spin-wave induced modulation instability (IMI) conducted in the classical regime. The experiment evidences strong phase locking of an idler wave parametrically generated in the film with a deterministic small-signal wave launched into the film from an external source. The theory predicts that the same behaviour will be observed for vacuum quantum noise, resulting in squeezing of the noise.

cond-mat.mes-hall↗

arXiv2018

Generic HKT geometries in the harmonic superspace approach

We explain how a generic HKT geometry can be derived using the language of N = 4 supersymmetric quantum mechanics. To this end, one should consider a Lagrangian involving several (4,4,0) multiplets defined in harmonic superspace and subject to nontrivial harmonic constraints. Conjecturally, this general construction worked out earlier by Delduc and Ivanov gives a complete classification of all HKT geometries. Each such geometry is generated by two different functions (potentials) of a special type that depend on harmonic superfields and on harmonics. Given these two potentials, one can derive the vielbeins, metric, connections and curvatures, but this is not so simple: one should solve rather complicated differential equations. We illustrate the general construction by giving a detailed derivation of the metric for the hyper-Kaehler Taub-NUT manifold. In the generic case, we arrive at an HKT geometry. In this paper, we give a simple proof of this assertion.

hep-th↗

arXiv2017

Transition from Fireball to Poynting-flux-dominated Outflow in Three-Episode GRB 160625B

The ejecta composition is an open question in gamma-ray bursts (GRB) physics. Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis, suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the "Band" function, consistent with a synchrotron radiation origin and suggesting that the jet is Poynting-flux-dominated at the central engine and likely in the emission region as well. There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component suggesting a likely hybrid jet composition. Here we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-rays and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each "sub-burst" being $\sim$ 0.8 s, 35 s, and 212 s, respectively. Its high brightness (with isotropic peak luminosity L$_{\rm p, iso}\sim 4\times 10^{53}$ erg/s) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet.

astro-ph.HE↗

arXiv2016

Long multiplets in supersymmetric mechanics

The "long" indecomposable N=2, d=1 multiplet (2, 4, 2) defined in arXiv:1503.05537 [hep-th] as a deformation of the pair of chiral multiplets (2, 2, 0) and (0, 2, 2) by a number of the mass-dimension parameters is described in the superfield approach. We present its most general superfield and component actions, as well as a generalization to the case with the superfields of the opposite Grassmann parities and dimensionless deformation parameter. We show that the long N=2, d=1 multiplets are naturally embedded into the chiral SU(2|1), d=1 superfields having nonzero external spins with respect to SU(2) \subset SU(2|1). A superfield with spin s contains 2s long multiplets and two short multiplets (2, 2, 0) and (0, 2, 2). Two possible N=4, d=1 generalizations of the N=2 long multiplet in the superfield approach are also proposed.

hep-th↗

arXiv2016

Meteor observations with Mini-MegaTORTORA wide-field monitoring system

Here we report on the results of meteor observations with 9-channel Mini-MegaTORTORA (MMT-9) wide-field optical monitoring system with high temporal resolution. During first 1.5 years of operation more than 90 thousands of meteors have been detected, at a rate of 300-350 per night, with durations from 0.1 to 2.5 seconds and angular velocities up to 38 degrees per second. The faintest detected meteors has the peak brightness about 10 mag, while the majority - from 4 to 8 mag. Some of the meteors have been observed in BVR filters simultaneously. Color variations along the trail for them are determined. All parameters of detected meteors are published online. The database also includes the information on 10 thousands meteors detected by our previous FAVOR camera in 2006-2009 years.

astro-ph.EP↗

arXiv2015

New realizations of the supergroup D(2,1;α) in N=4 superconformal mechanics

We present new explicit realizations of the most general N=4, d=1 superconformal symmetry D(2,1;α) in the models of N=4 superconformal mechanics based on the reducible multiplets (1,4,3)\oplus(0,4,4), (3,4,1)\oplus(0,4,4) and (4,4,0)\oplus(0,4,4). We start from the manifestly supersymmetric superfield actions for these systems and then descend to the relevant off- and on-shell component actions from which we derive the D(2,1;α) (super)charges by the Noether procedure. Some peculiarities of these realizations of D(2,1;α) are discussed. We also construct a new D(2,1;α) invariant system by joining the multiplets (3,4,1) and (4,4,0) in such a way that they interact with each other through an extra (0,4,4) multiplet. New fermionic conformal couplings appear as the result of elimination of the appropriate auxiliary fields.

hep-th↗

arXiv2015

On the Atmospheric Extinction Reduction Procedure in Multiband Wide-Field Photometric Surveys

We propose an improved method for the atmospheric extinction reduction within optical photometry. Our method is based on the simultaneous multicolor observations of photometric standards. Such data are now available within the modern wide-field sky surveys and contain a large amount of information about instant atmospheric conditions. So, it became possible to estimate the extinction parameters on the basis of a quite short observational dataset and, hence, to trace the rapid stars twinkling accurately. Having been developed for a new MiniMegaTORTORA observational system, the proposed method can be adopted for a wide range of modern observational programs.

astro-ph.IM↗

arXiv2015

SU(2|1) mechanics and harmonic superspace

We define the worldline harmonic SU(2|1) superspace and its analytic subspace as a deformation of the flat N=4, d=1 harmonic superspace. The harmonic superfield description of the two mutually mirror off-shell (4,4,0) SU(2|1) supermultiplets is developed and the corresponding invariant actions are presented, as well as the relevant classical and quantum supercharges. Whereas the σ-model actions exist for both types of the (4,4,0) multiplet, the invariant Wess-Zumino term can be defined only for one of them, thus demonstrating non-equivalence of these multiplets in the SU(2|1) case as opposed to the flat N=4, d=1 supersymmetry. A superconformal subclass of general SU(2|1) actions invariant under the trigonometric-type realizations of the supergroup D(2,1;α) is singled out. The superconformal Wess-Zumino actions possess an infinite-dimensional supersymmetry forming the centerless N=4 super Virasoro algebra. We solve a few simple instructive examples of the SU(2|1) supersymmetric quantum mechanics of the (4,4,0) multiplets and reveal the SU(2|1) representation contents of the corresponding sets of the quantum states.

