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Description
Intro to Covariant Quantum Gravity & Asymptotic SafetyThis book covers recent developments in the covariant formulation of quantum gravity. Developed in the 1960s by Feynman and DeWitt, by the 1980s this approach seemed to lead nowhere due to perturbative non renormalizability. The possibility of non perturbative renormalizability or "asymptotic safety", originally suggested by Weinberg but largely ignored for two decades, was revived towards the end of the century by technical progress in the field of
This book covers recent developments in the covariant formulation of quantum gravity. Developed in the 1960s by Feynman and DeWitt, by the 1980s this approach seemed to lead nowhere due to perturbative non-renormalizability. The possibility of non-perturbative renormalizability or "asymptotic safety", originally suggested by Weinberg but largely ignored for two decades, was revived towards the end of the century by technical progress in the field of the renormalization group. It is now a very active field of research, providing an alternative to other approaches to quantum gravity.
Written by one of the early contributors to this subject, this book provides a gentle introduction to the relevant ideas and calculational techniques. Several explicit calculations gradually bring the reader close to the current frontier of research. The main difficulties and present lines of development are also outlined.
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4.5 ★★★★★
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Product Reviews
★★★★★ 4
Quite Good, but maybe lacking a few inputs, Optical Audio and AM radio
Style: Stereo Receiver, Configuration: Receiver
Very basic, but seems to be the usual good quality Sony product. I bought this when my decades-old SOny receiver finally bit the dust.
This receiver, at a decent price is a LOT more basic than my decades-old earlier receiver. That receiver had multiple inputs-many which I didn't use but were there for audiophiles all the same. Things like inputs for DAT, inputs for MD audio. analog videos in and out, Super video in and out, Component video, standard cassette deck, phono, component video (multiple), DVD in and out, component video, and more audio channel options I can't even remember. And as old as this receiver was it actually had Optical audio as well! I REALLY wanted to replace that old receiver with the exact same thing. albeit the modern model but that doesn't exist.
SO I bought this one.
Take a look and you'll see very few inputs, but oddly it had all the ones I actually needed for my old set-up-with NO extras though. I'm kind of shocked that this receiver doesn't even have the Optical audio which is kind of a standard now for modern TVs and I had to actually buy a cheap little 'converter box' which takes the optical cable and converts the digital audio into the standard RCA analog audio and I plug that into one of the available inputs in the receiver so that I can play my TV sound through the receiver/stereo system. I'm still kind of shocked that this receiver doesn't have that Optical, that would be the first thing i'd add to really make this a bargain and much more desirable.
So I had to have a receiver for my old cassette deck, phono, etc. and standard CD player as well as DVD/Blu Ray audio sound (as concert DVDs don't sound too good on the standard speakers which come with modern TVs. So i've used EVRY input in this new unit and I really couldn't have bought it if it had a single less input.
So in addition to having an input for Optical audio the other thing I wished it had was a receiver for AM radio, even if AM isn't too popular anymore.
So maybe the lack of the Optical audio, additional inputs for other sources and no AM radio is the reason why this receiver is so reasonably priced, but well, i'm happy with it all the same.
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Reviewed in the United States on April 27, 2026
★★★★★ 5
Great product
Style: Stereo Receiver, Configuration: Receiver
This is a great basic receiver. It's very easy to understand, setup and operate. This receiver sounds excellent and includes Bluetooth so I can stream Apple Music and Spotify to the receiver. My only negative comments would be that the speaker connections are the spring-loaded terminals which require thin gauge speaker wires or Flex Pin Banana Plugs. Also, you should be aware the FM Antenna (provided) is a wire antenna utilizing a strange plug-in adapter. It was perfectly adequate for what I needed however I think it could be an issue if you were in a remote area that required a mast antenna.
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Reviewed in the United States on April 9, 2026
★★★★★ 5
Shockingly Great: Do Not Be Skeptical Of The Ultra Low Price
Style: Stereo Receiver, Configuration: Receiver
Do not allow the extremely low price on this Sony STRDH 190 stereo receiver to in any way prejudice you against considering it as a wonderful entry-level stereo receiver. I have purchased thousands of products on Amazon over the past 25 years, and I cannot think of any item that pleasantly surprised me more profoundly than this one. I also purchased the matching (style) Sony turntable PS-LX310BT which works perfectly with the STRDH 190 receiver.
Sony's lowest priced receiver now sells for the astounding bargain price of only around $200, though I caught it on sale for closer to $150... and as impossible as this is the believe, it has in recent years gone on sale for as little as $99(!) I have no idea how Sony makes a profit at these price levels.
Now I know, most people would think, "there is just no way a $200 receiver is high quality"... but I am telling you, that is dead wrong in this case, and you should prepare to be blown away by what you get at this crazy low price point.
This is NOT a no frills unit. It is feature packed.
