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Results for "Soonwon Choi"

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Symmetry-protected dissipative preparation of matrix product statesJun 06 2017We propose and analyze a method for efficient dissipative preparation of matrix product states that exploits their symmetry properties. Specifically, we construct an explicit protocol that makes use of driven-dissipative dynamics to prepare the Affleck-Kennedy-Lieb-Tasaki ... More
Quantum Convolutional Neural NetworksOct 09 2018We introduce and analyze a novel quantum machine learning model motivated by convolutional neural networks (CNN). Our quantum convolutional neural network (QCNN) makes use of only $O(\log(N))$ variational parameters for input sizes of $N$ qubits, allowing ... More
Dynamical engineering of interactions in qudit ensemblesMar 28 2017We propose and analyze a method to engineer effective interactions in an ensemble of d-level systems (qudits) driven by global control fields. In particular, we present (i) a necessary and sufficient condition under which a given interaction can be turned ... More
Dynamically induced many-body localizationMar 10 2017We show that a quantum phase transition from ergodic to many-body localized (MBL) phases can be induced via periodic pulsed manipulation of spin systems. Such a transition is enabled by the interplay between weak disorder and slow heating rates. Specifically, ... More
Periodic orbits, entanglement and quantum many-body scars in constrained models: matrix product state approachJul 04 2018Jan 30 2019We analyze quantum dynamics of strongly interacting, kinetically constrained many-body systems. Motivated by recent experiments demonstrating surprising long-lived, periodic revivals after quantum quenches in Rydberg atom arrays, we introduce a manifold ... More
Photonic tensor networks produced by a single quantum emitterFeb 07 2017We propose and analyze a protocol to generate two dimensional tensor network states using a single quantum system that sequentially interacts with a 1D string of qubits. This is accomplished by using parts of the string itself as a quantum queue memory. ... More
Quantum error correction and entanglement phase transition in random unitary circuits with projective measurementsMar 12 2019We analyze the dynamics of entanglement entropy in a generic quantum many-body open system from the perspective of quantum information and error corrections. We introduce a random unitary circuit model with intermittent projective measurements, in which ... More
Quantum Control of Many-body Localized StatesAug 27 2015We propose and analyze a new approach to the coherent control and manipulation of quantum degrees of freedom in disordered, interacting systems in the many-body localized phase. Our approach leverages a number of unique features of many-body localization: ... More
Quantum metrology based on strongly correlated matterDec 29 2017We propose and analyze a new method for quantum metrology based on stable non-equilibrium states of quantum matter. Our approach utilizes quantum correlations stabilized by strong interactions and periodic driving. As an example, we present an explicit ... More
Computational complexity of the Rydberg blockade in two dimensionsSep 13 2018We discuss the computational complexity of finding the ground state of the two-dimensional array of quantum bits that interact via strong van der Waals interactions. Specifically, we focus on systems where the interaction strength between two spins depends ... More
Critical Time Crystals in Dipolar SystemsMar 14 2017Jul 07 2017We analyze the quantum dynamics of periodically driven, disordered systems in the presence of long-range interactions. Focusing on the stability of discrete time crystalline (DTC) order in such systems, we use a perturbative procedure to evaluate its ... More
Quantum Approximate Optimization Algorithm: Performance, Mechanism, and Implementation on Near-Term DevicesDec 03 2018The Quantum Approximate Optimization Algorithm (QAOA) is a hybrid quantum-classical variational algorithm designed to tackle combinatorial optimization problems. Despite its promise for near-term quantum applications, not much is currently understood ... More
