75,017 research outputs found
Domains with a continuous exhaustion in weakly complete surfaces
No full textIn previous works, Tomassini and the authors studied and classified complex surfaces admitting a real-analytic plurisubharmonic exhaustion function; let X be such a surface and D⊆ X a domain admitting a continuous plurisubharmonic exhaustion function: what can be said about the geometry of D? If the exhaustion of D is assumed to be smooth, the second author already answered this question; however, the continuous case is more difficult and requires different methods. In the present paper, we address such question by studying the local maximum sets contained in D and their interplay with the complex geometric structure of X; we conclude that, if D is not a modification of a Stein space, then it shares the same geometric features of X
The Benefits of Being Economics Professor A (and not Z)
No full textAlphabetic name ordering on multi-authored academic papers, which is the convention in the economics discipline and various other disciplines, is to the advantage of people whose last name initials are placed early in the alphabet. As it turns out, Professor A, who has been a first author more often than Professor Z, will have published more articles and experienced afaster growth rate over the course of her career as a result of reputation and visibility. Moreover, authors know that name ordering matters and indeed take ordering seriously: Several characteristics of an author group composition determine the decision to deviate from the default alphabetic name order to a significant extent.performance measurement, incentives, economists, name ordering
Final word on Jersey Dutch
No full textIn this article, William Z. Shetter compares and contrasts the dialects that developed between different Dutch colonies in the New World. He explores in-depth the nuances of Jersey Dutch, and provides theories to explain how Dutch and colonial languages blended. The article is reprinted from American Speech, December 1958, Volum XXXIII, No. 4
Estudo das propriedades de galáxias compactas quiescentes massivas em z ~ 0
No full textEm z ≈ 0, observamos diferentes tipos de galáxias, o que pode sugerir que existem diversos caminhos evolutivos para elas. Uma classe de galáxias que destacamos são as galáxias compactas massivas (MCGs - Massive Compact Galaxies), definidas neste trabalho como galáxias quiescentes, massivas, pequenas e com altos valores de dispersão de velocidades quando comparadas com galáxias quiescentes típicas em z ≈ 0. As MCGs são raras em z ≈ 0, e muitas questões permanecem em aberto sobre a formação e evolução desse tipo de objeto. Para começar a entender a história das MCGs, nesta tese investigamos as propriedades das suas populações estelares (idade, metalicidade estelar e [α/Fe]) e suas propriedades estruturais (bojo, disco, envelope). Exploramos as propriedades das populações estelares a partir da análise de índices espectrais e da síntese espectral de 1 858 MCGs em z ≈ 0, disponíveis no levantamento Sloan Digital Sky Survey (SDSS). Comparamos as propriedades das populações estelares das MCGs a dispersão de velocidade efetiva (σe) fixa com as propriedades de galáxias típicas em z ≈ 0 (CSGs - Control Sample Galaxies). No regime de baixo σe (σe ≲ 225 km/s), encontramos que as MCGs são mais velhas, menos metálicas e mais α-enhanced que as CSGs a σe fixo. No regime de alto σe (σe ≳ 225 km/s), a idade e [α/Fe] não apresentam diferenças estatisticamente significativas, mas as MCGs continuam sendo menos metálicas que a amostra de controle. Verificamos também que MCGs em diferentes ambientes apresentam as mesmas propriedades das populações estelares, indicando que o ambiente não afeta o caminho evolutivo dessas galáxias. Os resultados que encontramos para a metalicidade estelar podem ter origem na variação da função de massa inicial, em variações na concentração de matéria escura na região central ou no gradiente de metalicidade estelar. Além disso, os resultados para a idade e [α/Fe] sugerem que as diferenças descritas no regime de baixo σe são compatíveis com o cenário de progenitor bias para as CSGs. Também comparamos nossa amostra com outros grupos de galáxias compactas e encontramos diferenças importantes na idade e na metalicidade estelar, sugerindo uma diversidade nos caminhos evolutivos desse tipo de galáxia. Para investigar as propriedades estruturais das MCGs, selecionamos 246 MCGs na banda r presentes no levantamento Hyper Suprime-Cam Subaru Strategic Program (HSCSSP) em z ≈ 0. Comparamos os resultados com uma amostra controle de galáxias quiescentes de tamanho médio (CSGs), selecionadas para terem massa estelar, taxa de formação estelar, redshift e cor g–i semelhantes às das