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Ye Li

Publications and source records attributed to Ye Li.

233 records · Page 13Linked to original sources
arXiv2013

The Quest-V Separation Kernel for Mixed Criticality Systems

Multi- and many-core processors are becoming increasingly popular in embedded systems. Many of these processors now feature hardware virtualization capabilities, such as the ARM Cortex A15, and x86 processors with Intel VT-x or AMD-V support. Hardware virtualization offers opportunities to partition physical resources, including processor cores, memory and I/O devices amongst guest virtual machines. Mixed criticality systems and services can then co-exist on the same platform in separate virtual machines. However, traditional virtual machine systems are too expensive because of the costs of trapping into hypervisors to multiplex and manage machine physical resources on behalf of separate guests. For example, hypervisors are needed to schedule separate VMs on physical processor cores. In this paper, we discuss the design of the Quest-V separation kernel, that partitions services of different criticalities in separate virtual machines, or sandboxes. Each sandbox encapsulates a subset of machine physical resources that it manages without requiring intervention of a hypervisor. Moreover, a hypervisor is not needed for normal operation, except to bootstrap the system and establish communication channels between sandboxes.

cs.OS↗
arXiv2013

Predictable Migration and Communication in the Quest-V Multikernel

Quest-V is a system we have been developing from the ground up, with objectives focusing on safety, predictability and efficiency. It is designed to work on emerging multicore processors with hardware virtualization support. Quest-V is implemented as a "distributed system on a chip" and comprises multiple sandbox kernels. Sandbox kernels are isolated from one another in separate regions of physical memory, having access to a subset of processing cores and I/O devices. This partitioning prevents system failures in one sandbox affecting the operation of other sandboxes. Shared memory channels managed by system monitors enable inter-sandbox communication. The distributed nature of Quest-V means each sandbox has a separate physical clock, with all event timings being managed by per-core local timers. Each sandbox is responsible for its own scheduling and I/O management, without requiring intervention of a hypervisor. In this paper, we formulate bounds on inter-sandbox communication in the absence of a global scheduler or global system clock. We also describe how address space migration between sandboxes can be guaranteed without violating service constraints. Experimental results on a working system show the conditions under which Quest-V performs real-time communication and migration.

cs.OS↗
arXiv2013

Quest-V: A Virtualized Multikernel for Safety-Critical Real-Time Systems

Modern processors are increasingly featuring multiple cores, as well as support for hardware virtualization. While these processors are common in desktop and server-class computing, they are less prevalent in embedded and real-time systems. However, smartphones and tablet PCs are starting to feature multicore processors with hardware virtualization. If the trend continues, it is possible that future real-time systems will feature more sophisticated processor architectures. Future automotive or avionics systems, for example, could replace complex networks of uniprocessors with consolidated services on a smaller number of multicore processors. Likewise, virtualization could be used to isolate services and increase the availability of a system even when failures occur. This paper investigates whether advances in modern processor technologies offer new opportunities to rethink the design of real-time operating systems. We describe some of the design principles behind Quest-V, which is being used as an exploratory vehicle for real-time system design on multicore processors with hardware virtualization capabilities. While not all embedded systems should assume such features, a case can be made that more robust, safety-critical systems can be built to use hardware virtualization without incurring significant overheads.

cs.OS↗
arXiv2013

Bounding the Higgs Boson Width Through Interferometry

We study the change in the di-photon invariant mass distribution for Higgs boson decays to two photons, due to interference between the Higgs resonance in gluon fusion and the continuum background amplitude for gluon pair to photon pair. Previously, the apparent Higgs mass was found to shift by around 100 MeV in the Standard Model in the leading order approximation, which may potentially be experimentally observable. We compute the next-to-leading order QCD corrections to the apparent mass shift, which reduce it by about 40%. The apparent mass shift may provide a way to measure, or at least bound, the Higgs boson width at the Large Hadron Collider through "interferometry." We investigate how the shift depends on the Higgs width, in a model that maintains constant Higgs boson signal yields. At Higgs widths above 30 MeV the mass shift is over 200 MeV and increases with the square root of the width. The apparent mass shift could be measured by comparing with the ZZ* channel, where the shift is much smaller. It might be possible to measure the shift more accurately by exploiting its strong dependence on the Higgs transverse momentum.

hep-ph↗
arXiv2013

Electroweak Corrections at High Energies

We present a survey of the most abundant processes at the LHC for sensitivity to electroweak corrections at \sqrt{s} = 8, 14, 33, and 100 TeV proton-proton collision energies. The processes studied are pp -> dijet, inclusive W and Z, W/Z+jets, and WW. In each case we compare the experimental uncertainty in the highest kinematic regions of interest with the relative magnitude of electroweak corrections and fixed-order α_S calculations.