Generation and manipulation of Schrödinger cat states in Rydberg atom arraysMay 14 2019May 15 2019Quantum entanglement involving coherent superpositions of macroscopically distinct states is among the most striking features of quantum theory, but its realization is challenging, since such states are extremely fragile. Using a programmable quantum ... More
Numerical study of the chiral $\mathbb{Z}_3$ quantum phase transition in one spatial dimensionJun 05 2018Jul 16 2018Recent experiments on a one-dimensional chain of trapped alkali atoms [arXiv:1707.04344] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous $\mathbb{Z}_3$ symmetry breaking is described ... More
Quantum Optimization for Maximum Independent Set Using Rydberg Atom ArraysAug 31 2018We describe and analyze an architecture for quantum optimization to solve maximum independent set (MIS) problems using neutral atom arrays trapped in optical tweezers. Optimizing independent sets is one of the paradigmatic, NP-hard problems in computer ... More
Probing entanglement in a many-body-localized systemMay 24 2018Jun 13 2018An interacting quantum system that is subject to disorder may cease to thermalize due to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to our understanding of this phenomenon lies in the system's entanglement, ... More
Depolarization dynamics in a strongly interacting solid-state spin ensembleAug 19 2016Oct 18 2016We study the depolarization dynamics of a dense ensemble of dipolar interacting spins, associated with nitrogen-vacancy centers in diamond. We observe anomalously fast, density-dependent, and non-exponential spin relaxation. To explain these observations, ... More
Critical thermalization of a disordered dipolar spin system in diamondSep 26 2016Statistical mechanics underlies our understanding of macroscopic quantum systems. It is based on the assumption that out-of-equilibrium systems rapidly approach their equilibrium states, forgetting any information about their microscopic initial conditions. ... More
Probing quantum thermalization of a disordered dipolar spin ensemble with discrete time-crystalline orderJun 26 2018We investigate thermalization dynamics of a driven dipolar many-body quantum system through the stability of discrete time crystalline order. Using periodic driving of electronic spin impurities in diamond, we realize different types of interactions between ... More
Depolarization dynamics in a strongly interacting solid-state spin ensembleAug 19 2016We study the depolarization dynamics of a dense ensemble of dipolar interacting spins, associated with nitrogen-vacancy centers in diamond. We observe anomalously fast, density-dependent, and non-exponential spin relaxation. To explain these observations, ... More
Imaging the local charge environment of nitrogen-vacancy centers in diamondSep 05 2018Characterizing the local internal environment surrounding solid-state spin defects is crucial to harnessing them as nanoscale sensors of external fields. This is especially germane to the case of defect ensembles which can exhibit a complex interplay ... More
Probing many-body dynamics on a 51-atom quantum simulatorJul 13 2017Nov 30 2017Controllable, coherent many-body systems can provide insights into the fundamental properties of quantum matter, enable the realization of new quantum phases and could ultimately lead to computational systems that outperform existing computers based on ... More
Emergent SU(2) dynamics and perfect quantum many-body scarsDec 13 2018Motivated by recent experimental observations of coherent many-body revivals in a constrained Rydberg atom chain, we construct a weak quasi-local deformation of the Rydberg blockade Hamiltonian, which makes the revivals virtually perfect. Our analysis ... More
The definability criterions for convex projective polyhedral reflection groupsJun 11 2012Oct 14 2013Following Vinberg, we find the criterions for a subgroup generated by reflections $\Gamma \subset \SL^{\pm}(n+1,\mathbb{R})$ and its finite-index subgroups to be definable over $\mathbb{A}$ where $\mathbb{A}$ is an integrally closed Noetherian ring in ... More
Observation of discrete time-crystalline order in a disordered dipolar many-body systemOct 25 2016Understanding quantum dynamics away from equilibrium is an outstanding challenge in the modern physical sciences. It is well known that out-of-equilibrium systems can display a rich array of phenomena, ranging from self-organized synchronization to dynamical ... More