hep-th↗

arXiv2015

The first light of Mini-MegaTORTORA wide-field monitoring system

Here we describe the first light of the novel 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which is being tested now at Special Astrophysical Observatory on Russian Caucasus. The system is able to observe the sky simultaneously in either wide (~900 square degrees) or narrow (~100 square degrees) fields of view, either in clear light or with any combination of color (Johnson B, V or R) polarimetric filters installed, with exposure times ranging from 100 ms to 100 s. The primary goal of the system is the detection of rapid -- with sub-second characteristic time-scales -- optical transients, but it may be also used for studying the variability of the sky objects on longer time scales.

astro-ph.IM↗

arXiv2015

Superconformal mechanics in SU(2|1) superspace

Using the worldline SU(2|1) superfield approach, we construct N=4 superconformally invariant actions for the d=1 multiplets (1, 4, 3) and (2, 4, 2). The SU(2|1) superfield framework automatically implies the trigonometric realization of the superconformal symmetry and the harmonic oscillator term in the corresponding component actions. We deal with the general N=4 superconformal algebra D(2,1;$α$) and its central-extended $α$=0 and $α$=-1 psu(1,1|2)$\oplus$su(2) descendants. We capitalize on the observation that D(2,1;$α$) at $α\neq$0 can be treated as a closure of its two su(2|1) subalgebras, one of which defines the superisometry of the SU(2|1) superspace, while the other is related to the first one through the reflection of $μ$, the parameter of contraction to the flat N=4, d=1 superspace. This closure property and its $α$=0 analog suggest a simple criterion for the SU(2|1) invariant actions to be superconformal: they should be even functions of $μ$. We find that the superconformal actions of the multiplet (2, 4, 2) exist only at $α$=-1, 0 and are reduced to a sum of the free sigma-model type action and the conformal superpotential yielding, respectively, the oscillator potential $\sim μ^2$ and the standard conformal inverse-square potential in the bosonic sector. The sigma-model action in this case can be constructed only on account of non-zero central charge in the superalgebra su(1,1|2).

hep-th↗

arXiv2014

Deformed Supersymmetric Mechanics

Motivated by a recent interest in curved rigid supersymmetries, we construct a new type of N=4, d=1 supersymmetric systems by employing superfields defined on the cosets of the supergroup SU(2|1). The relevant worldline supersymmetry is a deformation of the standard N=4, d=1 supersymmetry by a mass parameter m. As instructive examples we consider, at the classical and quantum levels, the models associated with the supermultiplets (1,4,3) and (2,4,2) and find out interesting interrelations with some previous works on non-standard d=1 supersymmetry. In particular, the d=1 systems with "weak supersymmetry" are naturally reproduced within our SU(2|1) superfield approach as a subclass of the (1,4,3) models. A generalization to the N=8, d=1 case implies the supergroup SU(2|2) as the candidate deformed worldline supersymmetry.

hep-th↗

arXiv2014

Super Kähler oscillator from SU(2|1) superspace

We construct a new version of the worldline SU(2|1) superspace as a deformation of the standard N =4, d=1 superspace and show that it naturally provides off- and on-shell description of general supersymmetric Kähler oscillator model considered earlier at the classical level within the Hamiltonian approach. The basic object is a generalized chiral SU(2|1), d=1 superfield with the off-shell field content (2, 4, 2). The frequency of the oscillator and the strength of external magnetic field are defined by two parameters: the contraction parameter $m$ and the new parameter $λ$ which reflects the freedom in defining the chiral SU(2|1), d=1 superspace. We treat both classical and quantum cases.

hep-th↗

arXiv2012

Super Landau Models on Odd Cosets

We construct d=1 sigma models of the Wess-Zumino type on the SU(n|1)/U(n) fermionic cosets. Such models can be regarded as a particular supersymmetric extension (with a target space supersymmetry) of the classical Landau model, when a charged particle possesses only fermionic coordinates. We consider both classical and quantum models, and prove the unitarity of the quantum model by introducing the metric operator on the Hilbert space of the quantum states, such that all their norms become positive-definite. It is remarkable that the quantum n=2 model exhibits hidden SU(2|2) symmetry. We also discuss the planar limit of these models. The Hilbert space in the planar n=2 case is shown to carry SU(2|2) symmetry which is different from that of the SU(2|1)/U(1) model.

hep-th↗

arXiv2012

N=4 Supersymmetric Landau Models

We present the first example of super Landau model with both N=4 worldline supersymmetry and non-trivial target space supersymmetry ISU(2|2). The model also reveals a hidden second N=4 supersymmetry which, together with the manifest one, close on a worldline SU(2|2). We start from an off-shell action in bi-harmonic N=4, d=1 superspace and come to the component action with four bosonic and four fermionic fields. Its bosonic core is the action of generalized U(1) Landau model on R^4 considered some time ago by Elvang and Polchinski. At each Landau level N>0 the wave functions are shown to form "atypical" (2N + 2N)-dimensional multiplets of the worldline supergroup SU(2|2). Some states have negative norms, but this trouble can be evaded by redefining the inner product, like in other super Landau models. We promote the action to the most general form compatible with off-shell N=4 worldline supersymmetry and find the corresponding background U(1) gauge field to be generic self-dual on R^4 and the target superspace metric to remain flat.

hep-th↗