331 research outputs found
A thermoviscoplastic model with damage for simultaneous hot/cold forging analysis
A constitutive model is presented for simultaneous hot/cold forming processes of steels. The phenomenological material theory is based on an enhanced rheological model and accounts temperature dependently for nonlinear hardening, thermally activated recovery eïŹects, an improved description of energy storage and dissipation during plastic deformations, and damage evolution as well. A thermomechanically consistent treatment of dissipative heating due to inelastic deformations, recovery processes and damage mechanisms is applied. The constitutive model is implemented into a commercial FE-code. The material parameters of the eïŹective model response are identiïŹed for a low alloyed steel and validated by means of a simultaneous hot/cold forging process
On the Generalization of Uniaxial Thermoviscoplasticity with Damage to Finite Deformations Based on Enhanced Rheological Models
The enhanced concept of rheological models, as proposed in Bršocker and Matzenmiller (2013), is generalized systematically to finite deformations. The basic bodies are defined individually for large deformations, and a rheological network of thermoviscoplasticity is assembled, representing nonlinear isotropic and kinematic hardening as well as an improved description of energy storage in metal plasticity. The constitutive equations are deduced in an analogous procedure as for the uniaxial model in Bršocker and Matzenmiller (2013). Furthermore, damage evolution is additionally accounted for
Symmetric mixed states of qubits: local unitary stabilizers and entanglement classes
We classify, up to local unitary equivalence, local unitary stabilizer Lie
algebras for symmetric mixed states into six classes. These include the
stabilizer types of the Werner states, the GHZ state and its generalizations,
and Dicke states. For all but the zero algebra, we classify entanglement types
(local unitary equivalence classes) of symmetric mixed states that have those
stabilizers. We make use of the identification of symmetric density matrices
with polynomials in three variables with real coefficients and apply the
representation theory of SO(3) on this space of polynomials.Comment: 10 pages, 1 table, title change and minor clarifications for
published versio
The Semiclassical Limit for and Gauge Theory on the Torus
We prove that for and quantum gauge theory on a torus,
holonomy expectation values with respect to the Yang-Mills measure d\mu_T(\o)
=N_T^{-1}e^{-S_{YM}(\o)/T}[{\cal D}\o] converge, as , to
integrals with respect to a symplectic volume measure on the moduli
space of flat connections on the bundle. These moduli spaces and the symplectic
structures are described explicitly.Comment: 18 page
In vitro evidence for senescent multinucleated melanocytes as a source for tumor-initiating cells
Oncogenic signaling in melanocytes results in oncogene-induced senescence (OIS), a stable cell-cycle arrest frequently characterized by a bi- or multinuclear phenotype that is considered as a barrier to cancer progression. However, the long-sustained conviction that senescence is a truly irreversible process has recently been challenged. Still, it is not known whether cells driven into OIS can progress to cancer and thereby pose a potential threat. Here, we show that prolonged expression of the melanoma oncogene N-RAS61K in pigment cells overcomes OIS by triggering the emergence of tumor-initiating mononucleated stem-like cells from senescent cells. This progeny is dedifferentiated, highly proliferative, anoikis-resistant and induces fast growing, metastatic tumors. Our data describe that differentiated cells, which are driven into senescence by an oncogene, use this senescence state as trigger for tumor transformation, giving rise to highly aggressive tumor-initiating cells. These observations provide the first experimental in vitro evidence for the evasion of OIS on the cellular level and ensuing transformation
Non-negative Wigner functions in prime dimensions
According to a classical result due to Hudson, the Wigner function of a pure,
continuous variable quantum state is non-negative if and only if the state is
Gaussian. We have proven an analogous statement for finite-dimensional quantum
systems. In this context, the role of Gaussian states is taken on by stabilizer
states. The general results have been published in [D. Gross, J. Math. Phys.
47, 122107 (2006)]. For the case of systems of odd prime dimension, a greatly
simplified proof can be employed which still exhibits the main ideas. The
present paper gives a self-contained account of these methods.Comment: 5 pages. Special case of a result proved in quant-ph/0602001. The
proof is greatly simplified, making the general case more accessible. To
appear in Appl. Phys. B as part of the proceedings of the 2006 DPG Spring
Meeting (Quantum Optics and Photonics section
Connectivity properties of moment maps on based loop groups
For a compact, connected, simply-connected Lie group G, the loop group LG is
the infinite-dimensional Hilbert Lie group consisting of H^1-Sobolev maps
S^1-->G. The geometry of LG and its homogeneous spaces is related to
representation theory and has been extensively studied. The space of based
loops Omega(G) is an example of a homogeneous space of and has a natural
Hamiltonian T x S^1 action, where T is the maximal torus of G. We study the
moment map mu for this action, and in particular prove that its regular level
sets are connected. This result is as an infinite-dimensional analogue of a
theorem of Atiyah that states that the preimage of a moment map for a
Hamiltonian torus action on a compact symplectic manifold is connected. In the
finite-dimensional case, this connectivity result is used to prove that the
image of the moment map for a compact Hamiltonian T-space is convex. Thus our
theorem can also be viewed as a companion result to a theorem of Atiyah and
Pressley, which states that the image mu(Omega(G)) is convex. We also show that
for the energy functional E, which is the moment map for the S^1 rotation
action, each non-empty preimage is connected.Comment: This is the version published by Geometry & Topology on 28 October
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