Critical thermalization of a disordered dipolar spin system in diamondSep 26 2016Oct 25 2017Statistical mechanics underlies our understanding of macroscopic quantum systems. It is based on the assumption that out-of-equilibrium systems rapidly approach their equilibrium states, forgetting any information about their microscopic initial conditions. ... More
Quantum Kibble-Zurek mechanism and critical dynamics on a programmable Rydberg simulatorSep 14 2018Apr 01 2019Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations. These fluctuations play a dominant role in the quantum critical region surrounding the transition point, where the dynamics ... More
Quantum Virtual CoolingDec 05 2018We propose a quantum information based scheme to reduce the temperature of quantum many-body systems, and access regimes beyond the current capability of conventional cooling techniques. We show that collective measurements on multiple copies of a system ... More
Dimensionally Constrained Symbolic RegressionJun 20 2011We describe dimensionally constrained symbolic regression which has been developed for mass measurement in certain classes of events in high-energy physics (HEP). With symbolic regression, we can derive equations that are well known in HEP. However, in ... More
The maximal tubes under the deformations of a class of 3-dimensional hyperbolic cone-manifoldsMay 14 2004Recently, Hodgson and Kerckhoff found a small bound on Dehn surgered 3-manifolds from hyperbolic knots not admitting hyperbolic structures using deformations of hyperbolic cone-manifolds. They asked whether the area normalized meridian length squared ... More
The module category weight of compact exceptional Lie groupsJul 14 2013We compute the lower bound estimate for the module category weight of compact exceptional Lie groups by analyzing several Eilenberg--Moore type spectral sequences.
Severi Degrees in Cogenus 4Jan 15 1996Jan 15 1996In this paper, we give closed-form formulae for Severi degrees in cogenus 3 and 4 using Ran's method. These formulae coincide with those of I. Vainsencher and for cogenus 3 case, that of J. Harris and R. Pandharipande. Another result of this paper is ... More
Minor-Embedding in Adiabatic Quantum Computation: I. The Parameter Setting ProblemApr 30 2008We show that the NP-hard quadratic unconstrained binary optimization (QUBO) problem on a graph $G$ can be solved using an adiabatic quantum computer that implements an Ising spin-1/2 Hamiltonian, by reduction through minor-embedding of $G$ in the quantum ... More
Faster Algorithms for Constructing a Concept (Galois) LatticeFeb 19 2006Jun 01 2006In this paper, we present a fast algorithm for constructing a concept (Galois) lattice of a binary relation, including computing all concepts and their lattice order. We also present two efficient variants of the algorithm, one for computing all concepts ... More
Small SUSY phases in string-inspired supergravityNov 24 1993In supersymmetric models, there are new CP violating phases which, if unsuppressed, would give a too large neutron electric dipole moment. We examine the possibility of small SUSY phases in string-inspired supergravity models in which supersymmetry is ... More
Dynamical gauge coupling unification from moduli stabilizationJun 12 2006In D-brane models, different part of the 4-dimensional gauge group might originate from D-branes wrapping different cycles in the internal space, and then the standard model gauge couplings at the compactification scale are determined by different cycle-volume ... More
Flavor Structure of Scherk-Schwarz Supersymmetry Breaking for Quasi-Localized Matter FieldDec 27 2003We discuss the flavor structure of soft supersymmetry breaking parameters in 5-dimensional orbifold field theories in which N=1 supersymmetry is broken by the Scherk-Schwarz boundary condition and hierarchical 4-dimensional Yukawa couplings are obtained ... More
Torus actions on cohomology complex generalized Bott manifoldsJan 29 2011Aug 31 2012A torus manifold is a closed smooth manifold of dimension $2n$ having an effective smooth $T^n = (S^1)^n$-action with non-empty fixed points. Petrie \cite{petrie:1973} has shown that any homotopy equivalence between a complex projective space $\CP^n$ ... More
The Lane-Emden system near the critical hyperbola on nonconvex domainsMay 26 2015Jan 05 2016In this paper we study the asymptotic behavior of minimal energy solutions to the Lane-Emden system $-\Delta u = v^p$ and $-\Delta v = u^q$ on bounded domains as the index $(p,q)$ approaches to the critical hyperbola from below. Precisely, we remove the ... More
