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Search Results: 1 - 10 of 138669 matches for " K. Lapidus "
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Dielectron production in pp and dp collisions at 1.25 GeV/u with HADES
K. Lapidus,for the HADES Collaboration
Physics , 2009,
Abstract: Inclusive production of e+e--pairs in pp and dp collisions at a kinetic beam energy of 1.25 GeV/u has been studied with the HADES spectrometer. In the latter case, the main goal was to obtain data on pair emission in quasi-free np collisions. To select this particular reaction channel the HADES experimental setup was extended with a Forward Wall hodoscope, which allowed to register spectator protons. Here, the measured invariant mass distributions demonstrate a strong enhancement of the pair yield for M > 140 MeV/c2 in comparison to pp data.
PFAPA: a single phenotype with genetic heterogeneity
Lapidus Sivia K,Chitkara Puja,Kim Peter W,Aksentijevich Ivona
Pediatric Rheumatology , 2012, DOI: 10.1186/1546-0096-10-s1-a86
Yo tengo sentido, tengo rima : Cano Estremera and the Art of the Soneo
Benjamin Lapidus
Centro Journal , 2004,
Abstract: Calling himself El due o del soneo, the boss of vocal improvisation, the Puerto Rican singer, Carlos Cano Estremera, is at the forefront of many innovations in soneos. For the uninitiated, a soneo is a vocal improvisation sung by a lead singer during the montuno, or call-and-response section in Afro-Cuban son-based musics, commercially referred to as salsa. As he is always up for a good duel, planned or unforseen, the results of Cano s duelos have been recorded both legally and illegally and spread throughout the world by salsa fans. Through conversations with Cano and a look at several techniques he uses when improvising, this article shows Cano Esteremera s improvisational framework to be a synthesis of previous soneros as well as singers and musicians from beyond the realm of salsa. His style can be summed up as unique and creative while remaining in the tradition.
Transformaciones económicas en los noventa y cambios espaciales en la provincia ciudad de La Habana, Cuba
Batia Lapidus Radlow
Investigaciones geográficas , 2000,
Abstract: Los a os noventa del siglo que recién culminó fueron particularmente difíciles para Cuba. Tal situación, propulsó la aplicación de una serie de medidas Y reformas económicas que, de modo gradual, han ido adoptando una dimensión regional. En especial, en la provincia ciudad de La Habana, es posible comprobar el contenido territorial de los nuevos procesos relacionados con el reajuste económico Es esta la perspectiva de análisis que propone el trabajo. Se hace referencia a algunas experiencias prácticas de corte sectorial a través de las cuales se reconocen diferentes vertientes de impacto. Finalmente se sugiere reflexionar en tomo a la capacidad que el territorio posee para adaptarse a los cambios, considerando al hombre como principal protagonista y receptor de los mismos.
Towards Quantized Number Theory: Spectral Operators and an Asymmetric Criterion for the Riemann Hypothesis
Michel L. Lapidus
Physics , 2015,
Abstract: This research expository article contains a survey of earlier work (in \S2--\S4) but also contains a main new result (in \S5), which we first describe. Given $c \geq 0$, the spectral operator $\mathfrak{a} = \mathfrak{a}_c$ can be thought of intuitively as the operator which sends the geometry onto the spectrum of a fractal string of dimension not exceeding $c$. Rigorously, it turns out to coincide with a suitable quantization of the Riemann zeta function $\zeta = \zeta(s)$: $\mathfrak{a} = \zeta (\partial)$, where $\partial = \partial_c$ is the infinitesimal shift of the real line acting on the weighted Hilbert space $L^2 (\mathbb{R}, e^{-2ct} dt)$. In this paper, we establish a new asymmetric criterion for the Riemann hypothesis, expressed in terms of the invertibility of the spectral operator for all values of the dimension parameter $c \in (0, 1/2)$ (i.e., for all $c$ in the left half of the critical interval $(0,1)$). This corresponds (conditionally) to a mathematical (and perhaps also, physical) "phase transition" occurring in the midfractal case when $c= 1/2$. Both the universality and the non-universality of $\zeta = \zeta (s)$ in the right (resp., left) critical strip $\{1/2 < \text{Re}(s) < 1 \}$ (resp., $\{0 < \text{Re}(s) < 1/2 \}$) play a key role in this context. These new results are presented in \S5. In \S2, we briefly discuss earlier joint work on the complex dimensions of fractal strings, while in \S3 and \S4, we survey earlier related work of the author with H. Maier and with H. Herichi, respectively, in which were established symmetric criteria for the Riemann hypothesis, expressed respectively in terms of a family of natural inverse spectral problems for fractal strings of Minkowski dimension $D \in (0,1),$ with $D \neq 1/2$, and of the quasi-invertibility of the family of spectral operators $\mathfrak{a}_c$ (with $c \in (0,1), c \neq 1/2$).
