9,687 research outputs found
The Effects of Inlet Flow Modification on Cavitating Inducer Performance
This paper explores the effect of inlet flow modification on the cavitating and noncavitating performance of two cavitating inducers, one of simple helical design and the other a model of the low-pressure LOX pump in the Space Shuttle Main Engine. The modifications were generated by sections of honeycomb, both uniform and nonuniform. Significant improvement in the performance over a wide range of flow coefficients resulted from the use of either honeycomb section. Measurements of the axial and swirl velocity profiles of the flows entering the inducers were made in order to try to understand the nature of the inlet flow and the manner in which it is modified by the honeycomb sections
Solving the One-Dimensional Time-Independent Schr\"odinger Equation with High Accuracy: The LagrangeMesh Mathematica Package
In order to find the spectrum associated with the one-dimensional
Schr\"oodinger equation, we discuss the Lagrange Mesh method (LMM) and its
numerical implementation for bound states. After presenting a general overview
of the theory behind the LMM, we introduce the LagrangeMesh package: the
numerical implementation of the LMM in Mathematica. Using few lines of code,
the package enables a quick home-computer computation of the spectrum and
provides a practical tool to study a large class of systems in quantum
mechanics. The main properties of the package are (i) the input is basically
the potential function and the interval on which is defined; and (ii) the
accuracy in calculations and final results is controllable by the user. As
illustration, a highly accurate spectrum of some relevant quantum systems is
obtained by employing the commands that the package offers. In fact, the
present work can be regarded as a user guide based on worked examples.Comment: File LagrangeMesh.wl can be provided to the interested reader, just
contact the author via email. Alternatively, it can be found at
https://github.com/JuanCarlosdelValle/LagrangeMesh-Packag
Production and decays of supersymmetric Higgs bosons in spontaneously broken R-parity
We study the mass spectra, production and decay properties of the lightest
supersymmetric CP-even and CP-odd Higgs bosons in models with spontaneously
broken R-parity (SBRP). We compare the resulting mass spectra with expectations
of the Minimal Supersymmetric Standard Model (MSSM), stressing that the model
obeys the upper bound on the lightest CP-even Higgs boson mass. We discuss how
the presence of the additional scalar singlet states affects the Higgs
production cross sections, both for the Bjorken process and the "associated
production". The main phenomenological novelty with respect to the MSSM comes
from the fact that the spontaneous breaking of lepton number leads to the
existence of the majoron, denoted J, which opens new decay channels for
supersymmetric Higgs bosons. We find that the invisible decays of CP-even
Higgses can be dominant, while those of the CP-odd bosons may also be sizeable.Comment: 21 pages, 8 figures; minor changes, final version for publicatio
Spontaneous, collective coherence in driven, dissipative cavity arrays
We study an array of dissipative tunnel-coupled cavities, each interacting
with an incoherently pumped two-level emitter. For cavities in the lasing
regime, we find correlations between the light fields of distant cavities,
despite the dissipation and the incoherent nature of the pumping mechanism.
These correlations decay exponentially with distance for arrays in any
dimension but become increasingly long ranged with increasing photon tunneling
between adjacent cavities. The interaction-dominated and the
tunneling-dominated regimes show markedly different scaling of the correlation
length which always remains finite due to the finite photon trapping time. We
propose a series of observables to characterize the spontaneous build-up of
collective coherence in the system.Comment: 9 pages, 4 figures, including supplemental material (with 4 pages, 1
figure). This is a shorter version with some modifications in the
supplemental material (a gap in the proof was closed and calculations
significantly generalized and improved
Exciting polaritons with quantum light
We discuss the excitation of polaritons---strongly-coupled states of light
and matter---by quantum light, instead of the usual laser or thermal
excitation. As one illustration of the new horizons thus opened, we introduce
Mollow spectroscopy, a theoretical concept for a spectroscopic technique that
consists in scanning the output of resonance fluorescence onto an optical
target, from which weak nonlinearities can be read with high precision even in
strongly dissipative environments.Comment: 5 pages, 3 figure
Degenerate neutrinos from a supersymmetric A_4 model
We investigate the supersymmetric A_4 model recently proposed by Babu, Ma and
Valle. The model naturally gives quasi-degenerate neutrinos that are bi-largely
mixed, in agreement with observations. Furthermore, the mixings in the quark
sector are constrained to be small, making it a complete model of the flavor
structure. Moreover, it has the interesting property that CP-violation in the
leptonic sector is maximal (unless vanishing). The model exhibit a close
relation between the slepton and lepton sectors and we derive the slepton
spectra that are compatible with neutrino data and the present bounds on
flavor-violating charged lepton decays. The prediction for the branching ratio
of the decay tau -> mu gamma has a lower limit of 10^{-9}. In addition, the
overall neutrino mass scale is constrained to be larger than 0.3 eV. Thus, the
model will be tested in the very near future.Comment: 11 pages, 6 figures. Talk given at the International Workshop on
Astroparticle and High Energy Physics (AHEP), Valencia, Spain, 14-18 Oct.
200
Radial power-like potentials: from the Bohr-Sommerfeld -state energies to the exact ones
Following our previous study of the Bohr-Sommerfeld (B-S) quantization
condition for one-dimensional case (del Valle \& Turbiner (2021) \cite{First}),
we extend it to -dimensional power-like radial potentials. The B-S
quantization condition for -states of the -dimensional radial
Schr\"odinger equation is proposed. Based on numerical results obtained for the
spectra of power-like potentials, with , the
correctness of the proposed B-S quantization condition is established for
various dimensions . It is demonstrated that by introducing the {\it WKB
correction} (supposedly coming from the higher order WKB terms) into
the r.h.s. of the B-S quantization condition leads to the so-called {\it exact
WKB quantization condition}, which reproduces the exact energies, while
remains always very small. For (any integer ) and for
(at ) the WKB correction : for states the B-S spectra
coincides with the exact ones.
Concrete calculations for physically important cases of linear, cubic,
quartic, and sextic oscillators, as well as Coulomb and logarithmic potentials
in dimensions are presented. Radial quartic anharmonic oscillator is
considered briefly.Comment: 15 pages, 4 figures, 4 tables; extended, some typos fixed, to be
published in IJMP
Radial Anharmonic Oscillator: Perturbation Theory, New Semiclassical Expansion, Approximating Eigenfunctions. II. Quartic and Sextic Anharmonicity Cases
In our previous paper I (del Valle--Turbiner, Int. J. Mod. Phys. A34,
1950143, 2019) it was developed the formalism to study the general
-dimensional radial anharmonic oscillator with potential . It was based on the Perturbation Theory (PT) in
powers of (weak coupling regime) and in inverse, fractional powers of
(strong coupling regime) in both -space and in -space, respectively.
As the result it was introduced - the Approximant - a locally-accurate uniform
compact approximation of a wave function. If taken as a trial function in
variational calculations it has led to variational energies of unprecedented
accuracy for cubic anharmonic oscillator. In this paper the formalism is
applied to both quartic and sextic, spherically-symmetric radial anharmonic
oscillators with two term potentials ,
respectively. It is shown that a two-parametric Approximant for quartic
oscillator and a five-parametric one for sextic oscillator for the first four
eigenstates used to calculate the variational energy are accurate in 8-12
figures for any and , while the relative deviation
of the Approximant from the exact eigenfunction is less than for any
.Comment: 52 pages, 17 figures, 3 appendice
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