On commutative, operator amenable subalgebras of finite von Neumann algebrasDec 20 2010Sep 12 2011An open question, raised independently by several authors, asks if a closed amenable subalgebra of ${\mathcal B}({\mathcal H})$ must be similar to an amenable C*-algebra; the question remains open even for singly-generated algebras. In this article we ... More
Singly generated operator algebras satisfying weakened versions of amenabilityFeb 06 2012Aug 03 2012We construct a singly generated subalgebra of ${\mathcal K}({\mathcal H})$ which is non-amenable, yet is boundedly approximately contractible. The example embeds into a homogeneous von Neumann algebra. We also observe that there are singly generated, ... More
Multiply Warped Products with Non-Smooth MetricsApr 25 2002In this article we study manifolds with $C^{0}$-metrics and properties of Lorentzian multiply warped products. We represent the interior Schwarzschild space-time as a multiply warped product space-time with warping functions and we also investigate the ... More
Splitting maps and norm bounds for the cyclic cohomology of biflat Banach algebrasOct 27 2009Apr 25 2010We revisit the old result that biflat Banach algebras have the same cyclic cohomology as $\mathbb C$, and obtain a quantitative variant (which is needed in forthcoming joint work of the author). Our approach does not rely on the Connes-Tsygan exact sequence, ... More
Small Flavor Conserving CP Violation in Superstring ModelsFeb 21 1994It is well known that supersymmetric models allow new sources for CP violation that arise from soft supersymmetry breaking terms. If unsuppressed, these new CP-violating phases would give too large a neutron electric dipole moment. We discuss a mechanism ... More
Twisted traces of singular moduli of weakly holomorphic modular functionsMay 06 2011Zagier proved that the generating series for the traces of singular moduli is a \textit{weakly holomorphic} modular form of weight 3/2 on $\Gamma_0(4)$. Bruinier and Funke extended the results of Zagier to modular curves of arbitrary genus. Zagier also ... More
The convex real projective orbifolds with radial or totally geodesic ends: a survey of some partial resultsJan 26 2016Oct 26 2017A real projective orbifold has a radial end if a neighborhood of the end is foliated by projective geodesics that develop into geodesics ending at a common point. It has a totally geodesic end if the end can be completed to have the totally geodesic boundary. ... More
A classification of radial and totally geodesic ends of properly convex real projective orbifolds III: the convex but nonproperly convex and non-complete-affine radial endsJul 03 2015Real projective structures on $n$-orbifolds are useful in understanding the space of representations of discrete groups into $\mathrm{SL}(n+1, \mathbb{R})$ or $\mathrm{PGL}(n+1, \mathbb{R})$. A recent work shows that many hyperbolic manifolds deform to ... More
Generalized Faraday law derived from classical forces in a rotating frameApr 02 2009Aug 19 2009We show the additional spin dependent classical force due to the rotation of an electron spin's rest frame is essential to derive a spin-Faraday law by using an analogy with the usual Faraday law. The contribution of the additional spin dependent force ... More
Probing quantum critical dynamics on a programmable Rydberg simulatorSep 14 2018Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations. These fluctuations play a dominant role in the quantum critical region surrounding the transition point, where the dynamics ... More
Avoid First Order Quantum Phase Transition by Changing Problem HamiltoniansOct 06 2010Aug 03 2011In Amin and Choi \cite{AC09}, we show that an adiabatic quantum algorithm for the NP-hard maximum independent set (MIS) problem on a set of special family of graphs in which there are exponentially many local maxima would have the exponentially small ... More
Minor-embedding in adiabatic quantum computation: II. Minor-universal graph designJan 18 2010Jan 19 2010In [Choi08], we introduced the notion of minor-embedding in adiabatic quantum optimization. A minor-embedding of a graph G in a quantum hardware graph U is a subgraph of U such that G can be obtained from it by contracting edges. In this paper, we describe ... More