MCGs. Apesar dessas semelhanças globais, as amostras apresentam diferenças estruturais marcantes. Nossos resultados indicam que as MCGs são compostas por duas ou três componentes Sérsic: um bojo tipicamente não resolvido com Re ≲ 1 kpc; um disco compacto, com Re ≈ 2 − 3 kpc; e um envelope com Re ≈ 5.3 kpc. Em contraste, as CSGs são bem descritas por duas componentes Sérsic, correspondentes a um bojo com Re ≈ 1 − 2 kpc e a um disco com Re ≈ 5 kpc. Não identificamos a presença de envelopes em CSGs; além disso, uma fração dessas galáxias apresenta barras e anéis, estruturas que não encontramos nas MCGs. Na relação massa estelar-tamanho, as MCGs e parte das CSGs retornam bojos compactos compatíıveis com resultados em alto redshift. Para os discos, as CSGs possuem discos típicos do Universo local, enquanto as MCGs retornam discos compactos que também se assemelham aos resultados em alto redshift. Por fim, sugerimos que a componente envelope nas MCGs, também identificada em galáxias relíquias, pode ser um halo estelar compacto ou ainda um disco espesso. Portanto, observa-se que as MCGs, embora pequenas, podem apresentar múltiplas componentes estruturais que, potencialmente, foram formados em redshifts mais altos.At z ≈ 0, we observe different types of galaxies, which suggest diversity of path formation and evolution for them. We highlight a class of massive compact galaxies (MCGs). In this work, we define MCGs as quiescent, massive, small, and with higher velocity dispersions in comparison with typical quiescent galaxies at z ≈ 0. MCGs are rare at z ≈ 0, and there are several unanswered questions about their formation and evolution. To begin understanding the history of MCGs, in this thesis we investigate the properties of their stellar populations (age, stellar metallicity, and [α/Fe]) as well as their structural properties (bulge, disk, envelope). We explore the stellar population properties based on the analysis of spectral indices and full spectral fitting for 1 858 MCGs at z ≈ 0, available in the Sloan Digital Sky Survey (SDSS). We compare the stellar population properties of MCGs at fixed velocity dispersion (σe) with those of typical galaxies at z ≈ 0 (CSGs - Control Sample Galaxies). In the low σe regime (σe ≲ 225 km/s), we find that MCGs are older, more metal-poor, and more α-enhanced than CSGs at fixed σe. In the high σe regime (σe ≳ 225 km/s), age and [α/Fe] do not show statistically significant differences, but MCGs remain more metal-poor than the control sample. We also find that MCGs in different environments exhibit similar stellar population properties, suggesting that environment does not affect the evolutionary path of these galaxies. The stellar metallicity results we find may originate from variations in the initial mass function, differences in the concentration of dark matter in the central region, or from stellar metallicity gradients. Additionally, the results for age and [α/Fe] suggest that the differences observed in the low-σe regime are consistent with a progenitor bias scenario for the CSGs. We also compared our sample with other groups of compact galaxies and found significant differences in both age and stellar metallicity, suggesting a diversity in the evolutionary pathways of this type of galaxy. To investigate the structural properties of MCGs, we selected 246 MCGs in the r-band from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) at z ≈ 0. We compared the results with a control sample of quiescent galaxies with average sizes (CSGs), selected to have stellar mass, star formation rate, redshift, and g-i color similar to those of MCGs. Despite these global similarities, the samples show marked structural differences. Our results indicate that MCGs are composed of two or three S´ersic components: a typically unresolved bulge with Re ≲ 1 kpc; a compact disk with Re ≈ 2 − 3 kpc; and a envelope with Re ≈ 5.3 kpc. In contrast, CSGs are well described by two S´ersic components, corresponding to a bulge with Re ≈ 1 − 2 kpc and a disk with Re ≈ 5 kpc. We do not identify the presence of envelopes in CSGs; furthermore, a fraction of these galaxies show bars and rings, structures that we do not find in MCGs. In the stellar mass–size relation, both MCGs and a subset of CSGs show compact bulges consistent with results at high redshift. Regarding disks, CSGs host typical local Universe disks, while MCGs show compact disks that also resemble those seen at high redshift. Finally, we suggest that the envelope component in MCGs, also identified in relic galaxies, may correspond to a compact stellar halo or a thick disk. Therefore, although MCGs are small, they can exhibit multiple structural components that were potentially formed at higher redshifts
Analytic perturbation of the Taylor spectrum