The Sound of Fractal Strings and the Riemann Hypothesis
Michel L. Lapidus
Physics , 2015,
Abstract: We give an overview of the intimate connections between natural direct and inverse spectral problems for fractal strings, on the one hand, and the Riemann zeta function and the Riemann hypothesis, on the other hand (in joint works of the author with Carl Pomerance and Helmut Maier, respectively). We also briefly discuss closely related developments, including the theory of (fractal) complex dimensions (by the author and many of his collaborators, including especially Machiel van Frankenhuijsen), quantized number theory and the spectral operator (jointly with Hafedh Herichi), and some other works of the author (and several of his collaborators).
The vertical hip fracture – a treatment challenge. A cohort study with an up to 9 year follow-up of 137 consecutive hips treated with sliding hip screw and antirotation screw
Enocson Anders,Lapidus Lasse J
BMC Musculoskeletal Disorders , 2012, DOI: 10.1186/1471-2474-13-171
Abstract: Background Femoral neck fractures with a vertical orientation have been associated with an increased risk for failure as they are both axial and rotational unstable and experience increased shear forces compared to the conventional and more horizontally oriented femoral neck fractures. The purpose of this study was to analyse outcome and risk factors for reoperation of these uncommon fractures. Methods A cohort study with a consecutive series of 137 hips suffering from a vertical hip fracture, treated with one method: a sliding hips screw with plate and an antirotation screw. Median follow-up time was 4.8 years. Reoperation data was validated against the National Board of Health and Welfare’s national registry using the unique Swedish personal identification number. Results The total reoperation rate was 18%. After multivariable Logistic regression analysis adjusting for possible confounding factors there was an increased risk for reoperation for displaced fractures (22%) compared to undisplaced fractures (3%), and for fractures with poor implant position (38%) compared to fractures with adequate implant position (15%). Conclusions The reoperation rate was high, and special attention should be given to achieve an appropriate position of the implant.
Localization on Snowflake Domains
Britta Daudert,Michel L. Lapidus
Mathematics , 2006,
Abstract: The geometric features of the square and triadic Koch snowflake drums are compared using a position entropy defined on the grid points of the discretizations (pre-fractals) of the two domains. Weighted graphs using the geometric quantities are created and random walks on the two pre-fractals are performed. The aim is to understand if the existence of narrow channels in the domain may cause the `localization' of eigenfunctions.
Fractal Complex Dimensions, Riemann Hypothesis and Invertibility of the Spectral Operator
Hafedh Herichi,Michel L. Lapidus
Mathematics , 2012,
Abstract: A spectral reformulation of the Riemann hypothesis was obtained in [LaMa2] by the second author and H. Maier in terms of an inverse spectral problem for fractal strings. This problem is related to the question "Can one hear the shape of a fractal drum?" and was shown in [LaMa2] to have a positive answer for fractal strings whose dimension is $c\in(0,1)-\{1/2}$ if and only if the Riemann hypothesis is true. Later on, the spectral operator was introduced heuristically by M. L. Lapidus and M. van Frankenhuijsen in their theory of complex fractal dimensions [La-vF2, La-vF3] as a map that sends the geometry of a fractal string onto its spectrum. We focus here on presenting the rigorous results obtained by the authors in [HerLa1] about the invertibility of the spectral operator. We show that given any $c\geq0$, the spectral operator $\mathfrak{a}=\mathfrak{a}_{c}$, now precisely defined as an unbounded normal operator acting in a Hilbert space $\mathbb{H}_{c}$, is `quasi-invertible' (i.e., its truncations are invertible) if and only if the Riemann zeta function $\zeta=\zeta(s)$ does not have any zeroes on the line $Re(s)=c$. It follows that the associated inverse spectral problem has a positive answer for all possible dimensions $c\in (0,1)$, other than the mid-fractal case when $c=1/2$, if and only if the Riemann hypothesis is true.
The Decimation Method for Laplacians on Fractals: Spectra and Complex Dynamics
Nishu Lal,Michel L. Lapidus
Mathematics , 2013,
Abstract: In this survey article, we investigate the spectral properties of fractal differential operators on self-similar fractals. In particular, we discuss the decimation method, which introduces a renormalization map whose dynamics describes the spectrum of the operator. In the case of the bounded Sierpinski gasket, the renormalization map is a polynomial of one variable on the complex plane. The decimation method has been generalized by C. Sabot to other fractals with blow-ups and the resulting associated renormalization map is then a multi-variable rational function on a complex projective space. Furthermore, the dynamics associated with the iteration of the renormalization map plays a key role in obtaining a suitable factorization of the spectral zeta function of fractal differential operators. In this context, we discuss the works of A. Teplyaev and of the authors regarding the examples of the bounded and unbounded Sierpinski gaskets as well as of fractal Sturm-Liouville differential operators on the half-line.
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