A sharp bound on the convergence rate of an aggregation-based algebraic multi-grid method applied to a 1D model problemOct 28 2012Mar 19 2013We consider the linear system Ax=b arising from one-dimensional Poisson's equation with Dirichlet boundary conditions, where A is the square matrix with the stencil form [-1 2 -1]. Here we show that a pairwise aggregation-based algebraic 2-grid method ... More
Drilling cores of hyperbolic 3-manifolds to prove tamenessOct 18 2004We supply a proof of the fact that a hyperbolic 3-manifold $M$ with finitely generated fundamental group and with no parabolics is topologically tame. This proves the Marden's conjecture. Our approach is to form an exhaustion $M_i$ of $M$ and modify the ... More
Hadron and Quarkmonium ExoticaMar 07 2014A number of charmonium-(bottmonium-)like states have been observed in $B$-factory experiments. Recently the BESIII experiment has joined this search with a unique data sample collected at the different center of mass energies ranging from 3.9 GeV to 4.42 ... More
Combinatorial embedded contact homology for toric contact manifoldsAug 29 2016Computing embedded contact homology (ECH) and related invariants of certain toric 3-manifolds (in the sense of Lerman) has led to interesting new results in the study of symplectic embeddings. Here, we give a combinatorial formulation of ECH chain complexes ... More
Moduli stabilization and the pattern of sparticle spectraSep 19 2008We discuss the pattern of low energy sparticle spectra which appears in some class of moduli stabilization scenario. In case that light moduli are stabilized by non-perturbative effects encoded in the superpotential and a phenomenologically viable de ... More
Moduli stabilization and the pattern of soft SUSY breaking termsNov 14 2005In string compactification preserving N=1 SUSY, moduli fields are plausible candidates for the messenger of SUSY breaking at low energy scales. In a scenario that moduli-mediated SUSY breaking is significant, the pattern of soft SUSY breaking terms depends ... More
A QCD Axion from Higher Dimensional Gauge FieldAug 04 2003We point out that a QCD axion solving the strong CP problem can arise naturally from parity-odd gauge field C_M in 5-dimensional (5D) orbifold field theory. The required axion coupling to the QCD anomaly comes from the 5D Chern-Simons coupling, and all ... More
Quintessence, Flat Potential and String/M Theory AxionDec 02 1999A slow-rolling scalar field (Quintessence) has been proposed as the origin of accelerating universe at present. We discuss some features of quintessence, particularly those related with the {\it flatness} of its potential. We distinguish two types of ... More
String or M theory axion as a quintessenceFeb 10 1999May 29 2000A slow-rolling scalar field ($Q\equiv$ Quintessence) with potential energy $V_Q\sim (3\times 10^{-3} {\rm eV})^4$ has been proposed as the origin of accelerating universe at present. We investigate the effective potential of $Q$ in the framework of supergravity ... More
Goldstone Supermultiplet as the Messenger of Supersymmetry BreakingOct 01 1995We consider supersymmetric models in which a (pseudo) Goldstone supermultiplet plays the role of the messenger of supersymmetry breaking. Such models lead to a highly predictive form of flavor and CP conserving soft terms, particularly the soft scalar ... More
Toroidal graphs containing neither $K_5^{-}$ nor 6-cycles are 4-choosableJul 11 2013The choosability $\chi_\ell(G)$ of a graph $G$ is the minimum $k$ such that having $k$ colors available at each vertex guarantees a proper coloring. Given a toroidal graph $G$, it is known that $\chi_\ell(G)\leq 7$, and $\chi_\ell(G)=7$ if and only if ... More
L2 and Hp boundedness of strongly singular operators and oscillating operators on Heisenberg groupsMay 06 2012Sep 08 2013In the first part, we obtain sharp results for L^2 boundedness of strongly singular operators on the Heisenberg group. We also define the oscillating convolution operators on the Heisenberg group and study their boundedness properties. In the second part, ... More
On strongly indefinite systems involving the fractional LaplacianFeb 26 2013May 20 2014In this paper we study strongly indefinite systems involving the fractional Laplacian on bounded domains. We obtain existence and non-existence results, $a priori$ estimates of Gidas-Spruck type, and the symmetric property.
