Daniel F. Litim
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View article: Matter Spectral Functions from Quantum Gravity
Matter Spectral Functions from Quantum Gravity Open
We investigate Lorentzian quantum gravity coupled to a template matter sector with gauge fields, scalars and fermions. In the absence of quantised gravity, the matter sector by itself is renormalisable, but UV-incomplete. Provided quantum …
View article: Fermions and the Renormalisation Group at Large N
Fermions and the Renormalisation Group at Large N Open
We investigate fermionic quantum field theories using functional renormalisation. In the limit of many fermion flavours $N$, we demonstrate that theories have exact solutions for their quantum effective actions given by quasi-local interac…
View article: Dilaton Physics from Asymptotic Freedom
Dilaton Physics from Asymptotic Freedom Open
The dilaton is investigated from first principles in an asymptotically free Gross-Neveu-Yukawa theory in three dimensions. In the limit of many fermion flavours, the theory features a finite line of strongly interacting fixed points with c…
View article: Vacuum stability in the Standard Model and beyond
Vacuum stability in the Standard Model and beyond Open
We revisit the stability of the Standard Model vacuum and investigate its quantum effective potential using the highest available orders in perturbation theory and the most accurate determination of input parameters to date. We observe tha…
View article: Old and new anomalies in charm
Old and new anomalies in charm Open
View article: Fermion mass generation without symmetry breaking
Fermion mass generation without symmetry breaking Open
We study the generation of fermion mass in a context where interactions break a discrete chiral symmetry. Then, fermion mass is not protected by a symmetry, no symmetry is broken by the generation of mass, and a vanishing mass no longer en…
View article: Scale symmetry breaking and generation of mass at quantum critical points
Scale symmetry breaking and generation of mass at quantum critical points Open
A bstract We study an asymptotically free theory of N relativistic Dirac fermions and a real scalar field coupled by Yukawa and scalar self-interactions in three dimensions using functional renormalisation. In the limit of many fermion fla…
View article: Fermion Mass Generation without Symmetry Breaking
Fermion Mass Generation without Symmetry Breaking Open
We study the generation of fermion mass in a context where interactions break a discrete chiral symmetry. Then, fermion mass is not protected by a symmetry, no symmetry is broken by the generation of mass, and a vanishing mass no longer en…
View article: Vacuum Stability in the Standard Model and Beyond
Vacuum Stability in the Standard Model and Beyond Open
We revisit the stability of the Standard Model vacuum, and investigate its quantum effective potential using the highest available orders in perturbation theory and the most accurate determination of input parameters to date. We observe th…
View article: Scale symmetry breaking and generation of mass at quantum critical points
Scale symmetry breaking and generation of mass at quantum critical points Open
We study an asymptotically free theory of $N$ relativistic Dirac fermions and a real scalar field coupled by Yukawa and scalar self-interactions in three dimensions using functional renormalisation. In the limit of many fermion flavours, t…
View article: Asymptotic safety guaranteed at four-loop order
Asymptotic safety guaranteed at four-loop order Open
We investigate a family of four-dimensional quantum field theories with weakly interacting ultraviolet fixed points up to four-loop order in perturbation theory. Key new ingredients are the three-loop gauge contributions to quartic scalar …
View article: Old and new anomalies in charm
Old and new anomalies in charm Open
The recent LHCb determination of the direct CP asymmetries in the decays $D^0 \to K^+ K^-, π^+ π^-$ hints at a sizeable breaking of two approximate symmetries of the SM: CP and U-spin. We aim at explaining the data with BSM physics and use…
View article: Why is zero spatial curvature special?