It has connections for TWO PAIR (four total) speakers, and PLENTY of clean no-distortion power to drive all four speakers to loud and clear volume levels. It also has an A/B speaker switch to play through speaker set A, or speaker set B, or all four speakers at once.
It has a phono stage pre-amp which is actually very good. Seriously, it is much better than the phono stage pre-amp built into my Emotiva integrated amp for which I paid $1,000. It plays vinyl loud with no distortion. You will NOT need an external phono pre-amp.
It has excellent Bluetooth wireless connectivity built in... no trouble getting it to instantly recognized sources and play them perfectly. You can play all the music on your iPhone or other digital device, wirelessly.
It has a huge allotment of extra connections, ... a whopping FOUR inputs... so you can also hook up a CD player, and another external device of your choice, and another one after that, and another one after that! (WOW). And that's is not counting your PHONO input which is actually a fifth input connection. Astounding accommodation of external sources at this (or almost any) price point.
If you are a dinosaur who listens to FM ... it's got an FM receiver with 30 station presets, and an output to hook up a proper external FM antenna, and a long-wire FM antenna is included in the package
Sony says the "HiRes" audio produced by this unit is "superior to CD quality"... though I am not sure how to measure that claim, especially if the extrnal source you are using is a CD player.
It comes with a very high quality remote control, with real buttons, and many features.
You can actually program each of your external sources to appear in the illuminated display as the specific names you want, rather than a generic default source name like "CD".
The low price may raise an eyebrow, and the fairly light weight (much heavier on one side than on the other curiously) nature of the unit may also cause doubt... but only until you set it up and start listening, and your jaw drops.
I would put this sub-$200 receiver up against any receiver on the market priced under $800, (and probably several of them priced at twice that much!) and I believe you will not be disappointed in the sound quality of Sony's entry-level unit. You certainly will NEVER find another receiver anywhere near this price point with so many features and inputs... all of which work flawlessly.
This is the greatest bargain in the world of affordably-priced HiFi equipment.
It is easily worth multiple times the asking price.
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Reviewed in the United States on May 18, 2025
★★★★★ 5
Overall Excellent - Thorough Review - READ ME
Style: Stereo Receiver, Configuration: Receiver
I'm not an audiophile per se, but I do have elevated listening preferences. I enjoy finding the value in devices, and system configs. So that's the reason I tried this more budget-friendly receiver.
Aesthetics: The look is very sleek and modern, which is great but sometimes I miss the nostalgia of more knobs. There is no base/treble knob and most everything is controlled by remote. That's fine I suppose, just be aware. The volume knob is very large and traditional which I love, but is also very stiff and not buttery smooth like you might expect. Perhaps that will break-in.
Sound Quality: Wow, this sounds incredible. There is definitely a DSP happening that is noticeably awesome. It's referred to by Sony as Pure Direct. If you want to by-pass this, you can, but you'll hear right away the difference is major. I'm using simple Klipsch bookshelf speakers, and my expectations are surpassed on how much they come to life with bright and rich sound. Definitely a nice pairing for those shopping for speakers along with this unit. Overall the SQ is gonna be tough to beat without spending exponentially more.
Remote: The remote is nice, sleek, and has what you need to quickly access. No complaints there.
Installation: Takes minutes, super easy. Didn't follow any instructions due to my general confidence hooking up home audio gear.
Overall: I highly recommend this one, and I'm picky. Initially, I fully expected to return this receiver, but plan to keep it. The only thing that may change my mind, is if I miss the nostalgia... then I'll have to go vintage. But no way a vintage receiver will sound this good. Props to Sony. Well done :)
A+
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Reviewed in the United States on January 18, 2024
★★★★★ 5
Nice amplifier for the cost.
Style: Stereo Receiver, Configuration: Receiver
I had been using my Marantz model 22 receiver now for a couple years now with the TV, dvd player, and youtube music from my tablet. I like lots of knots and switches on my audio gear, I'm an engineer. I was getting tired of the seemingly endless up and down to adjust volume and whatever. And my inputs on the Marantz were maxed out. I searched Amazon to see what was available as a possible replacement that had a REMOTE. This Sony caught my eye. Relatively inexpensive, plenty of inputs, and specs I could trust, not a 3x4x5 box offering 220+220 watts of unlimited power! Ordered it and been using it for over a month now. Only 2 knobs, how good could that be? Well, it's remote let's me control everything without getting up. Plenty of output power, 100+100 watts of true RMS power. I didn't plan on using the Bluetooth but I tried it with the tablet, keeping the tablet by me, and it really impressed this old audiophile. I really don't have any negatives about it, even the fm sounds great. It was heavier than expected but not as much as that old Marantz. I even popped the cover. The build quality was what I consider good. I only wish I could find a service manual with the schematic for it.
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Reviewed in the United States on September 23, 2025