Maximum drawdown, recovery and momentumMar 31 2014Mar 31 2015We test predictability on asset price using stock selection rules based on maximum drawdown and consecutive recovery. Monthly momentum- and weekly contrarian-style portfolios ranked by the alternative selection criteria are implemented in various asset ... More
Sphalerons in the Standard Model with a real Higgs singletSep 20 1994Sep 21 1994Sphaleron energies within the standard model with a real Higgs singlet added on are calculated. The coupled non-linear equations of motion are numerically solved and the sphaleron energy evaluated for a set of parameters in the Higgs potential. I find ... More
Canonical decomposition of manifolds with flat real projective structure into (n-1)-convex manifolds and concave affine manifoldsApr 23 1998We try to understand the geometric properties of $n$-manifolds ($n\geq 2$) with geometric structures modeled on $(\bR P^n, \PGL(n+1, \bR))$, i.e., $n$-manifolds with projectively flat torsion free affine connections. We define the notion of $i$-convexity ... More
The decomposition and classification of radiant affine 3-manifoldsDec 19 1997Jul 17 2000An affine manifold is a manifold with torsion-free flat affine connection. A geometric topologist's definition of an affine manifold is a manifold with an atlas of charts to the affine space with affine transition functions; a radiant affine manifold ... More
The universal cover of an affine three-manifold with holonomy of shrinkable dimension $\leq 2$Jun 23 1997Dec 21 1999An affine manifold is a manifold with an affine structure, i.e. a torsion-free flat affine connection. We show that the universal cover of a closed affine 3-manifold $M$ with holonomy group of shrinkable dimension (or discompacit\'e in French) less than ... More
Microstructure of Reflection Holographic Grating Inscribed in an Absorptive Azopolymer FilmSep 08 2015Microstructure of reflection holographic grating fabricated via a photo-isomerization process in an absorptive azopolymer film is analyzed. A surface relief formation takes place on the film surface even in the reflection holographic configuration. The ... More
Persistent Hidden States and Nonlinear Transformation for Long Short-Term MemoryJun 22 2018Dec 07 2018Recurrent neural networks (RNNs) have been drawing much attention with great success in many applications like speech recognition and neural machine translation. Long short-term memory (LSTM) is one of the most popular RNN units in deep learning applications. ... More
The number of orientable small covers over cubesDec 19 2008May 13 2010We count orientable small covers over cubes. We also get estimates for $O_n/R_n$, where $O_n$ is the number of orientable small covers and $R_n$ is the number of all small covers over an $n$-cube up to the Davis-Januszkiewicz equivalence.