No full textLet
T
1
(
z
)
,
…
,
T
m
(
z
)
{T_1}(z), \ldots ,{T_m}(z)
,
z
∈
G
⊂
C
k
z \in G \subset {{\mathbf {C}}^k}
, be analytic families of bounded operators in a complex Banach space
X
X
, such that for each
z
∈
G
z \in G
the operators
T
i
(
z
)
{T_i}(z)
and
T
j
(
z
)
{T_j}(z)
,
i
,
j
=
1
,
…
,
n
i,j = 1, \ldots ,n
, commute. Main result: If
K
(
z
)
K(z)
denotes the Taylor spectrum of the tuple
(
T
1
(
z
)
,
…
,
T
m
(
z
)
)
({T_1}(z), \ldots ,{T_m}(z))
, then the set-valued function
K
:
G
→
2
C
m
K:G \to {2^{{\mathbf {C}}m}}
is analytic. Analyticity of such set-valued functions is defined here by a simultaneous local maximum property of
k
k
-tuples of complex polynomials on the graph of
K
K
.</p
An analytic set-valued selection and its applications to the corona theorem, to polynomial hulls and joint spectra
No full textIt is shown that for every annulus
P
=
{
z
∈
C
n
:
δ
>
|
z
|
>
r
}
P = \{ z \in {{\mathbf {C}}^n}:\delta > |z| > r\}
,
δ
>
0
\delta > 0
, there exists a set-valued correspondence
z
→
K
(
z
)
:
P
→
2
C
n
z \to K(z):P \to {2^{{{\mathbf {C}}^n}}}
, whose graph is a bounded relatively closed subset of the manifold
{
(
z
,
w
)
∈
P
×
C
n
:
z
1
w
1
+
⋯
+
z
n
w
n
=
1
}
\{ (z,w) \in P \times {{\mathbf {C}}^n}:{z_1}{w_1} + \cdots + {z_n}{w_n} = 1\}
which can be covered by
n
n
-dimensional analytic manifolds. The analytic set-valued selection
K
K
obtained thereby is then applied to several problems in complex analysis and spectral theory which involve solving the equation
a
1
x
1
+
⋯
+
a
n
x
n
=
y
{a_1}{x_1} + \cdots + {a_n}{x_n} = y
. For example, an elementary proof is given of the following special case of a theorem due to Oka: every bounded pseudoconvex domain in
C
2
{{\mathbf {C}}^2}
is a domain of holomorphy.</p
Holomorphic motions and polynomial hulls
No full textA holomorphic motion of
E
⊂
C
E \subset \mathbb {C}
over the unit disc
D
D
is a map
f
:
D
×
C
→
C
f:D \times \mathbb {C} \to \mathbb {C}
such that
f
(
0
,
w
)
=
w
,
w
∈
E
f(0,w) = w,w \in E
, the function
f
(
z
,
w
)
=
f
z
(
w
)
f(z,w) = {f_z}(w)
is holomorphic in
z
z
, and
f
z
:
E
→
C
{f_z}:E \to \mathbb {C}
is an injection for all
z
∈
D
z \in D
. Answering a question posed by Sullivan and Thurston [13], we show that every such
f
f
can be extended to a holomorphic motion
F
:
D
×
C
→
C
F:D \times \mathbb {C} \to \mathbb {C}
. As a main step a "holomorphic axiom of choice" is obtained (concerning selections from the sets
C
∖
f
z
(
E
)
,
z
∈
D
)
\mathbb {C}\backslash {f_z}(E),z \in D)
. The proof uses earlier results on the existence of analytic discs in the polynomial hulls of some subsets of
C
2
{\mathbb {C}^2}
.</p
Operators with closed ranges in spaces of analytic vector-valued functions
No full textAbstractLet A+(P, X) denote the Banach space of X-valued analytic functions on a polydisc P ⊂ Cn with absolutely convergent Taylor series. Main result: Let T(z) be an analytic family of bounded operators from X to Y. Assume that all T(z) have closed ranges depending continuously on z. Then the “multiplication” operator T̃: A+(P, X) → A+(P, Y), induced by T(z), has closed range. (Equivalent characterization of such operator-valued functions are given.) This result makes it possible to construct Banach spaces of sections of some infinite-dimensional analytic sheaves. The construction is functorial and has certain exactness properties which help to study analytic perturbations of the joint spectrum of J. L. Taylor
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Statistics of the subgrid scales after the shock-turbulence interaction
No full textThe interaction of a normal shock with isotropic turbulence (IT) represents a basic problem for studying some of the phenomena associated with high speed flows, such as hypersonic flight, supersonic combustion and Inertial Confinement Fusion (ICF). In general, in practical applications, the shock width is much smaller than the turbulence scales and the upstream turbulent Mach number is modest. In this case, recent high resolution shock-resolved Direct Numerical Simulations (DNS) (Ryu and Livescu, J. Fluid Mech., 756, R1, 2014) show that the interaction can be described by the Linear Interaction Approximation (LIA). By using LIA to alleviate the need to solve the shock, DNS post-shock data can be generated at much higher Reynolds numbers than previously possible. Here, such results with Taylor Reynolds number around are used to investigate the properties of the subgrid scales (SGS). In particular, it is shown that the shock interaction decreases the asymmetry of the SGS dissipation PDF as the shock Mach number increases, with a significant enhancement in size of the regions and magnitude of backscatter
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