hep-ph↗
arXiv2013

Up Sector of Minimal Flavor Violation: Top Quark Properties and Direct D meson CP violation

Minimal Flavor Violation in the up-type quark sector leads to particularly interesting phenomenology due to the interplay of flavor physics in the charm sector and collider physics from flavor changing processes in the top sector. We study the most general operators that can affect top quark properties and $D$ meson decays in this scenario, concentrating on two CP violating operators for detailed studies. The consequences of these effective operators on charm and top flavor changing processes are generically small, but can be enhanced if there exists a light flavor mediator that is a Standard Model gauge singlet scalar and transforms under the flavor symmetry group. This flavor mediator can satisfy the current experimental bounds with a mass as low as tens of GeV and explain observed $D$-meson direct CP violation. Additionally, the model predicts a non-trivial branching fraction for a top quark decay that would mimic a dijet resonance.

hep-ph↗
arXiv2012

Combining QCD and electroweak corrections to dilepton production in FEWZ

We combine the next-to-next-to-leading order (NNLO) QCD corrections to lepton-pair production through the Drell-Yan mechanism with the next-to-leading order (NLO) electroweak corrections within the framework of the FEWZ simulation code. Control over both sources of higher-order contributions is necessary for measurements where percent-level theoretical predictions are crucial, and in phase-space regions where the NLO electroweak corrections grow large. The inclusion of both corrections in a single simulation code eliminates the need to separately incorporate such effects as final-state radiation and electroweak Sudakov logarithms when comparing many experimental results to theory. We recalculate the NLO electroweak corrections in the complex-mass scheme for both massless and massive final-state leptons, and modify the QCD corrections in the original FEWZ code to maintain consistency with the complex-mass scheme to the lowest order. We present phenomenological results for LHC studies that include both NNLO QCD and NLO electroweak corrections. In addition, we study several interesting kinematics features induced by experimental cuts in the distribution of photon radiation at the LHC.

hep-ph↗
arXiv2012

Testing the 130 GeV gamma-ray line with high energy resolution detectors

Recently some hints of the existence of $γ$-ray line around 130 GeV are reported according to the analysis of Fermi-LAT data. If confirmed it would be the first direct evidence to show the existence of new physics beyond the standard model. Here we suggest that using the forthcoming high energy resolution $γ$-ray detectors, such as CALET and DAMPE, we may test whether it is real line structure or just the background effect. For DAMPE like detector with designed energy resolution $\sim1.5%$, a line significance will reach $11σ$ for the same statistics as Fermi-LAT. For about 1.4 yr survey observation, DAMPE may detect a $5σ$ signal of such a $γ$-ray line.

astro-ph.HE↗
arXiv2012

W physics at the LHC with FEWZ 2.1

We present an updated version of the FEWZ (Fully Exclusive W and Z production) code for the calculation of W and gamma*/Z production at next-to-next-to-leading order in the strong coupling. Several new features and observables are introduced, and an order-of-magnitude speed improvement over the performance of FEWZ 2.0 is demonstrated. New phenomenological results for W production and comparisons with LHC data are presented, and used to illustrate the range of physics studies possible with the features of FEWZ 2.1. We demonstrate with an example the importance of directly comparing fiducial-region measurements with theoretical predictions, rather than first extrapolating them to the full phase space.

hep-ph↗
arXiv2011

Quest-V: A Virtualized Multikernel for High-Confidence Systems

This paper outlines the design of `Quest-V', which is implemented as a collection of separate kernels operating together as a distributed system on a chip. Quest-V uses virtualization techniques to isolate kernels and prevent local faults from affecting remote kernels. This leads to a high-confidence multikernel approach, where failures of system subcomponents do not render the entire system inoperable. A virtual machine monitor for each kernel keeps track of shadow page table mappings that control immutable memory access capabilities. This ensures a level of security and fault tolerance in situations where a service in one kernel fails, or is corrupted by a malicious attack. Communication is supported between kernels using shared memory regions for message passing. Similarly, device driver data structures are shareable between kernels to avoid the need for complex I/O virtualization, or communication with a dedicated kernel responsible for I/O. In Quest-V, device interrupts are delivered directly to a kernel, rather than via a monitor that determines the destination. Apart from bootstrapping each kernel, handling faults and managing shadow page tables, the monitors are not needed. This differs from conventional virtual machine systems in which a central monitor, or hypervisor, is responsible for scheduling and management of host resources amongst a set of guest kernels. In this paper we show how Quest-V can implement novel fault isolation and recovery techniques that are not possible with conventional systems. We also show how the costs of using virtualization for isolation of system services does not add undue overheads to the overall system performance.