Simplicial homology and Hochschild cohomology of Banach semilattice algebrasJun 15 2006The ${\ell}^1$-convolution algebra of a semilattice is known to have trivial cohom ology in degrees 1,2 and 3 whenever the coefficient bimodule is symmetric. We ex tend this result to all cohomology groups of degree $\geq 1$ with symmetric coef ficients. ... More
A classification of radial and totally geodesic ends of properly convex real projective orbifoldsApr 05 2013Jun 10 2014Real projective structures on $n$-orbifolds are useful in understanding the space of representations of discrete groups into $SL(n+1, \mathbb{R})$ or $PGL(n+1, \mathbb{R})$. A recent work shows that many hyperbolic manifolds deform to manifolds with such ... More
The convex real projective orbifolds with radial or totally geodesic ends: The closedness and openness of deformationsNov 04 2010May 28 2014A real projective orbifold is an $n$-dimensional orbifold modeled on $\mathbb{RP}^n$ with the group $PGL(n+1, \mathbb{R})$. We concentrate on an orbifold that contains a compact codimension $0$ submanifold whose complement is a union of neighborhoods ... More
Biflatness of ${\ell}^1$-semilattice algebrasJun 15 2006May 10 2007Building on an old result of Duncan and Namioka, we show that the ${\ell}^1$-convolution algebra of a semilattice $S$ is biflat precisely when $S$ is uniformly locally finite. The proof shows in passing that for such $S$ the convolution algebra is isomorphic ... More
The number of small covers over cubesFeb 14 2008Mar 04 2008In the present paper we find a bijection between the set of small covers over an $n$-cube and the set of acyclic digraphs with $n$ labeled nodes. Using this, we give a formula of the number of small covers over an $n$-cube (generally, a product of simplices) ... More
Observations of B335 in the Millimeter Continuum and the 226 GHz H2CO LineJul 18 2007The protostar B335 was observed in the 1.3 mm continuum and in the H2CO 312 - 211 line with an angular resolution of about 8 arcsec. The mass of the inner envelope detected by the dust continuum emission is about 0.02 Msun. The H2CO spectrum at the protostellar ... More
Newton-Wigner position operator and its corresponding spin operator in relativistic quantum mechanicsDec 01 2014A relativistic spin operator is to be the difference between the total and orbital angular momentum. As the unique position operator for a localized state, the remarkable Newton-Wigner position operator, which has all desirable commutation relations as ... More
Distribution of integral Fourier Coefficients of a Modular Form of Half Integral Weight Modulo PrimesMar 31 2007Recently, Bruinier and Ono classified cusp forms $f(z) := \sum_{n=0}^{\infty} a_f(n)q ^n \in S_{\lambda+1/2}(\Gamma_0(N),\chi)\cap \mathbb{Z}[[q]]$ that does not satisfy a certain distribution property for modulo odd primes $p$. In this paper, using Rankin-Cohen ... More
Adiabatic Quantum Algorithms for the NP-Complete Maximum-Weight Independent Set, Exact Cover and 3SAT ProblemsApr 13 2010The problem Hamiltonian of the adiabatic quantum algorithm for the maximum-weight independent set problem (MIS) that is based on the reduction to the Ising problem (as described in [Choi08]) has flexible parameters. We show that by choosing the parameters ... More
A Semidefinite Program for Structured BlockmodelsNov 16 2016Semidefinite programs have recently been developed for the problem of community detection, which may be viewed as a special case of the stochastic blockmodel. Here, we develop a semidefinite program that can be tailored to other instances of the blockmodel, ... More
Axino as a sterile neutrinoApr 14 2001We present a supersymmetric axion model in which the fermionic superpartner of axion, i.e. the axino, corresponds to a sterile neutrino which would accommodate the LSND data with atmospheric and solar neutrino oscillations.
Light Quark Masses and Quarkonium DecaysJun 24 1992After discussing the intrinsic ambiguity in determining the light quark mass ratio $m_u/m_d$, we reexamine the recent proposal that this ambiguity can be resolved by applying the QCD multipole expansion for the heavy quarkonium decays. It is observed ... More
Thermal Production of Axino Dark MatterFeb 21 2012We discuss certain features of the low energy effective interactions of axion supermultiplet, which are relevant for axino cosmology, and examine the implication to thermal production of axino in the early Universe.
Near-Online Multi-target Tracking with Aggregated Local Flow DescriptorApr 09 2015In this paper, we focus on the two key aspects of multiple target tracking problem: 1) designing an accurate affinity measure to associate detections and 2) implementing an efficient and accurate (near) online multiple target tracking algorithm. As the ... More
Maximal multiplier on Stratified groupsJun 13 2012Mar 17 2013In this paper, we prove Lp boundedness of maximal multipliers on stratified groups and maximal multipliers on product spaces of those groups.