Why is zero spatial curvature special? Open
Evidence for almost spatial flatness of the Universe has been provided from several observational probes, including the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) from galaxy clustering data. However, other th…
View article: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>U</mml:mi></mml:math>-spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math> anomaly in charm
-spin- anomaly in charm Open
The recent measurement of the CP-asymmetry in the decay $D \to K^+ K^-$ by LHCb, combined with $\Delta A_{\text{CP}}$, evidences a sizable CP-asymmetry in $D \to \pi^+ \pi^-$ decays, which requires a dynamical enhancement of standard model…
View article: Asymptotic Safety Guaranteed at Four Loop
Asymptotic Safety Guaranteed at Four Loop Open
We investigate a family of four-dimensional quantum field theories with weakly interacting ultraviolet fixed points up to four loop order in perturbation theory. Key new ingredients are the three loop gauge contributions to quartic scalar …
View article: Fixed points of quantum gravity and the dimensionality of the UV critical surface
Fixed points of quantum gravity and the dimensionality of the UV critical surface Open
We study quantum effects in higher curvature extensions of general relativity using the functional renormalisation group. New flow equations are derived for general classes of models involving Ricci scalar, Ricci tensor, and Riemann tensor…
View article: Vacuum Stability as a Guide for Model Building
Vacuum Stability as a Guide for Model Building Open
We explain why vector-like fermions are natural candidates to lift the Standard Model vacuum instability. Results are further discussed from the viewpoint of criticality. Several models allow for vector-like quarks and leptons in the TeV-r…
View article: Line of Fixed Points in Gross-Neveu Theories
Line of Fixed Points in Gross-Neveu Theories Open
In the limit of many fermion flavors it is demonstrated that the sextic Gross-Neveu theory in three dimensions displays a line of interacting UV fixed points, characterized by an exactly marginal sextic interaction. We determine the confor…
View article: Critical fermions with spontaneously broken scale symmetry
Critical fermions with spontaneously broken scale symmetry Open
We study relativistic fermions in three euclidean dimensions with four- and six-fermion interactions of the Gross-Neveu type. In the limit of many fermion flavors, and besides the isolated free fixed point, the theory displays a line of in…
View article: Lorentzian Quantum Gravity and the Graviton Spectral Function
Lorentzian Quantum Gravity and the Graviton Spectral Function Open
We present the first direct and nonperturbative computation of the graviton spectral function in quantum gravity. This is achieved with the help of a novel Lorentzian renormalization group approach, combined with a spectral representation …
View article: Spectral functions of gauge theories with Banks-Zaks fixed points
Spectral functions of gauge theories with Banks-Zaks fixed points Open
We investigate spectral functions of matter-gauge theories that are asymptotically free in the ultraviolet and display a Banks-Zaks conformal fixed point in the infrared. Using perturbation theory, Callan-Symanzik resummations, and UV-IR c…
View article: Critical Fermions with Spontaneously Broken Scale Symmetry
Critical Fermions with Spontaneously Broken Scale Symmetry Open
We study relativistic fermions in three euclidean dimensions with four- and six-fermion interactions of the Gross-Neveu type. In the limit of many fermion flavors, and besides the isolated free fixed point, the theory displays a line of in…
View article: Portals into Higgs vacuum stability
Portals into Higgs vacuum stability Open
We address the notorious metastability of the standard model (SM) and promote it to a model building task: What are the new ingredients required to stabilize the SM up to the Planck scale without encountering subplanckian Landau poles? Usi…
View article: Functional renormalization for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>f</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mi>R</mml:mi><mml:mrow><mml:mi>μ</mml:mi><mml:mi>ν</mml:mi><mml:mi>ρ</mml:mi><mml:mi>σ</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">)</mml:mo></mml:math> quantum gravity
Functional renormalization for quantum gravity Open
We derive new functional renormalization group flows for quantum gravity, in any dimension. The key new achievement is that the equations apply for any theory of gravity whose underlying $\mathrm{Lagrangian}\ensuremath{\sim}f({R}_{\ensurem…
View article: Two is better than one: The U-spin-CP anomaly in charm
Two is better than one: The U-spin-CP anomaly in charm Open
The recent measurement of the CP-asymmetry in the decay $D \to K^+ K^-$ by LHCb, combined with $ΔA_{\text{CP}}$, evidences a sizable CP-asymmetry in $D \to π^+ π^-$ decays, which requires a dynamical enhancement of standard model higher-or…
View article: Fixed points in supersymmetric extensions of the standard model
Fixed points in supersymmetric extensions of the standard model Open
View article: Why is zero spatial curvature special?
Why is zero spatial curvature special? Open
Evidence for almost spatial flatness of the Universe has been provided from several observational probes, including the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO) from galaxy clustering data. However, other th…
View article: Spectral Functions of Gauge Theories with Banks-Zaks Fixed Points
Spectral Functions of Gauge Theories with Banks-Zaks Fixed Points Open
We investigate spectral functions of matter-gauge theories that are asymptotically free in the ultraviolet and display a Banks-Zaks conformal fixed point in the infrared. Using perturbation theory, Callan-Symanzik resummations, and UV-IR c…
View article: Line of Fixed Points in Gross-Neveu Theories
Line of Fixed Points in Gross-Neveu Theories Open
In the limit of many fermion flavors it is demonstrated that the sextic Gross-Neveu theory in three dimensions displays a line of interacting UV fixed points, characterised by an exactly marginal sextic interaction. We determine the confor…
View article: Portals into Higgs vacuum stability
Portals into Higgs vacuum stability Open
We address the notorious metastability of the standard model (SM) and promote it to a model building task: What are the new ingredients required to stabilize the SM up to the Planck scale without encountering subplanckian Landau poles? Usi…