cs.OS↗
arXiv2011

An Exclusive Soft Function for Drell-Yan at Next-to-Next-to-Leading Order

We present next-to-next-to-leading-order (NNLO) results for an exclusive soft function that appears in a recently developed factorization theorem for transverse momentum distributions. The factorization theorem, derived using the Soft Collinear Effective Theory, involves both a soft function and unintegrated nucleon distribution functions fully differential in momentum coordinates. The soft function is given by the vacuum matrix element of soft Wilson lines and is also fully differential in all components. We give results and relevant technical details for the NNLO calculation of the soft function, including finite parts, and derive the corresponding anomalous dimension. These results are necessary for achieving low transverse momentum resummation at next-to-next-to-leading-logarithmic accuracy in this effective field theory approach with unintegrated distribution functions.

hep-ph↗
arXiv2010

FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order

We introduce an improved version of the simulation code FEWZ (Fully Exclusive W and Z Production) for hadron collider production of lepton pairs through the Drell-Yan process at next-to-next-to-leading-order (NNLO) in the strong coupling constant. The program is fully differential in the phase space of leptons and additional hadronic radiation. The new version offers users significantly more options for customization. FEWZ now bins multiple, user-selectable histograms during a single run, and produces parton distribution function (PDF) errors automatically. It also features a signifcantly improved integration routine, and can take advantage of multiple processor cores locally or on the Condor distributed computing system. We illustrate the new features of FEWZ by presenting numerous phenomenological results for LHC physics. We compare NNLO QCD with initial ATLAS and CMS results, and discuss in detail the effects of detector acceptance on the measurement of angular quantities associated with Z-boson production. We address the issue of technical precision in the presence of severe phase-space cuts.

hep-ph↗
arXiv2009

Smoothing Riemannian Metrics with Bounded Ricci Curvatures in Dimension Four, II

This note is a continuation of the author's paper \cite{Li}. We prove that if the metric $g$ of a 4-manifold has bounded Ricci curvature and the curvature has no local concentration everywhere, then it can be smoothed to a metric with bounded sectional curvature. Here we don't assume the bound for local Sobolev constant of $g$ and hence this smoothing result can be applied to the collapsing case.

math.DG↗
arXiv2009

Reconstructing a Z' Lagrangian using the LHC and low-energy data

We study the potential of the LHC and future low-energy experiments to precisely measure the underlying model parameters of a new Z' boson. We emphasize the complimentary information obtained from both on- and off-peak LHC dilepton data, from the future Q-weak measurement of the weak charge of the proton, and from a proposed measurement of parity violation in low-energy Moller scattering. We demonstrate the importance of off-peak LHC data and Q-weak for removing sign degeneracies between Z' couplings that occur if only on-peak LHC data is studied. A future precision measurement of low-energy Moller scattering can resolve a scaling degeneracy between quark and lepton couplings that remains after analyzing LHC dilepton data, permitting an extraction of the individual Z' couplings rather than combinations of them. We study how precisely Z' properties can be extracted for LHC integrated luminosities ranging from a few inverse femtobarns to super-LHC values of an inverse attobarn. For the several example cases studied with M_Z'=1.5 TeV, we find that coupling combinations can be determined with relative uncertainties reaching 30% with 30 fb^-1 of integrated luminosity, while 50% is possible with 10 fb^-1. With SLHC luminosities of 1 ab^-1, we find that products of quark and lepton couplings can be probed to 10%.

hep-ph↗
arXiv2009

Testing Lorentz Invariance with Ultra High Energy Cosmic Ray Spectrum

The GZK cutoff predicted at the Ultra High Energy Cosmic Ray (UHECR) spectrum as been observed by the HiRes and Auger experiments. The results put severe constraints on the effect of Lorentz Invariance Violation(LIV) which has been introduced to explain the absence of GZK cutoff indicated in the AGASA data. Assuming homogeneous source distribution with a single power law spectrum, we calculate the spectrum of UHECRs observed on Earth by taking the processes of photopion production, $e^+e^-$ pair production and adiabatic energy loss into account. The effect of LIV is also taken into account in the calculation. By fitting the HiRes monocular spectra and the Auger combined spectra, we show that the LIV parameter is constrained to $ξ=-0.8^{+3.2}_{-0.5}\times10^{-23}$ and $0.0^{+1.0}_{-0.4}\times10^{-23}$ respectively, which is well consistent with strict Lorentz Invariance up to the highest energy.

astro-ph↗
arXiv2005

The Application of Asymmetric Entangled States in Quantum Game

In the present letter, we propose a more general entangling operator to the quantization of Cournot economic model, in which players can access to a continuous set of strategies. By analyzing the relation between the von Neumann entropy of the entangled state and the total profit of two players precisely, we find that the total profit at the Nash equilibrium always achieves its maximal value as long as the entropy tends to infinity. Moreover, since the asymmetry is introduced in the entangled state, the quantum model shows some kind of "encouraging" and "suppressing" effect in profit functions of different players.

quant-ph↗