Fredrik Sandin

Prof. Dr. Fredrik Sandin


Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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30 September 2005 in Physical Review D
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David BlaschkeDavid Blaschke
David Blaschke
SFS. Fredriksson
S. Fredriksson
HGH. Grigorian
H. Grigorian
AÖA. M. Öztaş
A. M. Öztaş
FSFredrik Sandin
Fredrik Sandin
The phase diagram of three-flavor quark matter under compact star constraints is investigated within a Nambu–Jona-Lasinio model. Global color and electric charge neutrality is imposed for β-equilibrated superconducting quark matter. The constituent quark masses and the diquark condensates are determined self-consistently in the plane of temperature and quark chemical potential. Both strong and intermediate diquark coupling strengths are considered. We show that in both cases, gapless superconducting phases do not occur at temperatures relevant for compact star evolution, i.e., below T∼50  MeV. The stability and structure of isothermal quark star configurations are evaluated. For intermediate coupling, quark stars are composed of a mixed phase of normal (NQ) and two-flavor superconducting (2SC) quark matter up to a maximum mass of 1.21  M⊙. At higher central densities, a phase transition to the three-flavor color flavor locked (CFL) phase occurs and the configurations become unstable. For the strong diquark coupling we find stable stars in the 2SC phase, with masses up to 1.33  M⊙. A second family of more compact configurations (twins) with a CFL quark matter core and a 2SC shell is also found to be stable. The twins have masses in the range 1.30…1.33  M⊙. We consider also hot isothermal configurations at temperature T=40  MeV. When the hot maximum mass configuration cools down, due to emission of photons and neutrinos, a mass defect of 0.1  M⊙ occurs and two final state configurations are possible.

1 January 2019 in Automation in Construction
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Journal Article
Open access
SDSiddharth Dadhich
Siddharth Dadhich
FSFredrik Sandin
Fredrik Sandin
UBUlf Bodin
Ulf Bodin
UAUlf Andersson
Ulf Andersson
TMTorbjörn Martinsson
Torbjörn Martinsson

13 June 2007 in Physical Review D
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FSFredrik Sandin
Fredrik Sandin
David BlaschkeDavid Blaschke
David Blaschke
We study the effect of neutrino trapping in newborn quark stars within a three-flavor Nambu–Jona-Lasinio model with self-consistently calculated quark masses. The phase diagrams and equations of state for charge neutral quark matter in β equilibrium are presented, with and without trapped neutrinos. The compact star sequences for different neutrino untrapping scenarios are investigated and the energy release due to neutrino untrapping is found to be of the order of 1053  erg. We find that hot quark stars characterized, e.g., by an entropy per baryon of 1–2 and a lepton fraction of 0.4, as models for the cores of newborn protoneutron stars, are in the two-flavor color superconducting state. High temperatures and/or neutrino chemical potentials disfavor configurations with a color-flavor-locked phase. Stable quark star solutions with color-flavor-locked cores exist only at low temperatures and neutrino chemical potentials.

3 May 2024 in Sensors
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JNJacob Nilsson
Jacob Nilsson
Saleha JavedSaleha Javed
Saleha Javed
KAKim Albertsson
Kim Albertsson
Jerker DelsingJerker Delsing
Jerker Delsing
Marcus LiwickiMarcus Liwicki
Marcus Liwicki
FSFredrik Sandin
Fredrik Sandin
Interoperability is a central problem in digitization and System of Systems (SoS) engineering, which concerns the capacity of systems to exchange information and cooperate. The task to dynamically establish interoperability between heterogeneous cyber-physical systems (CPSs) at run-time is a challenging problem. Different aspects of the interoperability problem have been studied in fields such as SoS, neural translation, and agent-based systems, but there are no unifying solutions beyond domain-specific standardization efforts. The problem is complicated by the uncertain and variable relations between physical processes and human-centric symbols, which result from, e.g., latent physical degrees of freedom, maintenance, re-configurations, and software updates. Therefore, we surveyed the literature for concepts and methods needed to automatically establish SoSs with purposeful CPS communication, focusing on machine learning and connecting approaches that are not integrated in the present literature. Here, we summarize recent developments relevant to the dynamic interoperability problem, such as representation learning for ontology alignment and inference on heterogeneous linked data; neural networks for transcoding of text and code; concept learning-based reasoning; and emergent communication. We find that there has been a recent interest in deep learning approaches to establishing communication under different assumptions about the environment, language, and nature of the communicating entities. Furthermore, we present examples of architectures and discuss open problems associated with artificial intelligence (AI)-enabled solutions in relation to SoS interoperability requirements. Although these developments open new avenues for research, there are still no examples that bridge the concepts necessary to establish dynamic interoperability in complex SoSs, and realistic testbeds are needed.

28 February 2020 in Frontiers in Neuroscience
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FSFredrik Sandin
Fredrik Sandin
MNMattias Nilsson
Mattias Nilsson
Spiking neural networks are well-suited for spatiotemporal feature detection and learning, and naturally involve dynamic delay mechanisms in the synapses, dendrites, and axons. Dedicated delay neurons and axonal delay circuits have been considered when implementing such pattern recognition networks in dynamic neuromorphic processors. Inspired by an auditory feature detection circuit in crickets, featuring a delayed excitation by post-inhibitory rebound, we investigate disynaptic delay elements formed by inhibitory–excitatory pairs of dynamic synapses. We configured such disynaptic delay elements in the DYNAP-SE neuromorphic processor and characterized the distribution of delayed excitations resulting from device mismatch. Interestingly, we found that the disynaptic delay elements can be configured such that the timing and magnitude of the delayed excitation depend mainly on the efficacy of the inhibitory and excitatory synapses, respectively, and that a neuron with multiple delay elements can be tuned to respond selectively to a specific pattern. Furthermore, we present a network with one disynaptic delay element that mimics the auditory feature detection circuit of crickets, and we demonstrate how varying synaptic weights, input noise and processor temperature affect the circuit. Dynamic delay elements of this kind open up for synapse level temporal feature tuning with configurable delays of up to 100 ms.

13 January 2025 in IEEE Access
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Journal Article
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Tommaso DorigoTommaso Dorigo
Tommaso Dorigo
GBGary D. Brown
Gary D. Brown
CCCarlo Casonato
Carlo Casonato
Artemi CerdaArtemi Cerda
Artemi Cerda
JCJoseph Ciarrochi
Joseph Ciarrochi
NYNiloufar Yazdanpanah
Niloufar Yazdanpanah
The recent rise in relevance and diffusion of Artificial Intelligence (AI)-based systems and the increasing number and power of applications of AI methods invites a profound reflection on the impact of these innovative systems on scientific research and society at large. The Universal Scientific Education and Research Network (USERN), an organization that promotes initiatives to support interdisciplinary science and education across borders and actively works to improve science policy, collects here the vision of its Advisory Board members, together with a selection of AI experts, to summarize how we see developments in this exciting technology impacting science and society in the foreseeable future. In this review, we first attempt to establish clear definitions of intelligence and consciousness, then provide an overviewof AI’s state of the art and its applications. A discussion of the implications, opportunities, and liabilities of the diffusion of AI for research in a few representative fields of science follows this. Finally, we address the potential risks of AI to modern society, suggest strategies for mitigating those risks, and present our conclusions and recommendations.