Oscillating convolution operators on the Heisenberg groupApr 25 2012Jun 13 2012In this paper, we consider oscillating convolution operotors on the Heisenberg group $H^n_a$ with respect to the norm $\rho(x,t) = \rho_1(b x, b t)$ with $\rho_1(x,t)= (|x|^4 + t^2)^{1/4}$. We obtain $L^2$ boundedness properties using the oscillatory ... More
Multiplicity of the Protostar Serpens SMM 1 Revealed by Millimeter ImagingOct 13 2009The Serpens SMM 1 region was observed in the 6.9 mm continuum with an angular resolution of about 0.6 arcsec. Two sources were found to have steep positive spectra suggesting emission from dust. The stronger one, SMM 1a, is the driving source of the bipolar ... More
Directly finite algebras of pseudofunctions on locally compact groupsMay 19 2012Nov 12 2014An algebra $A$ is said to be directly finite if each left invertible element in the (conditional) unitization of $A$ is right invertible. We show that the reduced group ${\rm C}^\ast$-algebra of a unimodular group is directly finite, extending known results ... More
Single-Carrier Index Modulation for IoT UplinkApr 05 2019For the Internet of Things (IoT), there might be a large number of devices to be connected to the Internet through wireless technologies. In general, IoT devices would have various constraints due to limited processing capability, memory, energy source, ... More
On Error Rate Analysis for URLLC over Multiple Fading ChannelsApr 04 2019In this paper, we study ultra-reliable and low-latency communication (URLLC) under fading using multiple frequency or time bins. We investigate an approach to find an upper-bound on the packet error rate when a finite-length code is used. From simulation ... More
A note on some group $C^*$-algebras which are quasi-directly finiteMar 08 2010Jun 06 2010An algebra is said to be quasi-directly finite when any left-invertible element in its unitization is automatically right-invertible. It is an old observation of Kaplansky that the von Neumann algebra of a discrete group has this property; in this note, ... More
Layered Non-Orthogonal Random Access with SIC and Transmit Diversity for Reliable TransmissionsDec 08 2017In this paper, we study a layered random access scheme based on non-orthogonal multiple access (NOMA) to improve the throughput of multichannel ALOHA. At a receiver, successive interference cancellation (SIC) is carried out across layers to remove the ... More
Injective convolution operators on ${\ell}^{\infty}(Γ)$ are surjectiveJun 15 2006Aug 01 2007Let $\Gamma$ be a discrete group and let $f \in \ell^1(\Gamma)$. We observe that if the natural convolution operator $\rho_f:\ell^{\infty}(\Gamma)\to \ell^{\inf ty}(\Gamma)$ is injective, then f is invertible in $\ell^1(\Gamma)$. Our proof simplifies ... More
Group representations with empty residual spectrumJun 16 2009Jan 19 2010Let $X$ be a Banach space on which a discrete group $\Gamma$ acts by isometries. For certain natural choices of $X$, every element of the group algebra, when regarded as an operator on $X$, has empty residual spectrum. We show, for instance, that this ... More
Genus zero BPS invariants for local P^1Jun 23 2011Oct 09 2012We study the equivariant version of the genus zero BPS invariants of the total space of a rank 2 bundle on P^1 whose determinant is O(-2). We define the equivariant genus zero BPS invariants by the residue integrals on the moduli space of stable sheaves ... More
Persistence of Hölder continuity for non-local integro-differential equationsDec 28 2011In this paper, we consider non-local integro-differential equations under certain natural assumptions on the kernel, and obtain persistence of H\"{o}lder continuity for their solutions. In other words, we prove that a solution stays in $C^\beta$ for all ... More
Stability and ensemble inequivalence in a globally coupled systemSep 11 2003We consider a system of globally coupled rotors, described by a set of Langevin equations, and examine stability of the incoherent phase. The corresponding Fokker-Planck equation, providing a unified description of microcanonical and canonical ensembles, ... More
Stability of thermodynamic and dynamical order in a system of globally coupled rotorsJun 01 2005A system of globally coupled rotors is studied in a unified framework of microcanonical and canonical ensembles. We consider the Fokker-Planck equation governing the time evolution of the system, and examine various stationary as well as non-stationary ... More