4,582 research outputs found
Mechanisms for Stable Sonoluminescence
A gas bubble trapped in water by an oscillating acoustic field is expected to
either shrink or grow on a diffusive timescale, depending on the forcing
strength and the bubble size. At high ambient gas concentration this has long
been observed in experiments. However, recent sonoluminescence experiments show
that in certain circumstances when the ambient gas concentration is low the
bubble can be stable for days. This paper presents mechanisms leading to
stability which predict parameter dependences in agreement with the
sonoluminescence experiments.Comment: 4 pages, 3 figures on request (2 as .ps files
Blockchain technology as a support infrastructure in E-Government evolution at Dubai economic department
© 2019 Association for Computing Machinery. World is experiencing revolution with the proliferation of technologies like blockchain, artificial intelligence, IOT, and cloud computing in our lives. This study explores Dubai Economic Department\u27s (DED) electronic government (e-government) stages of integrating emerging technologies as its contribution in creating a smarter city. Our findings suggest that blockchain technology can be used as a platform to transform the e-business operating models in order to offer fully integrated services and to enforce common business rules. It can help governments in making processes simpler, faster and secure. It can be used for syncing of data across different departments, automatically & instantaneously. This work provides policy makers, enterprise architects and IT managers with useful guidelines to define and drive their e-government strategy and planning actions towards the most appropriate domains of implementation
Application of Pauli-Villars regularization and discretized light-cone quantization to a single-fermion truncation of Yukawa theory
We apply Pauli-Villars regularization and discretized light-cone quantization
to the nonperturbative solution of (3+1)-dimensional Yukawa theory in a
single-fermion truncation. Three heavy scalars, including two with negative
norm, are used to regulate the theory. The matrix eigenvalue problem is solved
for the lowest-mass state with use of a new, indefinite-metric Lanczos
algorithm. Various observables are extracted from the wave functions, including
average multiplicities and average momenta of constituents, structure
functions, and a form factor slope.Comment: 21 pages, 7 figures, RevTeX; published version: more extensive data
in the tables of v
To , or not to : Recent developments and comparisons of regularization schemes
We give an introduction to several regularization schemes that deal with
ultraviolet and infrared singularities appearing in higher-order computations
in quantum field theories. Comparing the computation of simple quantities in
the various schemes, we point out similarities and differences between them.Comment: 61 pages, 12 figures; version sent to EPJC, references update
Hydrogen-bond equilibria and life times in a supercooled monohydroxy alcohol
Dielectric loss spectra covering 13 decades in frequency were collected for
2-ethyl-1-hexanol, a monohydroxy alcohol that exhibits a prominent Debye-like
relaxation, typical for several classes of hydrogen-bonded liquids. The thermal
variation of the dielectric absorption amplitude agrees well with that of the
hydrogen-bond equilibrium population, experimentally mapped out using near
infrared (NIR) and nuclear magnetic resonance (NMR) measurements. Despite this
agreement, temperature-jump NIR spectroscopy reveals that the hydrogen-bond
switching rate does not define the frequency position of the prominent
absorption peak. This contrasts with widespread notions and models based
thereon, but is consistent with a recent approach.Comment: 4 pages, 4 figure
More Benefits of Semileptonic Rare B Decays at Low Recoil: CP Violation
We present a systematic analysis of the angular distribution of Bbar ->
Kbar^\ast (-> Kbar pi) l^+ l^- decays with l = e, mu in the low recoil region
(i.e. at high dilepton invariant masses of the order of the mass of the
b-quark) to account model-independently for CP violation beyond the Standard
Model, working to next-to-leading order QCD. From the employed heavy quark
effective theory framework we identify the key CP observables with reduced
hadronic uncertainties. Since some of the CP asymmetries are CP-odd they can be
measured without B-flavour tagging. This is particularly beneficial for
Bbar_s,B_s -> phi(-> K^+ K^-) l^+ l^- decays, which are not self-tagging, and
we work out the corresponding time-integrated CP asymmetries. Presently
available experimental constraints allow the proposed CP asymmetries to be
sizeable, up to values of the order ~ 0.2, while the corresponding Standard
Model values receive a strong parametric suppression at the level of O(10^-4).
Furthermore, we work out the allowed ranges of the short-distance (Wilson)
coefficients C_9,C_10 in the presence of CP violation beyond the Standard Model
but no further Dirac structures. We find the Bbar_s -> mu^+ mu^- branching
ratio to be below 9*10^-9 (at 95% CL). Possibilities to check the performance
of the theoretical low recoil framework are pointed out.Comment: 18 pages, 3 fig.; 1 reference and comment on higher order effects
added; EOS link fixed. Minor adjustments to Eqs 4.1-4.3 to match the (lower)
q^2-cut as given in paper. Main results and conclusions unchanged; v3+v4:
treatment of exp. uncert. in likelihood-function in EOS fixed and constraints
from scan on C9,C10 updated (Fig 2,3 and Eqs 3.2,3.3). Main results and
conclusions absolutely unchange
The Sound of Sonoluminescence
We consider an air bubble in water under conditions of single bubble
sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively
for subsonic gas-liquid interface motion. Sound emission being the dominant
damping mechanism, we also implement the nonperturbative sound damping in the
Rayleigh-Plesset equation for the interface motion. We evaluate numerically the
sound pulse emitted during bubble collapse and compare the nonperturbative and
perturbative results, showing that the usual perturbative description leads to
an overestimate of the maximal surface velocity and maximal sound pressure. The
radius vs. time relation for a full SBSL cycle remains deceptively unaffected.Comment: 25 pages; LaTex and 6 attached ps figure files. Accepted for
publication in Physical Review
Thermal analysis of production of resonances in relativistic heavy-ion collisions
Production of resonances is considered in the framework of the
single-freeze-out model of ultra-relativistic heavy ion collisions. The
formalism involves the virial expansion, where the probability to form a
resonance in a two-body channel is proportional to the derivative of the
phase-shift with respect to the invariant mass. The thermal model incorporates
longitudinal and transverse flow, as well as kinematic cuts of the STAR
experiment at RHIC. We find that the shape of the pi+ pi- spectral line
qualitatively reproduces the preliminary experimental data when the position of
the rho peak is lowered. This confirms the need to include the medium effects
in the description of the RHIC data. We also analyze the transverse-momentum
spectra of rho, K*(892), and f_0(980), and find that the slopes agree with the
observed values. Predictions are made for eta, eta', omega, phi, Lambda(1520),
and Sigma(1385).Comment: minor modifications, a reference adde
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